Cockburn Andrew, Lidicker William Z
Museum of Vertebrate Zoology, University of California, 94720, Berkeley, CA, USA.
Oecologia. 1983 Sep;59(2-3):167-177. doi: 10.1007/BF00378834.
Existing models of microtine population regulation and life history evolution rely on data derived from empirical studies which assume spatial homogeneity of the sampling unit, and infer that population dynamics can be described adequately by aggregation of individuals differing in sex, age and social status. These assumptions were not supported in the present study, and their application would have obscured relationships of ecological and evolutionary importance. From 1975 to 1981 a population of Microtus californicus exhibited seasonal fluctuations in numbers along with two extreme peaks in abundance. Floristic richness changed under the impact of heavy grazing by M. californicus, but floristic spatial pattern showed little interannual variation. All parameters of female survival and reproduction were correlated with floristic micropattern. Voles performed better in vegetation dominated by the native perennial grass Elymus triticoides. Female dispersion was more restricted than that of males. There are no reasons to believe the microhabitat preferred by females affords superior nutrition or protection from predation during peaks of abundance. However, it should provide higher probability of survival during summer, the time of greatest stringency in central California. The implications of these results for current theory are discussed, and a hypothesis developed which emphasises the importance of improved conditions in the most unfavourable season for peaks in abundance.
现有的田鼠种群调节和生活史进化模型依赖于实证研究得出的数据，这些研究假设采样单元在空间上是均匀的，并推断种群动态可以通过对不同性别、年龄和社会地位的个体进行汇总来充分描述。本研究不支持这些假设，应用这些假设会掩盖具有生态和进化重要性的关系。1975年至1981年，一群加利福尼亚田鼠的数量呈现季节性波动，同时出现了两个数量极峰。在加利福尼亚田鼠的重度啃食影响下，植物丰富度发生了变化，但植物空间格局的年际变化很小。雌性生存和繁殖的所有参数都与植物微观格局相关。田鼠在以本地多年生草本植物小麦状披碱草为主的植被中表现更好。雌性的扩散比雄性更受限制。没有理由认为雌性偏好的微生境在数量高峰期能提供更好的营养或免受捕食。然而，它应该在夏季（加利福尼亚中部最严峻的时期）提供更高的生存概率。本文讨论了这些结果对当前理论的影响，并提出了一个假设，该假设强调了在最不利季节改善条件对数量高峰期的重要性。
