Brain-Derived Neurotrophic Factor as a Potential Mediator of the Beneficial Effects of Myo-Inositol Supplementation during Suckling in the Offspring of Gestational-Calorie-Restricted Rats.

This study aims to investigate the potential mechanisms underlying the protective effects of myo-inositol (MI) supplementation during suckling against the detrimental effects of fetal energy restriction described in animal studies, particularly focusing on the potential connections with BDNF signaling. Oral physiological doses of MI or the vehicle were given daily to the offspring of control (CON) and 25%-calorie-restricted (CR) pregnant rats during suckling. The animals were weaned and then fed a standard diet until 5 months of age, when the diet was switched to a Western diet until 7 months of age. At 25 days and 7 months of age, the plasma BDNF levels and mRNA expression were analyzed in the hypothalamus and three adipose tissue depots. MI supplementation, especially in the context of gestational calorie restriction, promoted BDNF secretion and signaling at a juvenile age and in adulthood, which was more evident in the male offspring of the CR dams than in females. Moreover, the CR animals supplemented with MI exhibited a stimulated anorexigenic signaling pathway in the hypothalamus, along with improved peripheral glucose management and enhanced browning capacity. These findings suggest a novel connection between MI supplementation during suckling, BDNF signaling, and metabolic programming, providing insights into the mechanisms underlying the beneficial effects of MI during lactation.

Potential sources of time lags in calibrating species distribution models.

The Anthropocene is characterized by a rapid pace of environmental change and is causing a multitude of biotic responses, including those that affect the spatial distribution of species. Lagged responses are frequent and species distributions and assemblages are consequently pushed into a disequilibrium state. How the characteristics of environmental change-for example, gradual 'press' disturbances such as rising temperatures due to climate change versus infrequent 'pulse' disturbances such as extreme events-affect the magnitude of responses and the relaxation times of biota has been insufficiently explored. It is also not well understood how widely used approaches to assess or project the responses of species to changing environmental conditions can deal with time lags. It, therefore, remains unclear to what extent time lags in species distributions are accounted for in biodiversity assessments, scenarios and models; this has ramifications for policymaking and conservation science alike. This perspective piece reflects on lagged species responses to environmental change and discusses the potential consequences for species distribution models (SDMs), the tools of choice in biodiversity modelling. We suggest ways to better account for time lags in calibrating these models and to reduce their leverage effects in projections for improved biodiversity science and policy.

Patterns and drivers of climatic niche dynamics during biological invasions of island-endemic amphibians, reptiles, and birds.

Shifts between native and alien climatic niches pose a major challenge for predicting biological invasions. This is particularly true for insular species because geophysical barriers could constrain the realization of their fundamental niches, which may lead to underestimates of their invasion potential. To investigate this idea, we estimated the frequency of shifts between native and alien climatic niches and the magnitude of climatic mismatches using 80,148 alien occurrences of 46 endemic insular amphibian, reptile, and bird species. Then, we assessed the influence of nine potential predictors on climatic mismatches across taxa, based on species' characteristics, native range physical characteristics, and alien range properties. We found that climatic mismatch is common during invasions of endemic insular birds and reptiles: 78.3% and 55.1% of their respective alien records occurred outside of the environmental space of species' native climatic niche. In comparison, climatic mismatch was evident for only 16.2% of the amphibian invasions analyzed. Several predictors significantly explained climatic mismatch, and these varied among taxonomic groups. For amphibians, only native range size was associated with climatic mismatch. For reptiles, the magnitude of climatic mismatch was higher for species with narrow native altitudinal ranges, occurring in topographically complex or less remote islands, as well as for species with larger distances between their native and alien ranges. For birds, climatic mismatch was significantly larger for invasions on continents with higher phylogenetic diversity of the recipient community, and when the invader was more evolutionarily distinct. Our findings highlight that apparently common niche shifts of insular species may jeopardize our ability to forecast their potential invasions using correlative methods based on climatic variables. Also, we show which factors provide additional insights on the actual invasion potential of insular endemic amphibians, reptiles, and birds.

Amphibian Speciation Rates Support a General Role of Mountains as Biodiversity Pumps.

