Revealing a conservation challenge towards floodplain disconnection: Decreasing turnover and increasing nestedness of mollusc metacommunities

doi:10.21203/rs.3.rs-1995979/v2

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Revealing a conservation challenge towards floodplain disconnection: Decreasing turnover and increasing nestedness of mollusc metacommunities

https://doi.org/10.21203/rs.3.rs-1995979/v2

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published 28 May, 2023

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Floodplain disconnection (FDC) has become a profound threat to many large river floodplains. Despite current researches examining the impacts of FDC on aquatic biodiversity, little is known about how FDC affected freshwater molluscs from multifaceted biodiversity perspectives, especially at long-term temporal scales. We selected the 7 lakes in the Yangtze River floodplain to evaluate how river-lake disconnection impacted taxonomic, functional and phylogenetic alpha and beta diversity of molluscan assemblages during past 60 years. Our results showed that five disconnected lakes (DLs) experienced dramatic decline in species richness (decreased by 62.4%) and functional richness (54.6%) but increases in functional evenness (20.0%) and Δ⁺ (5.5%) after disconnection. Whereas such temporal changes in the two connected lakes (CLs) were much slighter. Somewhat unexpectedly, the overall taxonomic (increased by 7.0%) and phylogenetic (12.2%) dissimilarities only slightly increased through time, due to opposite changes in the turnover (40%-50% decrease) and nestedness-resultant (100%-110% increase) components through time. The functional nestedness experienced more significant increase (162.0%), leading to relatively considerable increase in functional overall dissimilarity (64.0%). Such opposite changes in multifaceted turnover and nestedness distinctly modified the structure of beta diversity and highlight the conservation priority of CLs keeping relative high levels of biodiversity. The overall correlations between changes in both alpha and beta diversity among different facets were generally weak, indicating the different diversity facets would provide complementary information for biodiversity conservation and restoration. Thus, we recommended incorporating functional and phylogenetic information of species into traditional taxonomy-based approaches in large river floodplains studies.

multiple diversity facets

hydrological disconnection

long-term biodiversity changes

turnover

nestedness-resultant

biodiversity conservation

Floodplains are one of the most important ecological landscapes and ecosystems in the world, which supported high levels of biodiversity and provided a set of ecological services (e.g., water supply and storage, food production, entertainment, aesthetic enjoyment and hydrologic regulation) to human society (Arantes et al., 2018; Tane et al., 2014; Wang et al., 2019). However, due to increasing human disturbances, most river floodplains in the world experienced dramatic and rapid biodiversity decline and ecological degradation during recent decades, making them become one of the most threatened ecosystems on Earth (Revenga et al., 2005; Tockner and Stanford, 2002; Wang et al., 2019). Among the multiple anthropogenic disturbances (e.g., hydrological alterations, overexploitation of biological resource, water pollution) which impacting floodplain ecosystems, the loss of river-lake connection was usually regarded as one of the most severe and widespread threats to aquatic biodiversity, especially in those large river floodplains (Revenga et al., 2005; Saunders et al., 2002). This is because river-lake connection played a pivotal role in the material, energetic and biological exchanges between the river mainstem and its surrounding waterbodies (Arthington et al., 2006).

Recently, assessing the impact of hydrological disconnection on the floodplain ecosystems has become a hot topic concerned by ecologists and environmental managers (Jiang et al., 2022; Li et al., 2022). The existing research indicated floodplains disconnection would significantly change the original hydrological rhythms and lead to a series of adverse impacts (e.g., habitat loss and degradation, weakening water self-purification), and finally caused dramatic losses of biodiversity and ecosystem balance. However, most of the studies examined the effects of hydrological disconnection on aquatic biodiversity were conducted at the spatial scale, only few studies evaluated the effects at the temporal scales (i.e., the comparisons for the same lake groups before and after the disconnection), such before-after comparisons in aquatic biodiversity is a more intuitive way to evaluate how local aquatic assemblages responded to the hydrological disconnection in river floodplains, and then provide suggestions for ecological managements and restoration (Steinfeld and Kingsford, 2013; Wang et al., 2019; Wegener et al., 2017).

According to previous studies, the hydrological connectivity played an important role in sustaining the local aquatic biodiversity (Bracken et al., 2013). Typically, a high level of hydrological connectivity would support a high level of local richness (i.e., alpha diversity), and it is convenient to the migration, diffusion and gene exchanges between river and lakes, allowing some species flow from optimal habitats to suboptimal habitats (i.e., mass effects) (Shmida and Wilson, 1985). Therefore, the highly connected floodplains usually appeared a high level of regional homogenization (i.e., a low level of beta diversity) (Liu and Wang, 2010; Wang et al., 2016). After the loss of hydrological connectivity, there would be a decrease in the alpha diversity but increase in beta diversity in these disconnected lakes, due to the decreased mass effect and increased environmental heterogeneity between disconnected lakes (Carrara et al., 2012; Liu and Wang, 2010; Paillex et al., 2013; Penha et al., 2017).

Many previous studies traditionally focused on the changes of taxonomic diversity (i.e., TD) to floodplain disconnection, whereas basically ignored the response of phylogenetic and functional diversity (i.e., PD and FD) (Cardoso et al., 2017; Lepš et al., 2001). The TD was an effective indicator of ecological status, but TD had some limitations, as it regarded different species as an identical unit and ignored the considerable differences in functional traits and phylogeny among different species (Dı́Az and Cabido, 2001). Thus, ecologists have realized the need of incorporating functional and phylogenetic information of species into the biodiversity studies (D’agata et al., 2014). Comparing to TD indices, the FD indices usually respond strongly and reliably to environment changes, due to their closer associations with environmental gradient (Mccarthy, 2004; Villéger et al., 2014). Furthermore, FD can directly reflect the influence of species to the ecosystem function (Lei et al., 2016; Mcgill et al., 2006). For PD, as it measures the evolutionary relationship among species, examinations from an PD perspective actually reflects the evolutionary history of species in the process of community assembly (Narwani et al., 2015). Furthermore, integrating PD and FD to biodiversity studies can provide important complements to TD, and guidance to environmental managers and ecologists for effective biodiversity conservation (Alahuhta et al., 2019; Dolédec et al., 2017; Liu and Wang, 2018).

Freshwater molluscs (i.e., gastropods and bivalves), are one of the most diverse and important organism groups in river floodplains, playing an important role in material and energy circulation of floodplain ecosystems (Christian and Harris, 2008; Gössling et al., 2004). Whereas floodplain disconnection led to dramatic biodiversity decline of freshwater molluscs, making them become one of the most threatened groups (Obolewski et al., 2009). Up to now, few studies evaluated the impacts of hydrological disconnection on the freshwater molluscs from multiple diversity dimensions (Jiang et al., 2021). Thus, there is an urgent need to evaluate how multifaceted alpha and beta diversity of molluscan assemblages respond to river-lake disconnection, especially through a comparison before and after disconnection.

