Evolutionary mechanisms underlying divergence in bill morphology and the timing of breeding using whole genome analysis

利用营养生态位的广泛排列，动物进化成了极其多样化的形式，这一过程可以由进化机制和可用生态位的限制来控制。形式的多样性及其相互作用确保了生态系统的运转，构成了生命最基本的基础之一。为了充分理解生物多样性的起源，我们需要了解物种形成，这是一个基本的进化过程。类群之间的亲缘关系仍然足够密切，以产生可存活的后代，物种形成可以通过渐进杂交来促进，它提供了适应和生殖隔离的基因。Pron(Pachyptila spp.)海鸟以喙的形态(由细到宽，有或没有片羽)和不同的繁殖时间表来区分。该属包括一个快速的上更新世辐射，其特征是不完全的生殖隔离，这表现为种间的渐渗。虽然通过同倍体杂交(HHS)在动物中形成物种被认为是极其罕见的，因为作为杂交产物建立生殖隔离是不常见的，但我们先前已经表明，中等嘴部的塞尔文(P.Salvini)可能是窄嘴型南极Pron(P.desolata)和宽嘴型Prion(P.vittata)(Mol.Biol.Evol.36：1671-1685)之间的杂交物种。然而，与大多数杂交物种不同的是，塞尔文的普里恩具有表型中间性状，这表明仅有不同亲本性状的加性就可以直接导致杂交适合度和生殖隔离的增加。这种杂交可能导致提高杂交适合度和生殖隔离，这表明某些基因或基因组在这些海鸟中具有多效性作用，然而另一方面，中间杂交表型反对通过分歧岛形成物种的概念，这是最近对几个杂交系统进化的假设。鉴于Pachyptila系统的耐人寻味的性质，包括通过发散和引入的物种形成，后者可能导致相加的杂交表型，我们建议使用该属作为一个模型，首先检验Pachyptila Salvini的同倍体杂交物种形成的假说，然后使用整个基因组来量化该系统的适应性变异。

Animals have evolved into a huge diversity of forms exploiting a wide arrangement of trophic niches, a process that can be controlled by evolutionary mechanisms and limits on available ecological niches. The diversity of forms and their interactions ensure the functioning of the ecosystems, forming one of the most essential bases of life. To fully comprehend the origin of biodiversity, we need to understand speciation, a fundamental evolutionary process. Between taxa still sufficiently closely related to produce viable offspring, speciation may be facilitated by introgressive hybridization, which provides genes for both adaptation and reproductive isolation. Prions (Pachyptila spp.) are seabirds distinguished by bill morphology (thin to broad, with or without lamellae) and distinct breeding schedules. The genus comprises a rapid Plio-Pleistocene radiation characterised by incomplete reproductive isolation, which manifests itself in inter-specific introgression. Although speciation through homoploid hybridization (HHS) is considered extremely rare in animals because the establishment of reproductive isolation as a product of hybridization is uncommon, we have shown previously that the medium-billed Salvin’s prion (P. salvini) could be a hybrid species between the narrow-billed Antarctic prion (P. desolata) and broad-billed prion (P. vittata) (Mol.Biol.Evol.36:1671–1685). However, unlike most hybrid species, Salvin's prion possesses phenotypically intermediate traits, suggesting that additivity of divergent parental traits alone can lead directly to both increased hybrid fitness and reproductive isolation. That hybridisation could lead to increased hybrid fitness and reproductive isolation, suggests the pleiotropic action of certain genes or groups of genes among these seabirds, however on the other hand, intermediate hybrid phenotypes speak against the notion of speciation through divergence islands, a recent idea previously hypothesised for the evolution of several hybrid systems. Given the intriguing nature of the Pachyptila system, comprising speciation through both divergence and introgression, and with the latter potentially leading to additive hybrid phenotypes, we propose using this genus as a model to first test the hypothesis of homoploid hybrid speciation for P. salvini and secondly to quantify adaptive variation with this system using whole genomes.