Intraspecific Sexual Size and Shape Dimorphism in an Australian Freshwater Fish Differs with Respect to a Biogeographic Barrier and Latitude
- 527 Downloads
Geographically structured variation in morphology is a common phenomenon in animals with environmental factors covarying with both latitude and biogeographic barriers having profound impacts on body size and shape. The Pacific blue-eye (Pseudomugil signifer) is a freshwater fish that lives along Australia’s east coast and occurs on either side of a terrestrial barrier, the Burdekin Gap. By quantifying the size and shape of males and females from 10 populations we found that Pacific blue-eyes are not sexually size dimorphism north of the Burdekin Gap whereas the degree of dimorphism was dependent upon latitude south of the barrier. Rensch’s rule was not supported as the degree of male-biased size dimorphism did not increase with increasing population mean body size. Body shape was related to body size and was sexually dimorphic south of the Burdekin Gap but not north of it. Our study represents a rare case of identifying how both body size and shape differ with respect to latitude and a major terrestrial biogeographic barrier and lends further support to the notion that P. signifer may comprise two species, or incipient species, that are separated by the Burdekin Gap.
KeywordsBody shape Body size Sexual selection Rensch’s rule Bergmann’s rule
We thank Mark McGrouther (Ichthyology, Collection Manager) for access to preserved P. signifer at the Australian Museum and Hugh Spencer (Cape Tribulation Tropical Research Station) for advice and hospitality and two anonymous referees for their valuable input. Fish were collected under a Queensland General Fisheries Permit. This work was supported by an A.N.U. Faculty of Science Research Grant and Iowa State University faculty start-up funds to CDK.
- Adams, D. C., & Otarola-Castillo, E. (2012). Geomorph: Software for geometric morphometric analyses. R package version 1.1-0. http://cran.r-project.org/web/packages/geomorph/index.html.
- Adams, D. C., & Otarola-Castillo, E. (2013). Geomorph: An R package for the collection and analysis of geometric morphometric shape data. Methods in Ecology and Evolution (in press).Google Scholar
- Adams, D. C., & Nistri, A. (2010). Ontogenetic convergence and evolution of foot morphology in European cave salamanders (Family: Plethodontidae). BMC Evol Biol, 10.Google Scholar
- Allen, G., Midgley, S., & Allen, M. (2003). Field guide to the freshwater fishes of Australia. Collingwood, Vic: CSIRO Publishing.Google Scholar
- Bergmann, C. (1847). Über die verhältnisse der wärmeökonomie der thiere zu ihrer grösse. Göttinger Studien, 3, 595–708.Google Scholar
- Claude, J. (2008). Morphometrics with R. Springer Verlag.Google Scholar
- McGlashan, D., & Hughes, J. (2002). Extensive genetic divergence among populations of the Australian freshwater fish, Pseudomugil signifer (Pseudomugilidae), at different hierarchical scales. Marine Freshwater Research.Google Scholar
- Pusey, B., Kennard, M., & Arthington, A. (2004). Freshwater fishes of North-Eastern Australia. Collingwood, Vic: Csiro Publishing.Google Scholar
- Rensch, B. (1960). Evolution above the species level. New York: Columbia University Press.Google Scholar
- Rohlf, F. J. (2010). tpsRelw: Relative warps analysis.Google Scholar
- Wong, B., Keogh, J., & McGlashan, D. (2004b). Current and historical patterns of drainage connectivity in eastern Australia inferred from population genetic structuring in a widespread freshwater fish Pseudomugil signifer (Pseudomugilidae). Molecular Ecology, 13, 391–401.PubMedCrossRefGoogle Scholar
- Zelditch, M., Swiderski, D., Sheets, H., & FINK, W. (2004). Geometric morphometrics for biologists. London: Academic Press.Google Scholar