The behavioral ecology of threshold evolution in a polyphenic beetle
The behavioral ecology of threshold evolution in a polyphenic beetle
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DOI：
10.1093/beheco/arg062
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发表时间：
2003-11-01
影响因子：
2.4
通讯作者：
Moczek, AP
中科院分区：
文献类型：
--
作者：
Moczek, AP
替代男性形态的兼性表达被认为允许个体男性选择具有最高适应性增益的表型，因为相对于他们竞争女性的其他男性，他们具有竞争地位。变体的选择或切换通常依赖于发育阈值反应。发育阈值反应的进化变化被认为是表型多样化和形态和行为新奇性进化的重要途径。然而，在何种程度上替代男性表型和其潜在的阈值反应，实际上在自然种群的演变是不清楚的。同样，生态因素，形状的阈值响应在自然种群的演变是未开发的大多数生物，因为是这样的修改形态多样性模式的后果。我研究了外来种群的角多形粪甲虫Onthophagus taurus的快速阈值进化的生态基础。雄性O.金牛座的身体大小随着幼虫的喂养条件而不断变化。只有超过临界身体尺寸的雄性在头上长出一对长角，而低于这个阈值的雄性仍然没有角。该物种的两个异国情调的范围内，美国东部和澳大利亚西部的人口，已经分歧的平均阈值身体大小，这导致了高度分歧和新的角的长度，身体大小异速生长在这些人群的演变。在第三个和以前未研究的外来范围的O。澳大利亚东部的金牛座的阈值体型大致介于美国东部和澳大利亚西部种群之间。我测试了三个假设来解释生态和人口因素的差异如何驱动种群之间的异速生长差异，使用的数据来自每个外来范围内大量种群的比较，标准化抽样。结果表明，在两个内部和种间竞争的强度差异，在这些人群中的分歧阈值的演变作出了贡献。我的研究结果不支持的假设，阈值的身体大小，以更大的身体大小的变化是一个结果，在平均身体大小的竞争男性的增加。我讨论我的研究结果的背景下Onthophagus交配系统和阈值进化的进化意义。
Facultative expression of alternative male morphologies is thought to allow individual males to select the phenotype with the highest fitness gain given their competitive status relative to other males with which they compete for females. Choice of, or switching between, morphs commonly relies on developmental threshold responses. Evolutionary changes in developmental threshold responses are thought to provide an important avenue for phenotypic diversification and the evolution of morphological and behavioral novelties. However, the extent to which alternative male phenotypes and their underlying threshold responses actually evolve in natural populations is unclear. Likewise, the ecological factors that shape the evolution of threshold responses in natural populations are unexplored for most organisms, as are the consequences of such modifications for patterns of morphological diversity. I examined the ecological basis of rapid threshold evolution in exotic populations of the horn-polyphenic dung beetle Onthophagus taurus. Male O. taurus vary continuously in body size as a function of larval feeding conditions. Only males that exceed a critical threshold body size develop a pair of long horns on their heads, whereas males below this threshold remain hornless. Populations in two exotic ranges of this species, the eastern United States and western Australia, have diverged in the mean threshold body size, which has resulted in the evolution of highly divergent and novel horn length-body size allometries in these populations. Populations in a third and previously unstudied exotic range of O. taurus in eastern Australia exhibit threshold body sizes roughly intermediate between the eastern U.S. and western Australian populations. I tested three hypothesis to explain how differences in ecological and demographic factors can drive allometric divergences between populations, using data derived from comparative, standardized sampling of a large number of populations in each exotic range. Results suggest that differences in the intensity of both intra- and interspecific competition have contributed to the evolution of divergent thresholds in these populations. My results do not support the hypothesis that shifts in threshold body sizes to larger body sizes are a consequence of increases in the mean body size of competing males. I discuss my results in the context of Onthophagus mating systems and the evolutionary implications of threshold evolution.