Understanding how species respond to habitat loss and fragmentation is a critical requirement for effective conservation action, particularly in biodiversity hotspots like Madagascar. Species with specialized, narrower ecological niche requirements are hypothesized to be more vulnerable to extinction than generalists, yet empirical tests of this prediction among closely related taxa remain limited. Here, we compare the ecological niche patterns and predicted distributions of two sympatric lemurs in northwestern Madagascar - the Vulnerable Common Brown Lemur (Eulemur fulvus) and the Critically Endangered Mongoose Lemur (Eulemur mongoz) - to assess how niche flexibility relates to extinction risk. Using presence-only data collected between 2015 and 2020 and ten environmental covariates, we developed species distribution models and ran niche equivalence analysis. The models indicate that E. fulvus occupies a broader and more continuous predicted distribution range (48,591 ha) than E. mongoz (17,757 ha). In comparison, E. mongoz is predicted to occur primarily in moist lowland forests near water basins, showing a stronger spatial association with these habitat conditions that E. fulvus. Despite these marked differences in their predicted geographic distributions, niche equivalence analysis showed substantial overlap in the environmental conditions occupied by the two species within the study area. Together, these results suggest that E. mongoz's restricted distribution is not explained solely by the measured environmental predictors, highlighting the need for future work that integrates additional environmental variables and evaluates potential behavioural or demographic constraints not captured here. These findings highlight how subtle differences in niche requirements can shape a species' habitat use and vulnerability to environmental change. From a management perspective, our findings support prioritizing the protection of moist lowland forests near water basins for E. mongoz while maintaining or enhancing habitat connectivity for E. fulvus in fragmented landscapes.
Résumé : Cette étude article « Toliara, capitale de la tortue radiée : otage des trafiquants » analyse les principaux facteurs qui favorisent le trafic de la tortue radiée, ses impacts sur l’espèce, son habitat et les communautés locales, ainsi que les stratégies susceptibles de renforcer sa conservation. Cette étude a été réalisée dans la région de Toliara auprès de 150 personnes enquêtées, dont 90 hommes et 60 femmes, en adoptant une approche basée à la fois sur des données quantitatives et qualitatives. La collecte des informations a été effectuée à l’aide d’une fiche d’enquête, d’entretiens ainsi que d’une recherche documentaire, tandis que le traitement des données a été réalisé avec le logiciel Microsoft Excel. Les résultats obtenus révèlent que le trafic de la tortue radiée est largement influencé par des facteurs socio-économiques tels que la pauvreté, le chômage, l’insuffisance d’activités génératrices de revenus et la volonté d’obtenir rapidement des ressources financières. Ces difficultés sont renforcées par plusieurs contraintes liées à la surveillance et à la lutte contre le trafic, notamment la faiblesse des contrôles, le manque de moyens disponibles pour les agents chargés de la protection ainsi que l’existence de réseaux organisés de trafiquants. Cette situation provoque une diminution progressive des effectifs de tortues radiées, perturbe leur capacité de reproduction, entraîne leur raréfaction dans certaines zones et accentue les menaces pesant sur leur habitat naturel. Au-delà des conséquences écologiques, le trafic affecte également les communautés locales ainsi que les perspectives de développement de la région de Toliara. L’étude met ainsi en avant la nécessité de renforcer les dispositifs de surveillance, l’application des réglementations, les actions de sensibilisation, l’implication des populations locales et la mise en place d’alternatives économiques durables. Elle souligne enfin l’importance d’une gouvernance intégrée permettant d’assurer un équilibre entre la conservation de la biodiversité, le développement local et les responsabilités des différents acteurs institutionnels. Mots-clés : Tortue radiée, trafic illicite, conservation, gouvernance environnementale, biodiversité
Diospyros comorensis Hiern is a medicinal plant traditionally utilized in the management of cardiovascular disorders. Despite its common use, the pharmacological properties and phytochemical composition remain unexplored. This study aimed to evaluate the vasorelaxant, diuretic, and antioxidant activities, as well as toxicity and phytochemical profiling, of a methanol–water extract of D. comorensis leaves (MDCR) and a decoction of D. comorensis leaf (DDCR) extract. The main phytochemicals were quantified using High-Performance Liquid Chromatography (HPLC). Antioxidant capacity was assessed using DPPH and FRAP assays. The vasorelaxant effect was evaluated in vitro on phenylephrine-precontracted aortic rings. Diuretic activity was determined by measuring Wistar rats’ urine output and electrolyte levels (Na+, Cl−, and K+). Toxicity was assessed using Swiss mice. The extracts showed a total phenolic content (TPC) of 29,693.02 ± 3493.75 mg GAE/100 g DW (Folin–Ciocalteu method), which was markedly higher than the total phenolics quantified by HPLC (3743.12 ± 457.32 mg/100 g DW, representing 76.38% of the total bioactive fraction). Among the quantified constituents, ellagic acid (56.36%) was the main compound. Both extracts exhibited marked antioxidant capacity along with significant vasorelaxant effects on phenylephrine-precontracted rat aorta rings, with EC50 values of 3.83 ± 0.81 µg/mL for MDCR and 4.87 ± 0.79 µg/mL for DDCR. Acute toxicity was not observed with either extract. The identified compounds may be involved in the observed antioxidant and pharmacological effects. These results show experimental evidence useful to support the traditional use of D. comorensis leaves in managing high blood pressure and highlight the antihypertensive potential of this Comorian endemic species. Further studies are necessary to characterize the biological mechanisms involved and relative bioactive substances. Reporting the pharmacological activities of D. comorensis may contribute to the sustainable use of natural resources in the Comoros Islands and Madagascar.
