Study area
The study area (Fig. 1A; N 48°17’13’’, E 16°49’43’’) is located in Lower Austria, south of the village Oberweiden. It is part of the Natura 2000 protected area “March-Thaya-Auen” and the protected habitat “Pannonic Inland Dunes” (European Environment Agency 2022).
For the apidological survey (2018–2019), the 126-hectare large area was divided into four study plots (Fig. 1B) representing differently structured parts of the landscape: The Hills in the northern part of the reserve (HG), the Old Area south of the Hills (AF), the New Area which has only recently been set under protection (NF) and is adjacent to the Old Area to the northwest, and a former horse racing track, which occupies a large area to the south (RB). Important foraging plants were qualitatively (i.e. not systematically) surveyed in the area to improve the definition of the four study plots.
Hills. The hills in the northern area provide a suitable habitat for many plant rarities, such as the common gypsophila (Gypsophila paniculata), the late carnation (Dianthus serotinus), and the immortelle (Helichrysum arenarium). Other flowering plants of interest to wild bees here include knapweed (Centaurea spp.), field eryngo (Eryngium campestris), and Odontites luteus. In the southern area, where the hills gradually transition into the flat, steppe-like meadow, the ground is sparsely vegetated. The open, sandy areas serve as nesting habitat for various species of wild bees and wasps. Prickly saltwort (Kali turgidum) grows on the open, sparsely vegetated soil patches.
Former horse racing course. An extensive steppe-like area is surrounded by the track of a former horse racing course. The edges of the race course form a low, sandy slope towards the meadow and are partially overgrown with flowering plants such as thyme (Thymus sp.), hoary alyssum (Berteroa incana), yellow scabious (Scabiosa ochroleuca), and knapweed (Centauerea spp.). Hoary alyssum seems to be particularly attractive to various wild bee species, blooming in large numbers especially in the southeast corner of the horse track. Very early in the year, sand cinquefoil (Potentilla incana) blooms in large number.
Old Area. The Old Area is a meadow west of the hills, crossed with several sandy paths. Flowering plant species include knapweed (Centaurea spp.), thorny knapweed (Ononis spinosa), and resede (Reseda sp.).
New Area. North of the old area and the hills is another meadow that has only recently become part of the nature preserve. Many flowering plants grow here, such as thorny knapweed (Ononis spinosa), yellow scabiosa (Scabiosa ochroleuca), knapweed (Centaurea spp.) and sage (Salvia sp.).
Due to imprecise locality on the specimen labels until the 1960ies, it must be assumed that until the 1960ies records labelled as “Oberweiden” are not restricted to the protected area today, but could also include the area between the steppe and the train station in the village in a few kilometres distance, where entomologists arrived (Fig. 1A). Thus, the entire area was considered in the analysis of the landscape changes.
Today, the protected area is managed by mowing. Though as a result of an EU LIFE-project (Wiesbauer 2002b) staggered mowing with a certain proportion of the area left standing each year was foreseen, own- and third-party observations (e.g. M. Lödl pers. comm.) have shown that the entire area is actually mowed in one go by selecting the overlapping time window for mowing that is open for all sub-areas in accordance with the management contract. The non-use areas should be rotated annually so that scrub encroachment due to long-term fallow is prevented, which is not the case. The management plan is currently being revised (pers. comm. Department of Nature Conservation, State Government of Lower Austria).
Field work. Surveys were conducted by visual collecting with a hand net from April until September 2018 and from April until August 2019 (for dates see Online Resource 1). For the determination of the species Amiet et al. (1999, 2001), Dathe et al. (2016), Ebmer (1969–1973), Scheuchl (1995, 1996), Schmid-Egger and Scheuchl (1997), as well as the Collections of the Natural History Museum Vienna (NHMW), Sabine Schoder and Herbert Zettel were used.
A complete list of the collected specimens including specimen-IDs and GPS coordinates is given as supplementary material (Online Resource 1).
Bumblebees (Bombus spp.) were not considered in the most recent survey (2018–2019). However, historical bumblebee records are included in Online Resource 2, but not further evaluated and discussed in comparison with recent data.
Nomeclature. Nomenclature follows Scheuchl and Willner (2016), with the following exceptions: classification of Eucera s.l. follows Dorchin et al. (2018); Andrena afzeliella is understood following Praz et al. (2022).
