Seasonality and long-term change in a savanna environment
Seasonality and long-term change in a savanna environment
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DOI：
10.1017/cbo9780511542343.007
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发表时间：
2005-01-01
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影响因子：
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通讯作者：
Altmann, Jeanne
中科院分区：
文献类型：
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作者：
Alberts, Susan C.;Hollister-Smith, Julie A.;Altmann, Jeanne
在过去的500万年里，非洲稀树草原的出现和蔓延经常被认为是人类进化的一个主要因素。热带稀树草原与森林的不同之处在于降雨量较少，降雨量具有强烈的季节性，即使在季节内也往往非常不可预测（Bourliere & Hadley 1983; Solbrig 1996）。人们认为人类祖先迁入热带稀树草原是对气候变冷和干燥的一种反应，而稀树草原环境的紧急状况——包括植物食物供应的显著季节性变化——经常被认为是形成原始人谱系的关键选择压力（参见Foley[1987, 1993]、Potts [1998a， 1998b]、Klein[1999]和第4、5、17章的评论和参考文献）。这种情况需要仔细研究现存的热带草原灵长类动物对季节性的反应。像大多数脊椎动物一样，绝大多数灵长类动物表现出生殖季节性，这反映了它们栖息地的季节性（见第11章的回顾）。事实上，在生活在大草原上的灵长类动物中，只有两种例外：人类和狒狒（Papio属）。这种共同的特征——在季节性环境中全年繁殖的能力——可能与这两个属的非凡成功有关。虽然只有人类（和他们的共生动物）遍布全球，但狒狒在非洲已经实现了几乎整个大陆的分布。的确，番木瓜属，越来越多地被视为具有多个亚种的单一物种（Jolly 1993），占据了从沙漠到半干旱的热带热带草原到温带山地草原到潮湿的常绿森林的栖息地（Estes 1991; Jolly 1993; Kingdon 1997）。Papio和homo的这些共同特征——广泛的地理分布，在稀树草原环境中成功但不限于稀树草原环境，以及非季节性繁殖——使得对狒狒行为的季节性分析特别有价值，因为季节性被认为在选择独特的人类特征方面发挥了作用（Foley 1987, 1993）。在本章中，我们研究了乞力马扎罗山脚下安博塞利盆地稀树草原狒狒种群的季节性行为模式。安博塞利是一个半干旱的栖息地，也是研究狒狒的干燥栖息地之一（见Dunbar[1992]的综述）。我们使用了16年的成年雌性狒狒的行为数据，结合人口统计和气象数据，来检验关于季节性环境对狒狒行为影响的假设。在我们的结果之前，首先是对热带草原季节性的描述，以及我们将用这些数据测试的假设大纲，然后是狒狒生态学和安博塞利生态系统的背景。
The emergence and spread of savannas in Africa during the past five million years is often cited as a major factor in hominid evolution. Tropical savannas are different from forests in having less rainfall, which is strongly seasonal and often very unpredictable, even within seasons (Bourliere & Hadley 1983; Solbrig 1996). Human ancestors are thought to have moved into savannas as a response to cooling and drying climates, and the exigencies of the savanna environment–including the marked seasonal changes in plant food availability–are often cited as key selective pressures shaping the hominid lineage (see reviews and references in Foley [1987, 1993], Potts [1998a, 1998b], Klein [1999], and Chapters 4, 5, and 17). This scenario invites a careful examination of responses to seasonality in extant savanna-dwelling primates.Like most vertebrates, the large majority of primate species exhibit reproductive seasonality that reflects the seasonality of their habitats (see review in Chapter 11). Indeed, among savanna-dwelling primates, there are only two exceptions to the rule of seasonal reproduction: humans and baboons (genus Papio). This shared characteristic–the ability to reproduce throughout the year in seasonal environments–may be related to the extraordinary success of these two genera. While only humans (and their commensals) have spread across the globe, baboons have achieved a nearly continental distribution in Africa. Indeed, the genus Papio, increasingly treated as a single species with multiple subspecies (Jolly 1993), occupies habitats ranging from desert to semi-arid tropical savanna to temperate montane grasslands to moist evergreen forest (Estes 1991; Jolly 1993; Kingdon 1997). These shared features of Papio and Homo–a wide geographic distribution, success in but not restriction to savanna environments, and nonseasonal reproduction–make analyses of seasonality in baboon behavior especially valuable in light of the role that seasonality is proposed to have played in selecting for unique human traits (Foley 1987, 1993). In this chapter, we examine seasonal patterns of behavior in the well-studied population of savanna baboons in the Amboseli basin at the foot of Mt Kilimanjaro. Amboseli is a semi-arid habitat and one of the drier habitats in which baboons have been studied (see review in Dunbar [1992]). We employ 16 years of behavioral data on adult females, combined with demographic and meteorological data, to test hypotheses about the impacts of the seasonal environment on baboon behavior. Our results are preceded first by a description of savanna seasonality and an outline of the hypotheses that we will test with these data and then by background on baboon ecology and on the Amboseli ecosystem.