Variable extent of parallelism in respiratory, circulatory, and neurological traits across lake whitefish species pairs

Authors

  • Melissa L. Evans,

    Corresponding authorCurrent affiliation:
    1. Melissa L. Evans,, Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
    • Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-Eugène-Marchand, Université Laval, Québec, Québec, Canada
    Search for more papers by this author
  • Lauren J. Chapman,

    1. Biology Department, McGill University, Montréal, Québec, Canada
    Search for more papers by this author
  • Igor Mitrofanov,

    1. Biology Department, McGill University, Montréal, Québec, Canada
    Search for more papers by this author
  • Louis Bernatchez

    1. Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-Eugène-Marchand, Université Laval, Québec, Québec, Canada
    Search for more papers by this author

  • This study was supported by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants and Canada Research Chair Grants to L. Bernatchez and L. Chapman and an NSERC PDF award to M. Evans.

Correspondence

Melissa L. Evans, Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-Eugène-Marchand, 1030 Avenue de la Médecine, Université Laval, Québec, Québec, G1V 0A6, Canada. Tel: +(418) 656-2131; Fax: +(418) 656-7176; E-mail: melissa.lea.evans@gmail.com

Abstract

Parallel adaptive radiation events provide a powerful framework for investigations of ecology's contribution to phenotypic diversification. Ecologically driven divergence has been invoked to explain the repeated evolution of sympatric dwarf and normal lake whitefish (Coregonus clupeaformis) species in multiple lakes in eastern North America. Nevertheless, links between most putatively adaptive traits and ecological variation remain poorly defined within and among whitefish species pairs. Here, we examine four species pairs for variation in gill, heart, and brain size; three traits predicted to show strong phenotypic responses to ecological divergence. In each of the species pairs, normals exhibited larger body size standardized gills compared to dwarfs – a pattern that is suggestive of a common ecological driver of gill size divergence. Within lakes, the seasonal hypoxia experienced in the benthic environment is a likely factor leading to the requirement for larger gills in normals. Interestingly, the morphological pathways used to achieve larger gills varied between species pairs from Québec and Maine, which may imply subtle non-parallelism in gill size divergence related to differences in genetic background. There was also a non-significant trend toward larger hearts in dwarfs, the more active species of the two, whereas brain size varied exclusively among the lake populations. Taken together, our results suggest that the diversification of whitefish has been driven by parallel and non-parallel ecological conditions across lakes. Furthermore, the phenotypic response to ecological variation may depend on genetic background of each population.

Ancillary