Knowledge Resource Center for Ecological Environment in Arid Area
| 长爪沙鼠生活史变量与其季节格局在种群调节中的作用研究 | |
| 其他题名 | The role of life-history variables and seasonal structure in population dynamics and regulation of Mongolian gerbils (Meriones unguiculatus) |
| 刘伟 | |
| 出版年 | 2008 |
| 学位类型 | 博士 |
| 导师 | 钟文勤 |
| 学位授予单位 | 中国科学院动物研究所 |
| 中文摘要 | 生活于温带和寒带地区的小型哺乳动物经历明显的季节性环境变化，这对动物生活史产生重要影响。由于种群动态是存活、生长发育、繁殖等生活史变量的综合结果，因而，生活史变量的季节结构影响小哺乳动物种群的季节动态，其内外因素的整合调节过程甚至在种群多年周期性或非周期性波动中起关键作用。本文以栖息于蒙古高原中南部典型草原区的长爪沙鼠(Meriones unguiculatus)为对象，于2000年－2004年间对该鼠野外围栏种群进行了系统的标志重捕和室内行为实验观测，通过标志重捕获取的资料和相关模型统计了种群性成熟、繁殖和存活参数，并比较了个体间的社群行为差异，综合分析了长爪沙鼠繁殖－存活及社群行为特征及其季节格局的适应机制和意义；采用回归分析和种群映射矩阵模型-弹性分析探讨了长爪沙鼠种群动态响应繁殖和存活变化的模式，并测定了上述响应过程中密度和水热条件的作用，同时考查了各项因子在繁殖和非繁殖季节的作用差异。\n主要结果和结论如下：\n1．\t长爪沙鼠繁殖显示明显季节变化，春季最为活跃，夏季开始降低，秋季休止。在冬季有部分个体开始繁殖。特定年龄群体的繁殖性能观测显示当年鼠性成熟月龄最小为2月龄。冬季和早春出生的个体性成熟快，多数个体当年即能参加繁殖；夏季出生的个体性成熟和繁殖延迟到下一个繁殖期。不同季节出生的雌鼠一年中最多产仔次数有差异，越冬鼠和冬季出生者可产3～4窝。当年春季3～5月份出生的雌鼠当年可产1窝。由性成熟的当年鼠与越冬鼠构成的种群繁殖格局反映了该鼠生活史适应对策的重要特征。\n2．\t长爪沙鼠种群存活率的性别差异不明显；年龄（以繁殖状态划分）差异特征仅在雌鼠中有显著表现；在春夏繁殖季节，早春繁殖初期（3月），成年鼠（性成熟和经产个体）的存活率和期望寿命低于未成年鼠（性未成熟个体）；此后成年鼠的存活优于未成年鼠，尤在繁殖末期（8-9月）差异明显；进入繁殖休止期和越冬期，未成年鼠显示存活优势。存活研究结果还显示该鼠种群存活率季节变化明显，从春季到冬季，其存活经历下降再升高的V形动态模式。繁殖竞争可能是导致雌鼠特定年龄群体存活格局及季节变化的主要原因。上述过程有其行为和生理学基础，并将影响其种群变化。\n3．\t社群行为研究结果显示，在繁殖期，成年雄性长爪沙鼠间的容忍性远远低于其他组合；未成年鼠与陌生成年鼠相遇时，未成年鼠被同性成年鼠攻击的频次明显高于被异性成体攻击的频次。而在繁殖休止－贮食期间，各类个体相遇时的社群行为表现基本相似。同时，经不同季节比较发现，唯雄－雄间的争斗行为在繁殖休止时较繁殖期间有显著降低，其它个体间的争斗和友好行为变化并不明显。这些结果表明长爪沙鼠个体间的竞争关系有其明显的性别差异和季节特征，且与其社会组织和生活方式相适应，并对种群存活、扩散、补充起明显的调节作用。\n4．\t综合分析长爪沙鼠特定年龄群体的繁殖－存活特征进一步表明，种群繁殖初期出生的个体，多采取“快速（fast）”生活对策即具有性成熟和产仔早、期望寿命短等生活史特征；而种群繁殖后期出生的个体则偏向“慢速(slow)”对策表现为性成熟延迟，存活期望高。研究结果还发现尽管未成年个体越冬存活优于成年个体，但是，两者间的差值远低于延迟繁殖最优决策模型的理论期望；同时结果显示成年雌鼠密度对未成年个体的性成熟率有所抑制；剔除成年鼠后的个体密度与未成年雌鼠的性成熟率呈显著负相关。这些结果表明未成年个体的性成熟延迟基于进化最优决策的证据较弱，而缘于个体间资源竞争的社群限制起主要作用。\n5．\t长爪沙鼠种群数量和增长率季节波动明显，种群变化的因子分析发现，月种群变化率与当月密度无显著相关关系，但与前一个月的种群密度负相关；气温和降水与种群增长显示明显的负相关；结合繁殖和存活指标的多元回归分析发现，繁殖性能和存活的增强在提高沙鼠种群变化率中起直接作用。密度、气候因子与繁殖和存活之间相关分析结果显示，在繁殖期，繁殖与密度无明显关系，但与气温和降水负相关明显；无论繁殖期还是繁殖休止期，存活受到前一个月密度的明显制约，同时受气温和降水的负面影响。上述结果表明在长爪沙鼠种群过程中，由密度反馈形成的社群环境以及气候效应介导的栖息地变化可引发生活史变量改变，进而影响了种群增长。其中，在春夏繁殖季节，水热效应对种群变化的贡献较大；而在秋季贮食-繁殖休止阶段，种群变化的密度效应尤为突出，不过，密度制约反馈调节有一定的时滞，不是直接产生作用。\n6．\t长爪沙鼠具特定年龄阶段结构的种群模型分析结果显示，各生活史变量的弹性效应在其种群过程中呈现明显的季节特征，在繁殖初期，生长发育-繁殖和存活对种群变化的贡献率均在50％左右，此后，存活对种群变化的影响逐渐显示主导作用，其中，夏末至深秋繁殖休止期间，对种群变化的80％－100％贡献均缘于种群个体的存活。基于生活史变量在种群水平上的进化趋向使种群增长率最大化，存活对长爪沙鼠种群增长的贡献贯穿整个年度，而生长发育和繁殖对种群变化的作用，仅在春夏繁殖初期显示与存活贡献相当，其促进要素仅在繁殖季节起选择作用。就其应用而言，如能在繁殖初期，通过干扰措施降低长爪沙鼠繁殖和存活将对其种群增长具有明显的抑制作用；此后的效果则可能大大降低。\n\n综上所述，通过本项研究明确了长爪沙鼠种群过程响应繁殖性能和存活变化的季节模式，并揭示了密度制约和水热条件在上述响应过程中的作用方式和强度。为全面理解生活史变量-行为-环境因子在长爪沙鼠种群过程中的整合调节作用，以及生活史对策的适应意义提供了重要依据，亦为深入探索干旱区群居型鼠类种群调节机制及管理对策提供了新的视角。 |
| 英文摘要 | In temperate and arctic regions small mammals experience highly seasonal environments, seasonal environments can have important effect on life cycle or life history. Because population processes represent the cumulate effects of variation or integrative patters of life history variables, seasonal structures of life history determine the seasonal dynamics of small mammals populations, or even the consequences of seasonality and its regulation processes involving endogenous and exogenous ecological factors appears to be the crucial role on the production of multi-annual cycles of small mammal population. In the current paper, we studied population dynamics of Mongolian gerbils under semi-natural conditions using monthly live trapping from 2000 Oct to 2004 Oct in south-central Inner Mongolian. We present population