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In many regions of tropical Asia, the expansion of rubber monoculture plantations is conducted by replacement of natural forest areas and strongly affects biodiversity and movement patterns of wild species, including insects. Against this background, we conducted a study on selected insect groups (longhorn beetles, bark beetles, wild bees and hoverflies) along transects between rainforest patches, open uncultivated land and rubber plantation habitats in a region of Xishuangbanna (southern Yunnan, China), with the objectives to identify (a) movement directions and patterns of selected insect groups based on their abundances in modified Malaise traps in the different habitats, and (b) the role of remaining natural rainforest patches and rubber plantations, respectively, for insect diversity maintenance and conservation. The highest total numbers of species and individuals of bark beetles, longhorn beetles and wild bees were recorded from the natural forest edge compared to open land and rubber plantation edge. This result clearly indicates that the natural forest plays an important role in maintenance of these three insect groups. However, the highest number of hoverfly species and individuals was recorded from the open land sites, indicating the most relevant habitat type for this group of species. Overall, the lowest species and individual numbers were recorded from the rubber plantation edge, indicating the unsuitability of this habitat type for all insect groups considered. The distribution of species and individuals in the opposite trap sides along the transect indicates that longhorn beetles, bark beetles and wild bees show not only movements from the forest to the surrounding habitats, but also return back after encountering the unsuitable rubber plantation habitat. Bark beetle composition showed the relatively highest similarity between all trap sites and opposite trap sides among the insect groups considered, indicating a higher movement activity than the other groups. The four insect groups considered in this study show different movement modes between the forest, open land and rubber plantation, which are not the same for all taxa. Except for hoverflies, the natural forest was found to be the most important habitat for the maintenance of species diversity in the different land use types of the study area. [ABSTRACT FROM AUTHOR]

The response of insects to monoculture plantations has mainly proceeded at the expense of natural forest areas, and is an outstanding and important issue in ecology and conservation biology, with pollination services declined around the world. In this study, species richness and distribution of hoverfly and wild bee communities were investigated in a changing tropical landscape in southern Yunnan, south-west China by Malaise traps periodically from 2008 to 2009. Species were recorded from the traditional land use types (natural forest, grassland, shrubland and rice field fallows), and from recently established rubber plantations of different ages. Hoverflies (total 53 species) were most common in young successional stages of vegetation, including rice field fallow and shrubland. Species richness was highest in rice field fallows and lowest in forests and showed a highly significant relationship with the number of forb species and ground vegetation cover. In contrast, the highest richness of wild bees (total 44 species) was recorded from the natural forest sites, which showed a discrete bee community composition compared to the remaining habitat types. There was no significant relationship between the bee species richness and the environmental variables, including the numbers of different plant life forms, coverage of canopy and ground vegetation, successional age of vegetation and land use type. At the landscape scale, open land use systems, including young rubber plantations, are assumed to increase the species richness of hoverflies; however, this might decrease wild bee diversity. The present land use change by rubber cultivation can be expected to have negative impacts on the native wild bee communities. [ABSTRACT FROM AUTHOR]

Wild bananas are abundant in tropical areas and many ecologists have observed that the succession process is quicker following increased disturbance. This study was conducted to analyze animal-seed interactions and their effects on the seed fate of a wild banana species ( Musa acuminata) in tropical southern Yunnan (China) through experiments considering spatial (site and habitat) and temporal (seasons) variation. The largest proportion of fruits (81%) was removed by frugivorous seed dispersers, especially by bats at nighttime. Only 13% of the fruits were removed by climbing seed predators (different species of rats). In the exclosure treatment, rodents accounted for a significantly higher total artificially exposed seed removal number than ants, but with spatial and temporal differences. The highest seed predation rate by rodents (70%) was found in forest with wild banana stands, corresponding with the highest rodent diversity (species numbers and abundance) among the habitat types. In contrast, the seed removal number by ants (57%) was highest in the open land habitats, but there was no close correlation with ant diversity. Seed removal numbers by ants were significantly higher in the dry compared to the rainy season, but rodent activity showed no differences between seasons. The overall results suggest that the largest proportion of seeds produced by wild banana are primarily dispersed by bats. Primary seed dispersal by bats at nighttime is essential for wild banana seeds to escape seed predation. [ABSTRACT FROM AUTHOR]