Biomedical subjects

J C Avise

Publications and source records attributed to J C Avise.

96 records · Page 6Linked to original sources

PubMedDate not supplied

Genetic perspectives on the natural history of fish mating systems.

Molecular analyses of bird and mammal populations have shown that social mating systems must be distinguished from genetic mating systems. This distinction is important in fishes also, where the potential for extrapair spawning and intraspecific brood parasitism is especially great. We review studies on fishes that have used molecular markers to document biological parentage and genetic mating systems in nature, particularly in species with extended parental care of offspring. On average, nest-guarding adults parented about 70-95% of their custodial offspring, and approximately one-third of the nests were cuckolded to some extent. Furthermore, nearly 10% of the assayed nests contained offspring tended by foster fathers either because of nest takeovers or egg thievery. On average, fish that provide parental care on nests spawned with more mates than did fish with internal fertilization and pregnancy. Overall, genetic markers have both confirmed and quantified the incidence of several reproductive and other social behaviors of fishes, and have thereby enhanced our knowledge of piscine natural history.

Animals↗

PubMedDate not supplied

Turtle mating systems: behavior, sperm storage, and genetic paternity.

As evidenced by the articles in this volume, a recent increase in interest in the mating systems of poikilothermic vertebrates has focused primarily on fishes, a few amphibians, and squamate reptiles. Turtles by contrast have received relatively little attention, yet they display a wide variety of mating behaviors and life-history characteristics that make them excellent candidates for addressing several aspects of genetic parentage that should contribute to a broader understanding of animal reproductive strategies. Here we focus on genetic studies of the mating systems and reproductive patterns of turtles, specifically with respect to multiple paternity and long-term sperm storage. These phenomena highlight the importance of a temporally extended perspective on patterns of individual reproductive success.

Animals↗

PubMedDate not supplied

Microsatellite variation and differentiation in North Atlantic eels.

We screened 11 populations of American, European, and Icelandic eels (Anguillidae) for allelic variation and genetic divergence at six polymorphic microsatellite loci. Within either of the two recognized Anguilla species in the North Atlantic (rostrata in the Americas, anguilla in Europe), population genetic structure was statistically significant but weak; fully 95% of the total genetic variation was present within geographic locales rather than distributed among them. The two Anguilla species also overlap greatly in allelic frequencies, so the available data proved ineffective for addressing hypotheses about the possible hybrid origins of some Icelandic eels. The overlapping microsatellite profiles contrast with nearly diagnostic species differences documented previously in allozymes and mtDNA. This and similar empirical findings in several other species support theoretical concerns that homoplasy (convergent evolution) in allelic states can compromise the utility of rapidly mutating microsatellite loci for certain types of microevolutionary questions regarding gene flow and species differences.

Anguilla↗

PubMedDate not supplied

Allelic expression and genetic distance in hybrid macaque monkeys.

Levels of structural genic divergence at 21 loci encoding blood proteins were quantified in six macaque (Macaca) species, using standard techniques of starch-gel electrophoresis. Genetic distances between all pairs of species fall within a narrow range (0.080 less than or equal to D less than or equal to 0.250; D = 0.164) which is near the lower limit of genetic distances typically observed between other congeneric organisms. In an effort to measure levels of regulatory gene differences between these species, we have examined the patterns of allelic expression in their F1, F2, and backcross hybrids. Nine of the 21 loci examined encode allelic forms of the proteins with different electrophoretic mobilities in at least some of the individual parents of the hybrids. In all cases where expected, hybrids express fully both maternal and paternal allelic products, thus providing no strong evidence ofr a breakdown in the regulatory mechanisms responsible for proper expression of these genes. Results are compared to degrees of allelic repression previously observed in other hybrids, and are discussed within the context of current ideas about rates of regulatory gene evolution in mammals.

Alleles↗

PubMedDate not supplied

Size polymorphism and heteroplasmy in the mitochondrial DNA of lower vertebrates.

The mitochondrial DNA of the bowfin fish and each of two species of treefrogs displays large-scale size variation. Within each species, mitochondrial genomes span more than a 700 base pair range, and the size polymorphism is localized to one portion of the genome. In addition, about 5 percent of the total 357 individuals surveyed were observed to carry two size classes of mtDNA. These findings are among the few documented instances of extensive within-species mtDNA size polymorphism and individual heteroplasmy, and constitute exceptions to previously reached generalizations about the molecular basis of mtDNA variation.

Animals↗

PubMedDate not supplied

Hybridization among the ancient mariners: characterization of marine turtle hybrids with molecular genetic assays.

Reports of hybridization between marine turtle species (family Cheloniidae) have been difficult to authenticate based solely on morphological evidence. Here we employ molecular genetic assays to document the sporadic, natural occurrence of viable interspecific hybrids between species representing four of the five genera of cheloniid sea turtles. Using multiple DNA markers from single-copy nuclear loci, eight suspected hybrids (based on morphology) were confirmed to be the products of matings involving the loggerhead turtle (Caretta caretta) x Kemp's ridley (Lepidochelys kempii) (N = 1 specimen), loggerhead turtle x hawksbill (Eretmochelys imbricata) (N = 2), loggerhead turtle x green turtle (Chelonia mydas) (N = 4), and green turtle x hawksbill (N = 1). Molecular markers from mitochondrial DNA permitted identification of the maternal parental species in each cross. The species involved in these hybridization events represent evolutionary lineages thought to have separated 10-75 million years ago (mya) and thus may be among the oldest vertebrate lineages capable of producing viable hybrids in nature. In some cases, human intervention with the life cycles of marine turtles (e.g., through habitat alteration, captive rearing, or attempts to establish new breeding sites) may have increased the opportunities for interspecific hybridization.

Animals↗