Ecological niche divergence between the brown recluse spiders Loxosceles laeta and L. surca (Sicariidae) in Chile

Abstract

ABSTRACT The laeta species group is the main source of Loxosceles species in Chile, a genus of medical importance due to the cytotoxic properties of its venom and the synanthropic habits of its dominant species, Loxosceles laeta. However, a poorly studied, cryptic, and putative sister species, Loxosceles surca, is also known to live in Chile at latitudes that overlap with L. laeta. In contrast to L. laeta, L. surca lives in natural areas away from humans. We used DNA sequences from L. surca to infer the phylogenetic history of this species and its congenerics. Additionally, we used ecological niche modelling to define the ecology of this species in contrast to its sister species. Our results show that L. surca does, indeed, belong to the laeta species group, and is likely a sister species to L. laeta. Although these species are fairly cryptic with respect to each other, the substantial genetic divergence between them is consistent with other distinct sister species in this genus. The laeta group is also sister to the large reclusa group that radiated into the Caribbean, Central, and North America. The phylogeny further supports the contention that L. diaguita belongs in its own species group separate from laeta. Our ecological niche analysis shows that L. surca and L. laeta have distinctly different allopatric habitats, and we suggest that these differences explain why one species became synanthropic, while the other did not.