The Geography of Morphological Convergence in the Radiations of PacificSebastesRockfishes

Abstract

The evolution of convergent phenotypes in lineages subject to similar selective pressures is a common feature of adaptive radiation. In geographically replicated radiations, repeated convergence occurs between clades occupying distinct regions or islands. Alternatively, a clade may repeatedly reach the same adaptive peaks in broadscale sympatry, resulting in extensive convergence within a region. Rockfish (Sebastes sp.) have radiated in both the northeast and northwest Pacific, allowing tests of the extent and geographic pattern of convergence in a marine environment. We used a suite of phylogenetically informed methods to test for morphological convergence in rockfish. We examined patterns of faunal similarity using nearest neighbor distances in morphospace and the frequency of morphologically similar yet distantly related species pairs. The extent of convergence both between regions and within the northeast Pacific exceeds the expectation under a Brownian motion null model, although constraints on trait space could account for the similarity. We then used a recently developed method (SURFACE) to identify adaptive peak shifts in Sebastes evolutionary history. We found that the majority of convergent peak shifts occur within the northeast Pacific rather than between regions and that the signal of peak shifts is strongest for traits related to trophic morphology. Pacific rockfish thus demonstrate a tendency toward morphological convergence within one of the two broad geographic regions in which they have diversified.

Fast and accurate detection of evolutionary shifts in Ornstein–Uhlenbeck models

“…Mahler et al . () also used OU models with varying optima, but without a preselected set of hypotheses for the number and placement of these optima (see also Ingram & Mahler ; Ingram & Kai ). To do so, they used a stepwise search among OU models to study how natural selection shaped the morphology of Caribbean Anolis lizards (Losos ), and then correlated the phylogenetic placements of shifts in OU optima to habitat changes.…”

The Geography of Ecological Niche Evolution in Mammals

“…the appearance of similar niches in independent lineages-is the result of natural selection acting on niche-related species traits ('traits' hereafter) and contrasts with neutral evolution [1][2][3][4]. While trait convergences are recognized as being of importance at the species scale, we still know little about the impact of species convergence on the overall trait and niche structure of entire biotas at large spatial scales [5].…”

“…However, parallelism and convergence are part of a continuum, hampering any clear distinction among them [1,4], thus, we use the term convergence for all phylogenetic scales (as proposed by ref [4], 'parallelism' should be restricted to characterize the degree of molecular similarities underlying phenotypic convergences). Convergent evolution leads to higher ecological niche and trait similarity between unrelated species than expected under neutral evolution, where niches or traits shift along a continuous axis or between discrete states in a random way through evolutionary time [2,3,6,7]. While these neutral-like evolution can be generated by randomly fluctuating natural selection [8] typical random walk models still represent the most realistic macroevolutionary models of neutral evolution so far.…”

Trait‐specific processes of convergence and conservatism shape ecomorphological evolution in ground‐dwelling squirrels

“…This approach is similar to previous studies (Mahler et al. ; Ingram and Kai ) except that the test statistic was the mean of squared among‐species distances within dietary groups (i.e., their disparity, or cohesion in morphospace), rather than similarities between individual species pairs presumed to be convergent. The former is more appropriate for our dataset because the majority of ecological and morphological diversity occurs above the species level in Marmotini.…”