Unravelling landscape variables with multiple approaches to overcome scarce species knowledge: a landscape genetic study of the slow worm

Abstract

Landscape genetics was developed to detect landscape elements shaping genetic population structure, including the effects of fragmentation. Multifarious environmental variables can influence gene flow in different ways and expert knowledge is frequently used to construct friction maps. However, the extent of the migration and the movement of single individuals are frequently unknown, especially for non-model species, and friction maps only based on expert knowledge can be misleading. In this study, we used three different methods: isolation by distance (IBD), least-cost modelling and a strip-based approach to disentangle the human implication in the fragmentation process in the slow worm (Anguis fragilis), as well as the specific landscape elements shaping the genetic structure in a highly anthropized 16 km2 area in Switzerland. Friction maps were constructed using expert opinion, but also based on the combination of all possible weightings for all landscape elements. The IBD indicated a significant effect of geographic distance on genetic differentiation. Further approaches demonstrated that highways and railways were the most important elements impeding the gene flow in this area. Surprisingly, we also found that agricultural areas and dense forests seemed to be used as dispersal corridors. These results confirmed that the slow worm has relatively unspecific habitat requirements. Finally, we showed that our models based on expert knowledge performed poorly compared to cautious analysis of each variable. This study demonstrated that landscape genetic analyses should take expert knowledge with caution and exhaustive analyses of each landscape element without a priori knowledge and different methods can be recommended

A metapopulation of the lizard Anguis fragilis (Squamata: Anguidae) on a local scale in Dorset, Great Britain, as indicated by spatial distribution and movement

“…Although males are more likely to disperse, there is a higher potential that interaction between a male and a random dispersal event from a female may result in recolonization. Previous research on slow-worms has shown that they are capable of travelling large distances and that dispersal events could be under represented (Geiser 2013). The same study also showed that slowworms can migrate over areas that were previously thought to be impassable, further supporting the theory that slow-worms exist in a metapopulation (Geiser 2013).…”

“…Previous research on slow-worms has shown that they are capable of travelling large distances and that dispersal events could be under represented (Geiser 2013). The same study also showed that slowworms can migrate over areas that were previously thought to be impassable, further supporting the theory that slow-worms exist in a metapopulation (Geiser 2013). For future conservation of the slow-worm, creating dispersal channels to promote a larger network of subpopulations would encourage recolonization and reduce the decline in British populations.…”

“…The biodiversity of a conserved area can be increased with the understanding that slow-worms exist in a metapopulation, because these lizards require less optimum habitat and can subsist in a heterogeneous area with multiple habitat types. However, this requires that dispersal channels are created between suitable sites (e.g., gardens) to link subpopulations (Geiser 2013). Male slow-worms are more likely to disperse than females, possibly because the viviparous females tend to aggregate at favorable basking sites.…”

“…The aim of this study is to ascertain whether slow-worms naturally cluster within preferred habitat types, and migrate among the clusters; if so, slowworms may represent a localized metapopulation. Previous studies reported that slow-worms can travel up to 34 m in a day, and Geiser (2013) suggested that this distance is undervalued and that dispersal could be much farther. Thus, if slow-worms naturally aggregate within the same habitat type and are capable of migrating among aggregations, the population may be a smallscale metapopulation.…”

The legless lizard Anguis fragilis (slow worm) has a potent metal-responsive transcription factor 1 (MTF-1)

“…The terms slow worm, and especially blind worm, are misnomers: Anguis fragilis is neither a worm nor is it blind (Petzold, 1971;Böhme, 1981;Völkl and Alfermann, 2007;Geiser et al, 2013). It is in fact a legless lizard of some 40 cm in length, with a wide distribution centered in the temperate climate zone of Europe (German: Blindschleiche; French: orvet; Italian: orbetto; Spanish: culebra de cristal).…”