De Bona Sebastiano, Sidhu Karendeep, Enroth Hanna M, López-Sepulcre Andrés
Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
Department of Biology, Bryn Mawr College, Bryn Mawr, Pennsylvania, USA.
Ecology. 2025 Jul;106(7):e70151. doi: 10.1002/ecy.70151.
Individual responses to density perturbations often depend on individual size or stage, and can include demographic changes (survival, reproduction, growth) and spatial responses (dispersal, habitat shift). While these responses are well characterized, their interaction is seldom considered. Size-specific effects of density can result from size- or stage-specific spatial responses mediated by dominance interactions: subordinate individuals might suffer disproportionately from overcrowding conditions if displaced from high-quality habitats by dominant individuals. To investigate this, we performed an experiment in wild guppies where we observed demographic and spatial responses to density manipulations and tested for an interaction between them. We found recruitment, growth, and female survival to be decreased at high density. Dispersal was costly, causing a reduction of body condition and growth. Shifts in microhabitat use with density were size-dependent: at increased density, large individuals were more likely to remain in a microhabitat, while small individuals were likely to move and suffer reduced growth. At decreased density, growth improved when remaining in the same microhabitat (for large individuals) or moving to a different one (for small individuals). Our results show that regulation under density perturbation can occur through asymmetric interactions that disproportionately affect smaller individuals.
个体对密度扰动的反应通常取决于个体大小或发育阶段，可能包括种群统计学变化（生存、繁殖、生长）和空间反应（扩散、栖息地转移）。虽然这些反应已有充分描述，但它们之间的相互作用却很少被考虑。密度的大小特异性效应可能源于由优势相互作用介导的大小或阶段特异性空间反应：如果从属个体被优势个体从优质栖息地排挤出去，它们可能会在拥挤条件下遭受更大的痛苦。为了对此进行研究，我们在野生孔雀鱼身上进行了一项实验，观察它们对密度操纵的种群统计学和空间反应，并测试它们之间的相互作用。我们发现，在高密度下，补充量、生长和雌性存活率会下降。扩散成本高昂，会导致身体状况和生长的下降。微生境利用随密度的变化取决于个体大小：在密度增加时，大型个体更有可能留在微生境中，而小型个体则可能移动并生长减缓。在密度降低时，如果留在相同的微生境（对于大型个体）或转移到不同的微生境（对于小型个体），生长会得到改善。我们的结果表明，在密度扰动下的调节可以通过对较小个体产生不成比例影响的不对称相互作用来实现。
