Genetic variation and conservation of stream fishes: influence of ecology, life history, and water quality

Abstract

Three stream-dwelling fish species were used to investigate effects of ecology, life history, and water quality on genetic variation. We sampled Etheostoma caeruleum, E. blennioides, and Campostoma anomalum from six streams of varying water quality. Allozyme electrophoresis revealed that the most ecologically specialized species, E. caeruleum, was the least variable (P = 68.4%, Hobs = 1.2%). Etheostoma blennioides was intermediate in specialization and variation (P = 77.8%, Hobs = 7.8%), and the least specialized species, C. anomalum, had the most variation (P = 90.0%, Hobs = 12.1%). This pattern conforms to Willis' niche-variation hypothesis and Selander and Kaufman's adaptation model. Differences in ecology, life history, and amount of genetic variation are responsible for differences in how variation is apportioned within and among populations and within and among rivers. Populations in the river with the worst water quality (Huron River) had the lowest within-population variation for each species; therefore, genetic variation may be a useful indicator of water quality. Lower genetic variation may result from selection associated with specific loci, e.g., PGM-2, in stoneroller minnows. However, indirect effects on population size probably contributed to the erosion of genetic variation. Ecology, life history, and pollution tolerance data combine as predictors of species' risk of genetic erosion.

Landscape genetic patterns of the rainbow darterEtheostoma caeruleum: a catchment analysis of mitochondrial DNA sequences and nuclear microsatellites

“…Etheostoma caeruleum populations in the Ohio River sites at Big Darby Creek and Little Miami River have greater mtDNA genetic diversity and more private haplotypes than are found in Lake Erie samples. Congruent with these results, the allozyme study by Heithaus & Laushman (1997) recovered higher genetic diversity values in an Ohio River sampling site than found in the Lake Erie catchment, which they attributed to decreased water quality in the latter. However, this is probably a historic trend, with higher genetic diversity characteristic of populations from unglaciated regions than found in once glaciated areas (Billington & Hebert, 1991; Bernatchez & Wilson, 1998).…”

“…Those studies raised two different hypotheses for whether E. caeruleum populations in the Great Lakes and Ohio River systems are or are not differentiated, which are tested here using higher resolution genetic markers and larger sample sizes. Notably, an allozyme study by Heithaus & Laushman (1997) discerned that samples from the Lake Erie catchment (Black, Huron, Rocky and Vermilion Rivers) and the Ohio River system (sampling only the Kokosing River) are divergent. A study by Ray et al (2006) based on mtDNA cytochrome (cyt) b sequences, however, examined very few fish (four individuals from two Lake Erie sites and 11 individuals from the Ohio River catchment) and resolved a single clade, finding no significant difference between them.…”

Comparison of gene flow estimates between species of darters in different streams

“…Observed heterozygosity was within the range noted for other vertebrate populations (Nevo, 1978) and the values for E. blennioides were similar to values obtained in another Ohio drainage, the Kokosing River (H obs 0·007-0·084; Heithaus & Laushman, 1997). Because values of not significantly different from zero indicate high gene flow among sites, apparently E. blennioides comprises panmictic populations in Big Walnut Creek and the Shade River.…”

Genetic diversity and structure of an estuarine fish (Fundulus heteroclitus) indigenous to sites associated with a highly contaminated urban harbor

“…More broadly, an expected consequence of pollutant toxicity is a reduction in population size in favor of only resistant phenotypes and, if severe, correlated reduction in genetic diversity (Gillespie and Guttman 1999). In some cases, reduction in genetic diversity following exposure to stressors was detected (e.g., Kopp et al 1992;Benton et al 1994;Keklak et al 1994;Murdoch and Hebert 1994;Heithaus and Laushman 1997;Street et al 1998), whereas in other cases genetic diversity was increased (Theodorakis and Shugart 1997) or the pattern of genetic diversity change was complicated (e.g., Nadig et al 1998). …”