This study clearly reports the role of genetic data in the identification of the origin of E. tetraedra a non-native species in Iran freshwater ecosystem. In fact, we investigated the origin of the introduction of the E. tetraedra in Iran and tried to explain how the suitable habitat will change using the SDMs approach. The beginning of studies on aquatic Oligochaeta back to 1920 (Stephenson 1920) and after about 100 years the Iranian fauna of aquatic Oligochaeta is inadequately known and limited to just a few studies (Egglishaw 1980; Ahmadi et al. 2012; Javidkar et al. 2019). Based on previous studies, 20 Oligochaeta species have been verified in Iran until 2015 (Jabłon´ska and Pesˇic´ 2014). Considering the area, mountainous landscapes, geographical features and specific hydrological characteristics of Iran, it seems that there will be an increase in the number of these species in the future.
Latif et al (2009) identified E. tetraedra based on morphology as a non-native species with European and Palearctic origin from Haraz and Chalus rivers in Iran. Then Javidkar et al (2019) reported the first molecular attempts to discover the aquatic oligochaetes in Iran and they confirmed the non-native of the species by combining samples from Jajroud and Karaj with sequences from NCBI from studies elsewhere in the world for the species.
Until this study and Javidkar et al (2020), the name of this species has not been listed in the native aquatic oligochaetes of Iran and our results reported E. tetraedra as a non-native species in Lar national park freshwater ecosystem. In line with our results, a number of researchers have reported E. tetraedra as a non-native species in other regions (Brinkhurst et al. 1960; Wood and James 1993; Martinsson et al. 2015; Sosa et al. 2017; Kim et al. 2017; Javidkar et al. 2020).
Haplotype and Genetic Diversity
The results of the haplotype network clearly showed that the samples of Lar National Park, Jajroud and Karaj rivers did not have a specific haplotype and haplotypes of the current study are shared with Jajroud and Karaj rivers. To explain this phenomenon three hypotheses can be suggested; (a): E. tetraedra was independently introduced into all three habitats in Iran, (b) initially, E. tetraedra was introduced in Lar National Park, and then transferred to Jajrud and Karaj river, and its diversity and abundance decreased over time in Lar National Park; considering the Karaj river has the highest haplotype diversity and specific haplotype and also from Karaj river to Jajroud and Lar National Park, the haplotype diversity decreases, the third hypothesis is proposed, (c) E. tetraedra was initially introduced the Karaj river and was transferred to Jajroud and then to Lar National Park. However, based on the evidence and results, the third hypothesis is stronger. As well as, according to studies, altitude is one of the important limiting factors of distribution for the species as the abundance and diversity of Oligochaeta decrease with increasing altitude (Salome et al. 2011). Considering that the Lar National Park is located at an altitude of about 3000 meters, it seems that the species was not native to the region and accidentally transferred to the area.
The molecular diversity indices depicted the haplotype and genetic diversity within the species were almost high (Table. 1). Also according to Table 1, the π of E. tetraedra in the three Iranian populations were 0.05502e0.05953 and in the Spanish population was 0.05148 that it showed almost no different genetic diversity in all populations and the Iranian population has not low genetic diversity than the Spanish population. Therefore, not having low genetic diversity compared to the origin population, can express the invasivation of the species in the introduced areas. Xu et al (2001) mentioned that for non-native species genetic diversity is so necessary to adapt to new habitats and maintain new population sizes. In addition, having high haplotype diversity one of the most important features affecting the success of invasivation of the species (Kolbe et al. 2004). The result (Table. 1) showed that E. tetraedra haplotype diversity in Iran's freshwater is increasing and it will have invasive success in Iran's freshwaters.
Species Distribution Modeling (Present–Future)
Our study showed the impact of climate change on the distribution range of non-native E. tetrahedra in Iran's freshwater ecosystems. Carosi et al (2019) believed that species can experience four reactions under climate-change effects (i.e. expansion, reduction, both, or stable) in their habitats.
The current map for E. tetrahedra clearly shows the suitable distribution for the species, that could occur in a wider distribution range especially in some regions out of the recorded areas (Fig. 4). Based on the outcome future maps of climate change modelling under SSPs scenarios, it will be predicted that climate change would significantly affect the distribution of E. tetrahedra as maps showed a sharp tendency to expand over time in its distribution areas (Fig. 4). In connection with our results, Mamun et al (2018) predicted future climate-change effects on an invasive alien species Micropterus salmoides in the Korean peninsula for 2050 and 2100. According to their results, the potentially suitable habitats for M. salmoides are most likely to increase by 2050 and 2100.
Moreover, regarding the output of the modelling, it seems where human population density is high, these areas are probably more affected by the species in the future. This is maybe due to the high human activities, travel and trade in these areas.
The temperature increase is an effective factor in the expansion of E. tetrahedra in Iran's freshwater ecosystems as expected climate change would benefit the species. In fact, temperature and precipitation were the most important role in model predictions. Based on the studies, E. tetraedra is expanding in most regions of the world and usually prefers humid habitats (Latif et al. 2009; Ezzatpanah et al. 2010; Mirmonsef et al. 2011; Yousefi et al. 2009). Therefore, it may be possible to justify their distribution in the humid regions of the country, including the northern and southern regions. Hong et al (2022) with SDMs tools mentioned temperature as the most reason for the expansion of range shifts in two invasive alien species under future climate-change scenarios.
However, the result of SDMs explicitly illustrated the invasion power of the E. tetrahedra in Iran's freshwater ecosystems over time. It is mentioned that with expansions of alien species the vulnerability of native species will probably be more significant (Hansen et al. 2017; Abdoli et al. 2022; Kim et al. 2022) and it results in lowering the species diversity and degrading the sustainability of native freshwater species (Shi et al. 2010).
One of the main drivers of worldwide biodiversity loss is biotic exchange in ecosystems by invasive species (Butchart et al. 2010). Although we did not appraise the effects of E. tetraedra as a non-native on other non-oligochaete species, studies e.g Migge-Kleian et al (2006) and Ziemba et al (2016) have shown the negative effects of non-native earthworms across trophic levels. According to the evidence in the present study and the identification of the success of Oligochaetes species in terms of being invasive in the river systems of Iran, it is assumed that freshwater ecosystems may be quite vulnerable to Oligochaetes of Western Palearctic origin and taking into account the negative consequences on native species, careful management strategies and regulations can help to mitigate these risks. It is essential that governments and individuals alike take a proactive approach to preventing the spread of invasive species and work to protect native ecosystems. Additionally, quarantine policies must be strictly enforced to help ensure that no potentially damaging organisms are imported into new environments.