Baobab Index

Many island archipelagos sit on shallow continental shelves, and during the Pleistocene, these islands were often connected as global sea levels dropped following glaciation. Given a continental shelf only 30-60 m below sea level, the terrestrial biota of the Seychelles Archipelago likely dispersed amongst now isolated islands during the Pleistocene. Hypogeophis rostratus is an egg-laying, direct-developing caecilian amphibian found on 10 islands in the granitic Seychelles. Despite the seemingly limited dispersal abilities of this salt-intolerant amphibian, its distribution on multiple islands suggests likely historic dispersal across now submerged continental shelf corridors. We tested for the genetic signature of these historic corridors using fine-scale genomic data (ddRADseq). We found that genomic clusters often did not correspond to islands in the archipelago and that isolation-by-distance patterns were more consistent with gene flow across a continuous landscape than with isolated island populations. Using effective migration surfaces and ancestral range expansion prediction, we found support for contemporary populations originating near the large southern island of Mahé and dispersing to northern islands via the isolated Frégate island, with additional historic migration across the flat expanse of the Seychelles bank. Collectively, our results suggest that biogeographic patterns can retain signals from Pleistocene 'palaeo-islands' and that present-day islands can be thought of as hosting bottlenecks or transient refugia rather than discrete genetic units. Thus, the signatures of gene flow associated with palaeo-islands may be stronger than the isolating effects of contemporary islands in terrestrial species distributed on continental shelf islands.

The recent Kunming-Montreal Global Biodiversity Framework (GBF) sets ambitious goals but no clear pathway for how zero loss of important biodiversity areas and halting human-induced extinction of threatened species will be achieved. We assembled a multi-taxa tracking dataset (11 million geopositions from 15,845 tracked individuals across 121 species) to provide a global assessment of space use of highly mobile marine megafauna, showing that 63% of the area that they cover is used 80% of the time as important migratory corridors or residence areas. The GBF 30% threshold (Target 3) will be insufficient for marine megafauna's effective conservation, leaving important areas exposed to major anthropogenic threats. Coupling area protection with mitigation strategies (e.g., fishing regulation, wildlife-traffic separation) will be essential to reach international goals and conserve biodiversity.

The gut microbiota plays a pivotal role in regulating the physiological functions of its host, including immunity, metabolism, and digestion. The impact of environment and age on microbiota can be assessed by observing long-lived animals across different age groups and environments. The Aldabra giant tortoise ( Using 16S rRNA gene amplicon analysis, we analyzed 52 fecal samples from giant tortoises in Seychelles (Curieuse and Mahé islands) and in a zoological park in Italy, from very young individuals to those of >100 years old. We performed Alpha and Beta diversity analysis, relative abundance analysis, and complex upset plot analysis, comparing the results of tortoises from different environments and age groups. The diversity and overall composition of the gut microbiota of tortoises were impacted mainly by geolocation rather than their age. The greater diversity of microbiota in wild tortoises was attributed to their food variance such as wild leaves and branches, compared to captive or domesticated conditions. Beta diversity analysis also revealed the contribution of both environment and age to the variation between samples, with environments accounting for a larger proportion of this contribution. Certain bacterial families, such as Spirochaetota and Fibrobacterota, were more prevalent in environments with higher fiber intake, reflecting dietary differences. Additionally, a range of host-independent environmental bacteria was found to be specific to individuals in Curieuse and not in other geolocations. On the other hand, there were no bacterial taxa specific to centenarians, whose microbial complexity was reduced compared to adult or elderly tortoises. Our records showed that environment is the primary influence in the overall composition and diversity of the gut microbiota of Aldabra giant tortoises. As giant tortoises are amongst the longest-lived vertebrate animals, these findings can be utilized to monitor their health according to their ages, and enhance their conservation efforts.

