Vertical distribution of spider of different colonization origin in Macaronesia native forests Island Biodiversity, Biogeography & Conservation

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Password • 109409

Insular biotas are very vulnerable to the expansion introduced species, as many native species occur only in the surviving fragments of native habitats. In Macaronesia, spiders are a well-studied group that tends to occur in high abundance in different microhabitats, which makes thhem good monitoring organisms. However, how they distribute from epigean to arboreal habitats in the native forests of these islands remains to be properly studied.

In this presentation I will show you how we characterized the vertical stratification of spiders in prefered stratum and amplitude of their occorrence on the native forests of Macaronesia using two indexes, average verticality (AVGV) and standard deviation verticality (STDV). These two values were obtained for each species studied, and we then used them to test diferences between the vertical stratification of groups with different colonization origin (endemic, native non-endemic and introduced) at Macaronesia and archipelago scale. Differences in AVGV between introduced species and the remaining categories were only found in Madeira, where introduced species seem to be more epigean. Native non-endemic species were mostly arboreal dwellers but with individual species having higher amplitude, while introduced species were more restricted. The approach taken here can be used in multiple other studies that aim to describe the differences in species abundance along a habitat or microhabitat gradient that are studied with standardized protocols.

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