典范对应分析是一种直观反映动物群落、属种分布与环境因子间关系的直接排序方法,已在生物界及生态环境研究方面得到广泛应用.为调查西藏地区介形类与环境因子间的关系,2012 年对藏北南部49 个不同水体表层沉积物中的介形类进行调查研究,获得介形类10 属22 种,其中Limnocythere dubiosa、Ilyocypris bradyi 和Candona candida 在49 个样点中出现频数分别达19 次、13 次和9 次,是藏北南部地区的常见种.介形类的生存环境同其水体的物化性质(pH 值、电导率及组分等)有重要关系,应用典范对应分析,对藏北南部地区49 个样点的22 种介形类与8 个环境因子的相关性进行研究,得出介形类分布与8 个环境因子间的相关性均在80%以上,表明该地区不同水体环境因子的变化对介形类分布的影响很大,水体的8 个环境因子中对介形类分布影响最大的是电导率、pH 值及亚硝酸盐含量.从物种分布看,Eucypris rischtanica、Leucocythere dilitata、Cypricercus moguntiensis 和Limnocytherellina kunlunensis 4 个种对环境的适应性相对较强.Leucocythere postericosta、Limnocytherellina bispinosa 和Candona houae 3 个种与电导率和亚硝酸盐含量明显正相关,且相关性较大,它们的高频度出现指示水体电导率及亚硝酸盐含量较高;在藏北南部地区的常见属种中,Limnocythere dubiosa 的分布与pH 值明显正相关,是水体高pH 值良好的指示生物,而Ilyocypris bradyi 和Candona candida 则对水体低电导率有着良好的指示作用.
Canonical correspondence analysis (CCA) is a direct sequencing method which can reflect the relationship among communities, distributions of species and environment factors in a simple way, and be used to study the relationship between the biology distribution and the environment factors effectively. It has been used in the biology and the ecological environment widely. In this paper, 49 surface sediment samples are collected to study the ecological distribution of extant ostracodes and their environmental implications for water bodies in south of northern Tibet in 2012. Total of 10 genera and extant ostracodes of 22 species are identified, among which, Limnocythere dubiosa, Ilyocypris bradyi and Candona candida are the common species with high occurrence frequency of 19, 13 and 9, respectively in Ali and Naqu regions, Tibet. CCA reveals a correlation coefficient of more than 80% between the extant ostracodes distribution and the eight environmental factors, suggesting that the distribution of many species is highly related to environmental changes. Among eight environmental factors, the conductivity, the pH value and the nitrite content are the most affective variables on the species occurrence. Eucypris rischtanica, Leucocythere dilitata, Cypricercus moguntiensis and Limnocytherellina kunlunensis have relatively strong adaptability to the water environment. The high occurrence frequency of Leucocythere postericosta, Limnocytherellina bispinosa and Candona houae corresponds to a high water conductivity and nitrite content, as the distribution of these species positively correlates with the water conductivity and the nitrite content, suggesting that the three species are good indicators for the water conductivity and the nitrite content. On the other hand, Ilyocypris bradyi and Candona candida are good indicators for the low conductivity. As for Limnocythere dubiosa, the most frequently occurred ostracode in Ali and Naqu regions, is a good indicator for the high pH value.
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