AbstractContinental mountain areas cover <15% of global land surface, yet these regions concentrate >80% of global terrestrial diversity. One prominent hypothesis to explain this pattern proposes that high mountain diversities could be explained by higher diversification rates in regions of high topographic complexity (HTC). While high speciation in mountains has been detected for particular clades and regions, the global extent to which lineages experience faster speciation in mountains remains unknown. Here we addressed this issue using amphibians as a model system (>7,000 species), and we found that families showing high speciation rates contain a high proportion of species distributed in mountains. Moreover, we found that lineages inhabiting areas of HTC speciate faster than lineages occupying areas that are topographically less complex. When comparing across regions, we identified the same pattern in five biogeographical realms where higher speciation rates are associated with higher levels of complex topography. Low-magnitude differences in speciation rates between some low and high complex topographies suggest that high mountain diversity is also affected by low extinction and/or high colonization rates. Nevertheless, our results bolster the importance of mountains as engines of speciation at different geographical scales and highlight their importance for the conservation of global biodiversity.

Niche Contraction of an Endangered Frog Driven by the Amphibian Chytrid Fungus.

Introduced pathogens can alter the geographic distribution of susceptible host species. For example, Batrachochytrium dendrobatidis (Bd) is a fungal pathogen that has been linked to the global decline and extinction of numerous amphibian species during the last four decades. A growing number of studies have described the distribution of Bd and susceptible hosts across the globe; however, knowledge on how Bd may shape the climatic niche of susceptible species is still missing. We estimated the effect of Bd on the geographic distribution and niche dynamics of the critically endangered lowland robber frog (Craugastor ranoides) in Costa Rica. We found a reduction of 98% in the geographic range of this species by 1995, following the epizootic outbreaks of Bd that affected Costa Rica in the 1980 and early 1990s. We also quantified niche contraction and found that the species is currently restricted to dry and warm environments that have been considered unsuitable for Bd. Our results contribute to the understanding of how emerging pathogens shape the climatic niches and geographic distribution of susceptible species.

Idiosyncratic responses to drivers of genetic differentiation in the complex landscapes of Isthmian Central America.

Isthmian Central America (ICA) is one of the most biodiverse regions in the world, hosting an exceptionally high number of species per unit area. ICA was formed <25 million years ago and, consequently, its biotic assemblage is relatively young and derived from both colonization and in situ diversification. Despite intensive taxonomic work on the local fauna, the potential forces driving genetic divergences and ultimately speciation in ICA remain poorly studied. Here, we used a landscape genetics approach to test whether isolation by distance, topography, habitat suitability, or environment drive the genetic diversity of the regional frog assemblage. To this end, we combined data on landscape features and mitochondrial DNA sequence variation for nine codistributed amphibian species with disparate life histories. In five species, we found that at least one of the factors tested explained patterns of genetic divergence. However, rather than finding a general pattern, our results revealed idiosyncratic responses to historical and ecological processes, indicating that intrinsic life-history characteristics may determine the effect of different drivers of isolation on genetic divergence in ICA. Our work also suggests that the convergence of several factors promoting isolation among populations over a heterogeneous landscape might maximize genetic differentiation, despite short geographical distances. In conclusion, abiotic factors and geographical features have differentially affected the genetic diversity across the regional frog assemblage. Much more complex models (i.e., considering multiple drivers), beyond simple vicariance of Caribbean and Pacific lineages, are needed to better understand the evolutionary history of ICA's diverse biotas.

Urbanization, habitat extension and spatial pattern, threaten a Costa Rican endemic bird / Urbanización, cantidad de hábitat y distribución espacial, amenazan un ave endémica de Costa Rica

