Wilby Andrew, Shachak Moshe
The Mitrani Department of Desert Ecology, Jacob Blaustein Institute of Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 84990, Israel, Israel.
Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, USA, USA.
Oecologia. 2000 Dec;125(4):495-503. doi: 10.1007/s004420000478. Epub 2000 Dec 1.
The influence of temporal and spatial heterogeneity in seed availability on the foraging behaviour of the harvester ant Messor arenarius was studied in an arid shrubland in the Negev Desert, Israel. The study investigated the implications of behavioural responses to heterogeneity in seed availability for the seed predation process and the potential for feedback effects on vegetation. Vegetation and seed rain were monitored across two landscape patch types (shrub patches and inter-shrub patches) in 1997. Shrub patches were shown to have higher plant and seed-rain density than inter-shrub patches. Patch use and seed selection by M. arenarius foragers were monitored through the spring, summer and autumn of 1997. After a pulse of seed production in the spring, the ants exhibited very narrow diet breadth, specialising on a single annual grass species, Stipa capensis. At this time, ants were foraging and collecting seeds mainly from inter-shrub patches. In the summer, diet breadth broadened and use of shrub patches increased, although the rate of seed collection per unit area was approximately equal in the two patch types. The increase in the use of shrub patches was due to colony-level selection of foraging areas with relatively high shrub cover and an increase in the use of shrub patches by individual foragers. In the autumn, a pulse of seed production by the shrub species Atractylis serratuloides and Noaea mucronata led to a reduction in diet breadth as foragers specialised on these species. During this period, foragers exhibited a large increase in the proportion of time spent in shrub patches and in the proportion of food items collected from shrub patches. The seasonal patterns in foraging behaviour showed linked changes in seed selection and patch use resulting in important differences in the seed predation process between the two landscape patch types. For much of the study period, there was higher seed predation pressure on the inter-shrub patches, which were of relatively low productivity compared with the shrub patches. This suggests that the seed predation process may help maintain the spatial heterogeneity in the density of ephemeral plants in the landscape.
在以色列内盖夫沙漠的一片干旱灌木丛中，研究了种子可获得性的时空异质性对收获蚁Messor arenarius觅食行为的影响。该研究调查了对种子可获得性异质性的行为反应对种子捕食过程的影响以及对植被产生反馈效应的可能性。1997年，在两种景观斑块类型（灌木斑块和灌木间斑块）中监测了植被和种子雨。结果表明，灌木斑块的植物和种子雨密度高于灌木间斑块。在1997年的春季、夏季和秋季，监测了Messor arenarius觅食者对斑块的利用情况和种子选择情况。春季种子产量脉冲过后，蚂蚁的食谱宽度非常狭窄，专门以一种一年生草本植物——南非细茎针茅为食。此时，蚂蚁主要在灌木间斑块觅食和收集种子。夏季，食谱宽度变宽，对灌木斑块的利用增加，尽管两种斑块类型单位面积的种子收集率大致相同。对灌木斑块利用的增加是由于蚁群层面选择了灌木覆盖率相对较高的觅食区域，以及个体觅食者对灌木斑块利用的增加。秋季，灌木物种锯齿状苍术和具短尖节蒴麻的种子产量脉冲导致食谱宽度减小，因为觅食者专门以这些物种为食。在此期间，觅食者在灌木斑块中花费的时间比例和从灌木斑块中收集的食物比例大幅增加。觅食行为的季节性模式表明，种子选择和斑块利用存在相关变化，导致两种景观斑块类型在种子捕食过程中存在重要差异。在研究的大部分时间里，灌木间斑块的种子捕食压力较高，与灌木斑块相比，其生产力相对较低。这表明种子捕食过程可能有助于维持景观中短命植物密度的空间异质性。
