Joseph M. Quattro

POPULATION DIFFERENTIATION DECREASES WITH DEPTH IN DEEP-SEA BIVALVES

Abstract The deep sea is the largest ecosystem on Earth. Recent exploration has revealed that it supports a highly diverse and endemic benthic invertebrate fauna, yet the evolutionary processes that generate this remarkable species richness are virtually unknown. Environmental heterogeneity, topographic complexity, and morphological divergence all tend to decrease with depth, suggesting that the potential for population differentiation may decrease with depth.To test this hypothesis, we use mitochondrial DNA (16S rRNA gene) to examine patterns of population differentiationin four species of protobranch bivalves (Nuculoma similis, Deminucula atacellana, Malletia abyssorum, and Ledellaultima) distributed along a depth gradient in the western North Atlantic. We sequenced 268 individuals from formalinfixed samples and found 45 haplotypes. The level of sequence divergence among haplotypes within species was similar, but shifted from between populations at bathyal depths to within populations at abyssal depths. Levels of population structure as measured by ST were considerably greater in the upper bathyal species (N. similis= 0.755 and D. atacellana= 0.931; 530–3834 m) than in the lower bathyal/abyssal species (M. abyssorum= 0.071 and L. ultima= 0.045; 2864–4970 m). Pairwise genetic distances among the samples within each species also decreased with depth. Population trees (UPGMA) based on modified coancestry coefficients and nested clade analysis both indicated strong population‐level divergence in the two upper bathyal species but little for the deeper species. The population genetic structure in these protobranch bivalves parallels depth‐related morphological divergence observed in deep‐sea gastropods.The higher level of genetic and morphological divergence, coupled with the strong biotic and abiotic heterogeneityal bathyal depths, suggests this region may be an active area of species formation. We suggest that the steep, topographically complex, and dynamic bathyal zone, which stretches as a narrow band along continental margins, plays a more important role in the evolutionary radiation of the deep‐sea fauna than the much more extensive abyss.

A genetic dimension to deep-sea biodiversity

Our knowledge of deep-sea biodiversity is based almost entirely on morphological distinctions at the species level. Here, we use haplotype variations in the mitochondrial 16S ribosomal gene to assess biodiversity at the genome level in four deep-sea molluscan morphospecies. Genetic divergence levels among populations of the morphospecies fall within the range of interspecific divergence found in coastal marine and aquatic molluscan genera. Results indicate a rich population structure at the genetic level in deep-sea mollusks, and suggest the possibility that some seemingly coherent morphospecies are composed of cryptic species.

Ontogeny of odorant receptor gene expression in zebrafish, Danio rerio

We cloned three putative odorant receptor (OR) genes from the zebrafish to use as in situ hybridization probes to follow the temporal patterns of neurons expressing OR genes through a developmental progression from embryo (12 h postfertilization) to adult. The identification of these genes is supported by sequence homology to previously reported ORs and by the morphology and location of labeled cells in in situ hybridization experiments. Cells expressing OR mRNA were first observed in the olfactory placodes between 31 and 38 h after fertilization (fish reared at 26 degrees C). Initially, only single cells were observed to hybridize the probe; the number of labeled cells increased throughout the remainder of embryogenesis and through postembryonic growth and morphogenesis of the olfactory organ. At all ages, the positively hybridizing cells were scattered throughout the olfactory epithelium but not in the nonsensory epithelium of the olfactory organ.

Molecular Clones within Organismal Clones

Some vertebrate “species”* exist predominantly or exclusively as females, exhibiting asexual or semisexual reproduction (Dawley and Bogart, 1989). Examples occur among the fishes, amphibians, and squamate reptiles. Essentially all known unisexual vertebrates carry the nuclear genomes of two or more bisexual species, and thus arose via interspecific hybridization. These all-female biotypes reproduce without genetic recombination, by one of three modes (Fig. 1): (a) parthenogenesis, in which the female’s nuclear genome is transmitted intact to the egg, which then develops into an offspring genetically identical to the mother; (b) gynogenesis, in which the process is the same except that sperm from a related bisexual species is required to stimulate egg development; and (c) hybridogenesis, in which an ancestral genome from the maternal line is transmitted to the egg without recombination, while paternally-derived chromosomes are discarded only to be replaced in each generation through fertilization by sperm from a related sexual species.

