Biology subjects

Schuessler, D.

Publications and source records attributed to Schuessler, D..

4 recordsLinked to original sources

bioRxiv2025

Influence of vegetation structure on lemur recolonization of post-fire habitats in northwestern Madagascar

Habitat quality is a key determinant of wildlife distribution and persistence. Any disturbance such as fire degrades forest habitats by increasing canopy openness, reducing tree basal area, and eliminating large, cavity-bearing trees providing shelter for many species. In Madagascar, fire has become a prominent disturbance, yet the mechanisms linking fire disturbance to lemur habitat occupation remain poorly understood. Using Generalized Linear Mixed Models, we assessed the effects of forest humidity, temperature, vegetation structural gradients, and tree species richness on lemur occurrence, and evaluated the impact of fire regime parameters on significant abiotic and structural vegetation gradients. Lemur responses varied by body size and ecological specialization. Eulemur fulvus most likely occurred in humid habitats with high floristic diversity. The latter also explained best the presence of Avahi occidentalis and Cheirogaleus medius, while Lepilemur edwardsi was rather connected to dense stands of overstory trees. Small-bodied Microcebus species displayed a higher structural and floristic tolerance. Tree species richness declined sharply in burnt areas and was highest in unburnt forest. Fires impacted vegetation structural gradients, increasing openness and understory density, while old burnt and unburnt forests maintained complex vertical layering. Tree species richness emerged as the strongest predictor of lemur species richness. These results indicate that fire primarily affects lemurs through floristic and structural pathways rather than microclimatic shifts, emphasizing the need to preserve intact forest refugia with mature canopies and species-rich tree communities to sustain lemur diversity under increasing fire pressure in dry forest landscapes of Madagascar. SummaryO_LIForest fires alter lemur habitats by reducing tree species richness and mature tree density. C_LIO_LIEulemur fulvus, Avahi occidentalis and Cheirogaleus medius preferentially occupied floristically diverse forests, suggesting the relevance of a diverse spectrum of food resources for species of divergent body size. C_LIO_LIThe medium-sized Lepilemur edwardsi was sensitive to fire-induced loss of canopy integrity, limiting their persistence in burnt forests, while small-bodied mouse lemurs (Microcebus ravelobensis and M. murinus) exhibited high resilience to fire-modulated habitat changes. C_LIO_LILemur species richness was strongly linked to tree species diversity, underscoring the role of floristic richness in post-fire lemur and habitat recovery. C_LI

ecology↗

bioRxiv2025

Ecological plasticity explains the distribution of sympatric and allopatric mouse lemurs (Microcebus spp.) in northeastern Madagascar

Species distributions are shaped by complex biotic and abiotic interactions. We studied major ecological drivers of the distribution of four cryptic mouse lemur species (Microcebus spp.) in northeastern Madagascar, across sympatric and allopatric ranges. Using structural habitat characteristics, adaptability to habitat degradation, bioclimatic niches, and morphology, we estimated n-dimensional hypervolumes of niche sizes and overlaps. Annual body mass variability was analyzed as an indicator of heterothermy, a potential indicator for ecological plasticity. M. jonahi and M. simmonsi were found almost equally often in forest- and fallow-derived habitats (52% and 58%, respectively), while M. lehilahytsara predominantly occupied fallow habitats (71%), likely driven by the coexistence with other species. M. lehilahytsara exhibited the largest niche and range size, followed by M. jonahi and M. simmonsi. In contrast, M. macarthurii was restricted to a narrow niche and range. M. jonahi and M. simmonsi displayed significant fat deposition before the austral winter, indicating heterothermy as an adaptation to unpredictable environmental conditions. These species were only found in allopatry, likely due to competition for critical resources like sleeping sites. The smaller M. lehilahytsara coexisted with M. jonahi and M. macarthurii potentially by adjusting its niche to avoid competition with these larger-bodied species. We hypothesize that heterothermy allowed M. jonahi, M. simmonsi, and M. macarthurii to persist in lowlands during Pleistocene climatic challenges but that it did not promote coexistence. In contrast, M. lehilahytsara may have lost lowland distributions due to a lower ability to store fat. Our findings require further testing but provide a plausible explanation for a complex distributional pattern of sympatric and allopatric occurrences.

ecology↗

bioRxiv2024

Invisible people: Exploring how well remote-sensed datasets reveal the distribution of forest-proximate populations

Accurate information on the location and density of people living at the forest frontier is vital for effective and equitable forest conservation. We compare the location of settlements and estimated population density from three global-scale, remote-sensed datasets (World Settlement Footprint 2015, Open Buildings, WorldPop) with a fine-scale, manually-derived dataset of 3,136 human settlements, of which 95% had fewer than 150 households. The study region is located in north-eastern Madagascar, contains three protected areas and the largest unprotected block of humid forest of the island. The Open Buildings dataset detected a much higher proportion (94%) of settlements than did World Settlement Footprint (15%). Population density from WorldPop matches poorly with that estimated from our manually-derived dataset. The accuracy of all three datasets is worse in more remote, forested areas, further away from basic infrastructure. Open Buildings appears to best reveal the distribution of low density scattered populations in forested areas. However, further testing in other climatic regions is still needed. Making good use of appropriate remote-sensed data could revolutionize the inclusion of local communities in conservation policy and practice, improve the quality of inference in conservation research, particularly in times of a planned expansion of the global protected area network.

ecology↗

bioRxiv2022

Thirty years of deforestation within the entire ranges of nine endangered lemur species (3 CR, 4 EN, 2 VU) in northwestern Madagascar

Forest cover change is of particular concern in tropical regions. In this study, we investigate the degree of deforestation in the entire ranges of nine highly threatened lemur species in northwestern Madagascar. Landsat satellite images were acquired from four different time stages (1990, 2000, 2011, 2020), classified into forest/non-forest, and changes quantified. Forest cover declined from 17.5% to 9.3% within the last 30 years. This decline varied across four protected areas (PAs) investigated: the forest cover of Ankarafantsika National Park (ANP) declined only moderately over time (from 76.3% to 67.4%), while it declined drastically in other PAs (e.g., from 54.9% to 18.9%, Bongolava Forest Corridor). Two lemur taxa are most affected (Lepilemur otto, Microcebus bongolavensis) by having only very few isolated forest patches left within their ranges (approximately 542.7 km{superscript 2}). For two other species (L. ahmansoni, L. aeeclis), most of the remaining forest is concentrated in two coastal PAs (in total 627.2 and 477.9 km{superscript 2}, respectively), while those species occurring inside ANP (5 taxa) experienced rather stable forest coverage until 2020. A reversal of these deforestation trends and active reforestation measures are desperately needed to reduce habitat loss for these nine lemur species. A practical experience-based guideline is therefore provided.

ecology↗