capture-mark-recapture (CMR) and behavioral observation data from the 4-year live-trapping in our enclosure and laboratory study of Mongolian gerbils in Inner Mongolia. First, using CMR statistical analysis to measure the temporal scale (between month and inter-seasonal) varies of the maturation, reproduction, recruitment and survival at the population lever in gerbils, we analyzed the adapted mechanism and significance of the characteristics and seasonal patterns in reproduction or survival. We also compared the difference of social behaviors among individuals between breeding (BP) and the breeding lull and food hoarding period periods (BNP) to investigate the behavioral adapted to annual life cycle. Second, using linear regression models to detect the relationships between monthly intrinsic per capita rate of population change (r) and population density, monthly average temperature, monthly total precipitation and life history variables, we aimed to: 1) determine whether the population of Mongolian gerbils was affected by density dependent feedbacks; 2) determine how gerbil population responded to seasonal weather changes (i.e., temperature and precipitation); 3) assess the roles of the reproductive and survival parameters in the seasonal population dynamics of gerbils; and 4) also examined the difference in the effects of the aforementioned factors between the breeding and nonbreeding seasons. Third, we estimated the elasticity (the relative change in population change rate due to a relative unit change in the parameter of concern) derived from projection linear matrix models to assess the relative contribution of survival and reproduction components to the realized population change rate (λ) and its seasonal structure.\nThe main results and conclusions are as fallows:\n1.\tMongolian gerbils’ reproductive performance and success showed distinct seasonal changes in our enclosure. Reproduction and recruitment occurred primarily from March-May and then declined in summer, with a breeding lull in autumn (September –October) and the winter reproductions in January or February. Results of age-specific reproductive performance revealed that maturity was first attained at about 2-month age, gerbils born in winter and spring usually matured and those born later in the summer seasonal commonly delayed maturation to the following breeding season. Age-specific litters were also found in female gerbils. Over-winter females and those born in winter could breed 3 or 4 litters, and those born in early spring (March to May) could breed 1 times during current year. The data indicated that the age-specific maturation and reproductive patterns were the vital characteristic of life history strategies of Mongolian gerbil born in different seasons. We suggested that they might be important variables in the population dynamics of Mongolian gerbils.\n2.\tThere were no gender significant differences in Mongolian gerbils’ survival in our enclosure. The stage–specific, defined according to the breeding condition, survival was only displayed markedly in females. Survival in autumn, winter and early spring breeding periods of young (having delayed maturation) females enjoyed better survival than adult (matured or breeding) ones. By contraries, adult female survivals were higher than those of young females from April to August. Especially in August, the difference was significant. Our results also found the survival of typical seasonal variation corresponded to a lower apparent survival in summer compared to the rest of the year, and showed a dynamic pattern of the “V” form. We demonstrated that the reproductive competition and senescence were evident for the survival of stage-specific patterns and that of seasonality, which were based on the physiological and behavioral variations. We also suggested that the survival patterns at the population lever might result in population fluctuation of Mongolian gerbils. \n3.