Contrasting results of multiple species delimitation approaches cause uncertainty in synecological studies: A case study on Sri Lankan chafers

Abstract

Abstract Biodiversity patterns are the sum of multiple overlapping species distributions. Their analysis therefore requires proper species inference. DNA‐based species delimitation has become increasingly popular for such assessments, but their robustness is often problematic due to incongruence between multiple delimitation approaches. Here, we explored how contrasting results of different species’ delimitations translate into conclusions of synecological studies, exemplified by assemblages of phytophagous scarab beetles in Sri Lanka from different elevations and forest types. Particularly, we compared estimates based on complete assemblages and on cumulated species inventories inferred from individually analysed subclades. The patterns of assemblage similarity were analysed across different spatial scales with reference to morphospecies, molecular operational taxonomic units (MOTUs) and haplotypes. Method‐related ambiguity of species (MOTUs) estimates, which also included subclade inferences, severely affected the certainty of apparent biodiversity patterns at most spatial scales. Even more contrasting patterns resulted from individual clade‐wise analyses of faunal similarity or even from cumulated species inventories from individual clade‐wise species delimitation analysis. In this case study of tropical chafer beetles, haplotypes provided only very little explanatory information, since genetically highly diverse populations widely lacked shared haplotypes. Therefore, searching proper species boundaries should be the ultimate goal of biodiversity assessments to lend an enduring meaning to biodiversity research and its sustainable application. Our study underlines the need for awareness when synecological observations from different studies are integrated, which use different species delimitation methods for their biodiversity assessment, and its potential impact on conservation management.