In this study, we selected 7 lakes in the Yangtze River floodplain to evaluate how river-lake disconnection affected taxonomic, functional and phylogenetic alpha and beta diversity of freshwater molluscs during the past 60 years. Historically, the 7 lakes were all connected with the Yangtze River stem, whereas only 2 lakes (Lakes Dongting and Poyang) remained connecting in the current period. Firstly, we tested the changes of alpha and beta diversity and compared the changed between historical and current periods. Secondly, we examined the correlations between changes in diversity among different facets. Specifically, we predicted the multiple facets of alpha diversity would decrease through time, whereas beta diversity would increase after disconnection we hypothesized the multiple facets of alpha diversity would decrease through time, but beta diversity would increase after disconnection.

Study area and data collection

The Yangtze River is the third largest river in the world, with a mainstream length of 6397 km, covering a drainage area of 180,000 km². The floodplain in the middle and lower reaches of the Yangtze River is China’s highest concentrations of freshwater lakes (Yin et al., 2020). This region’s ecology health had a great benefit on human beings, as it provided bioproduction, water resource, energy etc. for human beings (Wang et al., 2016; Zhang et al., 2018). However, over the past 50 years, the Yangtze floodplain was seriously impacted by human activities, such as hydrological construction projects, sand dredging, pollutant emission, overfishing (Wang et al., 2016; Wang et al., 2019). Among these threats, the hydrological disconnection was recognized as the most threaten factor (Jiang et al., 2021; Liu and Wang, 2010) .

We selected 7 lakes (Lakes Poyang, Dongting, Taihu, Chaohu, Honghu, Huama and Donghu) with molluscan investigation data both in the historical and current periods for subsequent analysis. The 7 studied lakes included the five largest freshwater lakes in China, and their lake area ranges from 27.5 to 3210.0 km², water depth varies from 2.2 to 6.4 m and the distance to the Yangtze Rivers is between 4.9 and 73 km (Table S2). Of the 7 lakes, only Lakes Poyang and Dongting kept connectivity in the current period, whereas other 5 lakes were disconnected from the Yangtze River stem. The molluscan presence/absence data were collected from published surveys (including scientific reports, books, online data and grey literature) since 1950s (supplementary file: Table S1). We updated the mollusc taxonomy according to He and Zhuang (2013), Bouchet et al., (2017) and MolluscaBase (2021).

Then given that the variable disconnection time (the hydraulic projects which caused river-lake disconnection continued up to 1980s in this floodplain) and data availability of the 7 lakes, we divided the data into two periods: historical period (1956–1982) and current period (2003–2018). For each period, all available data were gathered to build up exhaustive species lists. For each lake, multiple sampling gears were used in the molluscan survey, including modified trawl net, mussel rakes, hand-rakes and modified Petersen grab.

Mollusc trait and phylogenetic information

In our study, we selected 2 continuous traits (maximal body size, shell height/width) and 4 categorical traits (respiration, feeding habit, reproduction mode and locomotion and substrate relation) to calculate functional diversity. These biological traits have been widely used in recent mollusc and macroinvertebrate studies, as they were considered as key traits reflecting the response and adaptation of molluscs to environment (Cai et al., 2019; Usseglio-Polatera et al., 2000). All information of the molluscan biological traits was obtained by Liu et al. (1979) and He and Zhang (2013).

Because the true phylogeny data is lacked for the studied molluscs, we used taxonomic hierarchies as a proxy of true phylogeny. This method was widely applied in many recent studies involving the calculation of phylogenetic diversity of macroinvertebrate assemblages (Cai et al., 2019; Heino et al., 2015). We checked higher taxonomic levels each specie, and applied 6 taxonomic levels (i.e., species, genus, family, superfamily, order and class) in the present study.

Calculation of multifaceted alpha and beta diversities

We calculated three facets (i.e., taxonomic, functional and phylogenetic) of alpha and beta diversity of molluscan assemblages for 7 lakes between historical and current periods. We used the species richness (SR) to represents the taxonomic alpha diversity. Function alpha diversity was quantified with functional richness (FRic), functional evenness (FEve) and functional divergence (FDiv). The three indices represent complementary components of functional diversity, and measure the total spread of traits, evenness and divergence of spread in trait space, respectively (Mason et al., 2005; Villéger et al., 2008). In the computation process of functional alpha diversity, we first used the Gower distance to calculate trait distances between species (Gower, 1971), then applied the principal coordinates analysis (PCoA) trait vectors to generate the functional space composed of multiple dimensions. In this study, the first 4 PCoA vectors were applied, as these vectors usually considered as the minimum required dimension number (i.e., PCoA vectors) below which the quality of functional space was insufficient (Maire et al., 2015). All the three indices were calculated in the R packages FD (Laliberté et al., 2014) and vegan (Oksanen et al., 2012).

We used the average taxonomic distinctness (Λ⁺) and the variation in taxonomic distinctness (Δ⁺) as the proxies for phylogenetic alpha diversity. The two indices were widely applied in many macroinvertebrate studies dealing with phylogenetic diversity (Cai et al., 2018; Jiang et al., 2022). Δ⁺ measures the average taxonomic or phylogenetic distance between all species pairs within an assemblage, and Λ⁺ quantifies the unevenness of the taxonomic tree (Clarke and Warwick, 1998). The Δ⁺ and Λ⁺ were calculated in the function "taxondive" in the R package vegan.

We also calculated taxonomic, functional and phylogenetic beta diversity of molluscan assemblages and partition each facet of beta diversity into turnover and nestedness-resultant components, following the framework proposed by Baselga (2010; 2012). We firstly measured overall taxonomic beta diversity (Tβ_sor) and its turnover (Tβ_sim) and nestedness-resultant components (Tβ_sne) based on the partitioning of Sorensen dissimilarity (Baselga, 2012). Then, we used the derived Sorensen index to calculated overall functional beta diversity (Fβ_sor) based on the above constructed functional space (Villéger et al., 2013) and also partition it into functional turnover (Fβ_sim) and nestedness-resultant (Fβ_sne) components as taxonomic dissimilarities. Similarly, we applied the phylogenetic Sorensen (Pβ_sor) index to computed phylogenetic beta diversity and decompose it into phylogenetic turnover and nestedness-resultant components (Leprieur et al., 2012). The calculation of the three facets of beta diversity were all explored in the R package betapart. The percentage of turnover (p_turn) and nestedness (p_nest) of the overall dissimilarity for each beta diversity facet were also calculated.

Statistical analysis

Firstly, for the alpha diversity, we applied the paired t-test to compare whether the three facets of alpha diversity indices (i.e., Taxonomic: SR; Functional: FRic, FDiv, FEve; Phylogenetic: Δ⁺ and Λ⁺) differed between historical and current periods, using pairwise.t.test functions in R. Then we used the Spearman correlation analysis to examine the correlation among the changes (the current value minus the historical value) in six diversity indices.

