Fossil data are ambiguous regarding the evolutionary origin of contemporary desert bighorn sheep ( Ovis canadensis subspecies). To address this uncertainty, we conducted phylogeographic and population genetic analyses on bighorn sheep subspecies found in southwestern North America. We analyzed 515 base pairs of mtDNA control region sequence and 39 microsatellites in 804 individuals from 58 locations. Phylogenetic analyses revealed 2 highly divergent clades concordant with Sierra Nevada ( O. c. sierrae ) and Rocky Mountain ( O. c. canadensis ) bighorn and showed that these 2 subspecies both diverged from desert bighorn prior to or during the Illinoian glaciation (~315–94 thousand years ago [kya]). Desert bighorn comprised several more recently diverged haplogroups concordant with the putative Nelson ( O. c. nelsoni ), Mexican ( O. c. mexicana ), and Peninsular ( O. c. cremnobates ) subspecies. Corresponding estimates of effective splitting times (~17–3 kya), and haplogroup ages (~85–72 kya) placed the most likely timeframe for divergence among desert bighorn subspecies somewhere within the last glacial maximum. Median-joining haplotype network and Bayesian skyline analyses both indicated that desert bighorn collectively comprised a historically large and haplotype-diverse population, which subsequently lost much of its diversity through demographic decline. Using microsatellite data, discriminant analysis of principle components (DAPC) and Bayesian clustering analyses both indicated genetic structure concordant with the geographic distribution of 3 desert subspecies. Likewise, microsatellite and mitochondrial-based FST comparisons revealed significant fixation indices among the desert bighorn genetic clusters. We conclude these desert subspecies represent ancient lineages likely descended from separate Pleistocene refugial populations and should therefore be managed as distinct taxa to preserve maximal biodiversity. Los datos de fósiles sobre el origen evolutivo de las ovejas del desierto ( Ovis canadensis subespecies) contemporáneas son ambiguos. Para dilucidar esta incertidumbre, llevamos a cabo análisis filogeográficos y de genética de poblaciones entre cinco subespecies de ovejas del suroccidente de Norteamérica. Analizamos 515 pb de secuencia de la región control del ADN mitocondrial y 39 microsatélites en 804 ovejas de 58 localidades. Los análisis filogenéticos revelaron 2 clados altamente divergentes concordantes con ovejas de la Sierra Nevada ( O. c. sierrae ) y de las Montañas Rocosas ( O. c. canadensis ), y demostraron que estas dos subespecies divergieron antes o durante la glaciación de Illinois (315,000–94,000 años). Las ovejas del desierto formaron varios haplogrupos recientemente derivados concordantes con las subespecies de Nelson ( O. c. nelsoni ), México ( O. c. mexicana ) y peninsular ( O. c. cremnobates ). Las estimaciones correspondientes al tiempo de separación efectiva (17,000–3,000 años) y edades de haplogrupos (85,000–72,000 años) son los plazos más probables para las divergencia...

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SummaryThe role of polyploidy in vertebrate genome evolution remains a fertile area of research and sturgeons (order Acipenseriformes) provide a unique model of genome duplication, with species possessing 120, 250 or 360 chromosomes. Cytogenetic and molecular data have been used to support different hypotheses about the number of genome duplications in this polyploid series; however, few studies have examined inheritance in sturgeons, although evaluation of polysomic segregation ratios is crucial to inferring ancestral genome duplication level in a polyploid species. Here we examine the inheritance of eight microsatellite loci in fifteen white sturgeon (Acipenser transmontanus) families of known parentage to infer the level of genome duplication. Microsatellites were detected as four or eight copy loci. Numbers of alleles per locus, transmission frequencies of informative alleles, and gene copy numbers in parents reveal an ancient octoploid origin for white sturgeon.Comparison to the lake sturgeon genome suggests the 250 chromosome state in sturgeon was achieved by multiple independent polyploid events. The discovery of spontaneous autopolyploids via microsatellite analysis and flow cytometry provides additional evidence of the plasticity of highly duplicated sturgeon genomes.

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