Abstract
The spatial distribution of species has long sparked interest among ecologists and biogeographers, increasingly so in studies of species responses to climate change. However, field studies on spatial patterns of distribution, useful to inform conservation actions at local scales, are still lacking for many regions, especially the tropics. We studied elevational trends and species‐area relationships among anurans in wetland habitats within Volcanoes National Park (VNP) in Rwanda, part of the biodiverse Albertine Rift region. In VNP, wetlands are key sites for anuran reproduction, and anurans are likely threatened by wetland desiccation which has occurred for the last few decades. Between 2012 and 2017, we sampled anuran communities in ten VNP wetlands located along an elevational gradient of c. 600 m (from 2,546 to 3,188 m a.s.l.) and found at least eight species, including at least two Albertine Rift Endemics. We show that species richness, diversity, and abundance likely decline with a decrease in wetland size and with an increase in elevation, though additional sampling (e.g., at night) might be needed to derive definite conclusions. Larger wetlands at lower elevations contained most species and individuals, which indicates the potential threat of wetland size reduction (through desiccation) for anuran conservation. However, we also found that wetlands differed in species composition and that some species (e.g., Sclerophrys kisoloensis) were likely restricted in distribution to only a few of the smaller wetlands—suggesting that the conservation of each individual wetland should be prioritized, regardless of size. We propose that all wetlands in VNP require additional conservation measures, which should be based on knowledge gathered through long‐term monitoring of anuran communities and research on drivers of wetland decline. Only such extended research will allow us to understand the response of anurans in VNP to threats such as climate change and wetland desiccation.
Highlights
An understanding of the spatial distribution of biodiversity allows us to address how evolutionary and ecological processes shape ecosystems and guides conservation efforts, such as the spatial planning of protected areas
Given the morphological similarity between Leptopelis karissimbensis (ARE) and L. kivuensis (ARE), we acknowledge that certain individuals that we identified as L. karissimbensis in the field could be L. kivuen‐ sis, and as such we opted use L. karissimbensis/kivuensis for further analyses
We urge that our results should be interpreted with caution, due to biases introduced by skewed sampling efforts, such as a lack of nighttime sampling, we emphasize that there is considerable spatial variation among the anuran communities of the study wetlands in Volcanoes National Park (VNP)
Summary
A general tendency of increasing species richness with increases in area of investigation remains a common result of studies in biogeography and landscape ecology, there are many alternative explanations for underlying mechanisms (for an overview of some of the most important, long‐standing, hypotheses see McGuinness (1984) and Connor and McCoy (1979)) Given this complexity of underlying mechanisms and associated describing models, it is unsurprising that it is hard to generalize species‐area relationships, even within one taxon, such as amphibians. Previously permanently wet ponds in certain wetlands remain dry for parts of the year, while other wetlands have dried up completely and are experiencing associated vegetational succession toward shrubbery and forest This process of wetland desiccation is likely to have a negative impact on the anurans particular to this habitat (McMenamin, Hadly, & Wright, 2008), especially in combination with changes in climatic factors, such as altered frequency and periodicity of rainfall (Hartter et al, 2012). This information provides a baseline to test what drives anuran distribution and anuran responses to increasing threats in this biodiverse, but fragile, region of Central Africa
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