For the beta diversity, we used Principal Co-ordinates Analysis (PCoA) which was separately performed based on taxonomic, functional and phylogenetic dissimilarity matrices (β_sor, β_sim and β_sne) to visualize patterns of mollusc assemblages during the two different periods. Meanwhile, we applied the Permutational analysis of multivariate dispersions (PERMDISP, Anderson, 2006) with 999 permutations to test whether the multifaceted community compositional heterogeneity varied among two periods. In addition, we explored Pearson coefficient-based Mantel tests (999 permutations) to assess the relationships between temporal changes in pairwise dissimilarity among different diversity facets.

We ran all analyses (Spearman correlation analysis, PCoA, PERMDISP and Mantel tests) in the package vegan (Oksanen et al., 2019) in R version 4.0.1 (R Development Core team, 2020).

In the historical period, before the loss of river-lake connectivity, 151 species belonging to 48 genera, 18 families, 10 superfamilies, 10 orders and 2 classes were recorded across the 7 studied floodplain lakes (Table 1). In the current period, there were 83 species, belonging to 37 genera, 15 families, 10 superfamilies, 8 orders and 2 classes. Overall, 69 species, 12 genera, three families, one superfamily and one order were extirpated from the species pool through time, whereas one species (Ampullaria gigas) which belongs to a new order appeared in the current period.

Table 1

List of families, superfamily, class and order, and number of genera and species within each family in the 7 studied lakes during the historical (1959–1995) and the current (2003–2018) periods. Orders, superfamilies and families are listed from most to least species-rich. ^* indicated extirpated taxa from the historical to the current period. ^** indicated new recorded taxa in the current period.
Class&Order	Superfamily	Family	Historical		Current
			Number of taxa
			Genus	Specie	Genus	Specie
Gastropoda
Architaenioglossa	Viviparoidea	Viviparidae	7	28	5	11
Littorinimorpha^**	Ampullarioidea^**	Ampullariidae^**	0	0	1	1
	Truncatelloidea	Hydrobiidae^*	3	4	0	0
		Pomatiopsidae	1	1	1	1
		Bithyniidae	3	12	3	6
		Stenothyridae	1	2	1	1
Mesogastropoda	Cerithioidea	Semisulcospiridae	1	12	1	5
Basommatophora	Lymnaeoidea	Physidae	1	1	1	1
		Lymnaeidae	2	13	1	4
		Planorbidae	5	14	3	6
		Ancylidae^*	1	1	0	0
Stylommatophora^*	Succineoidea^*	Succineidae^*	1	1	0	0
Bivalvia
Mytilida	Mytiloidea	Mytilidae	1	1	1	1
Unionida	Unionoidea	Margaritiferidae	1	1	1	1
		Unionidae	16	52	15	41
Adapedonta	Solenoidea	Pharidae	1	1	1	1
Venerida	Cyrenoidea	Cyrenidae	1	5	1	2
Sphaeriida	Sphaerioidea	Sphaeriidae	2	2	1	1

Temporal change in multifaceted alpha diversity of mollusc assemblages

For the comparisons of the three facets of alpha diversity indices between historical and current periods, we found SR (t = 12.581, p < 0.001) and FRic (t = 2.233, p = 0.067) significantly or marginally significantly decreased through time, whereas FEve (t = -4.899, p = 0.003) significantly increased through time. The other three indices, Δ⁺ (t = 1.196, p = 0.277), Λ⁺ (t = -1.324, p = 0.234) and FDiv (t = 0.730, p = 0.493) did not show significantly change through time (Fig. 1). On average, SR decreased by 27.6 species per lake (accounting 54.0% of historical value), FRic decreased by (39.6%) and FEve increased by (16.9%), respectively. Specially, the two connected lakes experienced much more slight changes in three facets of alpha diversity compared to the 5 connected lakes: SR (32.8% vs. 62.4% decrease), FRic (2.0% vs. 54.6% decrease), FEve (9.2% vs. 20.0% increase), Δ⁺ (4.0% decrease vs. 5.5% increase) and Λ⁺ (6.4 increase vs. 12.0% decrease).

The correlations between the temporal changes in alpha diversity were generally insignificant among different diversity indices, except the correlations between Δ⁺ and FEve (r = 0.826, P = 0.022), Δ⁺ and Λ⁺ (r = 0.862, P = 0.013) were significant (Table 2).

Table.2 Spearman's correlations between the temporal changes (from the historical to current periods) in taxonomical (SR), phylogenetic (Δ⁺, Λ⁺) and functional (FRic, FDiv and FEve) alpha diversity indices of mollusc fauna across the 7 studied lakes.

	FRic	FDiv	FEve	Δ⁺	Λ⁺
SR	0.195	0.463	-0.219	0.344	-0.506
FRic		-0.006	-0.491	-0.275	-0.041
FDiv			-0.06	0.13	-0.358
FEve				.826*	-0.621
Δ⁺					− .862*
Λ⁺
^* denotes P < 0.05.

Temporal change in multifaceted beta diversity of mollusc assemblages

In the historical period, the mean value of taxonomic dissimilarity (Tβ_sor) among the 7 studied lakes was 0.533 (range 0.200 to 0.671), mainly contributed by the turnover component (Tβ_sim, mean value = 0.369, p_turn = 69.1%) (Table 3). The mean value of phylogenetic dissimilarity (Pβ_sor) was 0.360, also dominated by turnover component (Pβ_sim, mean value = 0.230, p_turn = 64.0%). The mean value of Functional dissimilarity (Fβ_sor) was 0.369, with balanced contribution of turnover (Fβ_sim, mean value = 0.190, p_turn = 51.1%) and nestedness-resultant (Fβ_sne, mean value = 0.179, p_nest = 48.9%) components (Table 3). In the current period, all the three facets of beta diversity and their nestedness component increased, but their turnover component all remarkably declined. Specifically, the Tβ_sor increased on average by 0.037 (an increase of 7.0% compared with historical value), Pβ_sor increased by 0.044 (12.2%), whereas Fβ_sor dramatically increased by 0.236 (65.6%). The nestedness-resultant component increased by on average by 0.195 (ca. 110%) for taxonomic facet, 0.155 (ca. 100%) for phylogenetic facet, and 0.290 (ca. 160%) for functional facets. In contrast, turnover component decreased by 0.158 (ca. 40%) for taxonomic facet, 0.111 (ca. 50%) for phylogenetic facet, and 0.054 (ca. 30%) for functional facets. Although the three facets of overall dissimilarity changed slightly through time, the two components dramatically changed (in opposite direction), resulting in the significant modification of multifaceted beta diversity structure (all from the domination of turnover component to the domination of nestedness-resultant component).

Furthermore, by comparing the different pairs of lakes, we found such decreases in turnover and increases in nestedness-resultant were both more remarkable in pairs of connected and disconnected lakes (C-Dis) than in pairs of disconnected lakes (Dis-Dis) (Tabl e 4).

