Elevated alpha diversity in disturbed sites obscures regional decline and homogenization of amphibian taxonomic, functional and phylogenetic diversity

Abstract

Loss of natural habitat due to land-use change is one of the major threats to biodiversity worldwide. It not only affects the diversity of local species communities (alpha diversity) but can also lead to large-scale homogenization of community composition (reduced beta diversity) and loss of regional diversity (gamma diversity), but these effects are still rarely investigated. We assessed the impact of land-use change on taxonomic, functional and phylogenetic diversity of amphibians in Rwanda, both on the local (community-level) and regional scale (country-wide). Alpha diversity in local communities was higher in farmland than in natural habitats; however, species turnover among farmland sites was much lower than among natural sites, resulting in highly homogenized communities and reduced taxonomic, functional and phylogenetic gamma diversity in farmland across Rwanda. Amphibians found in farmland were mostly disturbance-tolerant species that are widespread in eastern Africa and beyond. In contrast, most of the regionally endemic frog species that make this region a continent-wide hotspot of amphibian diversity were found only in the natural habitats. Ongoing habitat conversion might result in further homogenization of amphibian communities across sub-Saharan Africa and the loss of regional endemism, unique evolutionary lineages, and multifunctionality.

Amphibians of Rwanda: Diversity, Community Features, and Conservation Status

“…Only five of the 17 species found at the four montaneforest sites above 2000 m were also detected in farmland at similar elevations (see Ref. [79]), and only two of them were found at one of the three sites in farmland a lower elevation, rendering the faunal overlap between montane-forest sites above 2000 m and farmland sites below 2000 m (Sörensen index) to QS = 0.095. 25 of the 38 species were tolerant to anthropogenic alteration of habitat, of which 23 were found at the three farmland sites (cultivated wetland/marais).…”

“…Distribution: A wide geographical range from Uganda and Kenya, although much of eastern and southern Africa except for the southwestern parts at elevations from sea level to 2348 m [6,79,113]. Altitudinal range and province records in Rwanda: 960-2348 m; all 5 provinces.…”

“…Distribution: The species has a fragmented range from central Malawi to Uganda and western and central Kenya in altitudes from 1500 m to 3031 m [6,79,113]. Altitudinal range and province records in Rwanda: 1467-3031 m; Western, Northern, and Southern Provinces.…”

“…Distribution: The species is endemic to the Albertine Rift, occurring in eastern DR Congo, Rwanda, Uganda, and western Kenya at elevations of 1200-3031 m [23,79]. Altitudinal range and province records in Rwanda: 2379-3031 m; Western and Northern Provinces.…”

“…Furthermore, some recent phylogenetic studies, which comprised species from the Albertine Rift used samples from Rwanda [64][65][66][67][68][69][70][71][72][73][74][75]. Our own contributions published so far have focused on amphibian communities in anthropogenically altered habitats [76][77][78][79], studies on the taxonomy and ecology of the genera Hyperolius [58,62,[80][81][82][83][84][85], Afrixalus [86,87], and Ptychadena [88][89][90], and amphibian parasites [91][92][93][94][95].…”