Item – Theses Canada

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OCLC number
693657241
Link(s) to full text
LAC copy
LAC copy
Author
Lindell, Johan Sackarias,1973-
Title
Genetic consequences of plate tectonics : cytonuclear discordance in phrynosomatid lizards of Baja California, Mexico.
Degree
Ph. D. -- University of Toronto, 2007
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2009]
Description
3 microfiches
Notes
Includes bibliographical references.
Abstract
The peninsula of Baja California of northwestern Mexico has a complex geological history. Since the early Miocene, intense plate tectonic activity, volcanism, and sea level changes have combined to form a diverse landscape. The geological history has had profound effects on the regional biota. I evaluated the genetics of three common phrynosomatid lizards in relation to data from geology, paleontology, and stratigraphy to provide a better understanding of the historical biogeography of this region. I also addressed the evolutionary significance of temporary population fragmentation and the genetic interactions of reunited populations. Using sequence data from three mitochondrial genes (ca 2,000 bp), I reconstructed the genealogical histories of the zebra-tailed lizard ('Callisaurus draconoides') and the black-tailed brush lizard ('Urosaurus nigricaudus') based on samples spanning the entire peninsula and insular populations from the Gulf of California. The genealogies revealed several deep divergences (up to 11% sequence divergence in cytochrome 'b'), supporting the existence of temporary seaways across the mid-peninsular, Isthmus of La Paz, and Cape regions, and extensive inundation of the peninsula in the vicinity of Loreto. My results also suggest a significantly deeper time frame for the historical biogeography of Baja California than currently postulated. This includes evidence of a mid-peninsular seaway of late Miocene age (ca 7 million years ago). This event is also a more parsimonious explanation for the geographically congruent mitochondrial DNA (mtDNA) breaks of numerous species than the effects of climate on genetics, such as the cyclic pattern of Quaternary glaciation events. The deep divergences in mtDNA strongly contrast with variation in allozyme loci, which suggests limited population differentiation consistent with gene flow along the peninsula. This cytonuclear discordance stems from the different modes of inheritance of mtDNA and nuclear DNA (maternal versus biparental inheritance) and lack of recombination in mitochondria. Accordingly, mtDNA differentiation is a poor proxy for biparental population differentiation. Cytonuclear discordance is particularly strong in old secondary contact zones in the black-tailed brush lizard and the side-blotched lizard ('Uta stansburiana'). These contact zones show very little geographical overlap of divergent mtDNA lineages, suggesting some form of selection against mtDNA dispersal across contact zones.
ISBN
9780494394823
049439482X