Phylogenetic Implications of Nuclear Sequence Variation

in the Peromyscus maniculatus species group

Joshua A Broussard*, Mindy L. Walker, Scott E. Chirhart*,

Rodney L. Honeycutt†, Ira F. Greenbaum

*Department of Biology, Centenary College of Louisiana

 †Department of Wildlife and Fisheries Sciences, Texas A&M University

Previous research by Walker et al. (2005) was performed to evaluate the specific validity and phylogeographic origin of Peromyscus sejugis (Santa Cruz Island mouse).  The authors concluded that P. sejugis is an insular isolate of P. maniculatus (deer mouse) from Baja California because of a low level of sequence divergence between these populations in the ND3/ND4L/ND4 mitochondrial DNA region.  Additionally, the northern geographic extent of the P. maniculatus (Baja)/P. sejugis haplogroup was determined to exist in the region between Arcata and Fresno, California.  These data supported the assertion that P. maniculatus is polyphyletic.   Further, the study confirmed the unresolved sister-group relationship between P. maniculatus, P. sejugis and P. keeni (Northwestern deer mouse).  In order to support or refute these findings, we compared sequence phylogenies derived from an X-chromosome marker (USP) to the ND3/ND4L/ND4 phylogenies for P. maniculatus from Baja and California.  To test the validity of using the USP marker, we first generated a USP-derived phylogenetic tree and compared it to the known phylogeny (based on proteins, chromosomes, and morphology) for the P. maniculatus species group.  As we indeed obtained the corroborated phylogeny, we then assessed the level of intra- and interspecific variation in the USP gene for the P. maniculatus species group and P. leucopus (white-footed mouse) to determine whether this marker resolved the P. maniculatus/P.sejugis/P.keeni trichotomy.  Since the USP marker yielded low levels of both intra- and interspecific variation, it was ineffective in resolving the trichotomy; however, it did cluster the P. maniculatus from Baja and California as separate from other P. maniculatus populations, thus confirming the apparent polyphyletic nature of P. maniculatus.

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