The PCoA ordination plots based on taxonomic, functional and phylogenetic overall dissimilarity showed the heterogeneity of the mollusc communities in the current period were slightly higher (showing larger dispersion) than that in the historical period (Fig. 2. a to c). As for their turnover components, the Tβ_sim and Pβ_sim appeared smaller dispersion in the current period, whereas the dispersion of Fβ_sim were similar among two period (Fig. 2. d to f). In addition, the three facets of nestedness components were all showed obviously larger dispersion in the current period (Fig. 2. g to i). Similarly, the PERMDISP analyses showed that there are only narrow differences in the average distance to the group centroid for the Taxonomic (Tβ_sor) and Phylogenetic overall dissimilarity (Pβ_sor) between 2 periods, whereas the overall dissimilarity of Functional (Fβ_sor) showed a marginally significant higher (P = 0.111) average distance to the group centroid in the current periods (Fig. 3). As for their turnover components, such distances of Tβ_sim and Pβ_sim insignificantly declined through times, whereas the distance of Fβ_sim kept stable between 2 periods (Fig. 3). Moreover, the three facets of nestedness-resultant components all showed a marginally significant or significant increase in such distance through time (the P value of Tβ_sne, Pβ_sne and Fβ_sne is 0.123, 0.073 and 0.009, respectively) (Fig. 3).

Table 3

Taxonomic, phylogenetic and functional overall dissimilarity (β_sor), turnover (β_sim), nestedness-resultant (β_sne), and contribution of turnover (p_turn) and nestedness-resultant (p_nest) to dissimilarity for historical period and current period. Values are mean ± standard deviation with range in brackets.
		Historical	Current
Taxonomic	β_sor	0.533 ± 0.119(0.200 to 0.671)	0.570 ± 0.138(0.206 to 0.763)
	β_sim	0.369 ± 0.173(0.125 to 0.63)	0.211 ± 0.169(0 to 0.556)
	β_sne	0.164 ± 0.144(0 to 40.448)	0.359 ± 0.250(0.019 to 0.763)
	p_turn	0.691 ± 0.274 (0.218 to 0.994)	0.420 ± 0.335 (0 to 0.962)
	p_nest	0.309 ± 0.274 (0.06 to 0.782)	0.580 ± 0.335 (0.038 to 1)
Phylogenetic	β_sor	0.360 ± 0.092(0.149 to 0.508)	0.404 ± 0.124(0.153 to 0.617)
	β_sim	0.230 ± 0.120(0.049 to 0.432)	0.119 ± 0.120(0 to 0.441)
	β_sne	0.130 ± 0.107(0.007 to 0.34)	0.285 ± 0.180(0.034 to 0.6)
	p_turn	0.640 ± 0.293 (0.127 to 0.98)	0.336 ± 0.303 (0 to 0.894)
	p_nest	0.360 ± 0.293 (0.020 to 0.873)	0.664 ± 0.303 (0.106 to 1)
Functional	β_sor	0.369 ± 0.197(0.032 to 0.682)	0.605 ± 0.294(0.036 to 0.959)
	β_sim	0.190 ± 0.151(0 to 0.439)	0.136 ± 0.212(0 to 0.826)
	β_sne	0.179 ± 0.130(0.005 to 0.443)	0.469 ± 0.301(0.007 to 0.952)
	p_turn	0.511 ± 0.274 (0 to 0.908)	0.251 ± 0.314 (0 to 0.951)
	p_nest	0.489 ± 0.274 (0.092 to 1)	0.749 ± 0.314 (0.049 to 1)

Table 4

Temporal changes in taxonomic, phylogenetic and functional dissimilarities from the historical to current period. Values are means ± standard deviations. All pairs: 21 dissimilarity values between the 7 lakes pairing each other, C-C pair: one dissimilarity value between the 2 river-connected lakes pairing each other, C-Dis pairs: 10 values between the 2 river-connected lakes pairing 5 dis-connected lakes, Dis-Dis pairs: 10 values between the 5 dis-connected lakes pairing each other.
	∆β_sor	∆β_sim	∆β_sne	∆p_turn	∆p_nest
Taxonomic
All Pair	0.037 ± 0.100	-0.158 ± 0.155	0.195 ± 0.158	-0.271 ± 0.219	0.271 ± 0.219
C-C	0.006	0.000	0.006	-0.028	0.028
C-D	0.084 ± 0.061	-0.195 ± 0.181	0.279 ± 0.164	-0.327 ± 0.26	0.327 ± 0.260
D-D	-0.007 ± 0.117	-0.138 ± 0.128	0.130 ± 0.110	-0.239 ± 0.165	0.239 ± 0.165
Phylogenetic
All Pair	0.044 ± 0.083	-0.110 ± 0.106	0.154 ± 0.111	-0.303 ± 0.216	0.303 ± 0.216
C-C	0.004	-0.014	0.018	-0.116	0.116
C-D	0.073 ± 0.074	-0.119 ± 0.113	0.192 ± 0.118	-0.282 ± 0.235	0.282 ± 0.235
D-D	0.020 ± 0.089	-0.110 ± 0.104	0.130 ± 0.096	-0.343 ± 0.206	0.343 ± 0.206
Functional
All Pair	0.236 ± 0.326	-0.054 ± 0.206	0.29 ± 0.335	-0.260 ± 0.349	0.260 ± 0.349
C-C	-0.044	-0.068	0.024	-0.378	0.378
C-D	0.273 ± 0.331	-0.11 ± 0.133	0.383 ± 0.343	0.334 ± 0.411	0.334 ± 0.411
D-D	0.227 ± 0.34	0.003 ± 0.264	0.224 ± 0.332	-0.174 ± 0.400	0.174 ± 0.400

Relationships between changes in different facets of beta diversity

The correlations between changes in taxonomic beta diversity and its two components with their corresponding phylogenetic dissimilarities were quite strong (r of mantel tests ranges from 0.904 to 0.953), whereas the correlations between changes in functional dissimilarities and taxonomic and phylogenetic ones were less strong (r ranges from 0.339 to 0.808) (Fig. 4). Despite the major trends towards for multifaceted heterogenization for the changes in overall dissimilarities and nestedness-resultant components, the three facets of turnover component all appeared opposite homogenization tendency (Fig. 4).

Impacts of river-lake disconnection on alpha diversity

The lakes on the Yangtze floodplain were historically connected with the mainstream and constituted a highly diverse and complex floodplain ecosystem. This naturally formed environment often provided suitable and stable habitats, abundant foods, and resources for aquatic organisms, and thus supported high level of molluscan alpha diversity in the historical period (Lydeard et al., 2004; Obolewski et al., 2009). However, after river-lake disconnection, we found considerable decreases both in taxonomic (decreased by 54% for the 7 lakes and ca. 60% if only considering the five disconnected lakes) and functional richness (ca. 40%) through time. Such dramatic loss of molluscan species richness after river-lake disconnection were also reported in previous studies (Obolewski, 2011; Pringle et al., 2000) and can be attributed to following reasons. The river-lake disconnection usually caused a series of environmental changes, including the alterations of hydrological rhythm, decrease in the spatial and temporal heterogeneity of habitats, and simplification and degradation of aquatic macrophytes (Wang et al., 2019). These changes were usually reported as important threats to the survival, growth and reproduction of many mollusc species and the causes of molluscan biodiversity decline (Lopes-Lima et al., 2018; Reckendorfer et al., 2006; Zieritz et al., 2018). Moreover, the losses of the exchange pathways also negatively affected mollusc diversity. For example, the glochidium of some mussel species (e.g., Anodonta woodiana, Lamprotula leai, Hyriopsis cumingii) usually parasitized on migratory fishes to finish their life history and dispersion between lakes and the mainstream (Gillis et al., 2008; Rogers-Lowery and Dimock Jr, 2006). In addition, other human disturbances, e.g., water eutrophication, sand dredging and overfishing, were also responsible for the decline in molluscan species richness in the studied lakes, especially the five disconnected lakes (Jiang et al., 2022; Wang et al., 2019).

