Local stochastics and ecoclimatic situation shape phytophagous chafer
Very little is known about factors determining the assemblage structure
of megadiverse polyphagous-herbivore scarab chafers in the tropics
(Coleoptera: Scarabaeidae). Here, we examined the composition of Sri
Lankan chafer assemblages and investigated whether it is influenced more
by the general ecoclimatic situation, macrohabitat, of indetermined
stochastic biotic and abiotic factors of each locality. We also explored
the influence of the latter on separate lineages and general body size.
Based on dedicated field surveys conducted during the dry and wet
seasons, we examined 4847 chafer individuals of 105 species sampled
using multiple UV-light traps in 11 localities covering different forest
types and altitudinal zones. Assemblages were assessed for compositional
similarity, species diversity, and abundance within four major
eco-spatial partitions: forest types, elevational zones, localities, and
macrohabitats. Our results revealed that assemblages were shaped mainly
by locality stochastics, and to a minor extent by ecoclimatic
conditions. Macrohabitat had little effect on the assemblage
composition. This was true for the entire chafer assemblage as well as
for all single lineages or different body size classes. However, in
medium and large specimens the contrasts between localities were less
pronounced, which was not the case for individual lineages of the
assemblage. Contrasts of assemblage similarity between localities were
much more evident than those for forest types and elevation zones.
Significant correlation between species composition and geographic
distance was found only for the assemblage of small-bodied specimens.
Seasonal change (dry-wet) in species composition was minor and only
measurable in a few localities.