Distribution and interspecies contact of feral swine and cattle on rangeland in south Texas: implications for disease transmission.

The last outbreak of foot-and-mouth disease (FMD) in the United States occurred in 1929. Since that time, numbers and distribution of feral swine (Sus scrofa) have increased greatly, especially in the southern states. This creates a potential risk to livestock production because swine are susceptible to, and can be carriers of, several economically harmful diseases of livestock. Most importantly, swine are potent amplifiers of FMD virus. In this study, global positioning system (GPS) collars were placed on rangeland cattle (Bos indicus x taurus) and feral swine to determine shared habitat use by these species on a large ranch in south Texas from 2004 to 2006. The aim was to identify locations and rates of interspecies contact that may result in effective transfer of FMD virus, should an outbreak occur. In shrubland and riparian areas, animals were dispersed, so contacts within and between species were relatively infrequent. Indirect contacts, whereby cattle and feral swine used the same location (within 20 m) within a 360-min period, occurred primarily at water sources, and seasonally in irrigated forage fields and along ranch roads. Direct contacts between species (animals <20 m apart and within 15 min) were rare and occurred primarily at water sources. Changes in ranch management practices are suggested to reduce interspecies contact should an FMD disease outbreak occur. This information can also be used to improve current epidemiologic models to better fit free-ranging animal populations.

Genetic relationships of American alligator populations distributed across different ecological and geographic scales.

Although much work has been conducted on coastal populations of the American alligator (Alligator mississippiensis), less is known about the population dynamics and genetic structure of populations of alligators confined to inland habitats. DNA microsatellite loci, derived from the American alligator, were used to investigate patterns of genetic variation within and between populations of alligators distributed at coastal and inland localities in Texas. These data were used to evaluate the genetic discreteness of different alligator stocks relative to their basic ecology at these sites. Observed mean heterozygosities across seven loci for both coastal and inland populations ranged from 0.50-0.61, with both inland and coastal populations revealing similar patterns of variation. Measures of F(st) revealed significant population differentiation among all populations; however, analyses of molecular variance (AMOVAs) failed to demonstrate any apparent geographic pattern relative to the population differentiation indicated by F(st) values. Each population contained unique alleles for at least one locus. Additionally, assignment tests based on the distribution of genotypes placed 76% of individuals to their source population. These genetic data suggest considerable subdivision among alligator populations, possibly influenced by demographic and life history differences as well as barriers to dispersal. These results have clear implications for management. Rather than managing alligators in Texas as a single panmictic population, translocation programs and harvest quotas should consider the ecological and genetic distinctiveness of local alligator populations.

INTROGRESSIVE HYBRIDIZATION AND NONCONCORDANT EVOLUTIONARY HISTORY OF MATERNAL AND PATERNAL LINEAGES IN NORTH AMERICAN DEER.

Introgressive hybridization between mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) was studied using sequence analysis of the paternally inherited, Y-linked, Zfy gene. The distribution of Zfy genotypes indicate that male white-tailed deer disperse into the range of mule deer and successfully breed with mule deer does. In western Texas, F1 hybrids are rare, but a relatively high proportion of backcross individuals was observed. Phylogenetic analysis of Zfy among white-tailed, mule, and black-tailed deer was consistent with traditional systematic placement of the latter two being sister-taxa, whereas previous mtDNA studies suggested mule and white-tailed deer were sister taxa.