\tTo group-living rodents, levels of intra-specific interaction particularly agonistic action can play important roles in determining the processes of spacing, social systems and population dynamic. Compared our results of changes in social behaviors of intraspecific individuals in Mongolian gerbils, we found agonistic acts in adult male-male encounters were more than that of male-female or female-female encounters and adult gerbils aggressed to the same sex young more strongly than to the opposite sex ones during breeding period, whereas during the breeding lull and food hoarding period, no significant difference in the agonistic and amicable acts were showed among all kinds of dyadic encounters. In addition, results of behavior seasonal patterns revealed that only agonistic act of male-male encounters in BP more significantly intense than those of in BNP，and social acts of others encounters have similar exhibition between two season. We conclude that social competition interaction display distinct sex-specific and seasonal characters, which are the consequences of adapted to the social organization and annual breeding and hoarding life style. We account that the process of social aggression and affiliation may regulate the recruitment success survival and dispersal gerbils as well as dose the changes in individual spacing and social organization in nature.\n4.\tIn analyzing synthetically the characteristics of age-specific reproduction and survival, we suggested that gerbils born in winter and spring usually prefer to the “fast” strategies having relative shorter lives and early matured and breeding, contrarily, those born in summer selected the “slow” strategies with longer lives and delaying maturation and reproduction. Our results discriminated between two proposed adapted mechanisms of delay maturation - an evolutionary optimal decision or a social constraint due to environmental conditions, indicated that empirical values of young female and adult female survival were not consistent with survival values assumed in theoretical models on optimal deferred breeding although winter survival of young was higher than survival of adult gerbils. Results, at the same time, denoted that there was a trend of density-dependent relationships between the maturation rate of young gerbils and the density already established breeding female, and a significant density-dependent relationships between the maturation rate of young gerbils and the density already established gerbils except for breeding female. We concluded, on the basis of these findings, no evidence suggesting that the observed delayed maturation represents an evolutionary optimal strategy. Rather there was evidence suggesting that the delay is due to social constraints. \n5.