Evidence of past forest fragmentation in the Congo Basin from the phylogeography of a shade-tolerant tree with limited seed dispersal: Scorodophloeus zenkeri (Fabaceae, Detarioideae)

Background Comparative phylogeographic studies on rainforest species that are widespread in Central Africa often reveal genetic discontinuities within and between biogeographic regions, indicating (historical) barriers to gene flow, possibly due to repeated and/or long-lasting population fragmentation during glacial periods according to the forest refuge hypothesis. The impact of forest fragmentation seems to be modulated by the ecological amplitude and dispersal capacities of each species, resulting in different demographic histories. Moreover, while multiple studies investigated the western part of Central Africa (Lower Guinea), few have sufficiently sampled the heart of the Congo Basin (Congolia). In this study, we look for genetic discontinuities between populations of the widespread tropical tree Scorodophloeus zenkeri Harms (Fabaceae, Detarioideae) in Central Africa. Additionally, we characterize genetic diversity, selfing rate and fine-scale spatial genetic structure within populations to estimate the gene dispersal capacity of the species. Results Clear intraspecific genetic discontinuities occur throughout the species’ distribution range, with two genetic clusters in Congolia and four in Lower Guinea, and highest differentiation occurring between these bioregions. Genetic diversity is higher in Lower Guinea than Congolia. A spatial genetic structure characteristic of isolation by distance occurs within the genetic clusters. This allowed us to estimate gene dispersal distances (σg) for this outcrossing species with ballistic seed dispersal, which range between 100 and 250 m in areas where S. zenkeri occurs in high densities, and are in the low range of σg values compared to other tropical trees. Gene dispersal distances are larger in low density populations, probably due to extensive pollen dispersal capacity. Conclusions Fragmentation of S. zenkeri populations seems to have occurred not only in Lower Guinea but also in the Congo Basin, though not necessarily according to previously postulated forest refuge areas. The lower genetic diversity in Congolia compared to Lower Guinea parallels the known gradient of species diversity, possibly reflecting a stronger impact of past climate changes on the forest cover in Congolia. Despite its bisexual flowers, S. zenkeri appears to be mostly outcrossing. The limited dispersal observed in this species implies that genetic discontinuities resulting from past forest fragmentation can persist for a long time before being erased by gene flow.

A Preliminary Study on the Batraco-herpetological Fauna in the Forest Refuge of Albertine Rift, the Democratic Republic of the Congo

Aims: Amphibians and reptiles of the Albertine Rift in the Congolese part of the country are poorly documented. The objective of this research was to perform a preliminary inventory of the diversity of amphibians and reptiles in the region. Study Design: This study was designed following scientific expeditions related to studies on chimpanzees. Litterature search revealed that amphibians and reptiles are poorly documented in these habitats. Place and Duration of Study: Amphibians and reptiles were collected in 12 days between April and May 2017 in Dzu (N01.94753°; E030.88848°), Dzoo (N01.92742°; E030.89179°), Nzerku 3 (N01.94119°; E030.90612°) and Nzonzo (N01.90352°; E30.91030°). Methodology: To collect amphibians and reptiles, we used the most minimally invasive method. This method consists of capturing 1 specimen for a known species and a maximum of 5 specimens for those for an unknown species. The surplus specimens were released into their environment. During the night between 7 pm and 9 pm, amphibians were captured by hand using a flashlight. Snakes had been captured using the snake stick. All captured specimens were scanned with a camera and then identified using amphibian and snake species identification keys. Necropsies (tongue and muscle tissue) stored in Eppendorf tubes containing alcohol (90-75%). Specimens had been fixed with formaldehyde (10%), before being preserved in alcohol (75%) in the long term. Tissues were shipped for molecular analysis to the University of Texas (United States). Results: In the four study sites, 149 amphibian specimens were collected, consisting of 19 species, 9 genera and 8 families. According to the reptiles, 27 specimens divided into 21 species grouped into 19 genera and 11 families were recorded. Conclusion: The batraco-herpetological fauna in the Albertine Rift in Ituri province in the Democratic Republic of the Congo is rich and diversified, hence this deserves the attention of other researchers.

Tropical forest refuge in peripheral soils of slags in Caatinga

The influence of environmental factors on the structure and composition of plant communities in the Caatinga is complex and poorly explored. Spatial variation of biodiversity in Caatinga is poorly know and strictly attributed to climatic conditions. We investigated the influence of slags on floristic composition and structure of a shrubby-arboreal community in one of the driest region in Brazil. Chemical and physical analyses of soils were performed in samples of seven plots from savannic formations and from forest formations. Vegetation was characterized floristically and structurally in all plots. Habitats were structurally distinct, and diversity differed between peripheral and non-peripheral areas of slags. Nine of the ninety-seven species identified are reported to (sub)humid biomes. Soils are dominantly shallow, eutrophic and sandy loam. However, soils in the periphery of slags are more developed once paludization, melanization and bioturbation were verified. Our results suggest that soil fertility did not influence vegetable cover in Caatinga. The cover of plant species considered exclusive of (sub)humid biomes in Brazil extends beyond highlands in the semiarid, associated with high soil organic carbon content and water retention capacity of more developed soils than the typical of the Caatinga.

To forage or hide? Threat-sensitive foraging behaviour in wild, non-reproductive passerine birds

Because antipredator behaviours are costly, the threat-sensitive predator avoidance hypothesis predicts that individual animals should express predator-avoidance behaviour proportionally to the perceived threat posed by the predator. Here, we experimentally tested this hypothesis by providing wild passerine birds supplemental food (on a raised feeding platform) at either 1 or 4 m from the edge of forest cover (potential refuge), in either the presence or absence of a nearby simulated predation threat (a sharp-shinned hawk Accipiter striatus model). Compared with the control treatment, we observed proportionally fewer bird visits to the food patch, and the birds took longer to re-emerge from forest refuge and return to feed at the food patch, after the hawk presentation than before it. The observed threat-sensitive latency-to-return response was stronger when the food patch was further away from the nearest refuge. Overall, our results are consistent with the predictions of the threat-sensitive predator avoidance hypothesis in that wild passerine birds (primarily black-capped chickadees Poecile atricapillus) exhibited more intense antipredator behavioural responses with increasing level of apparent threat. The birds were thus sensitive to their local perceived threat of predation and traded-off safety from predation (by refuging) and foraging gains in open habitat in a graded, threat-sensitive manner.

Late Pleistocene and Holocene Vegetation, Climate Dynamics, and Amazonian Taxa in the Atlantic Forest, Linhares, SE Brazil

Analysis of biological proxies in lake sediment and geochemical analysis of soil profiles reveal natural vegetation dynamics, with climate inferences, since the late Pleistocene in a fragment of the pristine lowland Atlantic Forest of southeastern Brazil. Carbon isotopes from soil organic matter and 14C ages from the humin fraction indicate the dominance of C3 plants since ∼17,000 cal BP. Palynological analysis of a sediment core indicates the presence of Atlantic Forest vegetation since 7700 cal BP. Changes in the relative abundance of tree ferns and palms suggest the predominance of a humid period from ∼7000–4000 cal BP and establishment of the modern seasonal climate at ∼4000 cal BP. Data indicate maintenance of the regional forest coverage since the late Pleistocene, corroborating previous suggestions that this region was a forest refuge during less humid periods of the late Pleistocene and Holocene. Some plant taxa with currently divided distributions between Amazonia and the Atlantic Forest colonized the region since at least 7500 cal BP, indicating an earlier connection between Amazonia and Atlantic Forest.