Arthropods on plants in a fragmented Neotropical dry forest： A functional analysis of area loss and edge effects

Loss and fragmentation of natural ecosystems are widely recognized as the most important threats to biodiversity conservation, with Neotropical dry forests among the most endangered ecosystems. Area and edge effects are major factors in fragmented landscapes. Here, we examine area and edge effects and their interaction, on ensembles of arthropods associated to native vegetation in a fragmented Chaco Serrano forest. We analyzed family richness and community composition of herbivores, predators, and parasitoids on three native plant species in 12 fragments of varying size and at edge/interior positions. We also looked for indicator families by using Indicator Species Analysis. Loss of family richness with the reduction of forest fragment area was observed for the three functional groups, with sirnilar magnitude. Herbivores were richer at the edges without interaction between edge and area effects, whereas predators were not affected by edge/interior position and parasitoid richness showed an interaction between area and position, with a steeper area slope at the edges. Family composition of herbivore, predator, and parasitoid assemblages was also affected by forest area and/or edge/interior situation. We found three indicator families for large remnants and five for edges. Our results support the key role of forest area for conservation of arthropods taxonomic and functional diversity in a highly threatened region, and emphasize the need to understand the interactions between area and edge effects on such diversity.

Natural vegetation cover in the landscape and edge effects： differential responses of insect orders in a fragmented forest

Human activities have led to global simplification of ecosystems, among which Neotropical dry forests are some of the most threatened. Habitat loss as well as edge effects may affect insect communities. Here, we analyzed insects sampled with pan traps in 9 landscapes （at 5 scales, in 100-500 m diameter circles） comprising cultivated fields and Chaco Serrano forests, at overall community and taxonomic order level. In total 7043 specimens and 456 species of hexapods were captured, with abundance and richness being directly related to forest cover at 500 m and higher at edges in comparison with forest interior. Community composition also varied with forest cover and edge^interior location. Different responses were detected among the 8 dominant orders. Collembola, Hemiptera, and Orthoptera richness and^or abundance were positively related to forest cover at the larger scale, while Thysanoptera abundance increased with forest cover only at the edge. Hymenoptera abundance and richness were negatively related to forest cover at 100 m. Coleoptera, Diptera, and Hymenoptera were more diverse and abundant at the forest edge. The generally negative influence of forest loss on insect communities could have functional consequences for both natural and cultivated systems, and highlights the relevance of forest conservation. Higher diversity at the edges could result from the simultaneous presence of forest and matrix species, although ＂resource mapping＂ might be involved for orders that were richer and more abundant at edges. Adjacent crops could benefit from forest proximity since natural enemies and pollinators are well represented in the orders showing nositive edge effects.

Functional strategies and distribution of climbing plant communities in different vegetation patches in a subtropical dry forest, central Argentina

Aims In the context of global change,the impacts of forest structure alter-ation on climbing plants in extra-tropical ecosystems are poorly understood.It also remains little explored,the functional strategies among climbing plant species and its relationship with the local-scale distribution of climbing plant communities.Here,we aimed at three goals:(i)we studied how climbing plant community com-position responds to the modification of the original forest structure in a subtropical dry forest;(ii)we characterized climbing plant spe-cies according to functional traits related to the acquisition and use of resources;and(iii)we examined whether functional strategies at the community level are also responding to vegetation structure change,a much less addressed topic in the ecology of climbing plants.Methods The study was carried out in the Chaco forest of Córdoba Mountains,central Argentina.We selected 18 patches of‘native forests’,‘shrublands’and‘Ligustrum lucidum forests’.We counted and identified climbing plant individuals in each patch,including woody and herbaceous species.For each spe-cies,we measured 10 functional traits:leaf area,leaf area ratio,leaf dry matter content,leaf tensile strength,specific leaf area,stem density,wood saturated water content,inter-node length,petiole length and plant cover.We compared climbing plant composition,richness and abundance among the three vegeta-tion types.Then,we assessed trends of functional variation of climbing plant species by performing a principal component analysis.Finally,we investigated whether simple mean,weighted mean and Functional Richness index of principal component analysis(PCA)axes differed among the climbing plant communi-ties of the three vegetation types.Important Findings Multivariate analysis revealed that climbing plant composition of native forests significantly differed from that of shrublands and L.lucidum forests.Also,L.lucidum forests had the lowest climb-ing plant species richness.Functional variation of climbers was explained by three PCA axes:axis 1 represented the resource-use strategy,axis 2 was associated with light-foraging strategy,and axis 3 related to plant size.The most abundant species in native forests presented a more acquisitive functional strategy and larger sizes than those of shrublands and L.lucidum forest.Furthermore,the most abundant species in shrublands had shorter internodes and petioles than the most abundant climbers of the other vegeta-tion types.Finally,the climbing plant community in the native forests had the highest Functional Richness index regarding the resource-use and the size strategies.Here,we demonstrated that there are floristic and functional differences among climb-ing plant communities in patches of three vegetation types in a subtropical dry forest biome.Particularly,we found climbers spreading along three functional axes which were directly related to climbing plant community distribution among the different patches,highlighting their ecological importance and the need of further research.