Introduction: Migration of people from rural environments to cities has accelerated urbanization and modified the landscape as well as the ecological processes and communities in these areas. The Costa Rican endemic Cabanis´s Ground-Sparrow (Melozone cabanisi) is a species of limited distribution restricted to the "Gran Area Metropolitana", which is the biggest urban settlement of the country. This area has experimented and still experiment an ongoing fragmentation and loss of habitat used by this species (coffee plantations, shrubs, and thickets). Objective: To determine the effects of urbanization on habitat abundance and spatial pattern for the occurrence of Melozone cabanisi. Methods: We modeled the area of potentially suitable habitat for this species in Costa Rica using occurrence and bioclimatic data. Then, we estimated the actual suitable habitat using land cover type layers. Finally, we analyzed the connectivity among the actual suitable habitat patches using single-patch and multi-patch approaches. Results: From the area of potentially suitable habitat estimated by the bioclimatic model, 74 % were urban areas that are unsuitable for Melozone cabanisi. The largest suitable patches within urban areas were coffee plantations; which also were crucial for maintaining connectivity between habitat patches along the species' range. Conclusions: To preserve and protect the Melozone cabanisi, these areas must be taken into consideration by decision-makers in the present and future management plans. We recommend avoiding change shrubs and thickets to urban cover to preserve the occurrence of Melozone cabanisi, and implement a program for the payment of environmental services to landholders, supported by the local governments, to protect those habitats in urban contexts.

Introducción: La migración desde ambientes rurales hacia las ciudades ha incrementado la urbanización. Esto ha modificado el paisaje, así como los procesos ecológicos y comunidades dentro de estas áreas. El Cuatro-ojos de Jupa-roja (Melozone cabanisi) es una especie distribuida principalmente al interior del asentamiento urbano más grande de Costa Rica. Hasta el presente esta área sigue experimentando fragmentación y pérdida del hábitat utilizado por esta especie (plantaciones de café, charrales y tacotales). Objetivo: Determinar los efectos de la urbanización sobre la cantidad de hábitat y su distribución espacial, basada en datos de presencia para M. cabanisi. Métodos: Modelamos el hábitat potencialmente adecuado para M. cabanisi utilizando datos bioclimáticos y de presencia. Luego estimamos el hábitat real utilizando el hábitat potencialmente adecuado y las capas de cobertura del suelo. Finalmente analizamos la conectividad entre los parches de hábitat real utilizando un enfoque multi y mono-parche. Resultados: Del área del hábitat potencialmente adecuado estimada por el modelo bioclimático, 74 % fueron áreas urbanas, lo que consideramos es un porcentaje inadecuado para M. cabanisi. Los parches más grandes de hábitat real dentro de las áreas urbanas fueron plantaciones de café, que a su vez fueron cruciales para mantener la conectividad entre los parches a lo largo del rango de distribución de la especie. Conclusiones: Para conservar y proteger a M. cabanisi, los tomadores de decisiones deben tener en cuenta los charrales, tacotales y cafetales dentro de la distribución de las especies en los planes de gestión presentes y futuros, evitando su cambio a coberturas urbanas.

Batrachochytrium dendrobatidis infection in amphibians predates first known epizootic in Costa Rica.

Emerging infectious diseases are a growing threat to biodiversity worldwide. Outbreaks of the infectious disease chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), are implicated in the decline and extinction of numerous amphibian species. In Costa Rica, a major decline event occurred in 1987, more than two decades before this pathogen was discovered. The loss of many species in Costa Rica is assumed to be due to Bd-epizootics, but there are few studies that provide data from amphibians in the time leading up to the proposed epizootics. In this study, we provide new data on Bd infection rates of amphibians collected throughout Costa Rica, in the decades prior to the epizootics. We used a quantitative PCR assay to test for Bd presence in 1016 anuran museum specimens collected throughout Costa Rica. The earliest specimen that tested positive for Bd was collected in 1964. Across all time periods, we found an overall infection rate (defined as the proportion of Bd-positive individuals) of 4%. The number of infected individuals remained relatively low across all species tested and the range of Bd-positive specimens was shown to be geographically constrained up until the 1980s; when epizootics are hypothesized to have occurred. After that time, infection rate increased three-fold, and the range of specimens tested positive for Bd increased, with Bd-positive specimens collected across the entire country. Our results suggest that Bd dynamics in Costa Rica are more complicated than previously thought. The discovery of Bd's presence in the country preceding massive declines leads to a number of different hypotheses: 1) Bd invaded Costa Rica earlier than previously known, and spread more slowly than previously reported; 2) Bd invaded multiple times and faded out; 3) an endemic Bd lineage existed; 4) an earlier Bd lineage evolved into the current Bd lineage or hybridized with an invasive lineage; or 5) an earlier Bd lineage went extinct and a new invasion event occurred causing epizootics. To help visualize areas where future studies should take place, we provide a Bd habitat suitability model trained with local data. Studies that provide information on genetic lineages of Bd are needed to determine the most plausible spatial-temporal, host-pathogen dynamics that could best explain the epizootics resulting in amphibian declines in Costa Rica and throughout Central America.

