Although insects are crucial for maintaining ecosystem function, our understanding of their overall response to human activity remains limited. This is no less true of dungburying beetles (Coleoptera: Scarabaeidae: Scarabaeinae), which provide a suite of critical ecosystem functions and services, yet but face multiple conservation threats, particularly from landscape conversion. Here we use a review and meta-analysis to synthesize the current knowledge concerning response to tropical forest modification and fragmentation of dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae). For every modified habitat type and individual forest fragment across 33 studies, we calculated six dung beetle community parameters, standardized relative to intact tropical forest. We openUP (June 2007) organized modified habitats along an approximate disturbance gradient ranging from selectively logged, late and early secondary forest, through agroforestry, tree plantations, to annual crops, cattle pastures and clear-cuts. Secondary forests, selectively logged forest and agroforests supported rich communities with many intact forest species, while cattle pastures and clear-cuts contained fewer species overall with few forest-dwelling species. Abundance generally declined with increasing modification, but was quite variable. Communities in open habitats were often characterized by hyper-abundance of a small number of small-bodied species, leading to low evenness. Across fragmentation studies, dung beetle species richness, abundance and evenness declined in smaller forest fragments. Richness and abundance sometimes declined in more isolated fragments, although this response appeared to depend on matrix quality. Across both habitat modification and fragmentation studies, geographic location and landscape context appeared to modify dung beetle response by influencing the available pool of colonists.We discuss potential underlying mechanisms and conclude with recommendations for management and conservation and for future research.
This synthesis builds on the preceding articles of this Special Section and has three goals. We first review the nascent literature that addresses indirect effects of hunting for tropical forest plant communities. Next, we highlight the potential indirect effects of hunting for other groups of organisms. Our final goal is to consider what could be done to ameliorate the demographic threats to harvest-sensitive game species caused by unsustainable hunting. Three conclusions are possible at this time concerning the impact of hunting for tropical forest plant communities: (1) Hunting tends to reduce seed movement for animal-dispersed species with very large diaspores; (2) Hunting reduces seed predation by granivorous vertebrates for species with large seeds; and (3) Hunting alters the species composition of the seedling and sapling layers. The cascading effects of hunting are already known to affect bruchid beetles and dung beetles and are likely to affect other, nongame taxa. To ameliorate these problems, several lines of research should be further explored to facilitate the development of game management plans including: (1) alternative use of sources of animal protein; (2) income supplementation for local people from sources other than wild meat; (3) outreach and extension activities for communities; (4) recognition and facilitation of the shifting of attitudes towards hunting; (5) implementation of community-based wildlife management programs in regulated-use areas such as extractive reserves; and (6) landscape-scale conservation planning that maximizes the source-sink dynamics of harvested and unharvested game populations and enforces game regulations in strictly protected areas.Abstract in French is available at http://www.blackwell-synergy.com/loi/btp.
Mammal populations are increasingly hunted, yet the consequences of their disappearance from tropical forests have only recently been explored. Here, we summarize current research on the role of mammals in seed dispersal and postdispersal processes, such as seed predation and secondary dispersal, in different tropical regions. We evaluate how mammal features influence seedshadows and ultimately forest regeneration. Finally, we discuss the potential effect of changes in seedshadows caused by the elimination of many medium‐ and large‐sized mammals. The complex role that mammals play in creating and modifying seedshadows in tropical forests cannot be easily quantified, and in this review we emphasize the variation that exists both within and among mammal taxa and across continents. To bridge this gap in information, we suggest that more studies should evaluate the relative importance of the disappearance of both seed dispersers and seed predators for particular plant species so that we may begin to understand the balance between these two influences. We also suggest that future studies identify ecological redundancy in nonhunted vertebrates within any particular community to evaluate compensatory behavior that may help ameliorate some of the negative effects of hunting of large and medium mammals.
Seeds from tropical fiuiting trees ingested and defecated on the soil surface by primary dispersers (such as primates) are vulnerable to destruction from rodents, insects, and Fungi. Burial by dung beetles as an incidental result of their feeding and nesting activities often provides these seeds with rehgia from attack. To examine the effect of habitat disturbance on the dung beetle communities involved in this process, I surveyed dung beetles at three sites in the Amazon basin, in the states of Par& Amazonas, and Ronddnia, Brazil. Through principal component analysis on measurements of size and behavioral characters of beetles, I determined the relative quality of beetle species as seed dispersers (dispersal defined as horizontal or vertical movement of seeds) and ranked them into seed dispersal guilds. I used correspondence analysis to examine in what habitats (priiary forest or varying degrees of disturbed habitat) these guilds were abundant. Most guilds decreased with increasing habitat disturbance, but one g d d made up of large nocturnal burrowers (primarily Dichotomius) became more abundant with increasing disturbance (up to the level of highest disturbance surveyed), at which point all dung beetle species became scarce. Clear-cuts had lower species richness, lower abundance, and lower biomass than forested areas. These results imply that dear-cutting is detrimental to all seed dispersal dynamics in tropical rain forests, but that some levels of disturbance allow enough disperser activity to preserve this ecosystem function. RESUMOAs sementes de &ores tropicais ingeridas por dispersores primirios (como primatas, por exemplo) e depois defecadas na superficie do solo 60 vulnedveis h desuuiGo por roedores, insetos e fimgos. Como resultado de seu Mbito alimentar e de assentamento, 0 s besoms copr6fagos enterram as sementes, provendo refigio a estes ataques. A fim de examinar o efeito da permrbaGo do habitat nas comunidades dos besouros copr6fagos envolvidas no prOcesso, besoms copr6fagos foram estudados em trh locais da bacia Amdnica: nos estados do Pad, Amazonas e Ronddnia, n6 Brasil. Pela a d i s e do componente principal nas mediG6es de tamanho e caracteristicas de comportamento, foi determinada a qualidade relativa das espkies de besouros como dispersores de sementes (dispereo send6 aqui definida como 6 movimento vertical ou horizontal das sementes). As espkies foram agrupadas de acordo com sua preferencia de entern das sementes e criouse um ranking para estes grupos. Andise de correspondhcia foi utiliida para exarninar em quais habitats (floresta primiria ou locais corn niveis d v e i s de permrbaGo no ambiente) estes grupos de besouros eram abundantes. A maioria dos grupos diminuiu com o aumento da perterubaGo no ambiente, porkm um grupo (compost0 de grandes besouros de galerias noturnos, principalmente Dichotomius) tornou-se mais abundante com o aumento da permrb@o, atk o dvel mais alto de permrbaGo avaliado, quando todas as espkies de besouros ficaram escassas. As dareiras exibiram menor riqueza de esp...
Comparative analyses that link information on species' traits, environmental change, and organism response have rarely identified unambiguous trait correlates of vulnerability. We tested if species' traits could predict local-scale changes in dung beetle population response to three levels of forest conversion intensity within and across two biogeographic regions (the Neotropics and Afro-Eurasian tropics). We combined biodiversity surveys, a global molecular phylogeny, and information on three species' traits hypothesized to influence vulnerability to forest conversion to examine (1) the consistency of beetle population response across regions, (2) if species' traits could predict this response, and (3) the cross-regional consistency of trait-response relationships. Most beetle populations declined following any degree of forest conversion; these declines were strongest for Neotropical species. The relationship between traits and population trend was greatly influenced by local and biogeographic context. We discuss the ability of species' traits to explain population trends and suggest several ways to strengthen trait-response models.
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