Kelrick M I, MacMahon J A, Parmenter R R, Sisson D V
Department of Biology, UMC 53, Utah State University, 84322, Logan, UT, USA.
the Ecology Center, UMC 53, Utah State University, 84322, Logan, UT, USA.
Oecologia. 1986 Sep;68(3):327-337. doi: 10.1007/BF01036734.
This study established the preferences of shrubsteppe granivores among seeds of 6 common sagebrushsteppe plants and related the preferences observed to physical and nutritional attributes of the seeds. Seeds of big sagebrush (Artemisia tridentata), cheatgrass (Bromus tectorum), Indian ricegrass (Oryzopsis hymenoides), western wheatgrass (Pascopyrum smithii), bitterbrush (Purshia tridentata) and green needlegrass (Stipa viridula) were placed in groups of petri dishes designed such that seed removal could be ascribed to either diurnal vertebrates, nocturnal vertebrates or ants. Though absolute quantities of seeds removed varied among the 3 granivore classes, calculations of preference based on weights of each seed species removed by each granivore class indicated that all 3 ranked the seeds similarly. Preference hierarchies of the 3 granivore classes were highly positively correlated with both calories per seed and % soluble carbohydrate of the seeds. The first correlation supports a basic prediction of optimal foraging theory -that foragers should maximize energy intake per unit time spent foraging. Both correlations emphasize the role of seed nutritional qualities in granivore seed selectivity in that soluble carbohydrate is a water-efficient energy source and its percentage is a good indicator of the digestible energy available in a food item. A corollary experiment comparing granivore use of an exotic seed (millet [Panicum miliaceum]) and a preferred native seed (Oryzopsis) demonstrated a distinct preference for the exotic. Since millet seeds are particularly high in % soluble carbohydrate, this result reinforced the apparent value of this nutritional attribute as a predictor of granivore seed preference. Among many seed resource characteristics upon which granivore seed selectivity might operate, our results indicate that individual species' nutritional composition may be particularly important. Thus, inferences about seed selectivity and resource partitioning among arid-land granivores should be interpreted with caution, especially those based on experiments using seed introductions, since the influence of seed nutritional attributes has not been widely acknowledged heretofore.
本研究确定了灌丛草原食谷动物对6种常见蒿属草原植物种子的偏好，并将观察到的偏好与种子的物理和营养属性相关联。将三齿蒿（Artemisia tridentata）、披碱草（Bromus tectorum）、稻鼠草（Oryzopsis hymenoides）、西部小麦草（Pascopyrum smithii）、苦荆树（Purshia tridentata）和绿针茅（Stipa viridula）的种子放置在培养皿组中，其设计方式使得种子去除可归因于昼行性脊椎动物、夜行性脊椎动物或蚂蚁。尽管3类食谷动物去除的种子绝对数量有所不同，但根据每类食谷动物去除的每种种子物种的重量计算偏好表明，所有3类动物对种子的排名相似。3类食谷动物的偏好等级与每粒种子的卡路里含量和种子的可溶性碳水化合物百分比均呈高度正相关。第一个相关性支持了最优觅食理论的一个基本预测，即觅食者应在单位觅食时间内使能量摄入最大化。这两个相关性都强调了种子营养质量在食谷动物种子选择中的作用，因为可溶性碳水化合物是一种节水型能量来源，其百分比是食物中可消化能量的良好指标。一项比较食谷动物对外来种子（粟[Panicum miliaceum]）和首选本地种子（稻鼠草）利用情况的配套实验表明，它们对外来种子有明显偏好。由于粟种子的可溶性碳水化合物百分比特别高，这一结果强化了这种营养属性作为食谷动物种子偏好预测指标的明显价值。在食谷动物种子选择可能起作用的许多种子资源特征中，我们的结果表明，单个物种的营养成分可能尤为重要。因此，关于干旱地区食谷动物种子选择和资源分配的推断应谨慎解释，尤其是那些基于种子引入实验的推断，因为种子营养属性的影响迄今尚未得到广泛认可。
