Fragmentation, habitat composition and the dispersal/predation balance in interactions between the Mediterranean myrtle and avian frugivores
Fragmentation, habitat composition and the dispersal/predation balance in interactions between the Mediterranean myrtle and avian frugivores
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DOI：
10.1111/j.1600-0587.2009.06021.x
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发表时间：
2010-02-01
期刊：
影响因子：
5.9
通讯作者：
Gonzalez-Varo, Juan P.
中科院分区：
文献类型：
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作者：
Gonzalez-Varo, Juan P.
人类对自然栖息地的破坏和干扰会改变果食动物群落的丰度和组成，这可能会改变果树和种子传播的模式。然而，尽管它们与生态系统的功能有关，但到目前为止，对碎片化地区的植物-果食相互作用的研究还很少。我研究了地中海桃金娘灌木(Myrtus Commis)中鸟类食果虫群落的空间变化以及分散者和捕食者对果实的清除与9块林地(72种植物)的破碎化程度和栖息地特征的关系。这项研究是在瓜达尔基维尔山谷(西班牙西南部)长期支离破碎的景观中进行的，该山谷的特点是林地覆盖率接近1%。结果表明，分散者公会的丰度和组成不受破碎化程度、生境特征和地理位置的影响。然而，个别种类和群体的留鸟/候鸟的反应是不同的：留鸟的散布物在大片区域更多，而越冬的散布物在果实丰富的区域更多。捕食者的丰度在斑块之间是相似的，尽管行会组成随着碎片化而变化。传播者和捕食者消耗的桃金娘果实的比例在不同斑块之间差异很大，但不取决于鸟类的丰度。斑块的地理位置决定了桃金娘与种子捕食者之间是否存在相互作用(6个捕食性斑块和3个非捕食性斑块)，这一事实极大地影响了水果传播的成功。此外，在果实贫乏的异种环境(即以桃金娘为主)的大片土地上，捕食率较低(而分散率较高)。捕食者的饱腹感和分散者对异种水果的更高偏好可能解释了这些模式。这些结果表明，1)地中海温暖低地的果食动物群落主要由对景观变化反应不同的耐碎片化物种组成；2)受当地水果可获得性影响的分散者和捕食者的取食行为对于解释整个研究区域的果树格局可能是非常重要的。
Human-induced fragmentation and disturbance of natural habitats can shift abundance and composition of frugivore assemblages, which may alter patterns of frugivory and seed dispersal. However, despite their relevance to the functioning of ecosystems, plant-frugivore interactions in fragmented areas have been to date poorly studied. I investigated spatial variation of avian frugivore assemblages and fruit removal by dispersers and predators from Mediterranean myrtle shrubs (Myrtus communis) in relation to the degree of fragmentation and habitat features of nine woodland patches (72 plants). The study was conducted within the chronically fragmented landscape of the Guadalquivir Valley (SW Spain), characterized by similar to 1% of woodland cover. Results showed that the abundance and composition of the disperser guild was not affected by fragmentation, habitat features or geographical location. However, individual species and groups of resident/migrant birds responded differently: whereas resident dispersers were more abundant in large patches, wintering dispersers were more abundant in fruit-rich patches. Predator abundances were similar between patches, although the guild composition shifted with fragmentation. The proportion of myrtle fruits consumed by dispersers and predators varied greatly between patches, but did not depend on bird abundances. The geographical location of patches determined the presence or absence of interactions between myrtles and seed predators (six predated and three non-predated patches), a fact that greatly influenced fruit dispersal success. Moreover, predation rates were lower (and dispersal rates higher) in large patches with fruit-poor heterospecific environments (i.e. dominated by myrtle). Predator satiation and a higher preference for heterospecific fruits by dispersers may explain these patterns. These results show that 1) the frugivore assemblage in warm Mediterranean lowlands is mostly composed of fragmentation-tolerant species that respond differently to landscape changes; and 2) that the feeding behaviour of both dispersers and predators influenced by local fruit availability may be of great importance for interpreting patterns of frugivory throughout the study area.