Letcher Benjamin H, Coombs Jason A, Nislow Keith H
S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center Turners Falls, MA, USA.
S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center Turners Falls, MA, USA ; Program in Organismic and Evolutionary Biology, University of Massachusetts Amherst, MA, USA.
Evol Appl. 2011 Jul;4(4):602-15. doi: 10.1111/j.1752-4571.2011.00184.x. Epub 2011 Mar 8.
Phenotypic variation in body size can result from within-cohort variation in birth dates, among-individual growth variation and size-selective processes. We explore the relative effects of these processes on the maintenance of wide observed body size variation in stream-dwelling brook trout (Salvelinus fontinalis). Based on the analyses of multiple recaptures of individual fish, it appears that size distributions are largely determined by the maintenance of early size variation. We found no evidence for size-dependent compensatory growth (which would reduce size variation) and found no indication that size-dependent survival substantially influenced body size distributions. Depensatory growth (faster growth by larger individuals) reinforced early size variation, but was relatively strong only during the first sampling interval (age-0, fall). Maternal decisions on the timing and location of spawning could have a major influence on early, and as our results suggest, later (>age-0) size distributions. If this is the case, our estimates of heritability of body size (body length = 0.25) will be dominated by processes that generate and maintain early size differences. As a result, evolutionary responses to environmental change that are mediated by body size may be largely expressed via changes in the timing and location of reproduction.
体型的表型变异可能源于同批个体出生日期的变异、个体间生长差异以及大小选择过程。我们探究了这些过程对溪流栖息的溪红点鲑（Salvelinus fontinalis）中观察到的广泛体型变异维持的相对影响。基于对个体鱼多次重捕的分析，体型分布似乎很大程度上由早期体型变异的维持所决定。我们没有发现大小依赖的补偿性生长（这会减少体型变异）的证据，也没有发现大小依赖的生存对体型分布有实质性影响的迹象。非补偿性生长（较大个体生长更快）强化了早期体型变异，但仅在第一个采样间隔（0龄，秋季）期间相对较强。母体关于产卵时间和地点的决策可能对早期以及如我们结果所示的后期（>0龄）体型分布有重大影响。如果是这样，我们对体型遗传力（体长 = 0.25）的估计将主要由产生和维持早期体型差异的过程主导。因此，由体型介导的对环境变化的进化反应可能很大程度上通过繁殖时间和地点的变化来体现。
