Origin of the species richness and composition of Caribbean aquatic entomofauna

From a literature review, we constructed a database yielding comprising
>1000 freshwater insect species (especially Odonata, Coleoptera,
Trichoptera, Ephemeroptera; OCTE) in 26 Geographical Caribbean Units (GCU)
and quantified local filtering (climate heterogeneity, annual rainfall,
annual temperature), geography (area, distance from the mainland) and
emergence age as a proxy for island ontogeny. We investigated the relative
role of these variables on the species richness, endemism and composition
of the units using island species-area relationship (ISAR), generalised
linear modelling (GLM) and nonmetric multidimensional scaling (NMDS). In
addition, we analysed the spatial patterns of species richness and
composition using Moran’s I index. ISAR generally demonstrated one or two
thresholds and continuous or discontinuous responses according to OCTE
groups. A small island effect could be detected for Trichoptera and
Ephemeroptera richness, whereas Odonata and Coleoptera only demonstrated
differences in slope between smaller and larger GCUs. Area, climate
heterogeneity, maximal rainfall and distance from mainland were major
drivers of species composition in GCUs, whereas local climate variables
were of main importance for the endemism rate. Due to the potential
complexity of the Caribbean island ontogeny, middle-stage islands had an
expected higher freshwater invertebrate richness than younger ones but an
unexpected lower richness compared to older islands. Finally, the degree
of colonization of islands was linked to the dispersal ability of species,
with Odonata and Coleoptera having larger distribution ranges than
Trichoptera and Ephemeroptera, which were more restricted by their
comparatively narrow ecological niches. The high endemism (>60%)
found in the Caribbean freshwaters calls for more conservation effort in
managing these highly threatened freshwater environments.To assess the
relative contribution of geographical (area, distance from mainland) and
local filtering variables (e.g., climate heterogeneity) to the species
richness, endemism and composition of Caribbean aquatic entomofauna.