\t Mongolian gerbils displayed seasonal fluctuations of density and the intrinsic per capita rate of population change (r). Rate of population change in Mongolian gerbils were not directly related to population density but were negatively related to density of one-month ago, temperature and precipitation; moreover enhanced reproductive performance，success of females and survival increased population growth of gerbils in our enclosure. We also found that increased temperature and precipitation but not density during the plant growing season negatively affected recruitment, rate of pregnancy, and delayed density-dependence survival was more predominant during breeding lull and food-hoarding time than that of in breeding season. Mongolian gerbils prefer habitats with short, sparse vegetation and dry, loose and sandy soil. Increases in temperature and rainfall enhance vegetation growth; consequently, tall, dense and moist vegetation might reduce the suitability of habitats and retard population growth of Mongolian gerbils. Pronounced seasonal climatic fluctuations in northern latitudes in breeding season and delayed effect of competitions for territory or over-winter food result from density-dependence on survival in nonbreeding season may be the main causes of seasonal population dynamics of Mongolian gerbils, respectively. \n6.\tThe seasonally determined life-history variables structure and the elasticities of the realized population change rate (λ) to change in the stage-specific vital rates in Mongolian gerbils under our semi-natural condition populations was measured from female stage-specific projection linear matrix models. We found the elasticity coefficients of λ to change in the growth-reproduction and survival components both were about 0.5 from March to April, but from May through October, the elasticity coefficients of λ to change in survival components were predominant than that of the growth-reproduction components and the coefficients were ranged from 0.8 to 1.0 since August. We demonstrated that reproduction and survival during the early breeding season contribute approximately equally to population change or growth in Mongolian gerbils, whereas the survival contributes far more than growth-reproduction during the nonbreeding season. On this basis, we discuss evolutionary and applied (pest control) issues. Regarding the evolution of life histories (leading to a maximization of the overall net annual growth rate), we suggested that features favoring survival through the year will provide selective value, particularly outside the breeding season. But that during the early breeding season, features favoring growth-reproduction and survival are about equally favorable. Regarding pest control (aiming at reducing the overall net annual growth rate), we suggest that affecting growth and reproduction of female only in early breeding time is effective, but affecting survival especially outside the main breeding season is particularly effective for the Mongolian gerbil\n In sum, we demonstrate through this comparative study that much is to be learnt from studying the dynamics of fluctuating small rodents living the semi-arid or arid regions. |
| 中文关键词 | 长爪沙鼠(Meriones unguiculatus) ; 生活史变量 ; 社群行为 ; 生活史对策 ; 种群变化率 ; 种群调节 ; 矩阵模型 ; 弹性分析 |
| 英文关键词 | Mongolian gerbils (Meriones unguiculatus) life-history variable Social behavior Life-history strategies Rate of population change Population regulation Projection matrix model Elasticity analysis |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院动物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286645 |
| 推荐引用方式 GB/T 7714 | 刘伟. 长爪沙鼠生活史变量与其季节格局在种群调节中的作用研究[D]. 中国科学院动物研究所,2008. |
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