昆虫蛀蚀对鼠类介导下的锐齿槲栎种子扩散的影响

森林鼠类的种子贮藏行为对植物的扩散和自然更新有着非常重要的影响。然而,鼠类是否具有鉴别虫蛀种子的能力还存在一定的争议。此外,鼠类的鉴别能力是否受到食物丰富度变化的影响也未见相关报道。采用标签标记法,2011年秋季(9—11月,食物丰富季节)和2012年春季(4—6月,食物匮乏季节)分别在秦岭南坡的佛坪国家级自然保护区内,调查了森林鼠类对完好和虫蛀锐齿槲栎(Quercus aliena)种子的选择差异。结果显示:1)在秋季,尽管2种类型种子的存留动态没有显著差异,但是在后期虫蛀种子的存留时间相对更长;而在春季2种类型种子的存留动态则极为显著,几乎所有的完好种子(99%)在释放后的第3天就被鼠类全部扩散,虫蛀种子的存留时间则相对较长。2)在秋季,鼠类更喜好扩散后取食完好种子;而在春季,鼠类则喜好在原地取食绝大部分的种子,并且优先取食完好种子。3)在秋季,鼠类贮藏了更多的完好种子;而在春季,尽管完好种子在释放后第1天便达到贮藏高峰,然而由于后期的大量被捕食,2种类型种子在贮藏动态上没有显示出显著差异。研究结果表明秦岭地区森林鼠类可以准确区分完好与虫蛀种子,但是食物丰富度会影响鼠类对种子的选择策略。在食物丰富的秋季,鼠类更多地选择贮藏完好种子;而在食物相对匮乏的春季,鼠类更倾向于同时取食2种类型种子。森林鼠类通过对2种类型种子的鉴别和选择,影响不同种子的命运,从而可能对种子的扩散和自然更新产生重要影响。

Effects of weevil-infestation on seed dispersal of Quercus aliena handled by rodents

Forest rodents play important roles on the regeneration of plants by scattering seeds into microsites where they can germinate and grow. However, current research in this area has not been comprehensive enough, so considerable controversy exists over whether forest rodents have the ability to detect weevil-infested seeds. Moreover, no reports exist on the effects of food abundance on the ability of rodents to detect such seeds. Acorns of Quercus aliena, a common and often dominant Fagaceae species in many temperate and subtropical forests, are an important food resource for forest rodents. Much attention has been paid to the dispersal biology of Quercus spp.; however, knowledge related to the ability of rodents to detect weevil-infested Q. aliena acorns in the Qinling Mountains is still poor. The predation and dispersal of intact and weevil-infested acorns of Q. aliena were investigated using acorns with plastic tags in Foping National Nature Reserve (35°0'N, 105°30'E), located in the southern aspect of the Qinling Mountains in Shaanxi Province, China, during September-November, 2011 and March-May, 2012. Twenty plots (1 m× 1 m), separated by 15 m along a transect line, were established as acorn stations in a deciduous broad-leaved forest. In October 2011, 20 intact and 20 weevil-infested acorns were placed at each station and acorn fates were monitored at 1, 3, 5, 10, 17, 27 and 50 days after initial placement. During each visit, we searched the area around each station (radius<30 m) for acorns removed by rodents and recorded acorn fates. The results revealed significant differences in acorn lifetime when comparing the stations for intact and weevil-infested acorns in the two seasons. In spring, almost all intact acorns (99%) were removed from each station by the third day, while weevil-infested acorns remained on site for longer than three days during the lifetime of a station. In autumn, both intact and weevil-infested acorns were eaten in situ with no significant differences between use rates, while there were significant differences in spring when rodents prioritized eating intact acorns. Intact and infested acorns were also eaten at significantly different rates after removal not only in autumn but also in spring. In spring, rodents primarily removed and ate intact acorns early in the season. Intact and infested acorns were also cached at significantly different rates in autumn, when rodents cached more intact acorns than weevil-infested acorns. In spring, although caching of intact acorns peaked on the first day, as a result of the large number of cached acorns eaten at a later time, there were no significant differences in acorn caching rates between the two kinds of acorns in spring. This study indicated that forest rodents could accurately determine if acorns were weevil-infested in the Qiling Mountains, but food abundance may affect the acorn selection strategy of rodents when both intact and weevil-infested acorns are made available. In autumn with abundant food resources available, rodents primarily selected intact acorns to cache; in spring, when food resources were relatively poor, rodents weakened their selecting strategy and tended to eat both kinds of acorns simultaneously. This may affect the fates of intact and weevil-infested acorns and then influence the dispersal and natural regeneration of Quercus aliena.