Biological Journal of the Linnean Society, 2006, 87, 69–82. With 6 figures © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 69–82 69 G. PLATEI D. MILANO ET AL . *Corresponding author. Present address: Lab. Fotobiología, Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, (8400) Bariloche, Río Negro, Argentina. Email: danielamilano@yahoo.com Latitudinal and ecological correlates of morphological variation in Galaxias platei (Pisces, Galaxiidae) in Patagonia DANIELA MILANO 1,2 *, DANIEL E. RUZZANTE 3 , VICTOR E. CUSSAC 1,2 , PATRICIO J. MACCHI 1 , RICARDO A. FERRIZ 4 , JUAN P. BARRIGA 1,2 , JUANA C. AIGO 1 , MARIA E. LATTUCA 1,2 and SANDRA J. WALDE 3 1 Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, San Carlos de Bariloche, Río Negro, Argentina 2 Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina 3 Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4JI 4 Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Buenos Aires, Argentina Received 27 September 2004; accepted for publication 1 February 2005 We examined the morphological variability (23 morphometric traits) among individual Galaxias platei (N = 380) col- lected from 20 postglacial lakes in the southern Andes. The lakes were chosen to cover the latitudinal range of the species in Patagonia. Diet examined for a subset of these fish (N = 261) collected during the summer months (Jan- uary through March), differed among river basins but there were no clear latitudinal trends in the consumption of any prey type. Diet may, however, have partially shaped morphology, as pelvic measures were negatively correlated with consumption of amphipods. Substantial differentiation among populations was observed, primarily in the shape and dimensions of the head, in caudal morphology and in fin length. Our results indicate that the morphology of G. platei varies with latitude, and may be related to risk of predation and diet. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 69–82. ADDITIONAL KEYWORDS: allopatry – benthic fish – ecomorphology – lakes – landlocked – morphs – predation risk – sympatry. INTRODUCTION A fundamental problem in evolutionary biology is to understand the processes that are responsible for the phenotypic and genetic variability observed in nature at various hierarchical levels: among species, among populations belonging to one species, and within pop- ulations. Historical contingency (shared ancestry and/ or shared ancient environment), stochastic processes (genetic drift) and natural selection are generally thought of as the main factors influencing evolution- ary trajectories. The independent actions of historical contingency (e.g. ancestral secondary contact through shifting drainage connections) and natural selection have been invoked in studies on several northern hemisphere postglacial fish systems, including white- fish (Coregonus clupeaformis) and Arctic char (Salveli- nus alpinus) (Bernatchez, Chouinard & Lu, 1999; Gíslason et al., 1999; Skúlason, Snorrason & Jónsson, 1999). Probably the most complete understanding of the role that the various factors have played in pro- moting evolutionary novelty has been achieved for the North American three-spine stickleback, Gasterosteus aculeatus, where shared histories (repeated marine invasions) have been shown to have interacted with natural selection to cause divergence within popula- tions (Taylor & McPhail, 2000). The relative simplicity of southern and northern hemisphere post-Pleistocene lake ecosystems presents Downloaded from https://academic.oup.com/biolinnean/article/87/1/69/2691588 by guest on 05 August 2022