The gut microbiome (GM) -important for host health and survival- is partially shaped by host immunogenetics. However, to date, no study has investigated the influence of host Major Histocompatibility Complex (MHC) genes on gut microbiome functionality in a wild population. Here we use a natural population of the Seychelles warbler (Acrocephalus sechellensis) to assess the effects of MHC genes on GM taxonomy and functionality using shotgun metagenomics. Our results show that taxonomic GM composition was associated with MHC-II diversity and the presence of one specific MHC-I allele (Ase-ua 7). Specifically, MHC-II diversity was associated with decreased Lactococcus lactis and increased Staphylococcus lloydii abundance, while Ase-ua 7 was linked to reduced Enterococcus casselifavus and Gordonia sp OPL2 but increased Escherichia coli and Vulcaniibacterium thermophilum. These taxonomic changes may reflect differences in MHC-mediated microbial recognition. In contrast, functional GM composition was significantly associated with increasing individual MHC-I diversity but not MHC-II diversity. In particular, increasing MHC-I diversity was associated with an increased prevalence of microbial defence genes but a reduced prevalence of microbial metabolism genes. Analysis also revealed that functional GM networks were more fragmented in high compared to low MHC-I diversity hosts. These results suggest that MHC variation (particularly at MHC-I) plays an important role in shaping both the taxonomy and function of the GM in wild vertebrates. In the Seychelles warbler, this results in trade-offs whereby there is an increase in microbial defence and a reduction in GM metabolic potential in individuals with higher MHC-I diversity. Thus, this work sheds light on the possible costs and benefits of maintaining a healthy microbiome, which is essential for understanding how the GM and immune system co-evolve. Video Abstract.

Accurate species delimitation is essential for understanding biodiversity patterns and guiding conservation, yet cryptic species with minimal morphological variation often obscure the assessment of true species diversity, making the identification of reliable diagnostic characters critical. Island radiations exemplify this challenge by concentrating endemic diversity in restricted areas, which accentuates both the urgency of conservation and the need for accurate taxonomy, while often presenting species divergences masked by subtle morphological differences. Here, we investigated patterns of morphological differentiation in Ailuronyx geckos, a genus endemic to the Seychelles archipelago, comprising deeply divergent lineages and unresolved, possibly cryptic species boundaries. We applied 3D and 2D morphometric analyses across the range (16 islands) of the three recognised species: the bronze-eyed gecko A. seychellensis, dwarf bronze gecko A. tachyscopaeus, and giant bronze gecko A. trachygaster. 3D geometric morphometric analyses of cranial and mandibular landmark data from 42 geckos revealed strong species-level differences. Ailuronyx trachygaster exhibits extreme skull sculpturing with rugose textures on up to ten cranial and three mandibular bones, while the other two species have smooth skull surfaces. Skull elongation and narrowing increased with decreasing body size from the larger A. trachygaster, via the medium-sized A. seychellensis, to the smaller A. tachyscopaeus. Analysis of body size-corrected 2D measurements of ten external morphological traits from 567 geckos revealed similar differences in head dimensions among the species, but also showed changes in mass and toe length. While we observed substantial morphological variation between islands, we did not find support for the previously identified northern and southern island group divergence within either A. seychellensis or A. tachyscopaeus. Nevertheless, we found strong support for the proposed divergence between northern and southern Mahé populations of A. tachyscopaeus, with variation in mass and head size between the two populations. We provide morphometric parameters to guide species identification within this gecko genus and highlight distinct population units that warrant further genomic investigation and prioritisation for conservation. Our findings illustrate the complexity of morphological diversification in archipelagos, where island-specific processes may outweigh regional biogeographic patterns. This underscores the need for integrative approaches to species delimitation and conservation in insular systems.

Reef-building corals are under serious threat from ocean warming, which directly impacts their symbiotic partnership with dinoflagellates from the family Symbiodiniaceae; a partnership integral for the survival of coral reefs. Symbiodiniaceae types vary in their levels of tolerance to heat and light, with some reported to enhance a coral's ability to withstand thermal stress. This study investigated the composition and diversity of Symbiodiniaceae across different thermal regimes and latitudinal gradients covering three bioregions: Bahrain (Arabian Gulf-AG), the Seychelles (Western Indian Ocean-WIO), and Indonesia (Central Indo-Pacific-CIP). Coral fragments from 11 coral host species (

Sickle Cell Disease (SCD) is a chronic genetic disorder that impairs red blood cell function and contributes to recurrent complications, particularly vaso-occlusive crises. This study evaluates the level of CD4 + T-lymphocyte counts in adult SCD patients in Northwestern Nigeria, assessing their association with clinical states, and epidemiological factors, to better understand immunological vulnerability. A descriptive cross-sectional study was conducted at Specialist Hospital Sokoto, 45 adult SCD patients were recruited and stratified by clinical status (steady state versus crisis). CD4 + counts were measured via flow cytometry, and data were analyzed for relationships with haemoglobin levels, gender, and age. Patients in vaso-occlusive crisis observed reduction in CD4 counts compared to those in steady state. However, haemoglobin levels did not show a statistically significant difference between the crisis state (9.43 ± 1.98 g/dL) and steady state (10.08 ± 1.60 g/dL; These findings highlight significant reduced CD4 levels in SCD patients during crises, underscoring the need for regular immunological monitoring.

