Self-incompatible plants as well as common plant species are expected to be especially vulnerable to the deleterious effects of fragmentation on genetic diversity. Paypayrola blanchetiana (Violaceae) is a common, self-incompatible understory tree in the East Brazilian Atlantic forest. Its autochorous seed dispersal and occurrence in dense, well-separated clusters makes it an interesting model for studies of gene flow and genetic structuring on a small geographic scale. A previous study has found remarkably low fruit set and frequent seed abortions in this species in several populations situated in forest fragments. We tested the hypothesis that P. blanchetiana is affected by inbreeding and loss of genetic diversity in a fragmented landscape. Nine nuclear and three plastid microsatellite loci were genotyped for 285 individuals (149 adult trees and 136 saplings) across seven populations in five forest fragments in a 240-km² sugarcane-rainforest matrix. We found a low to moderate genetic diversity in nuclear loci of P. blanchetiana, population structuring on a small geographical scale and high levels of inbreeding. Haplotype distributions confirmed that seed dispersal is very limited. There were, however, no signs for lower genetic diversity or higher inbreeding in populations situated in the smallest forest fragments. Furthermore, genetic diversity was not lower in the sapling cohort, which was created in post-fragmentation condition. Therefore, we may be witnessing the genetic consequences of this species’ biology, rather than immediate effects of fragmentation.

自我不相容的植物以及普通植物物种特别容易受到片段化对遗传多样性的有害影响。Paypayrola blanchetiana（紫堇科）是东巴西大西洋森林中一种常见的，自相矛盾的林下树木。它的自发种子散布和分布在密集，分隔良好的簇中，使其成为在小地理范围内研究基因流和遗传结构的有趣模型。先前的研究发现该物种在森林碎片中的多个种群中的坐果率极低，种子流产频繁。我们检验了假单胞菌的假说在一个零散的景观中受到近亲繁殖和遗传多样性丧失的影响。在240 km ^2的甘蔗-雨林矩阵中，对五个森林碎片中的七个种群中的285个个体（149棵成年树和136棵幼树）的9个核和3个质体微卫星基因座进行了基因分型。我们在P. blanchetiana的核基因座中发现了低至中等的遗传多样性，人口结构小，近交程度高。单倍型分布证实种子的扩散非常有限。但是，没有迹象表明在最小森林碎片中的种群遗传多样性较低或近交程度较高。此外，幼树种群的遗传多样性并不低。因此，我们可能正在目睹该物种生物学的遗传后果，而不是看到分裂的直接影响。