内蒙古农牧交错带长爪沙鼠种群存活的季节格局及其动态机制

了解动物种群存活特征以及相关环境因子对其变化的独立或整合作用过程,有助于阐明动物种群动态的生态学机制。长爪沙鼠(Meriones unguiculatus)是分布于我国北方典型草原、荒漠草原及其毗邻的农牧交错带的优势鼠种之一。2000年10月至2004年10月通过标志重捕法研究了栖息于内蒙古农牧交错区草地生境的种群动态。本文通过MARK软件包中的CJS和MS模型分析了长爪沙鼠种群表观存活率(Φ,简称存活率)的性别(g)差异和年龄(as)特征表现及其季节变化格局,并对种群存活变化的密度和气候效应加以分析,旨在检验长爪沙鼠种群存活显示季节变化特征,并受密度制约和气候条件反馈调节的假设。结果发现,长爪沙鼠种群存活率初始最优模型Φ(t)p(g*t)中重捕时序(t)效应显著(ANODEV,F_27,47=11.05,P<0.001),月季效应最优模型Φ(month)p(g*t)也显示存活率季节变化明显(ANODEV,F_5,69=31.69,P<0.001),总体呈现从春季到冬季经历下降再升高的"V"字型动态模式。在无环境因子限制条件下,雌鼠(...

Seasonal dynamic of population survival and its mechanism in Mongolian gerbils (Meriones unguiculatus) in the Inner Mongolia agro-pastoral ecotone

Understanding differential and integral effects of climate and population density on vital rates e.g. survival, helps elucidate the ecological and demographic mechanisms underlying animal population dynamics.  The Mongolian gerbil (Meriones unguiculatus) is one of dominate rodents widely distributed in semi-arid, typical steppes, and desert grasslands in north of China.  We studied population dynamics of gerbils under semi-natural conditions using monthly capture–mark-recapture methods from October 2000 to 2004 in agro-pastoral ecotone of south-central Inner Mongolia, China. We used Cormack–Jolly–Seber (CJS) models to estimate apparent survival probability, and analyzed the difference of survival between males and females, or the survival seasonal variations.  Additionally, we used multistate （MS）models to test the difference of survival between adults with reproducing or reproduced strata and the sexually immature young.  Our results showed that the best approximating CJS model included the significant effect of full time（t）or season (month)- dependence on survival but not the effect of sex. These demonstrated that apparent survival probabilities displayed seasonal fluctuations of a lower apparent survival in summer compared to the rest of the year, and undistinguished survival between females( 0.788±0.013) and males (0.781±0.013）in the absence of limitation of environmental factors.  Our results also showed that the best and competition approximating MS model included age state (or stratum)-specific effect on apparent survival of gerbils with a monthly (or seasonal) patterns. It may reflect the important life-history strategies adapting to the semi-arid or desert environment in Mongolian gerbils, Furthermore, there was evidence that population density negatively influenced survival with a time lag of 1 month in M. unguiculatus.  Considering the extrinsic environmental factors, increases in monthly total precipitation reduced the apparent survival of gerbils.  Moreover, these effects of population density-dependent and precipitation on the survival of female and male gerbils are different.  Therefore, we suggested that weather conditions may mainly mediate the change of habitable environment, supporting the optimum habitat hypothesis, and integrate density-dependent feedback to shape the different response of survival models between female and male gerbils.  These processes might construct an adaptive sexual-structure of population, and then affect the change of the other population parameters, consequently population growth rates. Pronounced a primary mechanism to regulate the small mammal’s population dynamic in northern high latitudes.