Variation of community assembly rules of a whole turtle family (Pelomedusidae) from continental to local scales in Africa


Defining priorities is important both in research and in conservation, especially when knowledge gaps are hindering successful management. In this review, we quantify the knowledge gaps for all non-marine West African chelonians based on 21 criteria. Additionally, we combine these knowledge gaps with each species’ maximum size, range size, presence in nationally protected areas, and IUCN Red List or TFTSG provisional status to introduce a ranking of species conservation priority in the region. Our analyses revealed a divergence between which species are lacking research studies and which would benefit most from conservation actions, though Cyclanorbis elegans is the species that is both the least-known and most-in-need of conservation. Broadly, Pelomedusidae are in the greatest need of research, yet they are also collectively the least threatened. Conversely, Trionychidae and Testudinidae have received greater research attention in most cases, however, these two families represent the greatest conservation priorities amongst West African chelonians. Our analyses also enabled us to evaluate which criteria representing aspects of chelonian biology have been most overlooked by the scientific community. Priorities for future research include reproductive and long-term population studies, each of which are critical for informing conservation actions and evaluating the results of those actions.

Knowledge gaps and conservation priorities for west African chelonians

Extending from west Africa to Madagascar, from the vast lowland Congo Basin to the archipelago of forest islands on its eastern rim, the African rain forest is surpassed in size only by the Amazon. This book sheds light on the current efforts to understand and conserve the African rain forest, an area in need of urgent action to save its biological wealth, cultural heritage, and economic potential. Written by conservation scientists and practitioners based in the African rain forest, the book offers a multidisciplinary perspective that integrates many biological and social sciences. Early chapters trace the forces - from paleoecological factors to recent human actions - that have shaped the African forest environment. The next chapters discuss the dominant biological patterns of species ranging from the distinctive elephants, gorillas, and okapi to the less well known birds, butterflies, and amphibians. Other chapters focus on how such different groups as hunter-gatherers, forest farmers, bushmeat hunters, recent immigrants, and commercial foresters have used the forests. Several authors stress the need for tighter links between research and conservation action. The final section draws lessons from the collective experience of those working in an Africa wracked by political strife and economic hardship.

African Forest Conservation@@@African Rain Forest Ecology and Conservation: An Interdisciplinary Perspective

The Dahomey Gap is a human-derived savannah zone, interspersed by patches of moist tropical forest, that separates the forest zone into two blocks, the Upper Guinean and the Lower Guinean forests. Community ecology aspects of amphibians and reptiles are still relatively unexplored in this ecological zone of West Africa. Here, the overall species richness and the variation of the diversity metrics (dominance, evenness) of a whole herpetofaunal community in Togo was studied, with emphasis on the effects of the seasons (wet and dry) on the population structure. Overall, we observed 998 amphibian individuals from 27 species: 148 individuals belonging to 11 species during the dry season and 849 individuals belonging to 25 species during the wet season. For reptiles, we observed 517 individuals belonging to 44 species: 323 individuals belonging to 41 species during the dry season and 194 individuals belonging to 28 species during the wet season. The analyses on the diversity metrics showed opposite patterns between amphibians and reptiles in each season. Indeed, the dry season rank–abundance curve was systematically higher in reptiles than in amphibians for each rank of abundance, while the opposite pattern occurred in the wet season rank–abundance curve. Singletons and doubletons were much more numerous in the reptiles. Concerning the diversity indices, the Dominance index was significantly higher in amphibians during the dry season than in all other pairwise comparisons, whereas the Shannon’s index was significantly lower in dry season amphibians and significantly higher in wet season reptiles. Evenness index was significantly lower in reptiles than in amphibians and the mean number of individuals was significantly higher in amphibians by wet season compared to dry season amphibians or reptiles during both seasons. The ecological implications of these data are discussed. Most species were of minor conservation concern.

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Herpetofaunal Diversity in a Dahomey Gap Savannah of Togo (West Africa): Effects of Seasons on the Populations of Amphibians and Reptiles

. The rodent assemblages were studied in different habitat types of the Fazao-Malfakassa National Park located in Togo, West Africa. A suite of different methods was applied, including face-to-face interviews with local hunters, live trapping along standardized transects and opportunistic observations. A total of 20 rodent species were recorded based on the surveys carried out in villages. There was a clear gradient pattern in the univariate diversity indices by habitat type: Dominance index was remarkably higher in urban/plantation than in the other habitat types whereas Evenness index was remarkably higher in gallery forest than in the other habitat types. According to a Canonical Correspondence Analysis, three “ecological groups” (= guilds) of species were formed: a group from wooded habitats (savannahs and semiforests), a group from grassy savannah and a group from urban/plantation habitats. Null model analyses revealed that species tend to non-randomly congregate in some habitat types and/or localities.

Diversity patterns of rodent assemblages along habitat gradients in the dahomey gap (togo, west africa)

Despite increasing pressures on freshwater resources worldwide, and the threatened status of most freshwater turtles, there is still limited knowledge of habitat use and niche partitioning in Afrotropical freshwater turtle communities. In this study, we describe habitat associations, community diversity, and temporal patterns of occurrence of freshwater turtle species in the Dahomey Gap ecoregion of Ghana (West Africa). We gathered data from 13 sites in central Ghana and along the Sene Arm of Lake Volta in the Digya National Park (Bono East Region). We employed opportunistic short-term surveys (at seven sites) together with longer-term (six-months duration) standardized evaluations of turtle presence and numbers in different habitats (at six sites). Overall, a total of 210 turtle individuals of four species (Trionyx triunguis, Cyclanorbis senegalensis, Pelomedusa sp. and Pelusios castaneus) were recorded; precise capture sites and habitat type were recorded for 139 individuals, but the 71 individuals observed in marketplaces were not considered in our analyses. At a local scale, we observed three sympatric species in various study sites. In each of these sites, the dominant species was either C. senegalensis or Pelomedusa sp., with the latter species being more abundant in temporary waterbodies and C. senegalensis more numerous in permanent ones. A Multiple Correspondence Analysis suggested that, in permanent waterbodies all species were associated with similar physical habitat variables. In a Canonical Correspondence Analysis, we showed that the density of herbaceous emergent vegetation was more important for P. castaneus than for C. senegalensis. Comparisons of diversity metrics between our study sites and previous studies revealed that turtle community composition was similar across savannah sites.

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Suleman B. Gbewaa

Papers

Community Characteristics of Sympatric Freshwater Turtles from Savannah Waterbodies in Ghana