Burrowing into the forest: Phylogeny of the Asian forest scorpions (Scorpionidae: Heterometrinae) and the evolution of ecomorphotypes

Asian forest scorpions (Scorpionidae Latreille, 1802: Heterometrinae Simon, 1879) are distributed across South and Southeast Asia. All are fossorial, constructing burrows under stones or in open ground, in habitats differing in precipitation and vegetation cover, from rainforests and tropical deciduous forests to savanna and scrubland. The systematics of these scorpions has long been confused due to bad taxonomy and the absence of a phylogenetic framework. Although the monophyly of the group was previously confirmed as part of broader phylogenetic analyses based on exemplar species, the only quantitative analysis of species‐level variation to date was based on overall similarity. This contribution presents the first species‐level phylogenetic analysis of Asian Scorpionidae, based on 186 morphological characters and 4188 aligned base‐pairs of DNA sequence data from two nuclear and three mitochondrial loci for 132 terminals including all 41 ingroup species and four outgroup species. Simultaneous analyses of the morphological and molecular datasets with parsimony, Maximum Likelihood and Bayesian Inference provided the framework for a revised classification presented elsewhere. In order to understand how adaptation following dispersal into new habitats has driven the morphological diversification of Asian forest scorpions, species were scored for 10 characters concerning morphology and burrow architecture, which contributed to an ensemble index of adaptation to habitat aridity. Species were classified into three ecomorphotypes based on the index, and ancestral state reconstruction of ecomorphotypes performed on the phylogeny. A pattern was recovered in which lineages and species occurring in different habitats on a continuum from wet (evergreen forest) to dry (savanna, scrubland) exhibited characters presumed to be adaptive and hence responsible for driving scorpion diversification.