DOI: 10.5061/dryad.t4b8gtj2t
title: Spider species collected in Macaronesian islands using COBRA sampling protocols

description: Aim: Habitat diversity has been linked to the diversity and structure of
 island communities, however, little is known about patterns and processes
 within habitats. Here we aim to determine the contributions of habitat
 type and inferred dispersal frequency to the differences in taxonomic
 structure between assemblages in the same island habitat. Location: The
 Macaronesian archipelagos (Azores, Madeira, the Canary Islands and Cabo
 Verde). Taxon: Spiders (Araneae). Methods: We established forest and dry
 habitat sites (each with five plots) on two islands per archipelago. We
 collected spiders using standardised sampling protocols. We tested the
 differences in beta diversity separately for each habitat and for each
 inferred category of ballooning (an aerial dispersal strategy) frequency
 across geographic scales through nested non-parametric PerMANOVA. We then
 tested whether ballooning and habitat influenced heterogeneity in species
 composition (dispersion in beta diversity) in the two habitat types. We
 analysed the effects of habitat and ballooning on species abundance
 distribution (SAD) and rarity by fitting Gambin models and evaluating the
 contribution of ballooning categories to SAD. Results: Communities of the
 same archipelago and habitat were taxonomically more similar, and beta
 diversity increased with geographic scale, being greater in dry habitats.
 There was greater species replacement among assemblages in dry habitats
 than in forests, with greater differences for rare ballooners. There were
 no differences in SAD between habitats although dry habitat sites seemed
 to harbour more species with low abundances (rare species) than forests.
 Main conclusions: Habitat type does not only condition the differences
 between spider assemblages of the same habitat but also the scale at which
 they occur. These differences may be determined by the heterogeneity in
 the physical structure of each habitat as well as how much this structure
 facilitates aerial dispersal (ballooning), and should be considered in
 theories/hypotheses on island community assembly as well as in
 conservation strategies.
description: We collected spider specimens
 using the COBRA sampling protocol, a standardised and optimised protocol
 that combines different sampling methods to obtain the maximum possible
 number of species for a given amount of effort and produces comparable
 data⁠. The sampling methods of the COBRA protocol for dry habitat were
 pitfall trapping (12 samples, each one grouping four individual pitfall
 traps), nocturnal and diurnal sweeping (four samples each), and active
 ground search (four samples). In forest plots the COBRA protocol consisted
 of pitfall trapping (12 samples, as in the dry plots), diurnal and
 nocturnal sweeping (two plus two samples), diurnal and nocturnal foliage
 beating (two plus two samples), and nocturnal aerial active search (four
 samples). Therefore, we obtained a total of 24 samples per plot in both
 dry and forest
 habitats. In La Gomera and Tenerife dry habitats the great abundance of shrubs allowed the split of the four sweeping samples in two sweeping and two beating samples. Sampling occurred between 2012-2017 – Terceira forest (2012), Tenerife forest (2013), Pico forest (2016), Madeira forest (2016), La Gomera forest (2016), and all dry plots in Madeira, Canaries and Cabo Verde in 2017, always at the time of the year with the greatest levels of diversity (April to November).