Vergara-Tabares David L, Toledo Martín, García Emiliano, Peluc Susana I
Instituto de Diversidad y Ecología Animal (UNC-CONICET) and Centro de Zoología Aplicada (FCEFyN-UNC), Rondeau 798, X5000AVP, Córdoba, Argentina.
, Arenales 990, Torre Verde 7B, Córdoba, Argentina.
Oecologia. 2018 Sep;188(1):173-182. doi: 10.1007/s00442-018-4207-2. Epub 2018 Jun 26.
Frugivorous birds are able to track spatiotemporal changes in fruit availability. Food resource fluctuations, characteristic of seasonal environments, can be affected by the naturalization of exotic ornithocorous plants. In the mountain forest of central Argentina, invasive shrubs of the genus Pyracantha provide a new temporal resource that modifies fluctuations of natural resource availability because the invasives fructify in autumn-winter (largely uncoupled with the fruiting of native species). The contrasting patterns of resource fluctuation between non-invaded and invaded areas throughout the year provide a good study system to test predictions of the fruit-tracking hypothesis, and to understand the relationship between food resources offered by fleshy fruited invasives and abundances of avian trophic guilds. By means of point counts conducted during five time periods at invaded and non-invaded sites we found that the presence of Pyracantha, and time periods, significantly affected frugivorous bird abundance, which in autumn-winter was greater in invaded sites and in spring-summer similar between invaded and non-invaded sites. On the other hand, granivores and insectivores did not show a significant relationship with the presence of Pyracantha. Abundances of the most common seed disperser were significantly affected by the interaction between time period and presence of Pyracantha. These results indicate that the abundances of birds that legitimately disperse Pyracantha seeds are temporally and spatially associated with fruit abundance provided by this exotic plant. This underscores fruit availability as an important ecological factor affecting frugivorous bird abundance, and suggests that Pyracantha seed dispersers are capable of detecting changes in the availability of its fruit, likely contributing to the effectiveness of its dispersal.
食果鸟类能够追踪果实可获得性的时空变化。食物资源的波动是季节性环境的特征，可能会受到外来食果植物归化的影响。在阿根廷中部的山林中，火棘属的入侵灌木提供了一种新的季节性资源，改变了自然资源可获得性的波动，因为这些入侵植物在秋冬季节结果（这与本地物种的结果时间大体上不一致）。全年未受入侵和已受入侵地区资源波动的对比模式，为检验果实追踪假说的预测以及理解肉质果实入侵植物提供的食物资源与鸟类营养类群数量之间的关系，提供了一个良好的研究系统。通过在已受入侵和未受入侵地点的五个时间段进行的点计数，我们发现火棘的存在以及时间段，对食果鸟类的数量有显著影响，在秋冬季节，已受入侵地点的食果鸟类数量更多，而在春夏季节，已受入侵和未受入侵地点的数量相似。另一方面，食谷鸟类和食虫鸟类与火棘的存在没有显著关系。最常见的种子传播者的数量受到时间段和火棘存在之间相互作用的显著影响。这些结果表明，合法传播火棘种子的鸟类数量在时间和空间上与这种外来植物提供的果实丰度相关。这突出了果实可获得性作为影响食果鸟类数量的一个重要生态因素，并表明火棘种子传播者能够检测到其果实可获得性的变化，这可能有助于其传播的有效性。
