Abstract
The Baja California peninsula is the second longest, most geographically isolated peninsula on Earth. Its physiography and the presence of many surrounding islands has facilitated studies of the underlying patterns and drivers of genetic structuring for a wide spectrum of organisms. Chaetodipus spinatus is endemic to the region and occurs on 12 associated islands, including 10 in the Gulf of California and two in the Pacific Ocean. This distribution makes it a model species for evaluating natural historical barriers. We test hypotheses associated with the relationship between the range of the species, patterns in other species, and its relationship to Pleistocene-Holocene climatic changes. We analyzed sequence data from mtDNA genes encoding cytochrome b (Cytb) and cytochrome c oxidase subunits I (COI) and III (COIII) in 26 populations including all 12 islands. The matrilineal genealogy, statistical parsimony network and Bayesian skyline plot indicated an origin of C. spinatus in the southern part of the peninsula. Our analyses detected several differences from the common pattern of peninsular animals: no mid-peninsula break exists, Isla Carmen hosts the most divergent population, the population on an ancient southern Midriff island does not differ from peninsular populations, and a mtDNA peninsular discordance occurs near Loreto.
Highlights
The geography of the peninsula of Baja California (BCP) and surrounding islands has facilitated studies of the underlying patterns and drivers of genetic structuringPLOS ONE | DOI:10.1371/journal.pone.0116146 December 26, 2014Endemic Insular Breaks Patterns for Baja California of a wide spectrum of organisms
Much of the older stratigraphic history remains elusive after being overwritten by more modern geologies, such as Holocene volcanism and other forms of orogenesis
The genetic patterns of the biota may help infer the historical stratigraphy of the peninsula
Summary
The geography of the peninsula of Baja California (BCP) and surrounding islands has facilitated studies of the underlying patterns and drivers of genetic structuring. Endemic Insular Breaks Patterns for Baja California of a wide spectrum of organisms. The peninsula may have been an insular archipelago [6] formed by the ephemeral midpeninsular Vizcaino Seaway and another marine inundation at the Isthmus of La Paz [7, 5]. Populations of many taxa occur on adjacent islands in the Gulf of California and Pacific Ocean. These populations often differ phenotypically from their peninsular and mainland relatives and often exhibit some degree of genetic structure. Some insular populations have received taxonomic recognition as species or subspecies [8, 9]
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