Stirling G, Roff DA
Department of Biology, McGill University
Anim Behav. 2000 May;59(5):929-941. doi: 10.1006/anbe.1999.1386.
The swimming behaviour of adult Daphnia largely governs their depth, which has a direct effect on both individual foraging success and predation avoidance. We treated individual swimming behaviour as a threshold character and used directional changes in average clonal depth within experimental tubes as a test for character plasticity. We compared the swimming behaviours of two cohabiting, phenotypically similar Daphnia (Daphnia galeata and Daphnia galeata-Daphnia rosea hybrid) to determine (1) whether there is inherited variation (H(2)) for different traits (responses to hunger and predator cues); (2) whether changes in genetic parameters (norm of reaction and character state) across four environments could be simulated by combinations of the presence or absence of a predator cue and high or low hunger levels; and (3) whether these Daphnia would respond to directional selection, particularly in a trade-off environment (high hunger and predator cue treatments). Responses of both D. galeata and the D. galeata-rosea hybrid to hunger and a predator cue and the trade-off environment were plastic. Daphnia galeata expressed significant genetic variation within (H(2)) and between environments (heritability of plasticity). Both the character state and norm of reaction estimates of heritable variation in the hybrid were close to zero. Genetic correlations were positive and stable across six environmental pairs in Daphnia galeata. Most hybrid genetic correlations were not significant. The phenotypic distributions of both D. galeata and the hybrid were bimodal in the trade-off environment. The D. galeata distribution was partly due to between-clone variation and the hybrid distribution was almost entirely due to within-clone variation. Genetic variation expressed by D. galeata in the trade-off environment appears to depend on both clone by environment interactions and stable inherited differences. These results indicate that while plastic phenotypic responses cause a similar opportunity for selection in D. galeata and the hybrid, their responses to selection would be different in the trade-off and in related environments. Copyright 2000 The Association for the Study of Animal Behaviour.
成年水蚤的游泳行为在很大程度上决定了它们所处的深度，这对个体觅食成功率和避免被捕食都有直接影响。我们将个体游泳行为视为一个阈值性状，并将实验管内平均克隆深度的方向变化作为性状可塑性的测试。我们比较了两种同居的、表型相似的水蚤（盔形溞和盔形溞 - 玫瑰溞杂交种）的游泳行为，以确定：（1）不同性状（对饥饿和捕食者线索的反应）是否存在遗传变异（H(2)）；（2）四种环境下遗传参数（反应规范和性状状态）的变化是否可以通过有无捕食者线索以及高或低饥饿水平的组合来模拟；（3）这些水蚤是否会对定向选择做出反应，特别是在权衡环境（高饥饿和捕食者线索处理）中。盔形溞和盔形溞 - 玫瑰溞杂交种对饥饿、捕食者线索和权衡环境的反应都是可塑性的。盔形溞在环境内部（H(2)）和环境之间都表现出显著的遗传变异（可塑性的遗传力）。杂交种中可遗传变异的性状状态和反应规范估计值都接近于零。盔形溞在六个环境对中的遗传相关性是正的且稳定的。大多数杂交种的遗传相关性不显著。在权衡环境中，盔形溞和杂交种的表型分布都是双峰的。盔形溞的分布部分归因于克隆间变异，而杂交种的分布几乎完全归因于克隆内变异。盔形溞在权衡环境中表现出的遗传变异似乎取决于克隆与环境的相互作用以及稳定的遗传差异。这些结果表明，虽然可塑性表型反应在盔形溞和杂交种中产生了类似的选择机会，但它们在权衡和相关环境中对选择的反应会有所不同。版权所有2000动物行为研究协会。
