Shifts in the diversity of an amphibian community from a premontane forest of San Ramón, Costa Rica

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.

Range expansion of the Gulf Coast Toad, Incilius valliceps (Wiegmann, 1833) (Anura, Bufonidae), from Costa Rica

“…Such cases have been reported for two other Costa Rican species previously found in arid zones of the Pacific versant, that were recently recorded in the wet forests of the Caribbean versant: Leptodactylus poecilochilus (Cope, 1862) (Crawford et al 2003) and Engystomops pustulosus (Cope, 1864) (Weigt et al 2005). Also in several other groups of amphibians that have expanded their distribution from lower to higher altitude zones (Pounds et al 1997;Pounds et al1999;Acosta-Chaves et al 2015;Acosta-Chaves et al 2019). We believe that the deforestation and global drier conditions during the last decades (Sanchez-Azofeifa et al 2001;Pounds et al 2006) forced the movement of xeric species to current altered wet forests.…”

Anfibios del bosque nuboso de El Silencio de Los Ángeles, San Ramón de Alajuela, Costa Rica

“…The Costa Rican endemic and endangered salamander N. gamezi observed along the Ferns Trail was previously only registered for the Monteverde region (Pounds et al, 2008) and San Ramón (previously named N. abscodens by Bolaños and Ehmcke (1996), Acosta-Chaves et al 2019). According to the literature (Bolaños and Ehmcke, 1996;Savage, 2002;Leenders, 2016, Acosta- Sánchez-Porras, 2015, Acosta-Chaves et al,2019.…”

“…The diversity and distribution of amphibians in Costa Rica is considered among the best known in comparison with other Neotropical countries (Savage, 2002), but despite this, there is an absence of amphibian and reptile checklists from the Western region of Central Valley in comparison with areas such as Sarapiquí, Monteverde, San Vito or Fila Costeña (Rovito et al, 2015). Bolaños and Ehmcke (1996) inventoried the herpetofauna of "Alberto Manuel Brenes" Biological Reserve (hereafter AMBBR) in Northwest San Ramón from 1986 to 1996, and later that effort was updated by Morera-Chacón and Sánchez-Porras (2015), Morera-Chacón and Jiménez (2017), and Acosta-Chaves et al, (2019) to obtain 41 species of amphibians; unfortunately, some were enigmatically extirpated from the reserve. More recently the Nectandra Reserve was inventoried with 17 species of amphibians recorded (Rovito et al, 2015).…”

“…Based on similar elevation and life zones, we predicted that ESLA Cloud Forest amphibian diversity will be comparable to the richness of the Nectandra Reserve and San Lorencito River Station of AMBBR. In the future this research will be useful to compare with other checklists to determine which species are currently colonizing and/ or disappearing from the middle elevations in Costa Rica (Acosta-Chaves and Cossel, 2016;Acosta-Chaves et al, 2019).…”

Endemic Infection of Batrachochytrium dendrobatidis in Costa Rica: Implications for Amphibian Conservation at Regional and Species Level

“…It is also plausible that Bd-driven declines during the 1980s and 1990s were not exclusively restricted to highlands [30] but were relatively undetected at lower elevations. Another hypothesis is that species with high susceptibility historically occupied high elevations sites, but severely declined or went extinct after Bd was introduced, leaving only species with mid-to-low susceptibility across elevations [102]. On the other hand, the absence of samples from montane and subalpine belts and uncontrolled variables (e.g., changes in species composition, climatic disturbances) could have reduced the statistical power to determine changes in Bd prevalence across altitudinal belts.…”