Abstract
Populations of fishes are increasingly threatened by over‐exploitation, pollution, habitat destruction, and climate change. In order to better understand the factors that can explain the amount of genetic diversity in wild populations of fishes, we collected estimates of genetic diversity (mean heterozygosity and mean rarefied number of alleles per locus) along with habitat associations, conservation status, and life‐history information for 463 fish species. We ran a series of phylogenetic generalized least squares models to determine which factors influence genetic diversity in fishes after accounting for shared evolutionary history among related taxa. We found that marine fishes had significantly higher genetic diversity than freshwater fishes with marine fishes averaging 11.3 more alleles per locus than their freshwater counterparts. However, contrary to our expectations, genetic diversity was not found to be lower in threatened versus not‐threatened fishes. Finally, we found that both age at maturity and fecundity were negatively related to genetic variation in both marine and freshwater fishes. Our results demonstrate that both life‐history characteristics and habitat play a role in shaping patterns of genetic diversity in fishes and should be considered when prioritizing species for conservation.
Highlights
Fishes are the most speciose group of vertebrates, inhabit most major aquatic habitat types, and perform a diverse set of biological functions in ecosystems (Helfman, Collette, Facey, & Bowen, 2009)
We focused on microsatellite loci because 1. far fewer studies to date have used alternative nuclear markers to measure genetic diversity in fishes and 2. we wanted to make comparisons across similar marker types to avoid confounding factors
Based on International Union for Conservation of Nature (IUCN) category definitions, we considered species listed as least concern or near threatened as “not‐threatened” and species listed as vulnerable, endangered, or critically endangered as “threatened.” Species listed as extinct or extinct in the wild were excluded from our dataset, while species classified as not evaluated or data deficient were excluded only from models investigating the relationship between genetic diversity and conservation status
Summary
Fishes are the most speciose group of vertebrates (over 33,000 species described), inhabit most major aquatic habitat types, and perform a diverse set of biological functions in ecosystems (Helfman, Collette, Facey, & Bowen, 2009). One metric that may help predict which species are most likely to adapt to future conditions is genetic diversity. Reduced genetic diversity may result in decreased population viability and increased extinc‐ tion likelihood, for populations faced with stressful environmental conditions (Markert et al, 2010; Vandewoestijne, Schtickzelle, & Baguette, 2008; reviewed in Reed & Frankham, 2003). Understanding how patterns of genetic diversity vary across fishes could help inform predictions regarding which spe‐ cies are likely to adapt in response to future disturbance while simultaneously identifying species that might be sus‐ ceptible to extinction (Reed & Frankham, 2003; Stockwell, Hendry, & Kinnison, 2003). We ask how genetic diversity relates to species hab‐ itat needs, conservation status, and life‐history characteristics. Following DeWoody and Avise (2000), we predict that marine fishes should generally have higher genetic diversity than freshwater fishes even after accounting for species relatedness. (iii) life‐history characteristics by performing a quantitative review of 463 globally distributed fish species
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