Demographic and population-genetic tests provide mixed support for the abundant center hypothesis in the endemic plant Leavenworthia stylosa

The abundant centre hypothesis (ACH) assumes that population abundance, population size, density and per-capita reproductive output should peak at the centre of a species' geographic range and decline towards the periphery. Increased isolation among and decreased reproductive output within edge populations should reduce within-population genetic diversity and increase genetic differentiation among edge relative to central populations. The ACH also predicts asymmetrical gene flow, with net movement of migrants from the centre to edges. We evaluated these ecological assumptions and population-genetic predictions in the endemic flowering plant Leavenworthia stylosa. Although populations were more spatially isolated near range edges, the geographic centre was surrounded by and not coincident with areas of peak population abundance, and plant density increased towards range edges. Per-capita seed number was not associated with distance to the range centre, but seed number/m2 increased near r...

丰富中心假说（ACH）提出，物种地理分布范围内的种群丰度、种群规模、种群密度以及个体繁殖产出均应在分布中心达到峰值，并向分布边缘逐渐降低。边缘种群间的隔离程度上升、种群内部繁殖产出下降，将导致边缘种群的种群内遗传多样性降低，且相较于中心种群，边缘种群间的遗传分化程度升高。该假说同时预测存在不对称基因流，即迁移个体的净迁移方向为从分布中心指向分布边缘。本研究以特有开花植物长柱花荠（Leavenworthia stylosa）为研究对象，对上述生态学假设与种群遗传学预测展开了验证。尽管分布边缘区域的种群空间隔离程度更高，但该物种的地理分布中心并未与种群丰度峰值区重合，反而被此类区域环绕，且植物密度随向分布边缘推进而逐渐升高。个体结籽数与到分布中心的距离并无关联，但每平方米结籽数在分布边缘附近有所升高……