A phylogenetic community approach for studying termite communities in a West African savannah

Termites play fundamental roles in tropical ecosystems, and mound-building species in particular are crucial in enhancing species diversity, from plants to mammals. However, it is still unclear which factors govern the occurrence and assembly of termite communities. A phylogenetic community approach and null models of species assembly were used to examine structuring processes associated with termite community assembly in a pristine savannah. Overall, we did not find evidence for a strong influence of interspecific competition or environmental filtering in structuring these communities. However, the presence of a single species, the mound-building termite Macrotermes bellicosus, left a strong signal on structuring and led to clustered communities of more closely related species. Hence, this species changes the assembly rules for a whole community. Our results show the fundamental importance of a single insect species for community processes, suggesting that more attention to insect species is warranted when developing conservation strategies.     

Alarm communication networks as a driver of community structure in African savannah herbivores

Social information networks have the potential to shape the spatial structure of ecological communities by promoting the formation of mixed‐species groups. However, what actually drives social affinity between species in the wild will depend on the characteristics of the species available to group. Here we first present an agent‐based model that predicts trait‐related survival benefits from mixed‐species group formation in a multi‐species community and we then test the model predictions in a community‐wide field study of African savannah herbivores using multi‐layered network analysis. We reveal benefits from information transfer about predators as a key determinant of mixed‐species group formation, and that dilution benefits alone are not enough to explain patterns in interspecific sociality. The findings highlight the limitations of classical ecological approaches focusing only on direct trophic interactions when analysing community structure and suggest that declines in species occupying central social network positions, such as key informants, can have significant repercussions throughout communities.     

Effects of vertebrate predation on a caviomorph rodent,the degu (Octodon degus), in a semiarid thorn scrub community in Chile

The effects of vertebrate predation have been monitored since 1989 on 16 replicated 0.56 ha study plots in a semiarid thorn scrub community in north-central Chile. Using fences of different heights with and without holes and suspended game netting to alter principal predator (foxes and raptors) and large rodent herbivore (Octodon degus) access, four grids each have been assigned to the following treatments: 1) low fencing and holes allowing free access of predators and small mammals; 2) low fencing without holes to exclude degus only; 3) high fencing and netting with holes to exclude predators only; and 4) high fencing and netting without holes to exclude predators and degus. Small mammal population censuses are conducted monthly using mark-recapture techniques. Degu population trends during 1989 and 1990 showed strongly but nonsignificantly lower numbers in control plots during months when densities were characteristically low (September–November) for this seasonally reproductive species; since March 1991, differences have become persistent and increasingly significant. Predators appear to have greater numerical effects when their prey populations are low. Survival times of degus, particularly established adults, were significantly longer in predator exclusion grids during the 2 1/2 years of observation; thus, predation also affects prey population structure.     

Fish community characteristics of the lower Gambia River floodplains: a study in the last major undisturbed West African river

1. The Gambia River is the last major West African river that has not been impounded. However, a hydroelectric dam is being constructed and substantial changes to the hydrology and ecology of the system are expected. 2. Little information is available on the impact of water impoundments in semi‐arid regions on downstream floodplain fish communities, due to the scarcity of pre‐intervention data. Because profound impacts on physical habitat, salinity and nutrient transport can occur downstream of such impoundments, a knowledge of the species‐habitat associations of biota such as fishes is necessary for understanding likely changes and how to limit them. 3. Fish were sampled using cast and hand nets along two transects on the floodplain, and with fyke nets in two ‘bolongs’ (creeks) from May to November 2005 and 2006 in the lower reaches of the Gambia River, close to the salt water front where ecological changes due to the construction of the dam are likely to be pronounced. 4. Greatest fish species richness was associated with low conductivity, low pH and deep water. Bolongs held greater species richness compared with other floodplain habitats, probably because they acted as conduits for fish moving on and off the floodplain. Species richness and catch biomass increased rapidly following the first rains and then declined. 5. Using a multivariate analysis, three main species groups were identified on the floodplain; one associated with deeper water, one with less brackish water and one with shallow, open water. Tilapia guineensis was the commonest species on the floodplains. 6. The floodplains provide nursery habitats as many fish captured were immature, particularly for species where adults are mainly encountered in the main channel. Several small‐sized floodplain specialists were also represented by a high proportion of mature individuals. 7. Impoundment is expected to reduce seasonal flooding of the floodplain in the lower Gambia River, downstream of the impoundment, resulting in reduced occurrence of aquatic habitats, especially bolongs, together with lower dissolved oxygen and increased salinity, leading to alteration of the floodplain fish communities, benefiting salt‐tolerant species, reducing overall species richness and probably reducing floodplain fish production.     

Population dynamics of a generalist rodent in relation to variability in pulsed food resources in a fragmented landscape

1. Pulsed food resources are often considered equivalent in their potential impact on the reproduction and population dynamics of consumers, but differences in the attributes of food pulses and their distribution in the landscape may cause differences in their effects. 2. We tested whether a perishable pulsed resource (periodical cicadas, Magicicada spp.) had similar effects on the population dynamics of a generalist forest rodent, Peromyscus leucopus, as have been reported for a cacheable pulsed resource (acorn mast). 3. Because the availability of periodical cicadas may vary between edge and interior habitat, we also tested whether habitat type (edge vs. interior) and fragment size affected the abundance of cicadas and P. leucopus. 4. Nearly 90% of the variation in the relative population densities of P. leucopus was explained by the variation in the relative densities of periodical cicadas, and fragments with more cicadas tended to have more reproductive female mice and litters. 5. We found more cicadas and more P. leucopus in edge than interior habitat, but no differences in the relative densities of either in relation to fragment size. 6. Data from a non-emergence year revealed no differences other than the presence of periodical cicadas that could explain the 50% higher relative densities of P. leucopus in the emergence year. 7. At the beginning of the emergence of periodical cicadas, the three fragments with the highest numbers of emergence holes had three times more mice than the fragments with the lowest numbers of emergence holes, suggesting that P. leucopus is able to anticipate the emergence of periodical cicadas and increase reproduction prior to the pulse. 8. Hence, despite differences in perishability, seasonal timing and nutritional quality of pulsed food resources in a fragmented landscape, they appear to have similar positive effects on the population dynamics of the generalist rodent, P. leucopus and, in fact, P. leucopus may be able to anticipate resource pulses.     

