UC San Diego

This study employs a phylogeographic analysis aimed at revealing inter-island relationships among populations of Aphaenogaster patruelis , an ant species endemic and restricted to the southern California Channel Islands and Isla Guadalupe. We collected samples

from each of the five islands on which A. patruelis occurs, extracted the DNA, and constructed DNA libraries. We then enriched the libraries for ultraconserved elements (UCEs) and sent enriched product out for sequencing on an Illumina HiSeq 4000 at the Vincent J. Coates Genomic Sequencing Laboratory at UC Berkeley. After quality control and assembly, 847 UCE loci were recovered. We analyzed aligned sequence data using PAUP (parsimony), RAxML under GTR+G model for maximum likelihood, and MrBayes for partitioned Bayesian Inference. The resulting trees from all analyses were concordant in major splits between island populations.

Reconstructing the biogeographic history of this species is complicated by the lack of any extant mainland populations, but the topology of these phylogenies supports the hypothesis that the distribution of A. patruelis resulted from island hopping after a colonization event from the mainland. Santa Catalina Island could have been colonized first followed by San Clemente Island, which might have served as the origin of colonists that reached outlying islands to the south (Isla Guadalupe) and north (Santa Barbara and San Nicolas Islands). The distance between San Clemente Island and Isla Guadalupe (428 km) seems too great for an ant to reach via winged

dispersal of alates; rafting thus seems a more likely mode of colonization for this ground-nesting

ant species.