Biology subjects

Radespiel, U.

Publications and source records attributed to Radespiel, U..

7 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

Species-specific responses to paleoclimatic changes and landscape barriers drive contrasting phylogeography of co-distributed lemur species in northeastern Madagascar

Madagascar is a megadiverse island with exceptionally high levels of endemism, which resulted mainly from allopatric speciation promoted by the islands complex physical geography and paleoclimatic cycles. Northeastern Madagascar is uniquely suited to test the relative importance of river barriers, topography and climatic conditions for lemur genetic differentiation. Based on restriction site-associated DNA sequences, we inferred phylogeny, population structure, genetic diversity and rates of gene flow in four mouse lemur (genus Microcebus) and two woolly lemur (genus Avahi) species. In addition, we employed isolation-by-resistance models to test the importance of topography, river barriers, climate and forest cover in restricting intraspecific gene flow. Our results show that significant differences in genetic diversity and connectivity can be explained by varying responses to landscape features and species-specific phylogeographic histories. Rivers present a general barrier to gene flow, and dispersal between inter-river systems is predominantly mediated through high-elevation headwater regions. While this led to high connectivity and genetic diversity in M. lehilahytsara and A. laniger, gene flow among M. jonahi populations is limited by low climatic niche suitability at higher elevations. In addition, topographic complexity promotes connectivity among Microcebus populations, potentially by buffering impacts of seasonal or historic changes in climatic conditions. Finally, the more restricted distributions of M. macarthurii, A. mooreorum and, to some extent, M. simmonsi likely resulted from refugial dynamics and sea level fluctuations which led to geographic isolation, microendemism and secondary contact zones. Our findings generated informed hypotheses regarding the colonization history of the studied species while also having important implications for their conservation.

evolutionary biology↗

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↗

bioRxiv2023

Montane rain forest dynamics under changes in climate and human impact during the past millennia in northern Madagascar

Madagascar comprises one of the Earths biologically richest, but also one of most endangered, terrestrial ecoregions. Although it is obvious that humans substantially altered its natural ecosystems during the past decades, the timing of arrival of humans on Madagascar as well as their environmental impact is not well resolved. In this context, this research aims to study and compare the influence of early human impact and climate change on rain forests and wildlife in northern Madagascar during the past Millennia. By using palaeoenvironmental reconstructions from lake sediment cores in a montane environment (Montagne dAmbre), results indicate a major drought, starting approximately 1,100 years ago. This drought caused significant changes in lake levels and vegetation dynamics. Human impact, evidenced by fires, started a few decades later. Anthropogenic burning, limited to the low-altitude areas, was therefore not the driving force behind these early changes observed in the lake catchment areas. Although this does not dismiss the strong impacts humans had subsequently on these ecosystems, this work demonstrates that the late Holocene natural drought that intensified regionally about one thousand years ago, significantly impacted the ecosystems independently and prior to anthropogenic activities. At a regional scale, a review of demographic studies revealed a substantial number of inferred population bottlenecks in various wildlife species during the last millennia, likely resulting from this combination of both human-related impact and natural environmental changes (i.e., precipitation decline). This research highlights that the current state of ecosystems in northern Madagascar results from both human impact and natural climate changes. It also points to the importance of a multi-site and multi-proxy comparison for deciphering the nature and succession of past environmental changes.

ecology↗

bioRxiv2023

Not one, but multiple radiations underlie the biodiversity of Madagascar's endangered lemurs

Lemurs are often cited as an example of adaptive radiation. Since colonizing Madagascar, more than 100 extant lemur species have evolved to fill a variety of ecological niches on the island. However, recent work suggests that lemurs do not exhibit one of the hallmarks of other adaptive radiations: explosive speciation rates that decline over time. Thus, characterizing the tempo and mode of evolution in lemurs can help us understand alternative ways that hyperdiverse clades arise over time, which might differ from traditional models. We explore the evolution of lemurs using a phylogenomic dataset with broad taxonomic sampling that includes the lemurs sister group, the lorisiforms of Asia and continental Africa. Our analyses reveal multiple bursts of diversification (without subsequent declines) that explain much of todays lemur diversity. We also find higher rates of speciation in Madagascars lemurs compared to lorisiforms, and we demonstrate that the lemur clades with exceptionally high diversification rates have higher rates of genomic introgression. This suggests that hybridization in these primates is not an evolutionary dead-end, but a driving force for diversification. Considering the conservation crisis affecting strepsirrhine primates, with approximately 95% of species being threatened with extinction, this phylogenomic study offers a new perspective for explaining Madagascars exceptional primate diversity and reveals patterns of speciation, extinction, and gene flow that will help inform future conservation decisions.

evolutionary biology↗

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↗

bioRxiv2019

Complex processes of cryptic speciation in mouse lemurs from a micro-endemism hotspot in Madagascar

AO_SCPLOWBSTRACTC_SCPLOWMouse lemurs (Microcebus) are a radiation of morphologically cryptic primates distributed throughout Madagascar for which the number of recognized species has exploded in the past two decades. This taxonomic explosion has prompted understandable concern that there has been substantial oversplitting in the mouse lemur clade. Here, we take an integrative approach to investigate species diversity in two pairs of sister lineages that occur in a region in northeastern Madagascar with high levels of microendemism and predicted habitat loss. We analyzed RADseq data with multispecies coalescent (MSC) species delimitation methods for three named species and an undescribed lineage previously identified to have divergent mtDNA. Marked differences in effective population sizes, levels of gene flow, patterns of isolation-by-distance, and species delimitation results were found among them. Whereas all tests support the recognition of the presently undescribed lineage as a separate species, the species-level distinction of two previously described species, M. mittermeieri and M. lehilahytsara is not supported - a result that is particularly striking when using the genealogical discordance index (gdi). Non-sister lineages occur sympatrically in two of the localities sampled for this study, despite an estimated divergence time of less than 1 Ma. This suggests rapid evolution of reproductive isolation in the focal lineages, and in the mouse lemur clade generally. The divergence time estimates reported here are based on the MSC and calibrated with pedigree-based mutation rates and are considerably more recent than previously published fossil-calibrated concatenated likelihood estimates, however. We discuss the possible explanations for this discrepancy, noting that there are theoretical justifications for preferring the MSC estimates in this case.

evolutionary biology↗