Distribution modeling and lineage diversity of the chytrid fungus Batrachochytrium dendrobatidis (Bd) in a central African amphibian hotspot

Abstract

The amphibian disease chytridiomycosis in amphibians is caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) and has resulted in dramatic declines and extinctions of amphibian populations worldwide. A hypervirulent, globally-dispersed pandemic lineage (Bd-GPL) is thought to be largely responsible for population declines and extinctions, although numerous endemic lineages have also been found. Recent reports of amphibian declines have been linked to the emergence of Bd in Cameroon, a major hotspot of African amphibian diversity. However, it is not known whether Bd-GPL or other lineages have been found in this region. This study therefore aims to examine Bd lineage diversity in the region and predict the distribution of this pathogen under current and future climate conditions using data from this study and from historical records. Almost 15% (52/360) of individuals tested positive for Bd using a standard quantitative PCR diagnostic. Infected amphibians were found at all eight sites sampled in this study. Species distribution models generated in BIOMOD2 indicate that areas with highest predicted environmental suitability occur in the Cameroon highlands and several protected areas throughout the country. These areas of high environmental suitability for Bd are projected to shift or decrease in size under future climate change. However, montane regions with high amphibian diversity are predicted to remain highly suitable. Phylogenetic analysis of the ITS sequences obtained from a set of positive Bd samples indicate that most fall within the Bd-GPL lineage while the remainder group with isolates from either Brazil or South Korea. Although more in depth phylogenetic analyses are needed, identification of Bd-GPL lineages in areas of high amphibian diversity emphasizes the need to continue to monitor for Bd and develop appropriate conservation strategies to prevent its further spread.

Infection with Batrachochytrium dendrobatidis is common in tropical lowland habitats: Implications for amphibian conservation

“…The potential bias caused by this unbalanced sampling might lead researchers to overestimate the rate of decline or to miss less dramatic declines and environmental threats across the range of the declining species. Therefore, extending the sampling to heterogeneous habitats across the entire geographic distribution of threatened species is crucial to detect and quantify potential threats as well as to establish suitable and more effective conservation actions (Hitchman, Mather, Smith, & Fencl, ; Miller et al, ; Olson et al, ).…”

Genetic analysis of post‐epizootic amphibian chytrid strains in Bolivia: Adding a piece to the puzzle

“…This work contributes another piece of the puzzle to a growing understanding of the spread of Bd and its genetic diversity (e.g. Kaiser & Pollinger, 2012; Miller et al., 2018; O’hanlon et al., 2018; Rodriguez et al., 2014; Rosenblum et al., 2013; Schloegel et al., 2012; Valenzuela‐Sánchez et al., 2018).…”

Population dynamics ofRana sierraeat Dusy Basin: influence of non‐native predators, drought, and restoration potential

“…Disease outbreaks in the High Sierras could all be linked to the same genetic lineage, GPL-1 (global pandemic lineage 1; Knapp et al 2011). Bd lineage GPL-1 had already developed an extraordinary virulence by the time it arrived at Dusy Basin (Schloegel et al 2012, James et al 2015, Miller et al 2018. GPL-1 infection loads can reach lethal levels quickly in susceptible species and hence crash frog populations before the chytrid becomes limited by density-dependent factors (Lips et al 2006.…”