Isolating a role for natural selection in speciation:: Host adaptation and sexual isolation in Neochlamisus bebbianae leaf beetles
Isolating a role for natural selection in speciation:: Host adaptation and sexual isolation in Neochlamisus bebbianae leaf beetles
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DOI：
10.2307/2411347
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发表时间：
1998-12-01
期刊：
影响因子：
3.3
通讯作者：
Funk, DJ
中科院分区：
文献类型：
--
作者：
Funk, DJ
Muller (1942) 和 Mayr (1963) 假设自然选择通过引起多效性促进合子前或合子后不相容性的适应性遗传分化，间接导致异域种群之间生殖障碍的进化。在这种机制下，如果食草昆虫种群适应不同的寄主植物，它们应该更容易形成物种，因为生殖隔离的进化速度将超过遗传漂变和独立于寄主的选择来源所促进的速度。尽管穆勒-迈尔假说被广泛接受，但几乎没有收集到直接证据来支持选择在异域物种形成中的作用。本文提供了一种分离和评估寄主植物相关的自然选择压力对异地食草动物种群之间生殖隔离的贡献的方法。寄主相关选择假说（HRSH）预测，在其他条件相同的情况下，使用不同寄主植物的食草动物种群应该比使用相同寄主植物的食草动物种群更具生殖隔离性。在这里，我使用 Neochlamisus bebbianae 来测试这个假设，Neochlamisus bebbianae 是一种寡食性叶甲虫，其宿主范围在地理上有所不同。在两组实验中（对比 I、对比 II），我比较了自然界中使用相同宿主 (Acer) 的两个甲虫种群（乔治亚州和纽约州）和本地使用不同宿主的第三个种群（俄克拉荷马州的桦木 [CI]、安大略省的柳树 [CII]）。实验表明，“不同寄主”种群在寄主使用特征（产卵、寄主保真度、摄食反应、幼虫表现）方面比“同一寄主”种群有更强的差异，并且每个种群最容易使用来自其本地寄主的叶子。正如 HRSH 预测的那样，适应性分化的不同宿主种群（桦木与枫树、柳树与枫树）之间的性隔离也比同一宿主种群（枫树）之间的性隔离更大，后者在宿主使用特征上没有差异。在测试种群的 mtDNA 序列提供的历史背景下解释这些结果表明：（1）枫树和桦木相关的贝氏猪笼草代表了不同的兄弟物种，其因果关系起源已被历史遗忘，其不完全的性隔离因宿主相关的生态和“生理”隔离而得到加强； (2) 早期形成的 Acer 和 Salix 相关种群比这两个 Acer 相关种群彼此之间的关系更密切，这与 HRSH 一致。因此，这项研究说明了宿主相关选择对生殖隔离的起源和维持的影响。更重要的是，它提供了证据表明自然选择的多效性促进了异域物种形成。
Muller (1942) and Mayr (1963) hypothesized that natural selection indirectly causes the evolution of reproductive barriers between allopatric populations by causing adaptive genetic divergence that pleiotropically promotes prezygotic or postzygotic incompatibility. Under this mechanism, herbivorous insect populations should be more prone to speciate if they are adapting to different host plants, because the evolution of reproductive isolation will be accelerated above the rate promoted by genetic drift and host-independent sources of selection alone. Although the Muller-Mayr hypothesis is widely accepted, little direct evidence has been collected in support of selection's role in allopatric speciation. This paper offers a method for isolating and evaluating the contribution of host plant-related natural selection pressures to the reproductive isolation between allopatric herbivore populations.The host-related selection hypothesis (HRSH) predicts that herbivore populations using different host plants should be more reproductively isolated than those using the same host, other things being equal. Here, I test this hypothesis using Neochlamisus bebbianae, an oligophagous leaf beetle with a geographically variable host range. In each of two sets of experiments (contrast I, contrast II), I compared two beetle populations (Georgia and New York) that use the same host (Acer) in nature and a third population that natively uses a different host (Betula in Oklahoma [CI], Salix in Ontario [CII]). Experiments showed that "different-host" populations were more strongly differentiated in host-use traits (oviposition, host fidelity, feeding response, larval performance) than were "same-host" populations and that each population most readily uses foliage from its native host. As predicted by the HRSH, sexual isolation was also greater between the adaptively divergent different-host populations (from Betula vs. Acer, from Salix vs. Acer) than between the same-host populations (from Acer), which were undifferentiated in host-use traits.Interpreting these results in a historical context provided by mtDNA sequences from test populations indicated: (1) that Acer- and Betula-associated N. bebbianae represent separate sibling species whose causal origins have been lost to history, and whose incomplete sexual isolation is fortified by host-associated ecological and "physiological" isolation; and (2) that incipiently speciating Acer- and Salix-associated populations are more closely related to each other than are the two Acer-associated populations, which is consistent with the HRSH. This study thus illustrates the consequences of host-related selection for both the origin and maintenance of reproductive isolation. More important, it provides evidence that the pleiotropic effects of natural selection promote allopatric speciation.