The reduction in FRic (ca. 40%) is also considerable (especially in disconnected lakes) and only slightly lower than reduction in species richness, indicating a low level of functional redundancy of molluscan assemblages. Similar to significant decline in taxonomic richness, the molluscan assemblages in disconnected lakes experienced dramatic loss of functional traits and strategies. Several important traits occurred in historical periods (e.g., large body size, filter-feeding habits, burrower and ovoviviparity) showed substantial reduction (species number of these traits in the current periods were only ca. 1/3 ~ 1/4 of that in the historical period) after river-lake disconnection. Such dramatic losses of functional traits would inevitably lead to the decrease in functional richness. The considerable losses of functional traits and strategies of molluscan assemblages in the studied lakes deserves close attention by conservationists and environment managers, as this may impact overall lake ecosystem functioning and services (Biggs et al., 2020; Delgado et al., 2016). As one of the most important groups in freshwater lakes, mollusc assemblages are via their various traits to be of vital importance in maintain lake ecosystem functions, such as promoting material circulation, restoring the aquatic environment, and stabilizing the environment ecosystem (Lydeard et al., 2004; Ruehl and Trexler, 2011). Moreover, the increases in FEve through time implied that dramatic losses of unique functional traits made the overall functional traits of mollusc assemblages become more similar.

Despite the slightly and insignificantly temporal increases in the values of Δ⁺ for the 7 lakes, the 5 disconnected lakes showed a more obvious modification in phylogenetic diversity after the FDC. The increases in Δ⁺ after disconnection were somewhat surprising, as such results implied the mollusc assemblages became more phylogenetically diverse. In the studied lakes, there were widespread flocks of congeneric species (e.g., 12 species of Bellamya, 12 species of Semisulcospira, 11 species of Radix, 9 species of Lamprotula, 8 species of Sinosolenaia and 7 species of Parafossarulus) in the historical period. However, after the FDC, these congeneric species were extensively extirpated in the five disconnected lakes (Shu et al., 2014; Jiang et al., 2022). In general, the increase of Δ⁺ was considered as a positive signal of biodiversity change (Clarke and Warwick, 2001; Gladstone et al., 2021). Whereas in our study, the increase was generated by the dramatic losses of endemic congeneric species, which caused the decline of assemblages of shortest path in the phylogenetic tree and resulted in the increase in Δ⁺. Thus, such increases may be not positive signal but the warnings of decline in endemic molluscan species and associated aquatic resource losses (Shu et al., 2014).

Comparing with the 5 disconnected lakes, the two connected lakes (Lakes Poyang and Dongting) showed slight changes in the three facets of alpha diversity, especially the functional diversity. Lakes Poyang and Dongting kept hydrological connectivity and relatively well ecological status, and thus experienced slighter loss of mollusc species (ca. 33%) than the five disconnected lakes. The two lakes are the two largest freshwater lakes in China, supporting the species-richest mollusc assemblages (Shu et al., 2014) and higher level of functional redundancy (several species have the same or similar traits). Thus, their mollusc functional diversity showed a higher resistance (the ~ 33% decrease in species richness only resulted in ~ 3% decrease in functional richness) to the loss of species than species-poor lakes (Jiang et al., 2021; Mouchet et al., 2010; Mouillot et al., 2013).

Impacts of river-lake disconnection on beta diversity

For beta diversity, we found the overall taxonomic and phylogenetic dissimilarities only slightly increased (ca. 7% and 12%) through time, except relatively large increase (ca. 64%) in functional beta diversity. Such results were somewhat surprising, as previous studies showed the river-lake disconnection would block the species exchange pathway between river and lakes and increase the between-lake environmental heterogenization, and led aquatic assemblages tend to be heterogeneous (Ding et al., 2017; Zhang et al., 2019). In the present study, we found opposite change directions in all three facets of turnover (decrease) and nestedness-resultant (increase) components, which masking the changes in three facets of overall dissimilarities. For the taxonomic dimension, the decrease in turnover but increase in nestedness were induced by the imbalanced extirpation of species between different lakes, especially between connected (fewer extirpated species) and disconnected ones. Specifically, the percentage of common species (a) were nearly unchanged (on average decreased from 31.3–28.4%) and maximum non-shared species (b) slightly increased (49.4–61.4%) over time, whereas the percentage of minimum non-shared species (c) significantly decreased (19.3–10.1%) after river-lake disconnection. The unchanged a but decreasing c indicated the decrease in taxonomic turnover, while the increasing difference in species richness (b minus c) certainly led to the increase in taxonomic nestedness., After disconnection, several species-poor lakes were nearly completely nested by species-rich large lakes, i.e., Lake Huama was totally nested to Lakes Poyang and Dongting.

The decrease in phylogenetic turnover but increases in nestedness-resultant components were also attributed to similar reason. In the current period, despite a considerable number of species extirpated, the number of families in the CLs only appeared slight changes (Physidae disappeared in the Lake Poyang, and Ampullariidae appeared in the Lake Doting). However, the disappearances of higher taxa in the five DLs were more serious (on average, 3.4 of 11.4 families extirpated per lake). The imbalanced disappearance of higher taxa resulted in a considerable increase in between-lake difference in phylogenetic richness. Similarly, the decrease in taxonomic turnover led to a decrease in phylogenetic turnover.

Somewhat different from the nearly unchanged taxonomic and phylogenetic overall dissimilarities, the functional beta diversity experienced relatively large increase (64.0%), due to the considerably high increase in functional nestedness. Those disconnected lakes experienced significant loss of functional traits through time, whereas the trait losses in connected lakes were quite slight because of high functional redundancy. Thus, the increase in functional nestedness exceeds the increase in taxonomic nestedness and we observed a relatively large increase (increase in functional nestedness prevails over the decrease in functional turnover) in functional beta diversity.

The opposite changes in turnover and nestedness-resultant components highlight the necessity of partitioning overall beta diversity into independent components in biodiversity studies: the two components indeed represent complementary processes in community assembly (Angeler, 2013; Dapporto et al., 2014). In the studied lakes, despite the slight changes in overall dissimilarity, the structures of multifaceted beta diversity of mollusc assemblages were dramatic altered from the dominance of turnover to the dominance of nestedness. Such modification had strong implications for biodiversity conservation and restoration in the studies lakes. According to previous studies, the dominance of turnover component indicated that all the sites or most of sites in overall region should be considered and conservated, while the dominating nestedness implied a requirement to preferentially focus on the species-rich sites (Angeler, 2013; Baselga, 2012). Therefore, the temporal shift from the dominance of turnover to the dominance to nestedness-resultant components at three diversity facets means conservation of the high-diversity lakes (e.g., Lake Poyang and Doting) become more urgent and preferential.

