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The Ecology of Living in Small Fragments: Resource availability and feeding ecology of GHLTs groups in small fragments and the effects of matrix connectivity, hunting pressure and climate change on their long-term changes for persistence.
Golden-headed lion tamarins use both mature and degraded forest in addition to cabruca agroforest, the traditional form of cocoa cultivation used in Southern Bahia where cocoa is grown under the shade of native forest trees. Yet, cabruca can differ considerably in vegetation structure, which likely affects local habitat suitability and pathways for GHLTs to move between fragments. Cabruca is the principal habitat within the matrix connecting forest fragments, in addition to a variety of other landscape elements (e.g. pasture, agricultural areas) that are generally unsuitable for use as part of a group´s home range but vary in suitability for GHLT movement between forest fragments. Currently very little information exists on the factors that limit GHLT movement between fragments and those that determine mortality of dispersing individuals in the matrix. Such data, however, are important determinants for the outcome of population and landscape models that test the long-term survival of wild GHLT populations given current and future changes in the landscape. Genetic data suggest that, in the eastern part of the GHLT distribution range, gene flux is maintained in areas connected principally by mature and/or secondary forest, whereas gene flux in areas connected by cabruca alone seems compromised. This decreased gene flux is particularly important because the eastern region contains the only forest fragment large enough to sustain a genetically viable population of GHLTs. Given the extreme degree of fragmentation in the western portion of the GHLT distribution range, maintaining the integrity of the eastern forest block and its connectivity with other forest fragments in the landscape, thus ensuring gene flux, is critical for the long-term persistence of the species. In order to develop sound conservation measures for both eastern and western populations of GHLTs, it is critical to understand ecological pressures on individuals and groups in cabruca areas and in degraded fragments as well as factors that affect suitability and permeability of cabruca and other landscape elements. This will improve our understanding of the species´ flexibility in using extremely fragmented and degraded habitat and the actual potential of the matrix for maintaining connectivity and gene flux between GHLT populations in fragments across the landscape. Such information is essential for the definition of effective landscape management scenarios compatible with the long-term persistence of self-sustaining GHLT populations in southern Bahia. In addition to matrix permeability and the particular characteristics of the fragment in itself, additional factors acting on a larger scale (ecosystem) may affect the viability of GHLT groups in small and medium sized fragments. GHLTs, along with other frugivorous species are important dispersers of a large number of tree species. Particularly in small fragments, the disperser assembly is likely to be impoverished, both due to changes in the availability of resources to dispersers, difficulties with dispersers reaching fragments, and human activities e.g. hunting and logging or forest-degrading activities that directly impact on disperser presence and activity. Even if present in small fragments, the medium- and long term establishment of tree species that are key to GHLTs may be compromised as a result of these factors, implicating on the availability of GHLT resources in the long term. Additionally, larger scale factors such as climate change may impact on the distribution patterns of important tree species. The current overall research program conducted by Project BioBrasil intends to study the effects of forest fragmentation on GHLTs (and possibly other frugivores) in small to medium sized fragments from several perspectives: 1) By investigating matrix permeability around small fragments considered at the limit of carrying capacity for a group of GHLTs; 2) By investigating the ecology of GHLT groups living in small fragments; 3) By investigating the factors that affect the short-, medium and long-term availability of resources in small and medium sized fragments: spatial and temporal changes in seasonality (intra- and interannually), effects of climate change on the distribution of key tree species; diversity of the disperser assembly contributing to maintaining key plant resources for GHLTs and the resources available to them in small fragments; the intensity of hunting in fragments and its impact on the disperser assembly.
Datum:1 jan 2012 → Heden