Studies On Tardigrada Community Diversity On Nanwutai, Qinling Mountains

Tardigrades are a kind of hydrophilous micrometazoans and are generally considered to be an independent phylum, Tardigrada. Phylogenetically, tardigrades are a sister group of the arthropods. So far, most studies on Tardigrada community were carried out in Europe, but there haven't a certain conclusion of altitude and season imposing effect on tadigrades distribution, while very few similar studies were made in China.This dissertation studied the tardigrade community of the Mount Nanwutai on the northern slope of Qinling Mountains. Three sample localities were selected from altitude of 800 meters to 1,400 meters, selecting three big rocks having flaky mosses in each sample locality. Taking five point sampling method set up sample areas on each rock. A total of 540 sample areas within the three localities ware investigated. Species diversity, ordination, simple regression analysis and stepwise multiple regression analysis were used to analysis. Tardigrade species component, relationship between community component and environmental factors, relationship between species diversity and environmental factors were systematically studied. The main results of this study are listed as follows.1 A total of 7,947 specimens belonging to 25 species, 11 genera, 4 families, 3 orders and 2 classes, were collected. Of which, 4 species belonged to the family Macrobiotidae, 15 species belonged to the family Hypsibiidae, 5 species belonged to the family Echiniscidae, and 1 species belonged to the family Milnescidae. Species abundance in the families increased along the following ordination: Macrobiotidae > Hypsibiidae > Echiniscidae > Milnescidae. The dominant genus was Macrobiotus with two dominant species, Macrobiotus harmsworthi and Macrobiotus hufelandi.2 ANOVA results indicated that the mounths imposed significant effect on the number of tardigrades (F_11,108 = 5.937, P <0.01), but not on the number of species (F₁₁, 36 =1.31, P>0.05). Multiple comparison (LSD) of individual numbers in different months demonstrated that individual numbers in March, April, May and June weresignificant lower than other months.ANOVA results indicated that the individual numbers and species numbers were significantly influenced by altitude (F2,108= 87.667, P <0.01;F2)36 = 6.148, P <0.01). The individual numbers and species diversity increased with the altitude increasing. Multiple comparison (LSD) of species numbers and species diversity at different altitude indicated that the species numbers at higher altitude were significantly more than lower altitude, and the individual numbers at higher altitude were significantly more than middle altitude and lower altitude, and the individual numbers at middle altitude were significantly more than lower altitude.3 The fluctuation trend of species diversity in different months is presented as follows. Margalef index, Shannon-Wiener index and PIE were higher in months from October to next January, lower in April;while Simpson index was higher in April, lower in November, December and January;the improved Hill index were highest in June and September, lower in April, October, November and December. ANOVA results indicated that Simpson index, Shannon-Wiener index, Margalef index were significantly influenced by seasonal changes, while PIE was not significantly influenced by seasonal changes.Fluctuation trend in species diversity at different altitude is that PIE and Shannon-Wiener index were biggest at lower altitude, least at medium altitude, and Simpson index was exactly contrary to PIE and Shannon-Wiener index. Margalef index were biggest at medium altitude, least at higher altitude. Fluctuation trend in the improved Hill index is that it decreased from higher altitude to lower altitude. ANOVA results also indicated that altitude exerted no significant influence on the all diversity index, namely the characteristic of species diversity at different altitude was samely. Although the species diversity was not significantly changed, the individual numbers and species numbers of tadigrades were significantly changed. As a result, the composition of tadigrade communities were in fact changed, but the change was concealed by the balance of species richness and evenness of the individual distribution at a certain extent.4 Simple regression analyses between diversity index and environmental factors indicated that there were significant relationship between the indexes, including species number, margalef index, Simpson index, Shannon-Wiener index and PIE, and climate factors including monthly mean temperature, total evaporation and ground temperature.Simple regression analysis between diversity index and environmental factors also indicated that the improved Hill index and the climate factors such as the monthly mean temperature, total precipitation, ground temperature, precipitation strength were significantly related. Multiple regression analysis between diversity index and environmental factors further indicated that the main factor that affects the community abundance was ground temperature, while the main factor that affects the community uniformity was the total amount of precipitation.5 Principle component analysis of climate factors and tardigrade community in different months indicated that principle component accumulative total variance contribution ratio of tardigrade community and climate factors in different months respectively reached 96.441% and 96.180%, which occupies the most information content representing the character of the whole climate and community. Of the all climate factors that influence the habitat heterogeneity of tardigrade community, monthly mean temperature, total evaporation and ground temperature were the most important factors exerting the main roles, total precipitation, the longest continuous precipitation and precipitation strength were in the next place, finish up as U-relative humidity. Generally speaking, hydrothermal condition of habitat influenced habitat heterogeneity of community.