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Article Reference Ideal Free distribution of fixed dispersal phenotypes in a wing dimorphic beetle in heterogeneous landscapes
According to the ideal free distribution (IFD) theory, individuals that are able to perceive the quality of different patches in a landscape and disperse freely are expected to redistribute themselves proportionally to the carrying capacities of heterogeneous patches. Here, we argue that when dispersal is unconditional and genetically fixed, a coalition of sedentary and dispersing phenotypes can attain an IFD under spatio-temporally uncorrelated variation in fitness. This not only leads to a stable polymorphism of both dispersal phenotypes, but also implies that the number of dispersing individuals should on average be equal among patches and determined by the carrying capacity of the smallest local populations in the landscape. Differences in carrying capacity among patches are thus only reflected by changes in the number of sedentary individuals. Individual-based simulations show that this mechanism can be generalized over a wide range of spatio-temporal conditions and dispersal strategies. Moreover, these expectations are in strong agreement with empirical data on the density of both dispersal phenotypes of the wing dimorphic ground beetle Pterostichus vernalis within and among ten different landscapes. Hence, for the first time, these results demonstrate that this mechanism serves as a plausible alternative to the competition-colonization model to explain the spatial distribution of fixed dispersal phenotypes in heterogeneous landscapes. Understanding of the frequency distributions of individuals expressing discrete dispersal morphs moreover improves our predictive and management capabilities for a broad range of species, for which we currently typically rely on using mean dispersal rates.
Located in Library / RBINS Staff Publications
Article Reference Local extinction processes rather than edge effects affect ground beetle assemblages from fragmented and urbanized old beech forests
Local extinction of specialist species due to fragmentation is one of the major causes of biodiversity loss. Increased extinction rates in smaller fragments are expected to result from both smaller local population sizes, which increase the effect of environmental or demographic stochasticity, and increased edge effects. However, the relative effect sizes of these two factors are still poorly investigated. We attempt to disentangle these effects on ground beetle communities of temperate broadleaved woodland fragments situated in one of the most urbanized regions in Belgium. Assemblages were sampled along transects that extended from 30 m outside to 100 m inside both small and large historic forest fragments. Although species assemblages within the forest were highly distinct compared to those sampled outside the forest, species turnover along these transects was less pronounced within forest fragments indicating only weak edge effects. The magnitude of edge effects did not differ significantly between large and small fragments. However, larger differences in species composition were observed with respect to fragment size, wherein highly specialized species persisted only in the largest fragment. In sum, increased local extinction processes in smaller fragments, which led to a strong reduction of specialized and wingless forest species, appeared to be the most important factor that drives changes in species composition in this historic and fragmented woodland complex.
Located in Library / RBINS Staff Publications
Article Reference A mitochondrial phylogeographic scenario for the most widespread African rodent species , Mastomys natalensis
In order to evaluate the contribution of geological, environmental, and climatic changes to the spatial distri- bution of genetic variation of Mastomys natalensis, we analysed cytochrome b sequences from the whole dis- tribution area of the species to infer its phylogeographic structure and historical demography. Six well-supported phylogroups, differentiated during the Pleistocene, were evidenced. No significant correlation between genetic and geographic distances was found at the continental scale, and the geographic distributions of the observed phylogroups have resulted from extensive periods of isolation caused by the presence of putative geographic and ecological barriers. The diversification events were probably influenced by habitat contraction/expansion cycles that may have complemented topographic barriers to induce genetic drift and lineage sorting. According to our results, we propose a scenario where climate-driven processes may have played a primary role in the differ- entiation among phylogroups.
Located in Library / RBINS Staff Publications
Article Reference A molecular diagnostic for identifying central African forest artiodactyls from faecal pellets
Located in Library / RBINS Staff Publications
Article Reference Discovery of a new duiker species (Bovidae: Cephalophinae) from the Dahomey Gap, West Africa
Among the two most widely distributed duiker species, Philantomba monticola (Thunberg, 1789) and Philantomba maxwelli (C.H. Smith, 1827), the latter shows geographic variation in pelage color and body size. This issue was not investigated in detail so far, especially in the eastern region of its distribution area, notably due to the lack of material from the Dahomey Gap. We undertook a species-level revision of Philantomba in West Africa, notably including a series of specimens collected in Togo, Benin and Nigeria. Using morphological measurements (craniometry) and genetic data (two mitochondrial and three nuclear markers), we describe a new duiker species occurring in the Dahomey Gap (Togo, Benin) and the Niger delta, Philantomba walteri sp. nov. This discovery highlights the importance of the Dahomey Gap for the evolutionary history of the West African forest faunas. It also has conservation implications given that the new species is one of the main targets of the local bushmeat trade.