Databases, literature and Collection data. The data from the current survey were complemented by historical data from the Collection of the Natural History Museum Vienna (NHMW Coll.), the Collection of the Landesmuseum Burgenland (Coll. Bgl.), the database of the Natural History Museum Vienna (NHMW-DB), the Global Biodiversity Information Facility (GBIF 2022), the Zobodat specimen database (Zobodat 2022), and the private database of Herbert Zettel (HZ-DB in Online Resource 2), as well as for selected species the bee database Apidat owned by the Biologiezentrum Linz, and finally the Pittioni Bee Collection Index Cards held at and digitized by the Natural History Museum, London (Pittioni Index Cards, Funnell 2022) and a comprehensive literature search using the Zobodat literature database (Zobodat 2022). All literature references used for compiling the species list in Online Ressource 2 are listed in Online Resource 2.
Bruno Pittioni and Stefan Schmidt (1942, 1943) published an extensive survey of the bee fauna from Eastern Austria. For many species they listed all known records, but for more common species the localities were listed without reference to specific records. In cases in which such records were found in the Pittioni Index Cards, these were listed preferably. The high number of recorded species in the year 1942 is due to records published by Bruno Pittioni (1942) without a year date; these records were assigned the year of publication, but may have been collected in aforegoing years.
Assignment of ecological traits. The ecological traits, specifically feeding preferences (i.e. lecty: polylectic, oligolectic), preferred plant taxa of oligolectic species, nesting type (ground nesting vs. above ground nesting species; above ground includes nesting in dead wood, plant stems, beetle tunnels, cavities, snail shells and freely suspended), parasitism (nest-building- vs. parasitic species), host associations for parasitic species, habitat requirement (open land, forest edge, ubiquitous) and strong dependence on sand or steppe-like habitats were assigned following Scheuchl and Willner (2016) and Wiesbauer (2020). Additionally, the flight period was assessed: Species recorded as flying until July were coded as spring species, species flying from May onwards or later as summer-associated species, such flying from April or earlier until August or later were classified as species with a long flight period, and those starting in August as autumn species.
To correlate changes in wild bee community composition with temporal land use change we mapped land use categories (Table 1) from historical aerial photos and recent orthophotos. Historical aerial photos were georeferenced before mapping. Georeferencing and landscape mapping was done with ArcGis Pro 2.8 (ESRI 2021). Historical aerial photos/orthophotos were retrieved from the Austrian Federal Office of Metrology and Surveying (BEV, Bundesamt für Eich- und Vermessungswesen) and were available for 1966, 1994 and 2000. The most recent orthophoto when conducting the study was from 2018 (basemap.at s.a.). The land use categories were defined based on habitat requirements of wild bees, preliminary mapping of the 1966 aerial photo and expert discussion within the author team. Because of the above-mentioned uncertainty of location of specimen records until the 1960ies, the geographical frame for landscape mapping was extended from the protected area northwards to include the train station of Oberweiden (Fig. 1A).
Data analysis
All data analyses were done using the software R version 4.1.2 (R Core Team 2021). All wild bee data were analyzed as presence-absence data. The proportion of coverage per landscape category per year (1966, 1994, 2000, 2018) was calculated in ArcGis Pro 2.8. Changes of wild bee species richness per trait and land use changes between the mapped years were visualized with a stacked area chart with the R-package ggplot2 (Wickham 2016). To provide a measure for species turnover across all time periods, the Sørensen index was calculated in the R package vegan (Oksanen 2013; Oksanen et al. 2020).
The wild bee data from periods with approximately complete sampling (1931–1966 and 2000–2021) are compared descriptively. Due to very sparse wild bee data availability in some observation years, specifically between 1885 and 1930 as well as between the 1950ies and the 2010s these data were pooled (Table 2) for statistical analysis. To show differences of the wild bee community over time and relations to land use change, the data were attributed to time periods (before 1930, 1931–1966, 1967–2000, 2000–2021) in accordance with the available historical aerial photos/orthophotos (Table 2). Since the relation of wild bee data before 1950 with a landscape situation from 1966 (earliest aerial photo available for the region) seemed inadequate, no landscape data were attributed to wild bee data before 1950 (Table 2).