A new species of dink frog, genus Diasporus (Anura: Eleutherodactylidae), from the Caribbean foothills of the Cordillera de Talamanca, Costa Rica.

A new dink frog (Eleutherodactylidae: Diasporus) is described from the Tropical Wet Forest, in the northeastern foothills of Cordillera de Talamanca in Costa Rica at an elevation of ca. 1000 m. Analysis of DNA sequences of the 16S rRNA (16S) and cytochrome oxidase 1 (COI) mitochondrial genes revealed a distinct lineage within the genus Diasporus. Additional morphological, morphometric, and acoustic analyses support the differences of this lineage, which we recognize as a new species. This new taxon is distinguished from other members of the genus Diasporus inhabiting Isthmian Central America by its unique coloration: dorsum brown to brown-grayish and venter gray-bluish with pale blotches. The new species is distinguished from other members of the genus Diasporus by very significant genetic distances (higher than 5.6 % in 16S and 16.7 % in COI). The new taxon is most closely related to D. vocator from the south pacific of Costa Rica and to an unnamed taxon from western Panama.

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

Numerous species of amphibians declined in Central America during the 1980s and 1990s. These declines mostly affected highland stream amphibians and have been primarily linked to chytridiomycosis, a deadly disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Since then, the majority of field studies on Bd in the Tropics have been conducted in midland and highland environments (>800 m) mainly because the environmental conditions of mountain ranges match the range of ideal abiotic conditions for Bd in the laboratory. This unbalanced sampling has led researchers to largely overlook host-pathogen dynamics in lowlands, where other amphibian species declined during the same period. We conducted a survey testing for Bd in 47 species (n = 348) in four lowland sites in Costa Rica to identify local host-pathogen dynamics and to describe the abiotic environment of these sites. We detected Bd in three sampling sites and 70% of the surveyed species. We found evidence that lowland study sites exhibit enzootic dynamics with low infection intensity and moderate to high prevalence (55% overall prevalence). Additionally, we found evidence that every study site represents an independent climatic zone, where local climatic differences may explain variations in Bd disease dynamics. We recommend more detection surveys across lowlands and other sites that have been historically considered unsuitable for Bd occurrence. These data can be used to identify sites for potential disease outbreaks and amphibian rediscoveries.

Variación en la actividad acústica de Hyalinobatrachium fleischmanni (Anura: Centrolenidae) en un ambiente urbano con diferentes niveles de ruido antropogénico

26. Las señales acústicas producidas por animales pueden ser enmascaradas por el ruido del medio ambiente en que se encuentran, tanto de origen natural como antropogénico. Una especie que puede ver afectada su comunicación por el ruido medio ambiental es la rana de vidrio Hyalinobatrachium fleischmanni (Centrolenidae), porque la distribución actual de esta especie en gran parte se encuentra en ambientes urbanos con altos niveles de ruido. En este trabajo analizamos si existe una relación entre la variación de los niveles de ruido antropogénico a través de la noche y la actividad vocal (cantidad de vocalizaciones por unidad de tiempo) de H. fleischmanni, a lo largo de un gradiente de ruido urbano. El trabajo lo realizamos en tres sitios dentro del Campus Universitario Rodrigo Facio, San José, Costa Rica durante el mes de junio de 2015. Para contabilizar la actividad vocal de la especie en cada sitio instalamos grabadores programables de 17:00 a las 6:00 por dos días consecutivos cada dos semanas. De forma simultánea, cuantificamos el ruido en dB cada hora a lo largo del periodo de grabación utilizando sonómetros. Comparamos la abundancia promedio de vocalizaciones por hora contra los niveles de ruido promedio por hora y sitio utilizando modelos lineales mixtos. Nuestros resultados demuestran que, tanto el ruido como la actividad vocal de H. fleischmanni variaron a lo largo de la noche. Sin embargo, encontramos que en el sitio más ruidoso el patrón de actividad de H. fleischmanni difiere de los dos sitios menos ruidosos.El sitio menos ruidoso fue el que presento una mayor actividad vocal a lo largo de todo el periodo de muestreo. A pesar de que no se encontró una relación directa entre el nivel de ruido antropogénico y la actividad acústica de H. fleischmanni, sí observamos un efecto de los niveles de ruido en los patrones de actividad de la especie.

