Parallel and Nonparallel Aspects of Ecological, Phenotypic, and Genetic Divergence Across Replicate Population Pairs of Lake and Stream Stickleback

Abstract

Convergent (or parallel) evolution provides strong evidence for a deterministic role of natural selection: similar phenotypes evolve when independent populations colonize similar environments. In reality, however, independent populations in similar environments always show some differences: some non-convergent evolution is present. It is therefore important to explicitly quantify the convergent and non-convergent aspects of trait variation, and to investigate the ecological and genetic explanations for each. We performed such an analysis for threespine stickleback (Gasterosteus aculeatus) populations inhabiting lake and stream habitats in independent watersheds. Morphological traits differed in the degree to which lake-stream divergence was convergent across watersheds. Some aspects of this variation were correlated with ecological variables related to diet, presumably reflecting the strength and specifics of divergent selection. Furthermore, a genetic scan revealed some markers that diverged between lakes and streams in many of the watersheds and some that diverged in only a few watersheds. Moreover, some of the lake-stream divergence in genetic markers was associated within some of the lake-stream divergence in morphological traits. Our results suggest that convergent evolution, and deviations from it, are primarily the result of natural selection, which corresponds in only some respect to the dichotomous habitat classifications frequently used in such studies.

Testing for local host–parasite adaptation: an experiment with Gyrodactylus ectoparasites and guppy hosts

“…Our finding that patterns of local host and parasite maladaptation were not influenced by the predation regime but were strongly influenced by the drainage source and therefore host (and perhaps parasite) lineage runs counter to the idea that natural selection owing to ecological differences leads to deterministic patterns of parallel (or convergent) evolution (Endler, 1986;Schluter, 2000), and to evidence from a number of guppy traits for deterministic responses to predation (Reznick and Endler, 1982;Reznick et al, 1990;Rodd and Reznick, 1991;Endler, 1995, but see Torres-Dowdall et al, 2012. However, recent studies are increasingly emphasising the fact that evolution in similar environments is often not very similar (i.e., non-parallel or non-convergent) which suggests a considerable role for historical contingency (Kaeuffer et al, 2012;Fitzpatrick et al, 2013). Our study provides direct support for this contingency by showing that patterns of local host-parasite maladaptation are predictable by drainage source (and likely lineage) rather than the (otherwise) most important ecological context for guppies (predation regime).…”

Multiple evolutionary origins of Australian soil-burrowing cockroaches driven by climate change in the Neogene

“…Some have argued that evolution is fundamentally stochastic and unpredictable [3], while others have proposed that constraints commonly limit available phenotypic options, leading to parallelism and predictability [4]. Although parallel genotypic adaptation has been demonstrated across a diverse range of taxa at the intraspecific level [5][6][7][8][9][10][11], the widespread occurrence of parallel evolution across a clade has only rarely been shown [12,13]. The potential role of environmental change in driving parallel evolution also remains poorly understood [14].…”

Parallel Ecological Speciation in Plants?

“…However, parallel cases vary widely in the strength of reproductive isolation and genetic differentiation between local ecotypes (e.g. [125,127]). In some cases, evidence for reproductive isolation is conflicting despite evidence for genetic differentiation [128][129][130].…”