Individual variation in growth trajectories: phenotypic and genetic correlations in ontogeny of the house finch (Carpodacus mexicanus)

Abstract

We studied patterns of growth in a recently established natural population of the house finch (Carpodacus mexicanus) to examine whether phenotypic and genetic covariation among age‐specific trait values is likely to constrain morphological change favoured by selection acting on adults. We found variable patterns of allometric relationships during ontogeny, and documented relatively weak covariations among ages or among traits in individual growth trajectories. Frequent compensatory growth largely cancelled out the initial differences among nestlings, potentially enabling house finches to raise offspring under diverse and unpredictable environmental conditions. Moderate levels of additive genetic variance in morphological traits throughout ontogeny, and relatively low and fluctuating phenotypic and genetic covariation among ages imply strong potential for evolutionary change in morphological traits under selection. This conclusion is consistent with the profound population‐level divergence in morphological patterns that accompanied very successful colonization of most of North America by the house finch over the last 50 years.

Genetic covariance structure of growth in the salamander Ambystoma macrodactylum

“…This empirical evidence seems to suggest that in vertebrates, pronounced trade-offs for growth across ages are rare (but see Badyaev and Martin, 2000), and that the developmental processes that determine body size are often highly integrated across ontogeny. The general form of the genetic covariance functions described in this study may be relatively common across a broad range of taxa, but the evolutionary implications of genetic constraints on growth are an empirical issue based on specific selective environments.…”

“…There is a fairly extensive body of literature on the quantitative genetics of growth in laboratory and domesticated animals (Roberts, 1961;Timon and Eisen, 1969;Atchley and Rutledge, 1980;Cheverud et al, 1983;Leamy and Cheverud, 1984;Kirkpatrick and Lofsvold, 1992;Meyer, 1998a;Rocchetta et al, 2000), but few studies have attempted to quantify the genetic component of phenotypic variation for growth in natural populations (but see Bjö rklund, 1997;Badyaev and Martin, 2000). Here we explore quantitative genetic variation for growth trajectories in a natural population of the longtoed salamander (Ambystoma macrodactylum columbianum) in order to (1) characterize the genetic covariance structure of growth in a natural population and (2) identify any constraints that genetic architecture may place on the evolution of the growth trajectories.…”

Sexual Dimorphism in Relation to Current Selection in the House Finch

“…Consequently, recently established house finch populations strongly differed in the patterns of sexual dimorphism (Badyaev and Hill 2000a). Second, the analysis of phenotypic and genetic variation in the house finch growth revealed that, in contrast to other carduelines (e.g., Badyaev 1994; Bjö rklund 1993), house finch ontogeny is the least constrained (Badyaev and Martin 2000). Low and variable among-age and among-trait phenotypic and genetic covariations and moderate levels of additive genetic variance throughout the ontogeny (Badyaev and Martin 2000) imply significant potential for the evolutionary change, especially under the strong short-term selection that is likely to accompany colonization.…”

Faster Is Not Always Better: Selection on Growth Rate Fluctuates across Life History and Environments

“…Superficially, this might suggest that selection has ample scope to optimize colony growth rates throughout ontogeny, but correlations among age-specific values restrict this variation to only a subset of underlying dimensions that can be targeted independently, thereby limiting the ways in which selection can potentially act. Such a lack of independent variation among age-specific growth rates has been reported for other taxa (e.g., Kirkpatrick and Lofsvold 1992;Badyaev and Martin 2000). Its further impact on Hippopodina, however, is to render substantial amounts of growth-rate variation unavailable to selection, since virtually all of the selection on colony growth rates within any environment was confined to a single dimension of ontogeny, which excluded more than a third of their variation from midsuccession onward.…”

“…Growth rates tend to decline with increasing size and age due to the rising costs of maintaining existing biomass or the diversion of fixed resources to other vital functions such as reproduction (West et al 2001;Rose et al 2009). Since individuals can differ in the timing, magnitude, and speed of this decline, another framework for understanding the evolution of growth rates has focused on phenotypic or genetic covariation among age-specific values (Kirkpatrick and Lofsvold 1992;Badyaev and Martin 2000), which may restrict variation in the direction of selection in much the same manner as correlations among disparate traits. Age-specific variation in size or growth is often interpreted in the context of compensatory (catch-up) responses to periods of resource limitation, which are presumed to be adaptive (Mangel and Munch 2005).…”