Meeting Abstract
We tested the hypothesis that Gondwanan vicariance contributed to the circum-Antarctic distribution of Pettalidae, a family of small, dispersal-limited arachnids whose phylogeny, based on morphological or Sanger sequence data, has until now been unresolved. We generated transcriptomic data for a phylogeny of sixteen pettalids, from nine genera. Data were analyzed using ML, Bayesian, and coalescence methods. The phylogenetic position of a biogeographically critical genus from Sri Lanka was further explored using quartet likelihood mapping and gene-wise changes in log likelihood scores. We also performed a dating analysis using fossil calibrations on a previously published Sanger-based phylogeny with near complete species sampling, and the backbone constrained to match our transcriptomic results. We then reconstructed the biogeographic history of the family under the DEC model, using the posterior distribution of our dating analysis to incorporate divergence time uncertainty, and looked for signatures of mass extinction in the family. We recover a mostly stable topology, with a clear division between a clade from landmasses of East Gondwana, and a grade from West Gondwana. Further interrogation of phylogenetic signal suggests a sister-group relationship between taxa from Sri Lanka and eastern Australia. Given the coincident timing and order of cladogenetic events with tectonic activity, Gondwanan vicariance can explain several diversification events in Pettalidae. Some divergences predate rifting, suggesting some level of ancient regionalization, though not trans-oceanic dispersal. Despite the fact that there likely has been widespread extinction in the family, especially across Antarctica and Australia, diversification analyses find a consistent rate of speciation throughout time.
