Effect of leaf litter diversity in ponds on adult insect colonizers (primarily Coleoptera: Dytiscidae)

Leaf litter provides energy and nutrients to forested aquatic ecosystems.  The species of leaves affects decomposition rates, water chemistry, and the resources available to aquatic consumers.  Adult insects will select pond habitats based on the leaf species in those ponds, but it is unknown whether they use leaf diversity for selection as well.  We considered leaf diversity broadly and examined leaf species richness, functional diversity, and phylogenetic diversity to determine which most influenced insect habitat selection.  We established 45 aquatic mesocosms as potential colonization sites in Northern Louisiana.  Mixtures of leaves were randomly selected containing 0, 3, 5, 7, 9, or 11 species of leaves.  Leaf functional and phylogenetic diversity were estimated for each pool and designs were discarded if these variables were related to each other or leaf species richness.  Insect colonizers were collected from pools from late-April to mid-June.  Preliminary data over 1 month captured ~1,100 individual insects from 43 species.  Most individuals were from one species of dytiscid beetle, Copelatus glyphicus.  More individuals and more species colonized pools with leaves than those without.  We found no effect of leaf species, functional, or phylogenetic diversity on insect species richness, total abundance, or the abundance of the two most common species.  Future analyses will determine whether these patterns are consistent across the whole experiment and examine effects of water and leaf chemistry variables on colonizer communities.