Local adaptation in a phoretic mite-burying beetle symbiosis

当生物体适应它们的环境时，不同栖息地之间的差异可能会导致种群之间适应特征的差异。虽然这些局部适应在应对相对稳定的非生物因素(如温度)而进化时可能是直接的，但对本身也适应的其他物种的局部适应将更加复杂。这在共同进化的情况下尤其重要，这会导致共生体之间的互惠和潜在的无方向的共同适应，并可能导致共同进化的地理马赛克，其中适合性由基因(局部物种)、基因(共生体)和环境相互作用(GxGxE)决定。我建议研究与埋葬甲虫共生的磷螨类的局部适应。初步实验表明，螨类和甲虫的适合度呈负相关，表明它们是寄生的。多种螨类中的每一种都专门适应于多种甲虫中的一种，反之亦然。螨代时间是相互作用的关键性状，在不同的螨类种群之间存在差异，似乎对寄主甲虫和环境是局部适应的。到目前为止，我们收集的所有数据都表明，这是一个受环境参数影响的共同进化系统。该系统是研究局部适应和共同进化的理想系统，因为它服从于受控的实验室适应性实验和野外移植实验。结合遗传分析，我们将使用这些实验来检验这样的假设，即蠕虫和甲虫在共同进化的地理马赛克中彼此局部适应，并适应剩余环境。然后，每个生物体的适合度应该取决于生物体的基因和共生体的基因的相互作用，以及这种相互作用如何受到环境的影响(GxGxE)。可供选择的假设是具有局部适应非生物因素的纯GxE交互作用、纯GXG交互作用(共同进化交互作用不受环境影响)或不交互作用。与许多共同进化系统的研究不同，共同进化系统通常使用微生物共生体和/或以强烈的适应效应(例如致命的寄生虫)和排他性共生体(没有替代共生体)为特征，而螨虫-甲虫系统代表了一种更广泛的共同进化案例。通过划分环境和遗传效应以及甲虫协会中所有可能的相互作用，我们将有助于理解扩散共同进化，尽管扩散共同进化是物种相互作用的最常见形式，但由于它不明显，而且往往看起来是一个困难的实验系统，因此研究得很少。

When organisms adapt to their environment, differences between habitats can lead to differences between populations in the adapted traits. While these local adaptations can be straightforward when evolved in response to relatively stable abiotic factors, such as temperature, local adaptation to other species that themselves also adapt will be more complex. This is particularly important in cases of coevolution, which leads to reciprocal and potentially undirected co-adaptation between symbionts and can cause a geographic mosaic of coevolution, where fitness is determined by a gene (focal species) by gene (symbiont) by environment interaction (GxGxE). I propose to study local adaptation in phoretic mites that live in symbiosis with burying beetles. Preliminary experiments show that mite and beetle fitnesses are negatively correlated, indicating parasitism by the mites. Each of the multiple mite species is specifically adapted to one of the many beetle species, and vice versa. Mite generation time, a trait crucial to the interaction, varies between mite populations and seems to be locally adapted to the host beetles and to the environment. All data we collected so far indicate a coevolutionary system that is affected by environmental parameters. The system is ideal to study local adaptation and coevolution because it is amenable to controlled laboratory fitness experiments and to transplantation experiments in the field. Combined with genetic analyses, we will use these experiments to test the hypothesis that mites and beetles are locally adapted to each other and to the remaining environment in a geographic mosaic of coevolution. Then, each organism's fitness should depend on the interaction of the organism's genotype with that of its symbiont, and how the interaction is affected by the environment (GxGxE). The alternative hypotheses are a pure GxE interaction with local adaptation to abiotic factors, a pure GxG interaction (the coevolutionary interaction is not affected by the environment), or no interaction. Unlike many studies of coevolutionary systems, which are typically using microbial symbionts and/or are characterised by strong fitness effects (e.g. lethal parasites) and exclusive symbioses (no alternative symbionts), the mite-beetle system represents a more diffuse case of coevolution. By partitioning environmental and genetic effects and all possible interactions in the mite-beetle association, we will contribute to the understanding of diffuse coevolution, which despite being the most common form of species interaction is grossly understudied because it is inconspicuous and often seems a difficult experimental system.