Genetic variation among interconnected populations of Catostomus occidentalis: implications for distinguishing impacts of contaminants from biogeographical structuring

Abstract

Exposure to contaminants can affect survivorship, recruitment, reproductive success, mutation rates and migration, and may play a significant role in the partitioning of genetic variation among exposed and nonexposed populations. However, the application of molecular population genetic data to evaluate such influences has been uncommon and often flawed. We tested whether patterns of genetic variation among native fish populations (Sacramento sucker, Catostomus occidentalis) in the Central Valley of California were consistent with long-term pesticide exposure history, or primarily with expectations based on biogeography. Field sampling was designed to rigorously test for both geographical and contamination influences. Fine-scale structure of these interconnected populations was detected with both amplified fragment length polymorphisms (AFLP) and microsatellite markers, and patterns of variation elucidated by the two marker systems were highly concordant. Analyses indicated that biogeographical hypotheses described the data set better than hypotheses relating to common historical pesticide exposure. Downstream populations had higher genetic diversity than upstream populations, regardless of exposure history, and genetic distances showed that populations from the same river system tended to cluster together. Relatedness among populations reflected primarily directions of gene flow, rather than convergence among contaminant-exposed populations. Watershed geography accounted for significant partitioning of genetic variation among populations, whereas contaminant exposure history did not. Genetic patterns indicating contaminant-induced selection, increased mutation rates or recent bottlenecks were weak or absent. We stress the importance of testing contaminant-induced genetic change hypotheses within a biogeographical context. Strategic application of molecular markers for analysis of fine-scale structure, and for evaluating contaminant impacts on gene pools, is discussed.

High genetic diversity in population of Lepturichthys fimbriata from the Yangtze River revealed by microsatellite DNA analysis

“…No heterozygote deficits were detected in any of the 3 populations (the negative F IS mean values in Table 2). Unlike the potamodromous (or anadromous) and relatively long-lived fishes, such as bull trout (Salvelinus confluentus) [15], catostomids [16,17], and largemouth bronze gudgeon (Coreius guichenoti Sauvage et Dabry) [6], L. fimbriata has a relatively early age of maturity and a short lifespan [3,18]. The phenomena of inbreeding and genetic drift usually happen in a small population but not in a large one [15,19], which provides one possible reason for the maintenance of genetic diversity after about 10 years isolation between L22 and the other populations, in that there are sustainably large amounts of L. fimbriata fish in the Yalong River above the Ertan Dam.…”

Multi-Trial Ecotoxicological Diagnostic Tool in Cetacean Skin Biopsies

“…High genetic diversity within a population increases the chance for survival of at least some individuals, and possible changes in the environment, due to natural causes or anthropogenic pressures, can be better tolerated. Exposure to contaminants combined with other human impacts can affect survivorship, recruitment, reproductive success, mutation rates and migration, and may play a significant role in partitioning genetic variation among high stress exposed and less stress exposed populations (Whitehead et al, 2003). This is particularly true for populations inhabiting a closed basin characterized by considerable concentrations of environmental contaminants (OCs), orders of magnitude higher than those detected in oceanic environments.…”

Genetic diversity and population structure of Fenneropenaeus penicillatus determined by mitochondrial DNA analyses

“…Molecular markers, including protein, nuclear, and mitochondrial DNA (mtDNA) markers, are employed to assess genetic diversity and population structure in freshwater and marine species (Englbrecht et al, 2000;Whitehead et al, 2003). mtDNA is of great interest to population geneticists for the study of phylogeographic structure and historical demography due to its unique features, including maternal inheritance, absence of recombination, and faster mutation rate compared to nuclear genome markers (Francalacci et al, 1996).…”