QTL Mapping of Reproductive Isolation in Louisiana Irises

生殖隔离的进化在物种形成过程中至关重要，因为正是基因流动的停止，最终将不同的谱系置于不同的进化道路上，从而成为新的物种。物种形成和生殖隔离是如何发生的，取决于导致隔离的基因数量，以及合子前和合子后生殖障碍的相对重要性。确定涉及的基因的数量和大小也可以阐明物种形成所需的自然选择的时间和强度。我们将研究路易斯安那州蝴蝶花生殖隔离的遗传基础，这是一个近一个世纪来生态、遗传和进化研究的焦点。我们将构建一个QTL(数量性状基因座)图谱，用于区分两个物种，即蝴蝶花和短毛蝴蝶。我们的分析将定位对繁殖的交配前和交配后障碍的表达有最大影响的QTL。与交配前障碍相关的特征包括花卉差异，导致大黄蜂优先访问I.brevicaulis，蜂鸟优先访问I.fulva(例如，开花时间、花色、花蜜导向形状、花蜜糖浓度)。与交配后障碍相关的特征包括(I)配子竞争(即同种花粉管生长更快，从而使胚珠受精比来自交替物种的花粉管更有效)和(Ii)两个物种之间形成的杂种的花粉可育性。

0074159ArnoldThe evolution of reproductive isolation is critically important in the speciation process, because it is cessation of gene flow that definitively places diverging lineages onto separate evolutionary paths towards becoming new species. How speciation and reproductive isolation occur depends on the number of genes conferring isolation and the relative importance of pre- vs. post-zygotic reproductive barriers. Identifying the number and magnitude of genes involved can also elucidate both the time and strength of natural selection needed for speciation.We will study the genetic basis of reproductive isolation in the Louisiana Irises, a species complex has been a focus of ecological, genetic and evolutionary studies for almost a century. We will construct a QTL (quantitative trait loci) map of reproductive isolating mechanisms separating two species, Iris fulva and I. brevicaulis. Our analysis will locate QTLs that have the largest effect on the expression of both pre-mating and post-mating barriers to reproduction. The traits associated with the pre-mating barriers include floral differences that cause bumblebees to preferentially visit I. brevicaulis and hummingbirds to preferentially visit I. fulva (e.g., flowering time, flower color, nectar guide shape, nectar sugar concentration). The traits associated with post-mating barriers include (i) gamete competition (i.e., conspecific pollen tubes grow more quickly and thus fertilize ovules more efficiently than do pollen tubes from the alternate species) and (ii) pollen fertility of hybrids formed between the two species.