Neuroethological Basis to Evolution of New Olfactory Communication Systems

在大多数蛾类物种中寻找配偶涉及通过雌性发出的性信息素进行长距离信号传递，这些信息素已被证明包括化学结构的巨大多样性，即使在密切相关的物种中也是如此。这些通信信号在物种的配偶识别系统中的重要性支持了物种特异性信号的进化参与物种形成过程的观点。 然而，难题是信号发散是如何发生的，因为信息素通信系统似乎对信息素混合物中的任何变化都具有很强的抵抗力。 一个令人惊讶的发现，一个不活跃的基因在性信息素腺体的女性欧洲玉米螟，如果它被激活，可以用来产生不同的信息素化合物，揭示了一些重大转变可以发生在信息素生产。 这个基因不仅存在，但活跃，在信息素腺体的密切相关，最近（约。100万年前）进化出亚洲玉米螟物种，并创造了亚洲玉米螟雌性使用的不同混合物。 同样令人感兴趣的是，在实验室种群中，3%的雄性欧洲玉米螟（罕见的雄性）不仅能够被它们自己的雌性信息素成分所吸引，而且还能够被亚洲玉米螟雌性所释放的不同成分所吸引。 这些广泛响应的男性可能正是祖先群体中的类型，可以慢慢地，经过几代人，跟踪女性散发新的信息素混合物，然后发展出对新混合物的偏好。 转向喜欢新的混合物也可能包括对以前的一些化合物的抑制作用的发展，以关闭这些雄性对原始祖先信息素的吸引力。 这将为来自祖先种群的雄性缓慢地追踪到新的信息素混合物提供基础，可能与原始祖先信息素混合物的一些拮抗作用有关。为了了解雄蛾如何能够将它们的信息素反应从一种混合物转移到另一种由不同化合物组成的混合物，需要对正常和罕见的欧洲玉米螟雄性和亚洲玉米螟雄性进行比较研究。 这项研究将包括行为和电生理反应有吸引力的信息素成分，也化合物抑制这些男性的吸引力，以表征嗅觉受体的差异，将允许发生的转变。 预计欧洲玉米螟中现有受体的特异性和激动剂/拮抗剂性质的变化已经发生，以产生在亚洲玉米螟雄性中发现的受体谱。将进行更多的研究来检验这一假设，即一个主基因控制着罕见的雄性表型，并且该表型的群体频率可以通过选择来增加。 上述所有数据应该有助于阐明信息素混合物如何改变，并反过来影响新物种的进化。

Mate finding in most moth species involves long-distance signaling via female-emitted sex pheromones, which have been shown to include a great diversity of chemical structures, even amongst closely related species. The critical importance of these communication signals in the mate recognition system of a species supports the idea that the evolution of the species-specific signals is involved in the speciation process. The conundrum, however, is how signal divergence has occurred because pheromone communication systems appear to possess strong resistance to any changes in the pheromone blends. A surprising discovery of an inactive gene in the sex pheromone gland of female European corn borers that, if it were activated, could be used to produce different pheromone compounds, has shed some light on how major shifts can occur in pheromone production. This gene is not only present, but is active, in the pheromone gland of a closely related and recently (ca. 1 million yrs. ago) evolved species, Asian corn borer, and creates the different blend used by Asian corn borer females. Of equal interest is that 3% of the male European corn borers (rare males) in a laboratory population possess the ability to be attracted to not only to their own females' pheromone components, but also to the much different ones emitted by Asian corn borer females. These broadly responding males might be exactly the type in an ancestral population that could slowly, over generations, track females emitting the new pheromone blend and then develop a preference for the new blend. The shift to preferring the new blend might also include development of inhibition to some of the previous compounds to shut down the attraction of these males to the original ancestral pheromone. This would provide the basis for males from the ancestral population to track slowly over to the new pheromone blend, possibly with some antagonism developing for the original ancestral pheromone blend. In order to understand how male moths can shift their pheromone response from one blend to that of another composed of different compounds requires a comparative study of normal and rare European corn borer males and also Asian corn borer males. The study will include behavioral and electrophysiological responses to attractive pheromone components and also compounds inhibiting attraction of these males to characterize olfactory receptor differences that would allow the shift to occur. It is anticipated that changes in specificity and agonist/antagonist properties of existing receptors in the European corn borer have occurred to generate receptor profiles found in Asian corn borer males. Additional studies will be conducted to test the hypothesis that a major gene controls the rare male phenotype, and that the population frequency of the phenotype can be increased through selection. All the data above should help to shed light on how pheromone blends can change, and, in turn, influence the evolution of new species.