Data from: Spatial heterogeneity in landscape structure influences dispersal and genetic structure: empirical evidence from a grasshopper in an agricultural landscape

Dispersal may be strongly influenced by landscape and habitat characteristics that could either enhance or restrict movements of organisms. Therefore, spatial heterogeneity in landscape structure could influence gene flow and the spatial structure of populations. In the past decades, agricultural intensification has led to the reduction in grassland surfaces, their fragmentation and intensification. As these changes are not homogeneously distributed in landscapes, they have resulted in spatial heterogeneity with generally less intensified hedged farmland areas remaining alongside streams and rivers. In this study, we assessed spatial pattern of abundance and population genetic structure of a flightless grasshopper species, Pezotettix giornae, based on the surveys of 363 grasslands in a 430-km² agricultural landscape of western France. Data were analysed using geostatistics and landscape genetics based on microsatellites markers and computer simulations. Results suggested that small-scale intense dispersal allows this species to survive in intensive agricultural landscapes. A complex spatial genetic structure related to landscape and habitat characteristics was also detected. Two P. giornae genetic clusters bisected by a linear hedged farmland were inferred from clustering analyses. This linear hedged farmland was characterized by high hedgerow and grassland density as well as higher grassland temporal stability that were suspected to slow down dispersal. Computer simulations demonstrated that a linear-shaped landscape feature limiting dispersal could be detected as a barrier to gene flow and generate the observed genetic pattern. This study illustrates the relevance of using computer simulations to test hypotheses in landscape genetics studies.

生物的扩散过程极易受到景观与栖息地特征的调控——这类特征既可能促进生物移动，也可能限制其扩散。因此，景观结构的空间异质性可对种群的基因流与空间分布格局产生影响。过去数十年间，农业集约化进程导致草地面积缩减、草地景观破碎化，并提升了农业生产的集约化水平。由于这类景观变化的空间分布并不均匀，最终造就了新的空间异质性：溪流与河流沿岸往往保留着农业集约化程度较低、搭配树篱的农田区域。本研究以法国西部一片面积430平方千米的农业景观为研究区域，通过对363处草地的调查，分析了无翅蝗虫物种Pezotettix giornae的种群丰度空间格局与种群遗传结构。研究采用地统计学、基于微卫星标记（microsatellite markers）的景观遗传学方法，并结合计算机模拟对数据进行分析。研究结果表明，该物种凭借小规模高强度的扩散能力，得以在集约化农业景观中存续。同时，研究还发现了与景观及栖息地特征紧密相关的复杂空间遗传结构。通过聚类分析，可推断出两个被一条线性树篱农田分隔的Pezotettix giornae遗传聚类群。该线性树篱农田具有树篱与草地密度更高、草地时间稳定性更强的特征，推测其会延缓该物种的扩散过程。计算机模拟结果证实，若线性形态的景观特征对扩散形成限制，即可被识别为基因流屏障，并能产生本研究观测到的遗传格局。本研究印证了在景观遗传学研究中，采用计算机模拟验证假说的重要价值。