Matesanz S, Gómez-Fernández A, Alcocer I, Escudero A
Departamento de Biología y Geología, Universidad Rey Juan Carlos, Móstoles, Spain.
Plant Biol (Stuttg). 2015 Sep;17(5):1047-56. doi: 10.1111/plb.12329. Epub 2015 Apr 16.
Most habitat fragmentation studies have focused on the effects of population size on reproductive success of single species, but studies assessing the effects of both fragment size and connectivity, and their interaction, on several coexisting species are rare. In this study, we selected 20 fragments along two continuous gradients of size and degree of isolation in a gypsum landscape in central Spain. In each fragment, we selected 15 individuals of each of three dominant gypsophiles (Centaurea hyssopifolia, Lepidium subulatum and Helianthemum squamatum, 300 plants per species, 900 plants in total) and measured several reproductive traits: inflorescence number, fruit set, seed set and seed mass. We hypothesised that plant fitness would be lower on small and isolated fragments due to an interaction between fragment size and connectivity, and that response patterns would be species-specific. Overall, fragment size had very little effect on reproductive traits compared to that of connectivity. We observed a positive effect of fragment connectivity on C. hyssopifolia fitness, mediated by the increased seed predation in plants from isolated fragments, resulting in fewer viable seeds per capitulum and lower seed set. Furthermore, seed mass was lower in plants from isolated fragments for both C. hyssopifolia and L. subulatum. In contrast, few reproductive traits of H. squamatum were affected by habitat fragmentation. We discuss the implications of species-specific responses to habitat fragmentation for the dynamics and conservation of gypsum plant communities. Our results highlight the complex interplay among plants and their mutualistic and antagonistic visitors, and reinforce the often-neglected role of habitat connectivity as a key component of the fragmentation process.
大多数栖息地破碎化研究都集中在种群规模对单一物种繁殖成功率的影响上，但评估斑块大小和连通性及其相互作用对多个共存物种影响的研究却很少见。在本研究中，我们在西班牙中部的一个石膏地貌中，沿着斑块大小和隔离程度的两个连续梯度选择了20个斑块。在每个斑块中，我们选择了三种主要嗜石膏植物（牛膝菊、细叶独行菜和鳞状半日花，每种植物15株，每个物种300株，共900株）中的每一种，并测量了几个繁殖性状：花序数、座果率、结实率和种子质量。我们假设，由于斑块大小和连通性之间的相互作用，小的和隔离的斑块上植物的适合度会较低，并且响应模式将是物种特异性的。总体而言，与连通性相比，斑块大小对繁殖性状的影响很小。我们观察到斑块连通性对牛膝菊适合度有积极影响，这是由隔离斑块上植物种子捕食增加介导的，导致每个头状花序的 viable 种子减少和结实率降低。此外，牛膝菊和细叶独行菜来自隔离斑块的植物种子质量较低。相比之下，鳞状半日花的很少有繁殖性状受到栖息地破碎化的影响。我们讨论了物种对栖息地破碎化的特异性响应对石膏植物群落动态和保护的影响。我们的结果强调了植物与其互利和拮抗访客之间的复杂相互作用，并强化了栖息地连通性作为破碎化过程关键组成部分这一经常被忽视的作用。
