Diversity Of Ground-Dwelling Beetel Taxa In Fragmented Habitat Of The Thousand Island Lake

Thousand-Island Lake(TIL), which was formed by building reservoir, is one of the biggest artificial lakes in China. The original continuous habitat was split up into many islands of different areas and shapes as a result of water surface ascent. Consequently, the communication between different islands’ flora above population size was cut down, and TIL became a natural place of studying the effect of habitat fragmentation on flora. To understanding the composition of ground-dwelling beetle communities(GDBCs) systemically and comprehensively in TIL reservoir, grasping the spatiotemporal dynamic change rule of GDBCs in TIL’s fragments, providing scientific basis of protecting GDBCs reasonably to a certain extent, we sampled beetles from July,2012 to April,2014.26 plots on islands and 9 on mainland were chosen to investigate by pitfall traps. The diversity, spatial distribute, seasonal dynamic change of GDBCs and the correlation between islands’ characteristic parameters and GDBCs was studied at the family level.1. A total of 3763 beetle specimens belonging to 26 families were collected in the whole sampling period. Among these, Carabidae, whose individual numbers were more than 50% of the total individuals, was absolute dominant taxa in this region, while Curculionidae was dominant taxa, Scarabaeidae, Lucanidae, Melolonthinae, Scolytidae and Staphylinidae were common taxas. The GDBCs in TIL reservoir were formed by predators mostly, scavengers and phytophages secondly.2. During this sampling period, Paussidae, Erotylidae, Cetoniidae, Siliphidae, Meloidae and Cantharidae were only found on islands, Attelabidae and Valgidae were only found on mainland. Predators formed the main body of guilds on sampling islands, while the mainland’s was phytophages. Independent sample t-test and community similatiry analysis (S(?)rensen index=0.82, Morisita-Horn index=0.91) showed that no matter at the individual level or family abundances level,there were no significant differences in GDBCs to these two kinds of sampling plotsThe GDBCs’individuals and family abundances were no significant differences between different area gradients, but were significant differences between different islands’groups. The highest diversity index (H’) was of Jie Shou East islands, while the lowest was of center islands. The highest dominance index was of center islands, while the lowest was of Jie Shou East islands. The highest abundance index was of Mei Feng islands, while the lowest was of Xu Yuan islands. The highest evenness index was of Xu Yuan islands, while the lowest was of centre islands. Community similarity analysis showed that the degree of similarity among different islands’ groups were higher. Cluster analysis could classify these islands’groups well according to their relative locations, islands’groups that are closer to each other at the geographical position could classify into the same group.3. The correlation of five islands’characteristic parameters, including islands’ area(A), shape index(SI), distance to the nearest island(DI), distance to the nearest mainland(DM) and perimeter/area ratio(PAR), was analysed, also it was done between five islands’characteristic parameters and GDBCs’taxa abundances, including taxas with high-dispersal ability(Th), taxas with low-dispersal ability(Tl), predators(Pr) and Phytophages(Ph). The results showed there were significant correlations between A and SI, A and PAR, SI and PAR, DI and DM. As a whole there was no significant correlation between taxa abundances and islands’characteristic parameters. However the taxa abundances of islands’groups had a significant correlation with islands’characteristic parameters. Put it all together, Th, T1 and Ph had significant correlation with A and PAR, while there were no significant correlations between Pr and any characteristic parameters.4. Research on the seasonal dynamic of GDBCs in TIL indicated that seasonal fluctuations relation to GDBCs’individuals and family abundances were obvious. Individuals were highest in July,2012, then waved decline in the form of W type, and were lowest in April,2014. Family abundances were highest in July,2013, lowest in October,2012. Individuals in the same seasons had a great change, while family abundances didn’t. Ranking the family abundances from high to low according to months:July(summer)> April(Spring)> October(Autumn).Among the four community diversity indices, the curves’trend of diversity index(H’)、abundance index(D) and evenness index(J) were consistent, while the curve of dominance index had an opposite trend.The correlation of GDBCs’diversity indices, including individuals, family abundances, diversity index(H’), evenness index(J), abundance index(D) and dominance index(C), was analysed. The result showed that family abundances had a significant correlation with dominance index(C), diversity index(H’) and abundance index(D),so it is between dominance index(C) and diversity index(H’), abundance index(D). Also there was a significant correlation between diversity index(H’) and abundance index(D).