Abstract Among Madagascar primates, the sportive lemurs (family Lepilemuridae) have seen their species diversity increase from eight in 2005 to 26 in 2009 mostly by applying the phylogenetic species concept to DNA barcode data. Despite the genus being speciose, only one case of sympatry is known from northern Madagascar, where two sportive lemur species described based on low mtDNA divergence, Lepilemur ankaranensis and Lepilemur milanoii , were found to co-occur at the center of their joint distribution range. Here, to clarify the taxonomy of these two species and examine their sympatry, we apply an integrative taxonomic framework to genomic and morphological data from 84 individuals of L. ankaranensis and L. milanoii , encompassing their entire distribution range and the forest of Analafiana, beyond their southernmost limit. Using clustering, multivariate, and isolation by distance analyses, we find no evidence of a sympatric zone and show that despite clear genetic differentiation between regions, the genomic and morphological diversity of the L. ankaranensis - L. milanoii - Analafiana group is clinal and explained by geographic distance. These results clarify that L. milanoii is a junior synonym of L. ankaranensis and that the Analafiana forest population belongs to L. ankaranensis , extending its distribution. It further implies that the “sympatric” zone—the Andrafiamena forest—hosts conspecific individuals with slightly differentiated mtDNA backgrounds, rather than slightly differentiated sympatric species. Lastly, we re-evaluate the IUCN conservation metrics of L. ankaranensis , which continue to qualify as Endangered (EN) under the B1ab(i-v) criteria.
Wild edible yam species remain underutilized despite their recognized potential to enhance food security, dietary diversification, and biodiversity conservation. Among them, Dioscorea comorensis, an endemic and endangered species from the Comoros, has received little scientific attention, and its nutritional potential remains largely unexplored. This study provides the first comprehensive nutritional and phytochemical characterization of flour produced from its tubers. Tubers collected from Ouellah (Ngazidja Island) were processed into flour and analyzed using standardized AOAC methods. Proximate composition, mineral profile, phytochemical constituents, and nutritional indices (PRAL, Ca/P, and Na/K ratios) were determined using atomic absorption spectrophotometry, colorimetry, and qualitative phytochemical tests.The flour exhibited low moisture content (7.13%) and high dry matter (92.87%), with 6.37% protein, 83.37% carbohydrates, and a metabolizable energy value of 357.46 kcal/100 g. It was particularly rich in potassium (780.41 mg/100 g), sodium (599.41 mg/100 g), phosphorus (444.17 mg/100 g), and calcium (422.70 mg/100 g), while also containing appreciable amounts of magnesium, iron, zinc, manganese, and copper. Phytochemical screening confirmed the presence of several bioactive compounds. The negative PRAL value (−9.80 mEq/100 g) indicated an alkalizing effect, whereas the Ca/P (0.95) and Na/K (0.77) ratios suggested a favorable mineral balance. These findings demonstrate that D. comorensis flour is a promising nutrient-rich and functional food resource suitable for composite flour and breadmaking. This study establishes a scientific basis for the sustainable utilization, conservation, and valorization of this endemic species, supporting future strategies to strengthen food and nutritional security in the Comoros.
