Molecular and morphometric phylogenetics and biogeography of a Southeast Asian arachnid family (Opiliones, Cyphophthalmi, Stylocellidae)

In this dissertation I investigate a diverse family of tropical arachnids from Southeast Asia. This family, Stylocellidae, belongs to Cyphophthalmi, one of four suborders in Opiliones, commonly known as "daddy-long-legs" or "harvestmen." Cyphophthalmi have been shown to be excellent corroborators of ancient landmass movements, as the present distribution of its various lineages is best explained by the breakup of the ancient supercontinent Pangea. Southeast Asia is one of the most complex geologic regions of the World and a focal point for biogeographers since the beginnings of the discipline, so Stylocellidae are well positioned to play an important role in the development of Cyphophthalmi as a model system in biogeography. Moreover, the family is poorly understood in its own right, with an outdated taxonomic framework that includes only a tiny fraction of the many new species discovered in recent years, so they are also poised to add significantly to our inventories of described biodiversity. I begin by describing two new species from New Guinea, the first ever collected from that island, and constructing a molecular phylogenetic hypothesis for the family using two markers. This phylogeny recovers the family as monophyletic and identifies three main groups within it: the early lineages of the genus Fangensis , a clade of mostly Bornean species, and a large clade consisting mostly of species found in the Indo-Malay Archipelago. This analysis is then expanded with additional data and terminals, including the recently described but unassigned genus from the Eastern Himalayas, Meghalaya . I also date the phylogeny and optimize species localities on ancestral nodes. The resulting hypotheses strongly suggest that the family originated on the Sibumasu terrane, which broke off from Gondwana in the Paleozoic and now underlies the Thai-Malay Peninsula and Northern Sumatra. Finally, to make progress toward a taxonomic revision of the family, I develop a new method for the phylogenetic analysis of shape information and combine those data with sequence data to generate phylogenetic hypotheses that include stylocellid type specimens for which no molecular data are available.