Anthropogenic landscape change and amphibian diversity in tropical montane biodiversity hotspots: insights from satellite remote sensing in the Madagascar highlands

The magnitude of anthropogenic landscape change in tropical montane biodiversity hotspots and its relationship with biodiversity is a global issue that remains ‘locked-in’ in the broad narrative of tropical change in Africa. Over a montane biodiversity hotspot of Madagascar highlands (Ankaratra Massif), we conducted analysis on land cover change with Landsat satellite sensor data to identify the magnitude of change (1995–2016) and on the habitat change–amphibian diversity relationship to understand links with biodiversity. The results evidenced that 17.8% of the biodiversity hotspot experienced change in land cover in only 20 years. That pressured the already threatened forests, particularly since 2005. Of the total forest area in 1995 (2062.7 ha), 21.5% was cleared by 2016 (1618.3 ha). Changes in forest cover followed a bidirectional pattern. While in the period 1995–2005, forests expanded at a rate of 2.0% year−1 (from 2062.7 to 2524.8 ha), the area declined between 2005 and 2016 at a rate of − 4.1% year−1, fourfold the rate reported nationally for Madagascar (− 1.1% year−1). Forest-to-shrubland transitions emerged as being of increasing concern to forest integrity. We identified a significant link between habitat change and amphibian diversity, but only for species richness. Counter to expectations, no significant relationship was found between species richness and deforestation rates, and between microendemism rates and any of the habitat change variables. Species richness responded to the spatiotemporal variability in vegetation dynamics represented by the standard deviation of the Normalized Differenced Vegetation Index (NDVI_std). Species richness was strongly negatively related to NDVI_std in the short-term (R2 = 0.91, p = 0.003) and long-term (R2 = 0.69, p = 0.03), increasing where the spatiotemporal variability in NDVI was lower. The magnitude of changes in this biodiversity hotspot suggests that region-specific assessments are necessary in the context of the tropical change narrative in Africa and should consider conservation policies tailored for local conditions. Reducing deforestation and land conversion rates through a management plan codesigned with local communities is urgent. Habitat change appears to impact on amphibian diversity by altering the functional attributes of the habitat and not just by reducing habitat extent. NDVI_std seems a relevant indirect metric for monitoring such change although other biophysical attributes obtained from satellite sensor data should be integrated and explored.info:eu-repo/semantics/acceptedVersio

Morphological and ecological convergence at the lower size limit for vertebrates highlighted by five new miniaturised microhylid frog species from three different Madagascan genera

Miniaturised frogs form a fascinating but poorly understood amphibian ecomorph and have been exceptionally prone to taxonomic underestimation. The subfamily Cophylinae (family Microhylidae), endemic to Madagascar, has a particularly large diversity of miniaturised species which have historically been attributed to the single genus Stumpffia largely based on their small size. Recent phylogenetic work has revealed that several independent lineages of cophyline microhylids evolved towards highly miniaturised body sizes, achieving adult snout- vent lengths under 16 mm. Here, we describe five new species belonging to three clades that independently miniaturised and that are all genetically highly divergent from their relatives: (i) a new genus (Mini gen.nov.) with three new species from southern Madagascar, (ii) one species of Rhombophryne, and (iii) one species of Anodonthyla. Mini mum sp. nov. from Manombo in eastern Madagascar is one of the smallest frogs in the world, reaching an adult body size of 9.7 mm in males and 11.3 mm in females. Mini scule sp.nov. from Sainte Luce in southeastern Madagascar is slightly larger and has maxillary teeth. Mini ature sp.nov. from Andohahela in southeast Madagascar is larger than its congeners but is similar in build. Rhombophryne proportionalis sp.nov. from Tsaratanana in northern Madagascar is unique among Madagascar's miniaturised frogs in being a proportional dwarf, exhibiting far less advanced signs of paedomorphism than other species of similar size. Anodonthyla eximia sp.nov. from Ranomafana in eastern Madagascar is distinctly smaller than any of its congeners and is secondarily terrestrial, providing evidence that miniaturisation and terrestriality may be evolutionarily linked. The evolution of body size in Madagascar's microhylids has been more dynamic than previously understood, and future studies will hopefully shed light on the interplay between ecology and evolution of these remarkably diverse frogs

Functional diversity in a fragmented landscape — Habitat alterations affect functional trait composition of frog assemblages in Madagascar

Anthropogenic habitat alterations cause biodiversity loss, which in turn negatively affects ecosystem functioning and services, and thus human well-being. To be able to consider ecosystem functioning in conservation actions, analyzing the effects of habitat alteration on functional diversity is essential. Some altered habitats can maintain a significant part of regional biodiversity, however, functional diversity information in altered habitats is so far mostly lacking. We compared functional richness and functional β-diversity based on resource-use traits of frogs between three land-use categories in a rainforest ecosystem in Madagascar. Land-use categories represent a habitat alteration gradient ranging from continuous forest over forest fragments to matrix habitats including different agricultures. Our study revealed distinct changes in resource-use trait composition and complex patterns in the relationship between species richness and functional richness. Thus, the functional structure of frog assemblages changed due to habitat alterations. However, altered habitats likely provide different, rather than fewer functions compared to intact forest. Streams in all land-use categories were the functionally richest habitats, and thus important for ecosystem functioning. Species richness was one, but not the only driver of functional richness in our system. Functional clustering, potentially due to environmental filters depending on resource availability, was caused by anthropogenic and natural drivers. Our study shows that, even in systems where fragmented landscapes still maintain high species diversity, functional diversity can be altered in human altered habitats, which may affect ecosystem processes like productivity, nutrient cycling, and energy flows