Socioecology,predation, and cognition in a community of West African monkeys

The Ivory Coast's Taï Forest is home to a diverse primate fauna, including eight monkey species that interact daily with the environment, each other, and a web of predators. These interactions have led to an array of adaptations, some of which conform to theoretical expectations, and others are at odds with current behavioral ecology models. In this paper, we draw on fifteen years of observations to examine two central issues. First, how do broad trends in diet and resource distribution influence group size and levels of sociality? Second, what mechanisms are used to counter pressures exerted by the predator community? The general picture that emerges is that while the pressure exerted by predators at Taï has led to a host of behavioral and cognitive adaptations, it is food preferences and foraging habits, not predation pressure, that are the main determinants, not only of group size, but also its direct consequences ‐ mating systems and sociality levels.     

Evolutionary systematics and biogeography of the arid habitat‐adapted rodent genus Gerbillus (Rodentia,Muridae): a mostly Plio‐Pleistocene African history

The systematics of the arid‐adapted Old World Gerbillus rodent genus has always been challenging, with many different taxonomic arrangements proposed. Beyond such taxonomic aspects, the timing and geographical pattern of the evolutionary history of this group remains largely unknown. Based on mitochondrial (cytochrome b) and nuclear (interphotoreceptor retinoid‐binding protein) sequences obtained from the specimens of 21 species, we conducted a phylogenetic analysis of the group, estimated the ages and putative ancestral ranges of its major lineages. Four major clades were clearly retrieved within Gerbillus, for which we propose a subgenus rank. We showed that the emergence of the genus dates back to the end of the Miocene, which corresponds to a period of aridification and C4 vegetation expansion in open habitats, while the four sublineages originated at the end of the Pliocene. Most subsequent diversification events occurred during the Pleistocene, a period characterized by recurrent climatic/environmental shifts with increasing aridification during the last two millions of years. Finally, we suggested that most of the Gerbillus evolutionary history took place in Africa. Only in a few instances did dispersal events from Africa to Asia give birth to extant Asian lineages, a pattern that contrasts with what has been found in many animal groups.     

Effects of alien pine plantations on small mammal community structure in a southern African biodiversity hotspot

Commercial plantations and alien tree invasions often have substantial negative impacts on local biodiversity. The effect of plantations on faunal communities in the fire‐adapted fynbos vegetation of the Cape Floristic Region biodiversity hotspot is not yet well quantified. We studied small mammal community structure in alien Pinus radiata plantations and adjacent fynbos regenerating after clear‐felling of plantations on the Cape Peninsula, South Africa. Small mammal sampling over 1,800 trap‐nights resulted in 480 captures of 345 individuals (excluding recaptures) representing six species. Significantly more species, individuals (12 X) and biomasses (29 X) of small mammals occurred on recovering fynbos sites compared to plantations. This was commensurate with a higher diversity of plant growth forms, vegetation densities and live vegetation biomass. Only one small mammal species, the pygmy mouse (Mus minutoides), was consistently trapped within plantations. Fynbos sites were dominated by three small mammal species that are ecological generalists and early successional pioneer species, rendering the recovering fynbos slightly depauperate in terms of species richness and evenness relative to other studies done in pristine fynbos. We make three recommendations for forestry that would facilitate the restoration of more diverse natural plant communities and progressively more diverse and dynamic small mammal assemblages in a key biodiversity hotspot.     

Diversity,dynamics and reproduction in a community of small mammals in Upper Guinea,with emphasis on pygmy mice ecology

As part of a large survey on reservoirs of Lassa fever in Guinea, three villages were investigated in high endemic zone, close to Sierra Leone border. Biodiversity of the small mammal community is presented in this study through a standardized trapping in houses, cultivations and forest. Identification of the small mammals was based on morphology and by molecular technique for sibling species. Of the 1123 specimens collected in 2003–2005, we identified seventeen species (thirteen Muridae, four Soricidae), leading to high diversity (Shannon index = 1.6–1.8) and high equitability (evenness index = 0.7–0.8) in cultivations and forest. In houses conversely, the rodent community was dominated by Mastomys natalensis (95–98%), leading to low diversity and equitability. Dynamics and reproduction were investigated in two species of pygmy mice, Mus mattheyi and Mus minutoides, two species of Praomys, P. daltoni and P. rostratus, and in Mastomys erythroleucus. The pygmy mice were abundant in cultivations in early rainy season, and reproduced from rainy to dry season. Praomys daltoni was also found more abundant in cultivations and seemed to reproduce between rainy and dry season, whereas P. rostratus preferred forest and cultivations in late rainy season, and reproduced throughout the year. Finally, M. erythroleucus was more abundant in forest in dry season, and seemed to reproduce from late rainy to dry season. This species had a low occurrence (6.5%) in the Faranah’s zone, and probably lived at its southern limit in Guinea. The presence of other Murinae, such as M. natalensis, Praomys spp as possible competitors in the same habitats, is discussed. For the first time, this study relates population biology of pygmy mice with molecular identification.