Coastal Research Group, Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa.
PLoS One. 2012;7(12):e52076. doi: 10.1371/journal.pone.0052076. Epub 2012 Dec 20.
Organisms with different life-histories and abilities to disperse often utilise habitat patches in different ways. We investigated the influence of the size of patches of rock (separated by stretches of sand) on the density of pulmonate limpets (Siphonaria spp.) along 1500 km of the linear landscape of the South African coastline. We compared the influence of patch-size on two congeneric species with different modes of development, S. serrata a direct developer, and S. concinna a planktonic developer. We tested the spatial and temporal consistency of the effects of patch-size by sampling 7 independent regions spanning the distributional range of both species of limpets, and by sampling one region at monthly intervals for 1 year. Within each region or month, 4 small patches (<20 m in length) interspersed with the 4 large patches (>60 m in length) were sampled. Across the entire geographic range and throughout the year, there were more of both species of limpets in large patches than in small patches. In most regions, there was greater variability in large patches than small patches. Variability within patches in a single region was similar throughout the year, with greater variability of both species in large than in small patches. We found little influence of the mode of development on the response of limpets to patch-size. Our findings highlight the importance of understanding patterns of distribution of species with respect to habitat heterogeneity in linear landscapes, and contradict the idea that organism mobility at an early ontogenetic stage directly affects habitat use.
具有不同生活史和扩散能力的生物通常以不同的方式利用栖息地斑块。我们研究了岩石斑块（由沙滩隔开）大小对南非海岸线线性景观 1500 公里范围内的肺螺类石鳖（Siphonaria spp.）密度的影响。我们比较了两种具有不同发育方式的同属物种的斑块大小的影响，即直接发育的 S. serrata 和浮游发育的 S. concinna。我们通过在两个物种的分布范围内采样 7 个独立区域，并在 1 年内每月采样一个区域，测试了斑块大小对物种密度影响的时空一致性。在每个区域或月份内，采样了 4 个小斑块（<20 米长）和 4 个大斑块（>60 米长）。在整个地理范围内和全年，大斑块中的两种石鳖数量都多于小斑块。在大多数区域，大斑块的变异性大于小斑块。在一个区域内的斑块内变异性全年相似，大斑块中的两种石鳖的变异性都大于小斑块。我们发现，发育模式对石鳖对斑块大小的反应影响不大。我们的研究结果强调了了解线性景观中具有特定栖息地异质性的物种分布模式的重要性，并反驳了早期个体发育阶段的生物移动性直接影响栖息地利用的观点。
