Selection for developmental plasticity in a eurytopic species of African cichlid.
Chapman, Lauren *,1, 2, Galis, Frietson3, Albert, James 4, 1 McGill University, Montreal, Quebec, Canada2 Wildlilfe Conservation Society, Bronx, New York, USA3 Leiden University, Leiden, The Netherlands4 University of Louisiana at Lafayette, Lafayette, Louisiana, USA
ABSTRACT- The cichlid fishes of the Great Lakes of East Africa have been extensively explored for insights into the mechanisms of rapid speciation. For example, Lake Victoria was home to an estimated 600+ species of endemic haplochromine cichlids prior to the introduction of the predatory Nile perch (Lates niloticus) and other anthropogenic perturbations. By contrast, a small number of eurytopic cichlid species including Pseudocrenilabrus multicolor victoriae inhabit a broad range of habitats (rivers, streams and swamps) throughout the Lake Victoria watershed and adjacent areas. Pseudocrenilabrus multicolor from hypoxic swamp waters are characterized by larger gill size and smaller total brain mass than conspecifics from well-oxygenated habitats. To quantify the degree to which developmental plasticity explains the patterns observed, we raised F1s from multiple families of three field populations (low oxygen, high oxygen, and fluctuating oxygen) using a split-brood design with two treatments: extreme hypoxia and normoxia. We measured a suite of morpho-physiological response variables including gill metrics, the size and shape of surrounding elements, brain mass, and respiratory performance. Results provide evidence that (a) the amount of plasticity varies among populations, (b) there is a large element of developmental plasticity in some morpho-physiological traits in response to the dissolved oxygen environment, and (c) variation in gill size occurs in an adaptive direction both among and within populations, but can impact non-respiratory characters (e.g., trophic muscles).
Key words: diversification, hypoxia, phenotypic plasticity, morphology
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