Hendry A P, Day T, Cooper A B
Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
Am Nat. 2001 Apr;157(4):387-407. doi: 10.1086/319316.
Existing optimality models of propagule size and number are not appropriate for many organisms. First, existing models assume a monotonically increasing offspring fitness/propagule size relationship. However, offspring survival during certain stages may decrease with increasing propagule size, generating a peaked offspring fitness/propagule size function (e.g., egg size in oxygen-limited aquatic environments). Second, existing models typically do not consider maternal effects on total reproductive output and the expression of offspring survival/propagule size relationships. However, larger females often have greater total egg production and may provide better habitats for their offspring. We develop a specific optimality model that incorporates these effects and test its predictions using data from salmonid fishes. We then outline a general model without assuming specific functional forms and test its predictions using data from freshwater fishes. Our theoretical and empirical results illustrate that, when offspring survival is negatively correlated with propagule size, optimal propagule size is larger in better habitats. When larger females provide better habitats, their optimal propagule size is larger. Nevertheless, propagule number should increase more rapidly than propagule size for a given increase in maternal size. In the absence of density dependence, females with greater relative reproductive output (i.e., for a given body size) should produce more but not larger propagules.
现有的繁殖体大小和数量最优模型并不适用于许多生物。首先，现有模型假定后代适合度/繁殖体大小关系呈单调递增。然而，在某些阶段，后代存活率可能会随着繁殖体大小的增加而降低，从而产生一个峰值后代适合度/繁殖体大小函数（例如，在氧气受限的水生环境中的卵大小）。其次，现有模型通常不考虑母体效应在总繁殖输出以及后代存活率/繁殖体大小关系的表达方面的作用。然而，体型较大的雌性通常具有更高的总产卵量，并且可能为其后代提供更好的栖息地。我们开发了一个纳入这些效应的特定最优模型，并使用鲑科鱼类的数据来检验其预测结果。然后，我们概述了一个不假定特定函数形式的通用模型，并使用淡水鱼的数据来检验其预测结果。我们的理论和实证结果表明，当后代存活率与繁殖体大小呈负相关时，在更好的栖息地中最优繁殖体大小更大。当体型较大的雌性提供更好的栖息地时，它们的最优繁殖体大小更大。尽管如此，对于母体大小的给定增加，繁殖体数量的增加应该比繁殖体大小的增加更快。在不存在密度依赖的情况下，具有更高相对繁殖输出（即对于给定的体型）的雌性应该产生更多但不是更大的繁殖体。
