ABSTRACT

Passive transport has likely contributed to the post-glacial dispersal of species in temperate regions. However, identifying such processes from patterns can be obscured by confounding environmental conditions. We studied the distribution of ground beetles in Ontario’s Far North, a vast (450,000 km²) and largely intact region, to identify mechanisms that aid in species dispersal when confounding factors, such as temperature, are controlled. We tested a model of passive, riverine dispersal using recent records of flightless and flighted ground beetles from 34 sites across the region. The number of species declined with distance from main watershed rivers, as predicted from our model at the site level. Contrary to expectations, this pattern was evident with flighted species but not flightless species. The opposite pattern, with flightless species displaying a decrease with increasing distance from river, was evident at a regional level. These patterns are consistent with ground beetles carried along rivers since glacial retreat. We surmise that northward dispersal of these invertebrates into the boreal forest has been aided by vegetation and other debris flowing down rivers, including soil from eroded banks in which larvae and pupae reside. Biogeographic inferences, although often subtle, can be supported by broad-scale studies of intact landscapes.

摘要

被动运输可能导致了冰川后物种在温带地区的扩散。但是，通过混淆环境条件可能无法从模式中识别此类过程。我们研究了安大略省远北地区（450,000 km ²）和基本上完整的区域，以识别在混杂因素（例如温度）受到控制时有助于物种扩散的机制。我们使用了来自该地区34个地点的飞甲和飞甲虫的最新记录，测试了一种被动的河川扩散模型。正如我们在站点级别的模型所预测的那样，物种数量随着与主要流域河流的距离而减少。与预期相反，这种模式在飞行的物种中很明显，但在非飞行的物种中却不明显。相反的模式，即在区域一级，随着距离河流的距离增加，不会飞行的物种显示出减少的趋势。这些模式与冰川退缩以来沿河携带的地面甲虫一致。我们推测这些无脊椎动物向北散布到北方森林中的原因是植被和其他碎片顺着河流顺流而下，包括来自幼虫和reside居住的被侵蚀的河岸的土壤。生物地理学的推论尽管通常很微妙，但可以通过对完整景观的大规模研究来支持。