Effects of Intrinsic and Extrinsic Factors on Population Fragmentation in Three Species of North American Minnows (Teleostei: Cyprinidae)

Abstract

Geographic patterns of genetic variation (mitochondrial DNA [mtDNA] and allozymes) were used to examine effects of intrinsic characteristics (e.g., vagility, habitat specificity, and reproductive behaviors) and extrinsic factors (e.g., climatic and geological history) on population fragmentation. The three species of cyprinid fishes examined (Tiaroga cobitis, Meda fulgida, and Agosia chrysogaster) occupied similar historical ranges within the lower Colorado River drainage, but differ in intrinsic characteristics conducive to population fragmentation. Relationships among populations were similar across species, reflecting common historical influences, but results indicate the distribution of variation among species is strongly affected by intrinsic characteristics. Variation within two species (T. cobitis and M. fulgida) is subdivided among populations, suggesting little gene flow among rivers. In contrast, similarity of A. chrysogaster populations throughout the Gila River drainage supports the hypothesis that levels of gene flow are high for this species. Levels of mtDNA divergence were much higher than expected for both T. cobitis and A. chrysogaster suggesting long-term isolation of geographic regions. These results indicate that both long-term and short-term extrinsic factors have shaped basic patterns of variation within these fishes; however, the intrinsic characteristics of each species have strongly affected the population genetic structure of these fishes.

Genetic structure within and among populations of the endangered razorback sucker (Xyrauchen texanus) as determined by analysis of microsatellites

“…Samples from all locations were a subset of those analyzed in Dowling et al (1996a) with the exception of the Lake Mohave and upper Colorado River samples. The Lake Mohave sample was comprised of wild fish collected in 2000, and genomic DNA was extracted as described in Tibbets and Dowling (1996). Previous studies have identified hybridization with flannelmouth sucker (Catostomus latipinnis) in the off-channel bonds in the upper Colorado River.…”

Rarity, Fragmentation, and Extinction Risk in Desert Fishes

“…In particular, the presence (or absence) of an occurrence depends on the spatial scale of a record-a species may be absent from a specific reach but present in a river. In the arena of freshwater fish conservation, issues of scale are especially important because of the constrained connectivity in hierarchical river-creek networks (Dunham et al 1997) and because habitats suitable for particular fish species are often patchily distributed (Pringle et al 1988, Johnston 2000, resulting in substantial among-species variation in distributional fragmentation (Tibbets and Dowling 1996).…”

Ecological and Historical Associations of Gene Flow in Darters (Teleostei: Percidae)

“…We used regional glaciation history and lineage history as a framework to evaluate associations between gene flow and life-history traits in darters. A number of studies have hypothesized that fecundity and dispersal related life-history characters influence migration and/or gene flow in fishes, and there is some empirical evidence supporting this relationship (Waples 1987;Doherty et al 1995;Tibbets and Dowling 1996). McAllister et al (1986) noted an association between body size and size of geographic range in North American freshwater fishes and suggested that body size positively influences dispersal capability and migration.…”