Document Type

Honors Project - Open Access

Abstract

New Zealand is home to a remarkable number of endemic taxa, some of which existed on the archipelago before the breakup of Gondwana. The mite harvesters (suborder Cyphophthalmi), tiny arachnids which dwell in forest leaf litter and caves, are one such group. The mite harvester family Pettalidae exhibits a classic Gondwanan distribution, informative for describing ancient patterns of diversification. Within New Zealand, there are three genera of pettalids; our research focuses on the phylogeny of the most widespread and diverse of these: Rakaia. Through phylogenetic analysis, we provide a window into patterns of ancient diversification and infer historical biogeographic trends.

The culminating phylogeny, based on ultraconserved elements retrieved using an Arachnid designed probe-set, resulted in a total of 68 taxa. The taxa were of the following breakdown: 54 Rakaia specimens, six of the sister genus Aoraki, and eight part of Opiliones outgroups. The final 50% and 75% taxon-occupancy matrix retrieved 729 and 355 loci, a large improvement from historic attempts. The phylogeny retrieved was fully resolved, and time-calibration using Bayesian Analysis yielded divergence dates across the genus. The study validated that the origin of Rakaia predates that of Gondwana, and that divergence within the genus may have been spurred by geologic events such as the Oligocene Drowning and the Last Glacial Maximum. The results need further validation through repeated attempts at time-calibration using different models, as well as estimation of evolutionary rates using Bayesian Analysis of Macroevolutionary Mixtures (BAMM). But, this study provides a novel high resolution depiction of the genus Rakaia with accompanying deep-time divergences.

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