This study aims to evaluate the global burden of adverse effects of medical treatment (AEMT) using data from the Global Burden of Disease Study (GBD) 2021. Data were extracted from the GBD 2021, covering 204 countries/territories from 1990 to 2021. AEMT was defined using ICD-9 and ICD-10 codes, encompassing complications from medical procedures, treatments, or healthcare exposures. Estimates were categorized into fatal and non-fatal outcomes and stratified by age, sex, year, and covariates, including the Socio-demographic Index (SDI). Mortality-incidence ratios (MIRs), defined as the ratio of mortality calculated by dividing the number of deaths by the total incident cases, were analyzed. In 2021, the global age-standardized prevalence, incidence, disability-adjusted life years (DALYs), and mortality rates of AEMT were 11.48 (95% uncertainty interval [UI], 8.86-14.13), 150.44 (131.19-171.81), 64.19 (51.06-73.11), and 1.53 (1.29-1.68) per 100,000 population, respectively. DALY rates were highest in the early neonatal group (4,789.47 per 100,000 population [95% UI, 3,682.00-5,963.30]), while mortality rates followed a U-shaped pattern across age groups. In 2021, MIRs were highest at both ends of the age range: the early neonatal group (0.58 [95% UI, 0.55-0.58]) and the 95+ age group (0.05 [0.04-0.06]). This pattern was consistent across all SDI quintiles, with higher MIRs observed in lower SDI quintiles. The significantly higher prevalence and incidence rates of AEMT among the older population in high SDI quintiles, compared to lower SDI quintiles, could be attributed to the healthcare overutilization, highlighting the need for policy adjustments.

BACKGROUND: Neglected tropical diseases (NTDs) remain a major yet unevenly addressed public health challenge in Southeast Asia, where persistent transmission is closely linked to poverty, environmental vulnerability, and health-system constraints. Understanding the evolution of the regional research landscape is essential for informing integrated disease control strategies and strengthening evidence-based policy responses. This study investigated the scientific landscape of NTD research in Southeast Asia, examining temporal trends, thematic trajectories, and patterns of collaboration using a scientometric approach. METHODS: A retrospective scientometric analysis was conducted using Scopus-indexed publications (1906–2024). Eligible records included English-language original research and review articles with at least one Southeast Asian institutional affiliation. Bibliometric performance indicators and science mapping techniques were applied using Bibliometrix (R) and VOSviewer. Analyses included publication trends, citation impact, collaboration networks, keyword co-occurrence, thematic mapping, and conceptual structure modeling. RESULTS: A total of 12,119 publications were identified, demonstrating sustained growth (AGR: 5.48%), with marked acceleration after 2000. Research productivity was concentrated in Thailand, Indonesia, and Malaysia, while several lower-income ASEAN member states exhibited minimal indexed output. International collaboration networks were dense but asymmetrical, with strong linkages to the United States, United Kingdom, Japan, and Australia, and comparatively limited intra-ASEAN integration. Thematic analyses identified dengue as the dominant motor theme, supported by strong vector biology and molecular epidemiology clusters. Helminthic and zoonotic diseases occupied more peripheral positions. Emerging domains included spatial epidemiology, genomic surveillance, and climate-linked modeling, though One Health integration remained structurally underdeveloped. CONCLUSION: Findings delineate a maturing yet structurally bifurcated NTD research ecosystem in Southeast Asia. Strengthening intra-regional scientific networks, diversifying funding architectures, and promoting cross-disciplinary integration will be critical to aligning research production with regional disease burdens and advancing equitable progress toward the WHO 2030 NTD Roadmap. CLINICAL TRIAL REGISTRATION: Not applicable.