John Carlos Garza

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We demonstrate that the mean ratio of the number of alleles to the range in allele size, which we term M, calculated from a population sample of microsatellite loci, can be used to detect reductions in population size. Using simulations, we show that, for a general class of mutation models, the value of M decreases when a population is reduced in size. The(More)
The distributions of allele sizes at eight simple-sequence repeat (SSR) or microsatellite loci in chimpanzees are found and compared with the distributions previously obtained from several human populations. At several loci, the differences in average allele size between chimpanzees and humans are sufficiently small that there might be a constraint on the(More)
The major histocompatibility complex (MHC) contains genes integral to immune response in vertebrates. MHC genes have been shown to be under selection in a number of vertebrate taxa, making them intriguing for population genetic studies. We have conducted a survey of genetic variation in an MHC class II gene for steelhead trout from 24 sites in coastal(More)
Likelihood-based parentage inference depends on the distribution of a likelihood-ratio statistic, which, in most cases of interest, cannot be exactly determined, but only approximated by Monte Carlo simulation. We provide importance-sampling algorithms for efficiently approximating very small tail probabilities in the distribution of the likelihood-ratio(More)
Single nucleotide polymorphisms (SNPs) are appealing genetic markers due to several beneficial attributes, but uncertainty remains about how many of these bi-allelic markers are necessary to have sufficient power to differentiate populations, a task now generally accomplished with highly polymorphic microsatellite markers. In this study, we tested the(More)
Allelic variation in the major histocompatibility class (MHC) IIB gene of salmonids is analyzed for patterns indicative of natural selection acting at the molecular level. Sequence data for the second exon of this MHC gene were generated for 11 species in three salmonid genera: Oncorhynchus, Salmo, and Salvelinus. Phylogenetic analysis of nucleotide(More)
The effects of landscape features on gene flow in threatened and endangered species play an important role in influencing the genetic structure of populations. We examined genetic variation of trout in the species Oncorhynchus mykiss at 22 microsatellite loci from 20 sites in the Russian River basin in central California. We assessed relative patterns of(More)
Homoplasy (convergence in the size of different alleles) at microsatellite loci was examined by sequencing multiple alleles of two compound microsatellites and single copies of alleles of the same size at two other compound loci in both chimpanzees and humans. At one of the two loci for which multiple alleles were sequenced, extensive homoplasy for size was(More)
Among tuco-tucos, Ctenomys rionegrensis is especially amenable to the study of the forces driving population differentiation because of the restricted geographic range it occupies in Uruguay. Within this limited area, the Rio Negro tuco-tuco is limited to sandy soils. It nonetheless exhibits remarkable variation in pelage color, including melanic, agouti,(More)
The Mound-building mouse Mus spicilegus possesses a unique behaviour amongst mice. It constructs large earthen mounds and associated nesting chambers which serve to store food for immature individuals during the winter nesting period. We have used genetic analysis of four autosomal and four X-linked microsatellite loci to determine relationships between(More)