Ó Springer 2006
Hydrobiologia (2006) 559:297–304 DOI 10.1007/s10750-005-9400-8
Primary Research Paper
Geographical distribution of testate amoebae in Tibet and northwestern Yunnan and their relationships with climate Jun Yang1,2, Wenjing Zhang1,2, Weisong Feng1 & Yunfen Shen1,* 1
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 430072 Wuhan, P.R. China 2 Graduate School of the Chinese Academy of Sciences, 100039 Beijing, P.R. China (*Author for correspondence: E-mail:
[email protected]) Received 20 May 2005; in revised form 8 August 2005; accepted 28 August 2005
Key words: Protozoa, testacea, distribution, climate, Tibet, Yunnan, China
Abstract In Asia, especially in China, our knowledge of the distribution of testate amoebae is still limited. In this paper, the geographical distribution of testate amoebae in Tibetan Plateau and northwestern Yunnan Plateau, southwest China and their relationships with the climatic factors have been studied. We found testate amoebae shifted in the most dominant species and increased in species (or genus) richness from northwest to southeast. Further, the linear regression analyses revealed that both species richness and genus richness have higher positive correlations with the mean temperature of the warmest month and annual mean precipitation as contrasted with the mean altitude, which showed weak negative correlation. This indicates that the temperature and precipitation are more significant influences on the richness than the altitude. The cluster analysis based on the community structure, defined by Sørenson’s coefficient matrix, suggested four groups from the 10 physiographical regions. This geographical distribution pattern was also closely related with the climatic regionalization. The present climatic regionalization pattern of the study area originated from the uplift of Tibetan Plateau and mainly occurred in or after the late Pleistocene. Therefore, the geographical distribution of testate amoebae in our study area may have experienced complicated and drastic changes corresponding to the variation of the climate caused by the geological events.
Introduction The Qinghai-Tibetan Plateau, known as the roof of the world with an average elevation of 4500 m above sea level, is the highest, largest and youngest plateau on the Earth (Lin & Wu, 1981; Zheng, 1996). The biogeography of Qinghai-Tibetan Plateau is of special interest because of the particularly complex geological and biological history of the region. Recently, it has been considered as an independent and special zoogeographic unit and has an equal position with the Holarctic Region and the Oriental Region (Chen et al., 1996). The uplift of Tibetan Plateau is a major event in the natural history of the Earth and it has greatly
modified and changed the climate and environment of both itself and adjacent regions (Jackson, 1980; Molnar, 1989; Chung et al., 1998; Ruddiman, 1998; Shi et al., 1998; Li & Fang, 1999; An et al., 2001). Testate amoebae are a very widespread and ecologically important group of protozoa. They possess a shell enclosing the amoeboid body and are provided with an aperture for the pseudopodia (Foissner, 1987; Meisterfeld, 2002). In recent years, there have been a large number of studies on the biodiversity, ecology and biogeography based on the fauna data from the Antarctic and Arctic (Beyens et al., 1990; Beyens & Chardez, 1995; Smith, 1996; Wilkinson, 2001; Smith & Coupe, 2002). Nevertheless, in Tibetan Plateau the earlier
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Materials and methods
(Fig. 1). Tibetan Plateau has been divided into seven natural zones according to the temperature conditions, moisture regimes and variation in landforms (Zheng et al., 1979; Zheng, 1996). Also, Qomolangma Mountain (Everest) was included and separated into the northern and southern mountain (Wang, 1974; Shen, 1983). As an adjacent region of Tibet, northwestern Yunnan Plateau was chosen as a sole unit for analysis (Yang et al., 2005). Affected by atmospheric circulation and topographic configuration, different regions have different combination of temperature-moisture conditions, which change from semitropical-humid in the southeast to alpine coldarid in the northwest. For analytical purposes, the mean altitude of sampling sites and the climatic factors (mean temperature of the warmest month and annual mean precipitation) were derived from the previous publications (Zheng, 1975; Zheng et al., 1979; Lin & Wu, 1981; Zhang et al., 1982; Shen, 1983; Yang, 1983; Zhang, 1989; Yang et al., 2005). The natural conditions of the 10 regions are summarized in Table 1.
Study area
Testate amoebae data
The study area included both Tibetan Plateau and northwestern Yunnan Plateau, southwest China
A total of 665 samples were collected between 1966 and 1981 in diverse ecological conditions (ponds,
studies mainly focused on documenting and recording new records of species, rather than exploring the geographical distribution of testate amoebae (Wang, 1974, 1977; Shen, 1983). Moreover, the publications were in Chinese and not available to the greater part of occidental scientists. This means a gap in our basic knowledge on the biogeography and biodiversity of testate amoebae. In the most widespread survey to date, Shen (1983) documented the distribution of species in Tibetan Plateau, but no attempt was made to infer the factors involved in determining or controlling the distribution of species between different climatic regions. More recently, the faunistic data on testate amoebae in northwestern Yunnan (an adjacent region of Tibetan Plateau) were provided by Yang et al. (2005). The aim of this work is to make an analysis of the geographical distribution of testate amoebae in Tibet and northwestern Yunnan, and its relationship with climatic factors.
Figure 1. Map of China showing the locations of the 10 study regions. For region abbreviations see Table 1.
299 the community structure defined by Sørenson’s coefficient matrix, with 1-Pearson r as dissimilarity measure, was used to classify the 10 regions. Two methods including unweighted pair-group average and Ward’s method were employed. The goodness of the clustering method was assessed by computing the cophenetic correlation coefficient. All the statistical analyses were performed using the computer program STATISTICA ver. 6.0 (StatSoft Inc. USA).
streams, lakes, rivers, springs, ditches and others) from the study area. They were taken with a 64 lm mesh plankton net and scraped from substrates (e.g., stones and macrophytes), fixed with 5% formaldehyde, and preserved in the Herbarium of the Institute of Hydrobiology in Wuhan, China. The numbers of samples from different regions are listed in Table 1. The detail data on fauna of testate amoebae were given by Wang (1974, 1977) and Shen (1983) based on the investigations in Tibetan Plateau and by Yang et al. (2005) in northwestern Yunnan Plateau. The total number of species in the data set, from Tibetan Plateau and northwestern Yunnan Plateau combined, was 207.
Results The species (or genus) richness of testate amoebae varied widely between regions. It was highest for the northwestern Yunnan Plateau (29 genera, 151 species), while the lowest was recorded for the northern Tibet Kunlun Mountains (1 species) (Fig. 2). Within the 10 regions, both species and genus richness increased gradually from the northwest to the southeast (Fig. 2). The correlations between number of samples and other variables were not significant at p