Correlations between changes in different indices diversity facets

Although the three facets of mollusc biodiversity showed the same direction of changes after disconnection, the correlations between changes in both alpha and beta diversity among different facets were generally weak (except for some relative strong correlations between changes in taxonomic dissimilarities and phylogenetic dissimilarities). Such weak correlations indicated that evaluating functional and phylogenetic diversity dimensions indeed provided complementary information that cannot be portrayed by examining only taxonomic diversity. Thus, we recommend incorporating functional and phylogenetic information of mollusc species into traditional monitoring and assessment approaches in evaluating the impacts of FDC and other anthropogenic disturbances in the large river floodplains, for more effective conservation and restoration practices in the future.

Our study showed significant impacts of river-lake disconnection on mollusc assemblages in the Yangtze River floodplain lakes, but there still have some limitations and caveats. Firstly, the number of studied lakes were quite limited (five disconnected lakes and only two lakes kept connectivity through time), though we exhausted our ability to collect data. While there were still more available lake mollusc investigation data in the studied region, but unfortunately, the available historical mollusc data were quite limited before disconnection. For the connected lakes, Lakes Poyang and Dongting are the two remaining lakes which are currently connected to the Yangtze River stem. Therefore, it is impossible to compile dataset including more lakes for examining the temporal changes before and after disconnection. Secondly, the calculation of phylogenetic diversity was based on Linnaean taxonomic tree rather than true phylogeny. The use of taxonomic classification may lead to an imprecise calculation of true phylogenetic diversity (Clarke and Warwick, 1998; Woese, 2000). Nevertheless, since the DNA data are solely lacking for many mollusc species, especially for those extirpated or endanger species (Liu et al., 2022; Shu et al., 2014), it is unavailable to construct the true phylogeny. In this case, taxonomy can be used as a reasonable surrogate for phylogeny, as confirmed in many recent studies dealing with phylogenetic diversity of macroinvertebrates (Heino and Tolonen, 2017; Jiang et al., 2019; Zhang et al., 2019).

In this study, we examined how long-term river-lake disconnection drove multiple facets of alpha and beta diversity of molluscan assemblages in the Yangtze floodplain lakes. We found significant decrease in taxonomic and functional alpha diversity through time. Moreover, although the three facets of overall beta diversity change slightly, their turnover and nestedness-resultant component dramatically changes in opposite direction, indicating a significant modification of beta diversity structure. The dominance shifted from turnover component to nestedness-resultant component provided useful implication for biodiversity conservation in this region: the high-diversity lakes (i.e., Lake Poyang and Doting) should be protected and concerned preferentially. Moreover, the weak correlation between changes in different facets signified that embracing phylogenetic and functional information into taxonomy-based approaches would provide important and complementary information and enhance the ability to examine and evaluate aquatic biodiversity in the large river floodplains. Overall, our study showed that floodplain disconnection caused profound and severe impacts on the mollusc fauna in Yangtze River floodplain. We appeal to promote the conservation of freshwater molluscs and other organism groups in this floodplain, especially the high conservation priority for two connected lakes (i.e., Lake Poyang and Doting) with high diversity.

Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 31770460). We thank Drs. Zhengfei Li of Institute of Hydrobiology, Chinese Academy of Sciences, and Fengyue Shu of Qufu Normal University for their help in data collection.

Authors’ contributions Kun Zhang: Data analysis, Writing - Original draft preparation and Visualization. Xiaoming Jiang: Supervision. Conceptualization, Methodology, Formal analysis, Writing- Reviewing and Editing. Peng Zheng: Data collection and Data analysis Visualization.

Funding Our research were funded by the National Natural Science Foundation of China (No. 31770460).

Data availability Data are available in the supplementary file.

Code Availability Not applicable.

Conflict of interests The authors declare no conflict of interest.

Ethical Approval All applicable international, national and/or institutional guidelines for sampling, care and experimental use of organisms for the study were followed and all necessary permissions and approvals were obtained in respect of the original collections of the data.

Consent to participate Informed consent was obtained from all observers participating in the study.

Consent for publication Observers have consented to the submission of this manuscript for publication.

