Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century.

Humans have hunted wildlife in Central Africa for millennia. Today, however, many species are being rapidly extirpated and sanctuaries for wildlife are dwindling. Almost all Central Africa's forests are now accessible to hunters. Drastic declines of large mammals have been caused in the past 20 years by the commercial trade for meat or ivory. We review a growing body of empirical data which shows that trophic webs are significantly disrupted in the region, with knock-on effects for other ecological functions, including seed dispersal and forest regeneration. Plausible scenarios for land-use change indicate that increasing extraction pressure on Central African forests is likely to usher in new worker populations and to intensify the hunting impacts and trophic cascade disruption already in progress, unless serious efforts are made for hunting regulation. The profound ecological changes initiated by hunting will not mitigate and may even exacerbate the predicted effects of climate change for the region. We hypothesize that, in the near future, the trophic changes brought about by hunting will have a larger and more rapid impact on Central African rainforest structure and function than the direct impacts of climate change on the vegetation. Immediate hunting regulation is vital for the survival of the Central African rainforest ecosystem.

Social and ecological change over a decade in a village hunting system, central Gabon.

Despite widespread recognition of the major threat to tropical forest biological diversity and local food security posed by unsustainable bushmeat hunting, virtually no long-term studies tracking the socioecological dynamics of hunting systems have been conducted. We interviewed local hunters and collected detailed hunting data to investigate changes in offtake and hunter characteristics over 10 years (2001-2010) in Dibouka and Kouagna villages, central Gabon, in the context of hunter recollections of longer term trends since the 1950s. To control for changes in hunter behavior, such as trap location and characteristics, we report hunting offtake data per trap. Our results suggest the hunting area was already highly depleted by 2001; local hunters reported that 16 large-bodied prey species had become rare or locally extirpated over the last 60 years. Overall, we observed no significant declines in hunting offtake or changes in species composition from 2001 to 2010, and offtakes per trap increased slightly between 2004 and 2010. However, trapping distance from the villages increased, and there was a switch in hunting techniques; a larger proportion of the catch was hunted with guns in 2010. The number of hunters declined by 20% from 2004 to 2010, and male livelihood activities shifted away from hunting. Hunters with the lowest hunting incomes in 2004 were more likely than successful hunters to have moved away from the village by 2010 (often in response to alternative employment opportunities). Therefore, changes in trap success (potentially related to biological factors) were interacting with system-level changes in hunter number and composition (related to external socioeconomic factors) to produce a relatively static overall offtake. Our results highlight the importance of understanding the small-scale context of hunting to correctly interpret changes or apparent stasis in hunting effort and offtake over time.

Investigating temporal changes in hybridization and introgression in a predominantly bimodal hybridizing population of invasive sika (Cervus nippon) and native red deer (C. elaphus) on the Kintyre Peninsula, Scotland.

We investigated temporal changes in hybridization and introgression between native red deer (Cervus elaphus) and invasive Japanese sika (Cervus nippon) on the Kintyre Peninsula, Scotland, over 15 years, through analysis of 1513 samples of deer at 20 microsatellite loci and a mtDNA marker. We found no evidence that either the proportion of recent hybrids, or the levels of introgression had changed over the study period. Nevertheless, in one population where the two species have been in contact since approximately 1970, 44% of individuals sampled during the study were hybrids. This suggests that hybridization between these species can proceed fairly rapidly. By analysing the number of alleles that have introgressed from polymorphic red deer into the genetically homogenous sika population, we reconstructed the haplotypes of red deer alleles introduced by backcrossing. Five separate hybridization events could account for all the recently hybridized sika-like individuals found across a large section of the Peninsula. Although we demonstrate that low rates of F1 hybridization can lead to substantial introgression, the progress of hybridization and introgression appears to be unpredictable over the short timescales.

Two distinct STLV-1 subtypes infecting Mandrillus sphinx follow the geographic distribution of their hosts.

The mandrill (Mandrillus sphinx) has been shown to be infected with an STLV-1 closely related to HTLV-1. Two distinct STLV-1 subtypes (D and F) infect wild mandrills with high overall prevalence (27.0%) but are different with respect to their phylogenetic relationship and parallel to the mandrills' geographic range. The clustering of these new STLV-1mnd sequences with HTLV-1 subtype D and F suggests first, past simian-to-human transmissions in Central Africa and second, that species barriers are easier to cross over than geographic barriers.

Molecular evidence for deep phylogenetic divergence in Mandrillus sphinx.

Mandrills (Mandrillus sphinx) are forest primates indigenous to western central Africa. Phylogenetic analysis of 267 base pairs (bp) of the cytochrome b gene from 53 mandrills of known and 17 of unknown provenance revealed two phylogeographical groups, with haplotypes differentiated by 2.6% comprising seven synonymous transitions. The distribution of the haplotypes suggests that the Ogooué River, Gabon, which bisects their range, separates mandrill populations in Cameroon and northern Gabon from those in southern Gabon. The haplotype distribution is also concordant with that of two known mandrill simian immunodeficiency viruses, suggesting that these two mandrill phylogroups have followed different evolutionary trajectories since separation.

The human antiporcine cellular repertoire. In vitro studies of acquired and innate cellular responsiveness.

Discordant xenogeneic transplantation offers a potentially unlimited source of donor organs from easily bred, nonendangered, physiologically compatible animals, but has been limited by the inevitable occurrence of hyperacute rejection (HAR). The potential existence of cell-mediated discordant graft rejection has remained obscured by HAR, and hence is incompletely understood. To define the cellular elements capable of recognition of and subsequent response against discordant tissue in a clinically applicable species combination, we have studied the in vitro interaction of human peripheral blood lymphocytes against 3 porcine B lymphoblastoid cell lines and 6 primary porcine endothelial cell populations. PBL from all individuals tested (n = 10) proliferated in response to culture for 72 hr in xenogeneic mixed lymphocyte culture (XMLC) with cell lines expressing porcine MHC (SLA) class II antigens, while endothelial cultures lacking SLA class II generally failed to evoke a response. The proliferative response to class II-positive cells was attenuated by addition of anti-SLA class II antibody but not by anti-SLA class I antibody. Two endothelial populations expressing class II stimulated an inhibitable proliferative response. The magnitude of the short-term proliferative xenogeneic response was similar to that evoked by fully mismatched allogeneic human B lymphoblastoid stimulators. Additionally, extended XMLC was performed with PBL from 3 individuals. All populations responded with continued proliferation when repeatedly stimulated by porcine cells. This was characterized not only by T cell growth, but by prominent NK cell growth as well. Elucidation of the TCR V beta chain usage patterns by semiquantitative PCR documented selection of TCR transcripts from gene family V beta 2 in each group, complemented by a heterogeneous mixture of other transcripts including V beta 17.1, 20.1, and 6.1, suggesting that direct human TCR binding of porcine cells occurs, and that it is likely to be an individualistic response complemented by a more homogeneous NK response. A 51Cr release assay was utilized to demonstrate that unprimed PBL could also lyse porcine target cells. This cytotoxic response was maintained despite the complete removal of T cells, suggesting that porcine-directed NK cell activity is present prior to the maturation of any T cell response. Cytolysis was also demonstrated in serum-free medium and thus was not mediated solely by antibody-dependent cellular cytotoxicity. Chinese hamster ovary cells transfected with the human T cell receptor accessory molecule CD4 were used to study the ability of this molecule to stabilize the interaction between the human TCR and SLA class II.(ABSTRACT TRUNCATED AT 400 WORDS)