Resource polymorphism in a Patagonian fish Percichthys trucha (Percichthyidae): phenotypic evidence for interlake pattern variation

Abstract

Within‐species differentiation in phenotypic characters related to resource use (resource polymorphism) is frequently thought to result from divergent natural selection in a heterogeneous environment with ‘open niches’. In this study we found consistent resource‐based polymorphism within three different populations of Percichthys trucha , a lake‐dwelling fish native to the southern Andes. In each of three lakes we found two morphotypes that could be clearly distinguished by differences in gill raker length. However, the magnitude of the polymorphism, and the suite of phenotypic characteristics associated with the polymorphism, differed between lakes. Patterns of divergence were more similar between the two northern lakes which ultimately drain into a common river, than between these two lakes and a more southern, unconnected lake. The southern population, which had the largest divergence in gill raker length (32% vs. 16% and 19%), also showed substantial differences in diet. Evidence from the southern population suggests that polymorphism in P. trucha is present early during ontogeny. We conclude that while there are some strong parallels among lakes in the development of a trophic polymorphism, differences in environmental ­conditions and/or colonization history have led to substantial differences in the evolutionary history, resulting in ­different ecological roles of common morphotypes within different lakes. © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 78, 497–515.

Shared and Unique Features of Diversification in Greater Antillean Anolis Ecomorphs

“…Evolutionary biologists aim to understand the relative magnitudes of shared selective regimes, unique histories, and the interaction between these two evolutionary sources of diversification (e.g., Irschick et al 1997;Huey et al 2000;Matos et al 2002;Van Buskirk 2002;Ruzzante et al 2003;Blackledge and Gillespie 2004;Hendry et al 2006). Nonetheless, the explicit quantification and evaluation of the importance and nature of these mechanisms rarely has been attempted (Langerhans and DeWitt 2004).…”

“…To advance our knowledge of replicated evolution among multiple groups of organisms, evolutionary biologists must move beyond simply examining the significance of shared responses to shared selective regimes. Understanding the factors that contribute to divergent evolution among species occupying shared selective regimes is essential if we are to fully appreciate the relative generality or peculiarity of evolutionary trends (e.g., Huey et al 2000;Gould 2002;Matos et al 2002;Van Buskirk 2002;Ruzzante et al 2003;Langerhans and DeWitt 2004;Hendry et al 2006).…”

“…But which mechanism (shared selection vs. unique history) is generally more important in determining evolutionary patterns? Understanding the relative importance of shared selective regimes and unique histories in generating phenotypic outcomes is critical to elucidating the relative generality or peculiarity in evolutionary diversification (e.g., Irschick et al 1997;Huey et al 2000;Matos et al 2002;Van Buskirk 2002;Vanhooydonck and Irschick 2002;Langerhans et al 2003;Ruzzante et al 2003;Blackledge and Gillespie 2004;Langerhans and DeWitt 2004;Hendry et al 2006).…”

Fishes of southern South America: a story driven by temperature

“…The nominal species show a conspicuous morphological variation of the oropharyngeal apparatus-large and small mouths, and long and short gill rakes )-that are related to resource use (Logan 2000). The variation patterns are different in different lakes (Ruzzante et al 2003). Genetic studies have not yet found evidence of either specific differences or reproductive isolation between morphs , and some findings suggest that environmental cues plays a major role in determining oropharyngeal development.…”

“…Genetic studies have not yet found evidence of either specific differences or reproductive isolation between morphs , and some findings suggest that environmental cues plays a major role in determining oropharyngeal development. This variation can be identified during the juvenile period (Ruzzante et al 2003) and can also be observed among sibling larvae breeding in captivity, seemingly related with yolk amount (S. Crichigno, personal communication). Populations of 'perca' upstream and downstream of a hydroelectric dam can also show oropharyngeal differences, and these differences were identified within only a few years of the dam being built .…”