Alahuhta J, Erős T, Kärnä O, Soininen J, Wang J, Heino J. 2019. Understanding environmental change through the lens of trait-based, functional, and phylogenetic biodiversity in freshwater ecosystems. Environmental Reviews, 27(2): 263-273.
Angeler D. 2013. Revealing a conservation challenge through partitioned long‐term beta diversity: increasing turnover and decreasing nestedness of boreal lake metacommunities. Diversity and Distributions, 19(7): 772-781.
Arantes C, Winemiller K, Petrere M, Castello L, Hess L, Freitas C. 2018. Relationships between forest cover and fish diversity in the Amazon River floodplain. Journal of Applied Ecology, 55(1): 386-395.
Arthington A, Bunn S, Poff N, Naiman R. 2006. The challenge of providing environmental flow rules to sustain river ecosystems. Ecological Applications, 16(4): 1311-1318.
Baselga A. 2012. The relationship between species replacement, dissimilarity derived from nestedness, and nestedness. Global Ecology and Biogeography, 21(12): 1223-1232.
Biggs C, Yeager L, Bolser D, Bonsell C, Dichiera A, Hou Z, et al. 2020. Does functional redundancy affect ecological stability and resilience? A review and meta‐analysis. Ecosphere, 11(7): e03184.
Bracken L, Wainwright J, Ali G, Tetzlaff D, Smith M, Reaney S, et al. 2013. Concepts of hydrological connectivity: Research approaches, pathways and future agendas. Earth-Science Reviews, 119: 17-34.
Cai Y, Xu J, Zhang M, Wang J, Heino J. 2019. Different roles for geography, energy and environment in determining three facets of freshwater molluscan beta diversity at broad spatial scales. Science of the Total Environment, 659: 451-462.
Cai Y, Zhang M, Xu J, Heino J. 2018. Geographical gradients in the biodiversity of Chinese freshwater molluscs: Implications for conservation. Diversity and Distributions, 24(4): 485-496.
Cardoso S, Nabout J, Farjalla V, Lopes P, Bozelli R, Huszar V, et al. 2017. Environmental factors driving phytoplankton taxonomic and functional diversity in Amazonian floodplain lakes. Hydrobiologia, 802(1): 115-130.
Carrara F, Altermatt F, Rodriguez-Iturbe I, Rinaldo A. 2012. Dendritic connectivity controls biodiversity patterns in experimental metacommunities. Proceedings of the National Academy of Sciences, 109(15): 5761-5766.
Christian A & Harris J. 2008. An introduction to directions in freshwater mollusk conservation: molecules to ecosystems. Journal of the North American Benthological Society, 27(2): 345-348.
Clarke K & Warwick R. 1998. A taxonomic distinctness index and its statistical properties. Journal of applied ecology, 35(4): 523-531.
Clarke K & Warwick R. 2001. A further biodiversity index applicable to species lists: variation in taxonomic distinctness. Marine ecology Progress series, 216: 265-278.
D’agata S, Mouillot D, Kulbicki M, Andréfouët S, Bellwood D, Cinner J, et al. 2014. Human-mediated loss of phylogenetic and functional diversity in coral reef fishes. Current Biology, 24(5): 555-560.
Dapporto L, Fattorini S, Vodă R, Dincă V, Vila R. 2014. Biogeography of western Mediterranean butterflies: combining turnover and nestedness components of faunal dissimilarity. Journal of Biogeography, 41(9): 1639-1650.
Delgado B, Giaramida L, Reich P, Khachane A, Hamonts K, Edwards C, et al. 2016. Lack of functional redundancy in the relationship between microbial diversity and ecosystem functioning. Journal of Ecology, 104(4): 936-946.
Dı́Az S & Cabido M. 2001. Vive la différence: plant functional diversity matters to ecosystem processes. Trends in ecology & evolution, 16(11): 646-655.
Ding C, Jiang X, Xie Z, Brosse S. 2017. Seventy‐five years of biodiversity decline of fish assemblages in Chinese isolated plateau lakes: widespread introductions and extirpations of narrow endemics lead to regional loss of dissimilarity. Diversity and Distributions, 23(2): 171-184.
Dolédec S, Tilbian J, Bonada N. 2017. Temporal variability in taxonomic and trait compositions of invertebrate assemblages in two climatic regions with contrasting flow regimes. Science of the Total Environment, 599: 1912-1921.
Gillis P, Mitchell R, Schwalb A, Mcnichols K, Mackie G, Wood C, et al. 2008. Sensitivity of the glochidia (larvae) of freshwater mussels to copper: Assessing the effect of water hardness and dissolved organic carbon on the sensitivity of endangered species. Aquatic Toxicology, 88(2): 137-145.
Gladstone N, Niemiller M, Hutchins B, Schwartz B, Czaja A, Slay M, et al. 2021. Subterranean Freshwater Gastropod Biodiversity and Conservation in North America. Conservation Biology: the Journal of the Society for Conservation Biology.
Gössling S, Kunkel T, Schumacher K, Zilger M. 2004. Use of molluscs, fish, and other marine taxa by tourism in Zanzibar, Tanzania. Biodiversity & Conservation, 13(14): 2623-2639.
Gower J. 1971. A general coefficient of similarity and some of its properties. Biometrics: 857-871.
Heino J, Alahuhta J, Fattorini S. 2015. Phylogenetic diversity of regional beetle faunas at high latitudes: patterns, drivers and chance along ecological gradients. Biodiversity and Conservation, 24(11): 2751-2767.
Heino J & Tolonen K. 2017. Ecological drivers of multiple facets of beta diversity in a lentic macroinvertebrate metacommunity. Limnology and Oceanography, 62(6): 2431-2444.
Jiang X, Ding C, Brosse S, Pan B, Lu Y, Xie Z. 2019. Local rise of phylogenetic diversity due to invasions and extirpations leads to a regional phylogenetic homogenization of fish fauna from Chinese isolated plateau lakes. Ecological Indicators, 101: 388-398.
Jiang X, Li Z, Shu F, Chen J. 2022. Effects of river-lake disconnection and eutrophication on freshwater mollusc assemblages in floodplain lakes: Loss of congeneric species leads to changes in both assemblage composition and taxonomic relatedness. Environmental Pollution, 292: 118330.
Jiang X, Zheng P, Cao L, Pan B. 2021. Effects of long-term floodplain disconnection on multiple facets of lake fish biodiversity: decline of alpha diversity leads to a regional differentiation through time. Science of the Total Environment, 763: 144177.
Laliberté E, Legendre P, Shipley B, Laliberté M. 2014. Package ‘FD’. Measuring functional diversity from multiple traits, and other tools for functional ecology: 1.0-12.
Lei L, Kong D, Li X, Zhou Z, Li G. 2016. Plant functional traits, functional diversity, and ecosystem functioning: current knowledge and perspectives. Biodiversity Science, 24(8): 922-931.
Leprieur F, Albouy C, De Bortoli J, Cowman P, Bellwood D, Mouillot D. 2012. Quantifying phylogenetic beta diversity: distinguishing between ‘true’turnover of lineages and phylogenetic diversity gradients.
Lepš J, Brown V, Diaz Len T, Gormsen D, Hedlund K, Kailová J, et al. 2001. Separating the chance effect from other diversity effects in the functioning of plant communities. Oikos, 92(1): 123-134.
Li Y, Liao Y, Dong X, Xian H, Kattel G. 2022. Hydrological Disconnection From the Yangtze River Triggered Rapid Environmental Degradation in A Riverine Lake. Limnologica: 125993.
Liu X, Liu Y, Wu R, Zanatta D, Lopes‐Lima M, Gonçalves D, et al. 2022. Systematics, distribution, biology, and conservation of freshwater mussels (Bivalvia: Unionida) in China. Aquatic Conservation: Marine and Freshwater Ecosystems.
Liu X & Wang H. 2010. Estimation of minimum area requirement of river‐connected lakes for fish diversity conservation in the Yangtze River floodplain. Diversity and Distributions, 16(6): 932-940.
Liu X & Wang H. 2018. Effects of loss of lateral hydrological connectivity on fish functional diversity. Conservation biology, 32(6): 1336-1345.
Lopes-Lima M, Burlakova L, Karatayev A, Mehler K, Seddon M, Sousa R. 2018. Conservation of freshwater bivalves at the global scale: diversity, threats and research needs. Hydrobiologia, 810(1): 1-14.
