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Low levels of genetic variation at traditional molecular markers have hampered genetic research within the family Acipenseridae. In an effort to develop a large set of polymorphic genetic markers, 172 clones were sequenced from three subgenomic libraries of shovelnose sturgeon Scaphirhynchus platorynchus; the libraries were enriched for two dinucleotide and one tetranucleotide microsatellite motifs (CA, GA, and TAGA). Primers were designed for 113 of the sequences and tested against shovelnose sturgeon, pallid sturgeon S. albus, white sturgeon Acipenser transmontanus, lake sturgeon A. fulvescens, and green sturgeon A. medirostris. Of the 113 primer sets tested, 96% amplified in one or more species (58 dimeric and 50 tetrameric). In Scaphirhynchus species, 93% of all loci amplified, and 76% were polymorphic. Within the individual Acipenser species, 65–80% of loci amplified, with 42–58% being polymorphic. Polymorphic systems for Scaphirhynchus species predominately displayed simple, disomic banding patterns, while those for Acipenser species typically displayed banding patterns characteristic of tetraploid or higher polyploid levels. These new microsatellite loci provide a group of genetic markers that are detectable with noninvasive sampling and that should prove useful in the preservation of threatened and endangered sturgeon species worldwide.

Landscape genetics is an emerging discipline that utilizes environmental and historical data to understand geographic patterns of genetic diversity. Niche modelling has added a new dimension to such efforts by allowing species-environmental associations to be projected into the past so that hypotheses about historical vicariance can be generated and tested independently with genetic data. However, previous approaches have primarily utilized DNA sequence data to test inferences about historical isolation and may have missed very recent episodes of environmentally mediated divergence. We type 15 microsatellite loci in California mule deer and identify five genetic groupings through a Structure analysis that are also well predicted by environmental data. We project the niches of these five deer ecotypes to the last glacial maximum (LGM) and show they overlap to a much greater extent than today, suggesting that vicariance associated with the LGM cannot explain the present-day genetic patterns. Further, we analyse mitochondrial DNA (mtDNA) sequence trees to search for evidence of historical vicariance and find only two well-supported clades. A coalescence-based analysis of mtDNA data shows that the genetic divergence of the mule deer genetic clusters in California is recent and appears to be mediated by ecological factors. The importance of environmental factors in explaining the genetic diversity of California mule deer is unexpected given that they are highly mobile species and have a broad habitat distribution. Geographic differences in the timing of reproduction and peak vegetation as well as habitat choice reflecting natal origin may explain the persistence of genetic subdivision.

Nine tetramer motif (GATA)n microsatellite systems were developed for use in the white sturgeon, Acipenser transmontanus. We report inheritance patterns for these nine systems, which range from one possible disomic system to tetrasomy and octosomy, with some systems containing null alleles. Because of the complex modes of inheritance underlying these systems and the highly duplicated nature of the genome, we propose each allele be scored as its own dominant marker, similar to AFLPs or RAPDs. The utility of this method is validated by the observation that individual alleles within a microsatellite system generally fit the expectation for independent transmission and fit the expected transmission frequency for single copy nuclear markers.

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Sixty-eight primer sets for microsatellite loci were developed from microsatellite motif enriched genomic libraries of pooled DNA from the polyploid green and white sturgeon (Acipenser medirostris and A. transmontanus). Four individuals from each species were screened for polymorphism at these loci. Forty-eight loci amplified in both species, and some exhibited species-specific amplification for white or green sturgeon (8 and 12 loci, respectively). The number of alleles per locus ranged from one to 12. At least 68% of the green and 65% of the white sturgeon loci we developed are polysomic.

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