Abstract
Conservation genetics is a powerful tool to assess the population structure of species and provides a framework for informing management of freshwater ecosystems. As lotic habitats become fragmented, the need to assess gene flow for species of conservation management becomes a priority. The eastern hellbender (Cryptobranchus alleganiensis alleganiensis) is a large, fully aquatic paedamorphic salamander. Many populations are experiencing declines throughout their geographic range, yet the genetic ramifications of these declines are currently unknown. To this end, we examined levels of genetic variation and genetic structure at both range-wide and drainage (hierarchical) scales. We collected 1,203 individuals from 77 rivers throughout nine states from June 2007 to August 2011. Levels of genetic diversity were relatively high among all sampling locations. We detected significant genetic structure across populations (Fst values ranged from 0.001 between rivers within a single watershed to 0.218 between states). We identified two genetically differentiated groups at the range-wide scale: 1) the Ohio River drainage and 2) the Tennessee River drainage. An analysis of molecular variance (AMOVA) based on landscape-scale sampling of basins within the Tennessee River drainage revealed the majority of genetic variation (∼94–98%) occurs within rivers. Eastern hellbenders show a strong pattern of isolation by stream distance (IBSD) at the drainage level. Understanding levels of genetic variation and differentiation at multiple spatial and biological scales will enable natural resource managers to make more informed decisions and plan effective conservation strategies for cryptic, lotic species.
Highlights
Rivers are complex, dynamic systems that shape aquatic ecosystems at the landscape scale through a combination of biotic and abiotic processes
Bayesian clustering tools derived from the field of landscape genetics, or ‘‘riverscape genetics’’ [6], can be utilized to infer the numbers of populations that exist across the ranges of aquatic species [7,8], as well as to resolve fine-scale patterns of genetic structure across basins, subbasins, and stream reaches at the drainage level [9,10,11]
Estimates of genetic variation were surprisingly high among stream reaches
Summary
Dynamic systems that shape aquatic ecosystems at the landscape scale through a combination of biotic and abiotic processes. A central theme in stream conservation biology involves assessing spatial and temporal patterns of genetic variation within species inhabiting streams distributed across landscapes [1]. Conservation geneticists have developed a number of statistically rigorous tools for characterizing the genetic attributes of species inhabiting lotic ecosystems, including examining genetic diversity across multiple scales, and evolutionary potential [2]. Bayesian clustering tools derived from the field of landscape genetics, or ‘‘riverscape genetics’’ [6], can be utilized to infer the numbers of populations that exist across the ranges of aquatic species [7,8], as well as to resolve fine-scale patterns of genetic structure across basins, subbasins, and stream reaches (individual streams) at the drainage level [9,10,11]
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