Lydeard C, Cowie R, Ponder W, Bogan A, Bouchet P, Clark S, et al. 2004. The global decline of nonmarine mollusks. BioScience, 54(4): 321-330.
Maire E, Grenouillet G, Brosse S, Villéger S. 2015. How many dimensions are needed to accurately assess functional diversity? A pragmatic approach for assessing the quality of functional spaces. Global Ecology and Biogeography, 24(6): 728-740.
Mason N, Mouillot D, Lee W, Wilson J. 2005. Functional richness, functional evenness and functional divergence: the primary components of functional diversity. Oikos, 111(1): 112-118.
Mccarthy B. 2004. Measuring biological diversity. Journal of the Torrey Botanical Society, 131(3): 277.
Mcgill B, Enquist B, Weiher E, Westoby M. 2006. Rebuilding community ecology from functional traits. Trends in ecology & evolution, 21(4): 178-185.
Mouchet M, Villéger S, Mason N, Mouillot D. 2010. Functional diversity measures: an overview of their redundancy and their ability to discriminate community assembly rules. Functional Ecology, 24(4): 867-876.
Mouillot D, Graham N, Villéger S, Mason N, Bellwood D. 2013. A functional approach reveals community responses to disturbances. Trends in ecology & evolution, 28(3): 167-177.
Narwani A, Matthews B, Fox J, Venail P. 2015. Using phylogenetics in community assembly and ecosystem functioning research. Functional Ecology, 29(5): 589-591.
Obolewski K. 2011. Macrozoobenthos patterns along environmental gradients and hydrological connectivity of oxbow lakes. Ecological Engineering, 37(5): 796-805.
Obolewski K, Glińska L, Kobus S. 2009. Effect of hydrological connectivity on the molluscan community structure in oxbow lakes of the Łyna River. Oceanological and Hydrobiological Studies, 38(4): 75-88.
Oksanen J, Blanchet F, Friendly M, Kindt R, Legendre P, Mcglinn D, et al. 2019. Vegan: community ecology package (version 2.5-6). The Comprehensive R Archive Network.
Oksanen J, Guillaume B, Friendly M, Kindt R, Legendre P, Mcglinn D, et al. 2012. Package “vegan”: Community ecology package. Time Int, 1997: 15-17.
Paillex A, Dolédec S, Castella E, Mérigoux S, Aldridge D. 2013. Functional diversity in a large river floodplain: anticipating the response of native and alien macroinvertebrates to the restoration of hydrological connectivity. Journal of Applied Ecology, 50(1): 97-106.
Penha J, Landeiro V, Ortega J, Mateus L. 2017. Interchange between flooding and drying, and spatial connectivity control the fish metacommunity structure in lakes of the Pantanal wetland. Hydrobiologia, 797(1): 115-126.
Pringle CM, Freeman M, Freeman B. 2000. Regional effects of hydrologic alterations on riverine macrobiota in the new world: tropical-temperate comparison. BioScience, 50(9): 807-823.
Reckendorfer W, Baranyi C, Funk A, Schiemer F. 2006. Floodplain restoration by reinforcing hydrological connectivity: expected effects on aquatic mollusc communities. Journal of Applied ecology, 43(3): 474-484.
Revenga C, Campbell I, Abell R, De Villiers P, Bryer M. 2005. Prospects for monitoring freshwater ecosystems towards the 2010 targets. Philosophical Transactions of the Royal Society B: Biological Sciences, 360(1454): 397-413.
Rogers-Lowery C & Dimock Jr R. 2006. Encapsulation of attached ectoparasitic glochidia larvae of freshwater mussels by epithelial tissue on fins of naive and resistant host fish. The Biological Bulletin, 210(1): 51-63.
Ruehl C & Trexler J. 2011. Comparison of snail density, standing stock, and body size between Caribbean karst wetlands and other freshwater ecosystems. Hydrobiologia, 665(1): 1-13.
Saunders D, Meeuwig J, Vincent A. 2002. Freshwater protected areas: strategies for conservation. Conservation Biology, 16(1): 30-41.
Shmida A & Wilson M. 1985. Biological determinants of species diversity. Journal of biogeography: 1-20.
Shu F, Wang H, Cui Y, Wang H. 2014. Species diversity and distribution pattern of freshwater mollusks in the Yangtze River Basin. Acta Aquatic Biology, 38(1): 19-26.
Steinfeld C & Kingsford RT. 2013. Disconnecting the floodplain: earthworks and their ecological effect on a dryland floodplain in the Murray–Darling Basin, Australia. River Research and Applications, 29(2): 206-218.
Tane H, Sun T, Zheng Z, Liu J. 2014. Auditing reforested watersheds on the loess plateau: Fangshan Shanxi. Ecological indicators, 41: 96-108.
Tockner K & Stanford J. 2002. Riverine flood plains: present state and future trends. Environmental conservation, 29(3): 308-330.
Usseglio‐Polatera P, Bournaud M, Richoux P, Tachet H. 2000. Biological and ecological traits of benthic freshwater macroinvertebrates: relationships and definition of groups with similar traits. Freshwater Biology, 43(2): 175-205.
Villéger S, Grenouillet G, Brosse S. 2013. Decomposing functional β‐diversity reveals that low functional β‐diversity is driven by low functional turnover in E uropean fish assemblages. Global Ecology and Biogeography, 22(6): 671-681.
Villéger S, Grenouillet G, Brosse S. 2014. Functional homogenization exceeds taxonomic homogenization among E uropean fish assemblages. Global ecology and biogeography, 23(12): 1450-1460.
Villéger S, Mason N, Mouillot D. 2008. New multidimensional functional diversity indices for a multifaceted framework in functional ecology. Ecology, 89(8): 2290-2301.
Wang H, Liu X, Wang H. 2016. The Yangtze River floodplain: threats and rehabilitation. Pages 263-291 in Proc. American Fisheries Society Symposium. American Fisheries Society Bethesda, MD, USA.
Wang H, Liu X, Wang H. 2019. Threats to the Yangtze River-Floodplain Ecosystem and Overall Conservation Strategies. Acta Hydrobiologica Sinica 43: 157-182.
Wegener P, Covino T, Wohl E. 2017. Beaver‐mediated lateral hydrologic connectivity, fluvial carbon and nutrient flux, and aquatic ecosystem metabolism. Water Resources Research, 53(6): 4606-4623.
Woese C. 2000. Interpreting the universal phylogenetic tree. Proceedings of the National Academy of Sciences, 97(15): 8392-8396.
Yin S, Wu S, Yue J, Wang N. 2020. Remote Sensing Monitoring and Analysis of the Shoreline Types of the Main Stream of the Yangtze River. People's Yangtze River, 51(11): 16-21+120. [ in Chinese].
Zhang C, Ding C, Ding L, Chen L, Hu J, Tao J, et al. 2019. Large-scale cascaded dam constructions drive taxonomic and phylogenetic differentiation of fish fauna in the Lancang River, China. Reviews in Fish Biology and Fisheries, 29(4): 895-916.
Zhang M, García M J, Zhang X, Xu J. 2018. Functional and taxonomic differentiation of macrophyte assemblages across the Yangtze River floodplain under human impacts. Frontiers in Plant Science, 9: 387.
Zieritz A, Bogan A, Froufe E, Klishko O, Kondo T, Kovitvadhi U, et al. 2018. Diversity, biogeography and conservation of freshwater mussels (Bivalvia: Unionida) in East and Southeast Asia. Hydrobiologia, 810(1): 29-44.

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Revealing a conservation challenge towards floodplain disconnection: Decreasing turnover and increasing nestedness of mollusc metacommunities

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Abstract

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Introduction

Materials And Methods

Study area and data collection

Mollusc trait and phylogenetic information

Calculation of multifaceted alpha and beta diversities

Statistical analysis

Result

Temporal change in multifaceted alpha diversity of mollusc assemblages

Temporal change in multifaceted beta diversity of mollusc assemblages

Relationships between changes in different facets of beta diversity

Discussion

Impacts of river-lake disconnection on alpha diversity

Impacts of river-lake disconnection on beta diversity

Correlations between changes in different indices diversity facets

Conclusion

Declarations

References

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Supplementary Files

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