The Effects Of Habitat Fragmentation On Termite Species Diversity And Functional Traits In The Thousand Islands Lake,China

As an important taxa of soil arthropod decomposers,termites play a key role in maintaining ecosystem functions.Habitat fragmentation is one of the main factors for the loss of biodiversity which causes yearly increasing species extinction,thus has received great attention from ecologists.In addition,habitat fragmentation can also cause the changes in environmental factors,and then influences the functional traits of organisms including termites.The land-bridge island system formed by the construction of reservoir dam is an ideal experimental platform for studying the effects of habitat fragmentation,due to clear landscape pattern,well-delineated boundaries of patches(islands)as well as synchronous isolation time.The Thousand Island Lake(TIL)with more than 1000 islands in Chun'an County,Zhejiang Province,is a typical land-bridge island system.We have been studying termite biodiversity and functional traits on 25 islands in TIL by field survey,sampling,and experiments.Termites species identification is the basis for studying diversity,but the results of the traditional morphological identification are not exactly accurate.Therefore,molecular identification was used as a supplement for this study.The results are mainly as followings:1.Species diversity(1)We identified 4 species termites that were hard to tell morphologically through molecular identification based on the mitochondrial CO? gene,and found the results were basically consistent with those of morphological identification.(2)We got 13 species termites from 8 genera and 2 families which belonged to 42100 m × 100 m transects in 25 islands.The dominant groups were Macrotermes barneyi and Odontotermes formosanus.All the termites could be divided into 8species of wood-feeder,2 species of fungus-grower and 3 species of soil-feeder.(3)Termite species richness had a significantly positive correlation with the island area,but had a significantly negative correlation with the isolation(distance to nearest island).Structural equation model showed that island parameters(area and isolation)affected the food resources(dead wood)of termites through various environmental factors,and finally affected termite diversity.(4)Termites of different feeding types had different responses to habitat fragmentation.Soil-feeding termite species richness had a significantly positive correlation with the island area,but had a significantly negative correlation with the isolation.Termite species richness of the other two feeding types had no significantly correlation with both the island area and isolation.Fungus-growing termite relative abundance had a significantly positive correlation with the island area,while that of wood-feeding termite was opposite.There was no significant correlation between soil-feeding termite and the area.The relative abundance of fungus-growing termite had a significant negative correlation with isolation,while the relative abundance of the other two feeding termites had no significant correlation with isolation.The different responses of different feeding types may be due to the different selection strategies of food resources,the fungus-growers prefer the wood of evergreen broad-leaved trees(higher proportion on larger islands),while the wood-feeders prefer the wood of coniferous trees(higher proportion on smaller islands).2.Functional trait(1)Most of the morphological functional traits of termites had no significant difference between the large island and the small island,but some of them still had significant differences.For example,the pronotum length of the small soldier of Macrotermes barneyi in big island was slightly larger than in small island;The head height of the soldier of Reticulitermes chinensis in big island was slightly smaller than in small island.In addition,to compare the length of the hind tibia in different termite species,we found the hind tibia length of Macrotermes barneyi and Odontotermes formosanus were larger.(2)We designed a controlled experiment to compare the desiccation tolerance of Macrotermes,Odontotermes and Reticulitermes,and found that under the dry experimental conditions,termites had higher water loss rates(that is,poor desiccation tolerance),but there was no significant difference between tolerance in large islands and small islands.