Amphibian and reptile communities and functional groups over a land‐use gradient in a coastal tropical forest landscape of high richness and endemicity

Abstract

Information on the response of herpetofauna to different land uses is limited though important for land-use planning to support conservation in human-modified landscapes. Though transformation is dogmatically associated with extinction, species respond idiosyncratically to land-use change, and persistence of species in habitat fragments may depend on careful management of the human-modified matrix. We sampled herpetofauna over a vegetation-type gradient representative of regional land uses (old-growth forest, degraded forest, acacia woodland (i.e. new-growth forest), eucalyptus plantation, and sugar cane cultivation) in the forest belt skirting the southeastern coast of Africa, part of a biodiversity hotspot hosting many endemic herpetofaunal species in a highly transformed landscape. We categorized species into 1 Author Contributions: MJT and RJvA designed the study. MJT carried out the project, analyzed the data, and wrote the manuscript with input from RJvA, who supervised the study.2 trait-derived functional groups, and assessed abundance and richness of groups and compared community metrics along the gradient. We further assessed the capacity of environmental variables to predict richness and abundance. Overall, old-growth forest harbored the highest richness and abundance, and frogs and reptiles responded similarly to the gradient. Richness was low in cultivation and, surprisingly, in degraded forest but substantial in acacia woodland and plantation. Composition differed between natural vegetation types (forest, degraded forest) and anthropogenic types (plantation, cultivation), while acacia woodland grouped with the latter for frogs and the former for reptiles. Functional group richness eroded along the gradient, a pattern driven by sensitivity of fossorial/ground-dependent frogs (F2) and reptiles (R2) and vegetationdwelling frogs (F4) to habitat change. Variables describing temperature, cover, and soil were good predictors of frog abundance, particularly of functional groups, but not for reptiles.Conserving forest and preventing degradation is important for forest herpetofaunal conservation, restoration and plantations have intermediate value, and cultivation is least beneficial. Our study demonstrates the utility of function-related assessments, beyond traditional metrics alone, for understanding community responses to transformation. Particularly, fossorial/ground-dependent frogs and reptiles and vegetation-dwelling frogs should be closely monitored.

Opportunistic records reveal Mediterranean reptiles’ scale‐dependent responses to anthropogenic land use

“…Snakes tended to correlate more negatively than lizards with urbanization at the regional scale, consistent with previous observations that carnivore, fossorial and ground-dwelling reptiles are negatively affected by the human footprint (Trimble andvan Aarde 2014, Todd et al 2017). Snakes tended to correlate more negatively than lizards with urbanization at the regional scale, consistent with previous observations that carnivore, fossorial and ground-dwelling reptiles are negatively affected by the human footprint (Trimble andvan Aarde 2014, Todd et al 2017).…”

“…Reptiles have recently undergone declines at regional (Driscoll 2004) and global scales (Gibbons et al 2000, Keinath et al 2017, partly explained by ecological trait suites associated with vulnerability to anthropogenic disturbance of resources and habitats (Cardillo et al 2005, Trimble andvan Aarde 2014). As ectothermic predators, most reptile species combine small home ranges, high habitat and dietary specialization, low dispersal and sensitivity to microclimates (Huey 1982).…”

Evolutionarily distinct amphibians are disproportionately lost from human‐modified ecosystems

“…There is evidence that land conversion functionally homogenises amphibian assemblages (Ernst et al . ; Trimble & van Aarde ), which is logical given that susceptible species tend to share certain traits (Hirschfeld & Rödel ; Nowakowski et al . ).…”

“…These patterns raise the question of what consequences will the loss of evolutionarily distinct amphibians from converted habitats have for ecosystem integrity and function? There is evidence that land conversion functionally homogenises amphibian assemblages (Ernst et al 2006;Trimble & van Aarde 2014), which is logical given that susceptible species tend to share certain traits (Hirschfeld & R€ odel 2017;Nowakowski et al 2017). Although there is some empirical evidence that evolutionarily isolated species have more distinctive suites of traits (e.g.…”

Supporting conservation with biodiversity research in sub-Saharan Africa’s human-modified landscapes

“…Similarly, South African forest remnants embedded in various matrix types have similar bird species richness, but abundance is highest in fragments in agricultural matrices due to the presence of forest generalists and open-habitat species, while forest specialists are rare (Neuschulz et al 2011). Additionally, herpetofaunal richness does not decline monotonically along a land-use gradient from forest to cultivation, while richness of functional groups erodes along the gradient due to sensitivity of some specialist groups (Trimble and van Aarde 2014). Forest fragments and grasslands in the agricultural mosaic outside a PA in southern Mozambique have more beetle species and higher abundance, while endemic beetle species are better represented inside the PA (Jacobs et al 2010).…”