To analyze changes in wild bee community composition, traits and related land use change, a multivariate statistical approach was chosen. We performed a NMDS (non-metric multidimensional scaling) with the R package vegan (Oksanen et al. 2020) using a binary bray-curtis distance matrix to show differences in the wild bee community among the defined time periods (Table 2). To analyze how ecological traits were associated over time, community weighted means (CWM) per observation (year or aggregated observation years; Table 2) were calculated with the R package FD (Laliberté et al. 2014; Laliberté and Legendre 2020) using the ecological traits nesting type, lecty, parasitism, flight period and habitat requirements. The CMWs and the proportion per land use category were fitted onto the NMDS using the function “envifit” of the R package vegan (Oksanen et al. 2020). Some traits appeared to be dominant over time (nest building vs. parasitism, nesting type; Table 2), thus these CWM had to be excluded from this fitting step. Due to significant heterogeneity of the wild bee community among the timespans (Permutation test in vegan: 999 permutations, p = 0.001) we did not perform an ADONIS to assess significant variation among the timespans, but instead we included the timespans in the vector fitting.
Table 2
Information about observation year and data pooling, attributed time period, associated land use data, community weighted means (CWM) and species richness for analyzing the wild bee community in Oberweiden over 100 years. Abbreviations: pl = polylectic, ol = oligolectic, OL Steppe = species requiring open land and steppe habitat, OL Sand = species requiring open land and sandy habitat, OL Sand & Steppe = species requiring open land and sandy steppe habitat.
Observation year incl. aggregation | Time period | Land use aerial photo/orthophoto | Lecty | Parasitism | Habitat requirements | Nesting type | Flight period/Main activity | Species richness |
1882 | Before1930 | No data available | Pl | nest_building | Ubiquist | Ground nesting | Two or more Seasons | 14 |
1883 | Before1930 | No data available | Pl | nest_building | OL Steppe | Ground nesting | Two or more Seasons | 12 |
1885 | Before1930 | No data available | Pl | nest_building | OL Sand | Ground nesting | Two or more Seasons | 18 |
1908–1930 | Before1930 | No data available | Pl | nest_building | Forestedge | Ground nesting | Two or more Seasons | 57 |
1931 | 1931_1966 | No data available | Pl | nest_building | OL Sand&Steppe | Ground nesting | Two or more Seasons | 8 |
1932 | 1931_1966 | No data available | Pl | nest_building | OL Sand | Ground nesting | Summer | 5 |
1933 | 1931_1966 | No data available | Pl | nest_building | Forestedge | Ground nesting | Spring | 13 |
1934 | 1931_1966 | No data available | Pl | nest_building | Forestedge | Ground nesting | Spring | 41 |
1935 | 1931_1966 | No data available | Pl | nest_building | Open land | Ground nesting | Spring | 56 |
1936 | 1931_1966 | No data available | Pl | nest_building | Open land | Ground nesting | Summer | 31 |
1937 | 1931_1966 | No data available | Pl | nest_building | Open land | Ground nesting | Summer | 43 |
1938 | 1931_1966 | No data available | Ol | nest_building | Open land | Ground nesting | Summer | 35 |
1939–1941 | 1931_1966 | No data available | Ol | nest_building | OL Sand&Steppe | Ground nesting | Summer | 11 |
1942 | 1931_1966 | No data available | Pl | nest_building | Ubiquist | Ground nesting | Two or more Seasons | 104 |
1943 | 1931_1966 | No data available | Pl | nest_building | Ubiquist | Ground nesting | Spring | 37 |
1944 | 1931_1966 | No data available | Pl | nest_building | OL Steppe | Ground nesting | Two or more Seasons | 4 |
1948 | 1931_1966 | No data available | Ol | nest_building | Open land | Ground nesting | Summer | 7 |
1950–1959 | 1931_1966 | 1966 | Pl | nest_building | Open land | Ground nesting | Summer | 60 |
1960–1969 | 1931_1966 | 1966 | Pl | nest_building | Ubiquist | Ground nesting | Two or more Seasons | 39 |
1972–1987 | 1967_2000 | 1994 | Pl | nest_building | Ubiquist | Ground nesting | Summer | 9 |
1990–2000 | 1967_2000 | 1994 | Ol | nest_building | Open land | Ground nesting | Spring | 11 |
2001–2012 | 2001_2021 | 2000 | Pl | nest_building | OL Steppe | Ground nesting | Spring | 13 |
2018 | 2001_2021 | 2018 | Pl | nest_building | Open land | Ground nesting | Summer | 52 |
2019 | 2001_2021 | 2018 | Pl | nest_building | Forestedge | Ground nesting | Summer | 87 |
2020–2021 | 2001_2021 | 2018 | Pl | nest_building | Open land | Ground nesting | Summer | 29 |