DISENTANGLING THE MECHANISMS OF ECOLOGICAL SPECIATION IN SYMPATRIC PALM SPECIES

物种如何起源和分化是生物学中的关键问题之一。地理隔离导致的分化是物种形成的一个众所周知的驱动力，但在理论上，在没有地理隔离的情况下，种群也可能分化为不同的物种，这种机制通常被称为伴随着基因流动的物种形成。记录在案的初始基因流动非常高的病例仍然很少。Savolainen等人。在对Howea属两种棕榈树的案例研究中提供了令人信服的证据，这两种棕榈树是塔斯曼海豪伯爵岛(LHI)严格特有的棕榈树。尽管这个案例研究被许多人认为可能是迄今为止共域物种形成最令人信服的例子之一，但它仍然受到激烈的辩论。当不同选择下的生态性状(例如，土壤偏好或觅食行为)和与种类交配相关的性状(例如，开花时间或体型)在遗传上相关时，面对高基因流动的物种形成最容易发生。这两种棕榈树有不同的开花时间高峰，并具有与底物偏好相关的相反的分布：Belmore ana仅限于较老的火山岩，而H.forsteriana主要生长在石灰性土壤上，但也生长在受干扰的地点的火山土上。鉴于这些特点，提出了生态物种形成的设想。然而，尽管生态物种形成被认为是生物多样性的主要来源，但这一过程背后的遗传基础仍然知之甚少。在此，我们将在我们以前研究的基础上，确定共生的Howea棕榈树进化中生殖隔离的机制，并确定物种形成的基因。

How species originate and diverge from their progenitor is one of the key questions in biology. Divergence resulting from geographical isolation is a well-known driving force of speciation, but in theory populations could also diverge into separate species in the absence of geographical isolation, a mechanism generally referred to as speciation with gene flow. Documented cases with very high initial gene flow remain rare. Savolainen et al. provided compelling evidence for in situ speciation in a case study of two species of palm in the genus Howea, H. forsteriana and H. belmoreana, strictly endemic to the minute Lord Howe Island (LHI) in the Tasman Sea. Although this case study is viewed by many as probably one of the most convincing examples of sympatric speciation to date, it has still been hotly debated. Speciation in the face of high gene flow would occur most readily when ecological traits under divergent selection (e.g. soil preference or foraging behaviour) and traits associated with assortative mating (e.g. flowering time or body size) are correlated genetically. The two Howea palm species have distinct peaks of flowering time and have contrasting distributions related to substrate preferences: H. belmoreana is restricted to the older volcanic rocks, whereas H. forsteriana grows predominantly on calcareous soils but also on volcanic soils in disturbed sites. Given these features, a scenario for ecological speciation has been proposed. However, although ecological speciation is thought to be a major generator of biodiversity, the genetic basis behind this process is still poorly understood. Here, building on our previous research, we will determine the mechanisms of reproductive isolation in the evolution of sympatric Howea palms and identify the genes underlying speciation.