Post-Logging Recovery of Amphibian Assemblages and Habitat Preferences of the Endangered Giant Squeaker Frog (Arthroleptis krokosua) in Ghana’s Moist Semi-Deciduous Forests
T he Giant West African squeaker frog (Arthroleptis krokosua) is evolutionarily distinct from any... more T he Giant West African squeaker frog (Arthroleptis krokosua) is evolutionarily distinct from any West African amphibian. It differs from all known members of its genus Arthroleptis by its large size, coloration and other morphological characters, such as a very broad head. This unusual frog, may be one of West Africa's rarest and most endangered amphibians. To date, only 16 individuals of the Giant squeaker frog have been observed in spite of four successive years of intense surveys. Unfortunately, the fate of these surviving individuals hangs in the balance due to prevailing threats from mining, logging, farming and the non-native and invasive Devil weed (Chromolaena odorata) at their only remaining home on earth, Sui River Forest Reserve. In the light of the persistent threats, to save the Giant squeaker frog from imminent extinction, we have proposed herein drastic and focused measures including the upgrading of its conservation status from Endangered to Critically Endangered.
Temperature and moisture regimes are the two key variables that determine the distribution, growt... more Temperature and moisture regimes are the two key variables that determine the distribution, growth, productivity, and reproduction of plants and animals on which humans depend for their nutritional and medicinal needs (Alcamo et al. 1998; MEA, 2005; van Vuuren and Pereira, 2006; Hof et al. 2011) (Fig. 1-3). Climate change increasingly alters temperature and moisture regimes to the threat of plants and animals that support humans. Thus, increasingly threatening the very existence of humans (Hof et al., 2010; Hof et al., 2011a and Hof et al., 2011b). Current projections do not point to this trend changing in subsequent centuries, based on UNFCCC's report that the average temperature of the earth's surface has risen by 0.74°C since the late 1800s, and is expected to increase by another 1.8°C to 4°C by the year 2100 (UNFCCC, 2011) (Fig. 1). Rising temperature is emerging as the one single variable that spells the most uncertainty for human survival on earth ever since anthropoge...
Making generalizations about the impact of commercial selective logging on biodiversity has so fa... more Making generalizations about the impact of commercial selective logging on biodiversity has so far remained elusive. Species responses to logging depend on a number of factors, many of which have not been studied in detail. These factors may include the natural forest conditions (forest types) under which logging impacts are investigated; but this question has so far remained unexamined. In a largescale replicate study we aimed at clarifying the relationship between logging and forest types on leaf litter frogs. We contrast three distinct and naturally occurring forest types, including wet evergreen, moist evergreen and semi-deciduous forests. Selectively logged sites were compared with primary forest sites for each forest type. We found that the response of frog communities to logging varies in different forest types. In the wet evergreen forest, richness was higher in logged forest than primary forest, while diversity measures were not different between logged and primary forest habitats. In the moist evergreen, richness and diversity were higher in selectively logged areas compared with primary forest habitats. In the semi-deciduous, logged forests were characterized by drastic loss of forest specialists, reduced richness, and diversity. These results indicate that the net effect of logging varies with respect to forest type. Forest types that are characterized by adverse climatic conditions (i.e., low rainfall and protracted dry seasons) are more likely to produce negative effects on leaf litter anuran communities. For comparisons of the impact of logging on species to be effective, future research must endeavor to include details of forest type.
Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habit... more Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadive...
Making generalizations about the impact of commercial selective logging on biodiversity has so fa... more Making generalizations about the impact of commercial selective logging on biodiversity has so far remained elusive. Species responses to logging depend on a number of factors, many of which have not been studied in detail. These factors may include the natural forest conditions (forest types) under which logging impacts are investigated; but this question has so far remained unexamined. In a largescale replicate study we aimed at clarifying the relationship between logging and forest types on leaf litter frogs. We contrast three distinct and naturally occurring forest types, including wet evergreen, moist evergreen and semi-deciduous forests. Selectively logged sites were compared with primary forest sites for each forest type. We found that the response of frog communities to logging varies in different forest types. In the wet evergreen forest, richness was higher in logged forest than primary forest, while diversity measures were not different between logged and primary forest habitats. In the moist evergreen, richness and diversity were higher in selectively logged areas compared with primary forest habitats. In the semi-deciduous, logged forests were characterized by drastic loss of forest specialists, reduced richness, and diversity. These results indicate that the net effect of logging varies with respect to forest type. Forest types that are characterized by adverse climatic conditions (i.e., low rainfall and protracted dry seasons) are more likely to produce negative effects on leaf litter anuran communities. For comparisons of the impact of logging on species to be effective, future research must endeavor to include details of forest type.
Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habit... more Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary
A putative driver of global amphibian decline is the panzootic chytrid fungus Batrachochytrium de... more A putative driver of global amphibian decline is the panzootic chytrid fungus Batrachochytrium dendrobatidis (Bd). While Bd has been documented across continental Africa, its distribution in West Africa remains ambiguous. We tested 793 West African amphibians (one caecilian and 61 anuran species) for the presence of Bd. The samples originated from seven West African countries -Bénin, Burkina Faso, Cô te d'Ivoire, Ghana, Guinea, Liberia, Sierra Leone -and were collected from a variety of habitats, ranging from lowland rainforests to montane forests, montane grasslands to humid and dry lowland savannahs. The species investigated comprised various life-history strategies, but we focused particularly on aquatic and riparian species. We used diagnostic PCR to screen 656 specimen swabs and histology to analyse 137 specimen toe tips.
There is a lack of quantitative information on the effectiveness of selective-logging practices i... more There is a lack of quantitative information on the effectiveness of selective-logging practices in ameliorating effects of logging on faunal communities. We conducted a large-scale replicated field study in 3 selectively logged moist semideciduous forests in West Africa at varying times after timber extraction to assess post logging effects on amphibian assemblages. Specifically, we assessed whether the diversity, abundance, and assemblage composition of amphibians changed over time for forest-dependent species and those tolerant of forest disturbance. In 2009, we sampled amphibians in 3 forests (total of 48 study plots, each 2 ha) in southwestern Ghana. In each forest, we established plots in undisturbed forest, recently logged forest, and forest logged 10 and 20 years previously. Logging intensity was constant across sites with 3 trees/ha removed. Recently logged forests supported substantially more species than unlogged forests. This was due to an influx of disturbance-tolerant species after logging. Simultaneously Simpson's index decreased, with increased in dominance of a few species. As time since logging increased richness of disturbance-tolerant species decreased until 10 years after logging when their composition was indistinguishable from unlogged forests. Simpson's index increased with time since logging and was indistinguishable from unlogged forest 20 years after logging. Forest specialists decreased after logging and recovered slowly. However, after 20 years amphibian assemblages had returned to a state indistinguishable from that of undisturbed forest in both abundance and composition. These results demonstrate that even with low-intensity logging (≤3 trees/ha) a minimum 20-year rotation of logging is required for effective conservation of amphibian assemblages in moist semideciduous forests. Furthermore, remnant patches of intact forests retained in the landscape and the presence of permanent brooks may aid in the effective recovery of amphibian assemblages.
Re-discovery of the Giant West African Squeaker, Arthroleptis krokosua Ernst, Agyei & Rödel, 2008 (Amphibia: Anura: Arthroleptidae) in two forests of south- …
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