Located in Library / RBINS Staff Publications
Incollection Reference DNA Barcoding Amphibians and Reptiles
Only a few major research programs are currently targeting COI barcoding of amphibians and reptiles (including chelonians and crocodiles), two major groups of tetrapods. Amphibian and reptile species are typically old, strongly divergent, and contain deep conspecifi c lineages which might lead to problems in species assignment with incomplete reference databases. As far as known, there is no single pair of COI primers that will guarantee a suffi cient rate of success across all amphibian and reptile taxa, or within major subclades of amphibians and reptiles, which means that the PCR amplifi cation strategy needs to be adjusted depending on the specifi c research question. In general, many more amphibian and reptile taxa have been sequenced for 16S rDNA, which for some purposes may be a suitable complementary marker, at least until a more comprehensive COI reference database becomes available. DNA barcoding has successfully been used to identify amphibian larval stages (tadpoles) in species-rich tropical assemblages. Tissue sampling, DNA extraction, and amplifi cation of COI is straightforward in amphibians and reptiles. Single primer pairs are likely to have a failure rate between 5 and 50\% if taxa of a wide taxonomic range are targeted; in such cases the use of primer cocktails or subsequent hierarchical usage of different primer pairs is necessary. If the target group is taxonomically limited, many studies have followed a strategy of designing specifi c primers which then allow an easy and reliable amplifi cation of all samples.
Located in Library / RBINS Staff Publications
Article Reference Repeated unidirectional introgression of nuclear and mitochondrial DNA between four congeneric Tanganyikan cichlids.
With an increasing number of reported cases of hybridization and introgression, interspecific gene flow between animals has recently become a widely accepted and broadly studied phenomenon. In this study, we examine patterns of hybridization and introgression in Ophthalmotilapia spp., a genus of cichlid fish from Lake Tanganyika, using mitochondrial and nuclear DNA from all four species in the genus and including specimens from over 800 km of shoreline. These four species have very different, partially overlapping distribution ranges, thus allowing us to study in detail patterns of gene flow between sympatric and allopatric populations of the different species. We show that a significant proportion of individuals of the lake-wide distributed O. nasuta carry mitochondrial and/or nuclear DNA typical of other Ophthalmotilapia species. Strikingly, all such individuals were found in populations living in sympatry with each of the other Ophthalmotilapia species, strongly suggesting that this pattern originated by repeated and independent episodes of genetic exchange in different parts of the lake, with unidirectional introgression occurring into O. nasuta. Our analysis rejects the hypotheses that unidirectional introgression is caused by natural selection favoring heterospecific DNA, by skewed abundances of Ophthalmotilapia species or by hybridization events occurring during a putative spatial expansion in O. nasuta. Instead, cytonuclear incompatibilities or asymmetric behavioral reproductive isolation seem to have driven repeated, unidirectional introgression of nuclear and mitochondrial DNA into O. nasuta in different parts of the lake.
Located in Library / RBINS Staff Publications
Article Reference Ecophysiology of dorsal versus ventral cuticle in flattened sawfly larvae.
Platycampus larvae are highly cryptic leaf feeders characterised by a dorso-ventrally flattened body, the dorsal integument resembling a shield. Dorsal and ventral cuticles from Platycampus luridiventris were compared by histology and gel electrophoresis. By Azan-staining, a red and a blue layer were distinguished in the dorsal cuticle, while the ventral cuticle showed one, almost uniform blue layer, as in both cuticles of control species. The two cuticles from P. luridiventris had similar amounts and sodium dodecyl sulphate-polyacrylamide gel electrophoresis profiles of soluble proteins, but not insoluble proteins. One insoluble protein (MW approximately 41 kDa) was visible as a large band in the ventral cuticle only. It is likely that this protein renders the cuticle elastic, and that the dorsal, red layer is the exocuticle, mainly composed of insoluble proteins. We discuss eco-physiological implications of the exocuticle in insects. Further, data from the literature indicate that the defence strategy in P. luridiventris larvae relies on being visually cryptic towards avian predators and tactically cryptic towards arthropod predators and parasitoids. Crypsis in both senses is favoured by the shield effect, itself based on an abnormally thick dorsal exocuticle. Although the larvae are external feeders, they may be considered as hidden from an ecological perspective.
Located in Library / RBINS Staff Publications
Article Reference Octet Stream Impacts of logging and hunting on western lowland gorilla (Gorilla gorilla gorilla) populations and consequences for forest regeneration. A review
Located in Library / RBINS Staff Publications
Article Reference Octet Stream Recent decline in suitable environmental conditions for African great apes
Located in Library / RBINS Staff Publications