Ecotoxicology and Population Genetics: The Emergence of "Phylogeographic and Evolutionary Ecotoxicology"

Genetics of ecotoxicology has recently emerged as a priority research field. The advent of polymerase chain reaction and molecular population genetics has made it possible to examine the genetics in even the smallest individuals. Although a potentially powerful technique, current approaches oversimplify the relationship of change in gene frequency to contaminant exposure. Many of these approaches cannot control for random correlation or accessory abiotic factors that impinge on the system tested. Indeed, the gestalt approaches of laboratory exposure or natural field experiments may ignore significant genome-level interactions that are important within a given system. At the very least, these approaches would benefit by a biogeographic survey of genetic variation to understand geographic microevolutionary patterns, or phylogeography, within a species to reduce spurious correlations and erroneous conclusions. Other single locus approaches can be chosen to enhance this approach if genetic/environmental interactions have been characterized for laboratory populations or for other model systems.

PATTERNS OF GENE DUPLICATION IN LEPIDOPTERAN PHEROMONE BINDING PROTEINS

Abstract. We have isolated and characterized cDNAs representing two distinct pheromone binding proteins (PBPs) from the gypsy moth, Lymantria dispar. We use the L. dispar protein sequences, along with other published lepidopteran PBPs, to investigate the evolutionary relationships among genes within the PBP multigene family. Our analyses suggest that the presence of two distinct PBPs in genera representing separate moth superfamilies is the result of relatively recent, independent, gene duplication events rather than a single, ancient, duplication. We discuss this result with respect to the biochemical diversification of moth PBPs.

Use of restriction fragment length polymorphisms to identify sea turtle eggs and cooked meats to species

One of the many threats to sea turtlepopulations is the take of turtles and theireggs for consumption and sale. Improved speciesidentification methods for sea turtle eggs andcooked meats would facilitate prosecution ofthose involved. Fatty acid-based methods toidentify eggs cannot resolve loggerheads andthe two ridley species. Protein-based methodsare not applicable to eggs or cooked meat. Wepresent methods to extract DNA from turtle eggand cooked meat and to produce diagnosticrestriction fragment length polymorphismpatterns in the cytochrome b region of themitochondrial DNA. This method works on DNAfrom any tissue, and provides wildlife lawenforcement another tool to combat illegal takeof endangered species.

Estimated contribution of Atlantic Coastal loggerhead turtle nesting populations to offshore feeding aggregations

AbstractSeasonal feeding grounds for loggerhead sea turtles present relatively unchecked anthropogenic hazards. Commercial fisheries, recreational boating and environmental contamination indirectly threaten subadult feeding areas. The potential effects of these types of threats are difficult to establish without an understanding of the relationship between the feeding areas and individual nesting areas. We perform a mixed stock analysis on seasonal subadult feeding grounds from North Carolina to northern Florida. A total of 216 individuals were captured using either commercial shrimping vessels or vessels with standardized sea turtle trawls. A fragment of the mitochondrial control region was sequenced from each of the individuals and compared with haplotypes at nesting beaches identified previously. Twelve haplotypes were resolved among individuals captured. Mixed stock analysis indicates that the nearby NEFL-NC nesting populations disproportionately contribute to the feeding aggregate and thus perturbations to this feeding ground would weigh most heavily on this nesting area.

Genetic diversity in black howler monkeys (Alouatta pigra) from Belize

To assess the level of genetic variation in a threatened black howler monkey (Alouatta pigra) population, we examined 36 allozyme loci and restriction fragment profiles of mitochondrial DNA (mtDNA). Mean heterozygosity at allozyme loci was only 0.021 and 5.6 percent of the loci were polymorphic. Analyses of mtDNA also revealed low genetic diversity compared with other primates. F-statistics revealed no significant genetic heterogeneity among troops within the Bermudian Landing preserve, but did indicate a deficiency of heterozygotes at one of the two loci. We explore several explanations for this result, which is unexpected in a socially structured primate. Low genetic diversity in this population may reflect its history of demographic bottlenecks.

Amplification primers for the mitochondrial control region and sixth intron of the nuclear-encoded lactate dehydrogenase A gene in elasmobranch fishes

D.S. Stoner1,3, J.M. Grady2, K.A. Priede1 & J.M. Quattro1,∗ 1Department of Biological Sciences, Marine Science Program, and School of the Environment, University of South Carolina, Columbia, South Carolina 29208; 2Department of Biological Sciences, University of New Orleans, New Orleans, Louisiana 70148; 3Present address: 513 Thornewood Court, Columbia, South Carolina 29212 (∗Author for correspondence: Phone: 803-777-3240; Fax: 803-777-4002; E-mail: quattro@mail.biol.sc.edu)