Yes, a non‐random distribution, but why do dragonflies and damselflies
not follow latitudinal gradient rules?
Abstract
1. Latitudinal diversity gradient (LDG) is the increase in species
richness towards the equator and is one of the most consistent patterns
in biogeography, where current and historical processes contribute to
shape the pattern. 2. Despite that LDG patterns have been described for
some insects, the underlying mechanisms associated with community
assembly and diversification along modern latitudinal diversity gradient
pattern remain unknowledge for many groups. 3. Odonata is an old order
of insects that originated during the Carboniferous and has diversified
through different eras. Here, we defined co-occurrence based on the
presence in ecoregions and 1°×1° grid cells of Odonata species in North
America NA, to address their species richness, phylogenetic structure,
and species diversification rate along the latitudinal gradient. 4. For
the whole order, we found the highest species richness at mid-latitudes,
while phylogenetic diversity showed a linear positive pattern along the
gradient. Our results showed dragonfly assemblages were clustered along
all the gradient, suggesting that environmental filtering sorted the
assemblages. Whereas damselfly species assemblages were clustered at
mid-latitude and overdispersed into both extremes of gradient, probably
community assembly is driving by thermal gradients at mid-latitude, by
competitive exclusion at south extreme, and by different origins of the
biota at the boreal zone. Our results show that apparently most
ancestral lineages of Odonata inhabit tropical zones, where diversified
and dispersed to the temperate region, although likely also have been
diversified into regions of NA, which might be linked with the highest
species richness at mid-latitude for both suborders.