Evol Ecol Res 15: 155-170 (2013)     Full PDF if your library subscribes.

Pelvic girdle reduction and asymmetry in threespine stickleback from Wallace Lake, Alaska

Emily A. Lescak1, Frank A. von Hippel1, Richard R. Bernhardt1 and Michael A. Bell2

1Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska, USA and  2Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York USA

Correspondence: E.A. Lescak, Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Dr., Anchorage, AK 99508, USA.
e-mail: elescak@alaska.edu

ABSTRACT

Questions: Can a bimodal frequency distribution of phenotypes persist over multiple generations despite ecological changes? Can an organism’s environment elicit fitness trade-offs between armour development and somatic growth?

Background: Wallace Lake, located in south-central Alaska, contains a population of threespine stickleback (Gasterosteus aculeatus) exhibiting a bimodal distribution of pelvic phenotypes with modes at both highly reduced and fully developed pelvic armour. The lake has low ion availability, abundant macroinvertebrate predators, and introduced piscivorous fish.

Methods: Analyse temporal variability of the bimodal frequency distribution of pelvic phenotypes, direction and degree of asymmetry in bilateral armour traits, and whether extent of pelvic girdle development is inversely related to body size.

Conclusions: Distributions of pelvic phenotypes and of individuals with asymmetrical pelvic girdles persist over a 20-year time span. Individuals with greater pelvic expression exhibit more symmetrical anterior processes and ascending branches than those with pelvic reduction. Both directional and fluctuating asymmetry are present in armour traits. Stickleback with complete pelvic structures do not appear to experience reduced somatic growth compared with those with reduced pelvic girdles.

Keywords: directional asymmetry, disruptive selection, fluctuating asymmetry, frequency-dependent selection, stickleback.

DOWNLOAD A FREE, FULL PDF COPY
IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.

 

        © 2013 Emily A. Lescak. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.