Robinson-Wolrath S I, Owens I P F
Department of Zoology and Entomology, University of Queensland, St Lucia, Queensland, Australia.
J Evol Biol. 2003 Nov;16(6):1106-14. doi: 10.1046/j.1420-9101.2003.00615.x.
Differences between island- and mainland-dwelling forms provide several classic ecological puzzles. Why, for instance, are island-dwelling passerine birds consistently larger than their mainland counterparts? We examine the 'Dominance hypothesis', based on intraspecific competition, which states that large size in island passerines evolves through selection for success in agonistic encounters. We use the Heron Island population of Capricorn silvereyes (Zosterops lateralis chlorocephalus), a large-bodied island-dwelling race of white-eye (Zosteropidae), to test three assumptions of this hypothesis; that (i) large size is positively associated with high fitness, (ii) large size is associated with dominance, and (iii) the relationship between size and dominance is particularly pronounced under extreme intraspecific competition. Our results supported the first two of these assumptions, but provided mixed evidence on the third. On balance, we suggest that the Dominance Hypothesis is a plausible mechanism for the evolution of large size of island passerines, but urge further empirical tests on the role of intraspecific competition on oceanic islands versus that on mainlands.
岛屿物种与大陆物种之间的差异带来了几个经典的生态谜题。例如，为什么栖息在岛屿上的雀形目鸟类总是比它们在大陆上的同类体型更大？我们研究了基于种内竞争的“优势假说”，该假说认为岛屿雀形目鸟类的大体型是通过在争斗中选择成功而进化而来的。我们利用赫伦岛的摩羯座银眼鸟（Zosterops lateralis chlorocephalus）种群进行研究，它是白眼鸟（Zosteropidae）的一个大体型岛屿栖息亚种，以检验该假说的三个假设：（i）大体型与高适合度呈正相关，（ii）大体型与优势地位相关，（iii）在极端种内竞争下，体型与优势地位之间的关系尤为明显。我们的结果支持了前两个假设，但对第三个假设的证据则好坏参半。总体而言，我们认为优势假说可能是岛屿雀形目鸟类大体型进化的一种机制，但敦促对种内竞争在海洋岛屿与大陆上所起的作用进行进一步的实证检验。
