Abstract
Biological communities are experiencing rapid shifts of composition in Neotropical ecosystems due to several factors causing population declines. However, emerging evidence has provided insights on the adaptive potential of multiple species to respond to illnesses and environmental pressures. In Costa Rica, the decline of amphibian populations is a remarkable example of these changes. Here we provide evidence of variation in the amphibian richness of a premontane forest of San Ramón (Costa Rica) across a ~30 year period. We also quantified changes in the composition and abundance of the leaf-litter frog community occurring in the same premontane forest, by comparing diversity data with a difference of ~18 years. We evaluated the similarity of species richness from 1980s to 2010s based on several sources, and the dissimilarity of species diversity in the site comparing 28 standardized surveys from 1994-1995 and 2011-2012. We compared the relative abundance of some frogs that inhabit the leaf-litter layer between these same periods. Our results show that there is more similarity in amphibian richness between 1980s and 2010s (~ 52 %) than between 1980s and 1990s (~ 40 %). The richness of leaf-litter anurans was ~ 65 % similar between 1990s and 2010s. The diversity of leaf-litter anuran was clearly different between 1994-1995 and 2011-2012, and it was clustered among those periods. We determined that the amphibian community in this premontane forest drastically changed: many species have disappeared, or gradually declined through the decades (e.g. Pristimantis ridens, P. cruentus, Craugastor bransfordii) as in other well studied localities of Costa Rica, while some few species flourished after being almost absent from the site in the 1990s (e.g. Craugastor crassidigitus, Lithobates warszewistchii). Currently dominant species such as C. crassidigitus would be using developed resistance against Bd-fungus as an advantage (apparent competition) in the premontane forest where the disease is more virulent than in lowlands. Our analysis supports the hypothesis of individualized responses of anuran populations under distinct site and elevations. We suggest to continue monitoring the amphibian communities of premontane tropical forests to understand how this ecosystem gradually resist and adapts to this catastrophic time of biodiversity loss.
Highlights
We report those specimens as C. cf. stejnegerianus based on clear morphological differences with C. bransfordii, and similarities that resembles to C. stejnegerianus clade (Chaves, pers. obs.)
The alpha taxonomy of the genus Pristimantis, –including the clade of P. cruentus, is difficult and present a high degree of cryptic diversity (Rivera-Correa, Jiménez-Rivillas, & Daza, 2017), we adopted a conservative position due to most Costa Rican frogs assigned to P. cruentus require further study
There is a specimen of E. miliaria (UCR 5142) from Finca Orlich (Alajuela, Costa Rica; circa 800 masl) (Savage & Kubicki, 2010), a site in the proximities of RSR
Summary
Biological communities are experiencing rapid changes in Neotropical ecosystems driven by species local extinction and colonization of new sites, resulting by the interaction and additive effects of factors such as climate change, emerging diseases and habitat degradation; yet there is emerging evidence of adaptive potential of species to respond to environmental change (Mendelson et al, 2004; Colwell, Brehm, Cardelús, Gilman, & Longino, 2008; Bickford, Howard, Ng, & Sheridan, 2010; Ryan et al, 2014; Acosta-Chaves & Cossel, 2016; Lister & García, 2018; Voyles et al, 2018). In the lowlands and middle elevations more gradual declines resulting in extirpation throughout this same time period has been reported mainly in forest leaf-litter anurans (Whitfield et al, 2007; Hilje & Aide, 2012, Ryan et al, 2014, 2015; Acosta-Chaves et al, 2016) Despite this negative scenario for amphibian communities, some hope still remains. More recently the Red-eyed Tree Frog (Agalychnis callydrias) was reported in the site (Morera-Chacón & Jiménez-Castro, 2017) These authors mentioned some apparent changes in species richness; they lacked the data that could help understand those population oscillations. This study aims to 1) provide evidence of changes in the amphibian richness of RSR across a ~30 year period, and 2)
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