Identifying environmental correlates of intraspecific genetic variation.
Genetic variation is critical to the persistence of populations and their capacity to adapt to environmental change. The distribution of genetic variation across a species' range can reveal critical information that is not necessarily represented in species occurrence or abundance patterns. We identified environmental factors associated with the amount of intraspecific, individual-based genetic variation across the range of a widespread freshwater fish species, the Murray cod Maccullochella peelii. We used two different approaches to statistically quantify the relative importance of predictor variables, allowing for nonlinear relationships: a random forest model and a Bayesian approach. The latter also accounted for population history. Both approaches identified associations between homozygosity by locus and both disturbance to the natural flow regime and mean annual flow. Homozygosity by locus was negatively associated with disturbance to the natural flow regime, suggesting that river reaches with more disturbed flow regimes may support larger, more genetically diverse populations. Our findings are consistent with the hypothesis that artificially induced perennial flows in regulated channels may provide greater and more consistent habitat and reduce the frequency of population bottlenecks that can occur frequently under the highly variable and unpredictable natural flow regime of the system. Although extensive river regulation across eastern Australia has not had an overall positive effect on Murray cod numbers over the past century, regulation may not represent the primary threat to Murray cod survival. Instead, pressures other than flow regulation may be more critical to the persistence of Murray cod (for example, reduced frequency of large floods, overfishing and chemical pollution).
School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
K A
KA
Harrisson
School of Physics & Astronomy, Monash University, Clayton, Victoria, Australia.
J D L
JD
Yen
School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
A
A
Pavlova
Department of Primary Industries, DPI Fisheries, Narrandera, New South Wales, Australia.
M L
ML
Rourke
Department of Primary Industries, DPI Fisheries, Batemans Bay Fisheries Office, Batemans Bay, New South Wales, Australia.
D
D
Gilligan
Fisheries Victoria, Department of Economic Development, Jobs, Transport and Resources, Alexandra, Victoria, Australia.
B A
BA
Ingram
Arthur Rylah Institute, Department of Environment, Land, Water & Planning, Heidelberg, Victoria, Australia.
J
J
Lyon
Arthur Rylah Institute, Department of Environment, Land, Water & Planning, Heidelberg, Victoria, Australia.
Z
Z
Tonkin
School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
P
P
Sunnucks
D000818:Animals; D001315:Australia; D001499:Bayes Theorem; D017753:Ecosystem; D014644:Genetic Variation; D018895:Microsatellite Repeats; D008957:Models, Genetic; D010473:Perciformes / Q000235:genetics*; D045483:Rivers