23. Acoustic signals produced by animals can be masked by natural or anthropogenic environmental noise. A high proportion of the current distribution of the glass-frog Hyalinobatrachium fleischmanni (Centrolenidae) overlaps with noisy urban habitats, and this may affect the species acoustic communication. In this work, we analyzed the relationship between changes in anthropogenic noise level throughout the night and the diel acoustic variation (vocalization per time) in H. fleischmanni, within three sites with different noise level. We conducted this study in three sites inside the Rodrigo Facio University Campus, San José, Costa Rica in June 2015. We used an automated recorder per site to record glass-frog vocalizations, from 17:00 to 6:00 h, during two consecutive days, every two weeks, for a month. Simultaneously, we measured the noise levels in dB each hour using a soundmeter. We used linear mixed models to compare the vocalization mean per hour against the noise levels per hour and site. Our results showed that noise levels and H. fleischmanni acoustic activity varied throughout the night. The H. fleischmanni acoustic activity at the noisier site was different from sites with lower noise levels. The highest acoustic activity was found in the less noisy site throughout the sampled period. Although we fail to found a direct relationship between noise level and H. fleischmanni acoustic activity, noise level variation affects vocal activity pattern in this species.

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

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.

Las comunidades biológicas están experimentando rápidos cambios de composición en los ecosistemas neotropicales debido a varios factores que causan disminuciones de las poblaciones. Sin embargo, la evidencia emergente ha proporcionado información sobre el potencial de adaptación de múltiples especies para responder a enfermedades y presiones ambientales. En Costa Rica, el declive de las poblaciones de anfibios es un ejemplo notable de estos cambios. Aquí proporcionamos evidencia de variación en la riqueza de anfibios de un bosque premontano de San Ramón (Costa Rica) en un período de ~ 30 años. También cuantificamos los cambios en el ensamblaje, y las oscilaciones poblacionales, de la comunidad de ranas de hojarasca que ocurren en el mismo bosque premontano, tras comparar datos de diversidad con una diferencia de ~ 18 años. Evaluamos la similitud de la riqueza de especies desde la década de 1980 hasta la de 2010 basados en varias fuentes, así como la disimilitud de la diversidad de especies en el sitio comparando 28 muestreos estandarizados entre 1994-1995 y 2011-2012. Comparamos la abundancia relativa de algunas ranas que habitan la hojarasca entre 1994-1995 y 2011-2012. Nuestros resultados muestran que existe una similitud un poco mayor en la riqueza de anfibios entre los años 1980 y 2010 que entre los 1980 y 1990 (~ 40 %). La riqueza de los anuros de la hojarasca fue aproximadamente un 65 % similar entre la década de 1990 y 2010. La diversidad de anuros de la hojarasca fue claramente diferente entre 1994-1995 y 2011-2012, y se agrupó entre esos períodos. Determinamos que la comunidad de anfibios en este bosque premontano cambió drásticamente: muchas especies han desaparecido o han disminuido gradualmente a lo largo de las décadas como en otras localidades bien estudiadas de Costa Rica (por ejemplo, Pristimantis ridens, P. cruentus, Craugastor bransfordii), mientras algunas pocas especies florecieron tras casi desaparecer de nuestro sitio en la década de 1990 (por ejemplo, Craugastor crassidigitus, Lithobates warszewistchii). Actualmente, las especies dominantes como C. crassidigitus podrían tener resistencia contra el hongo quitridio, desarrollada como una ventaja (competición aparente) en el bosque premontano donde la enfermedad es más virulenta que en las tierras bajas. Nuestro análisis apoya la hipótesis de las respuestas individualizadas de las poblaciones de anuros en distintos sitios y elevaciones. Sugerimos continuar con el monitoreo de las comunidades de anfibios de los bosques neotropicales premontanos para comprender cómo este ecosistema resiste gradualmente y se adapta a este momento catastrófico de pérdida de biodiversidad.