Effects of ocean acidification on learning in coral reef fishes

Ocean acidification has the potential to cause dramatic changes in marine ecosystems. Larval damselfish exposed to concentrations of CO2 predicted to occur in the mid- to late-century show maladaptive responses to predator cues. However, there is considerable variation both within and between species in CO2 effects, whereby some individuals are unaffected at particular CO2 concentrations while others show maladaptive responses to predator odour. Our goal was to test whether learning via chemical or visual information would be impaired by ocean acidification and ultimately, whether learning can mitigate the effects of ocean acidification by restoring the appropriate responses of prey to predators. Using two highly efficient and widespread mechanisms for predator learning, we compared the behaviour of pre-settlement damselfish Pomacentrus amboinensis that were exposed to 440 µatm CO2 (current day levels) or 850 µatm CO2, a concentration predicted to occur in the ocean before the end of this century. We found that, regardless of the method of learning, damselfish exposed to elevated CO2 failed to learn to respond appropriately to a common predator, the dottyback, Pseudochromis fuscus. To determine whether the lack of response was due to a failure in learning or rather a short-term shift in trade-offs preventing the fish from displaying overt antipredator responses, we conditioned 440 or 700 µatm-CO2 fish to learn to recognize a dottyback as a predator using injured conspecific cues, as in Experiment 1. When tested one day post-conditioning, CO2 exposed fish failed to respond to predator odour. When tested 5 days post-conditioning, CO2 exposed fish still failed to show an antipredator response to the dottyback odour, despite the fact that both control and CO2-treated fish responded to a general risk cue (injured conspecific cues). These results indicate that exposure to CO2 may alter the cognitive ability of juvenile fish and render learning ineffective.

Experience-dependent corticofugal adjustment of midbrain frequency map in bat auditory system

Recent studies of corticofugal modulation of auditory information processing indicate that cortical neurons mediate both a highly focused positive feedback to subcortical neurons “matched” in tuning to a particular acoustic parameter and a widespread lateral inhibition to “unmatched” subcortical neurons. This cortical function for the adjustment and improvement of subcortical information processing is called egocentric selection. Egocentric selection enhances the neural representation of frequently occurring signals in the central auditory system. For our present studies performed with the big brown bat (Eptesicus fuscus), we hypothesized that egocentric selection adjusts the frequency map of the inferior colliculus (IC) according to auditory experience based on associative learning. To test this hypothesis, we delivered acoustic stimuli paired with electric leg stimulation to the bat, because such paired stimuli allowed the animal to learn that the acoustic stimulus was behaviorally important and to make behavioral and neural adjustments based on the acquired importance of the acoustic stimulus. We found that acoustic stimulation alone evokes a change in the frequency map of the IC; that this change in the IC becomes greater when the acoustic stimulation is made behaviorally relevant by pairing it with electrical stimulation; that the collicular change is mediated by the corticofugal system; and that the IC itself can sustain the change evoked by the corticofugal system for some time. Our data support the hypothesis.

Applying network analysis to the conservation of habitat trees in urban environments: a case study from Brisbane, Australia

In Australia more than 300 vertebrates, including 43 insectivorous bat species, depend on hollows in habitat trees for shelter, with many species using a network of multiple trees as roosts, We used roost-switching data on white-striped freetail bats (Tadarida australis; Microchiroptera: Molossidae) to construct a network representation of day roosts in suburban Brisbane, Australia. Bats were caught from a communal roost tree with a roosting group of several hundred individuals and released with transmitters. Each roost used by the bats represented a node in the network, and the movements of bats between roosts formed the links between nodes. Despite differences in gender and reproductive stages, the bats exhibited the same behavior throughout three radiotelemetry periods and over 500 bat days of radio tracking: each roosted in separate roosts, switched roosts very infrequently, and associated with other bats only at the communal roost This network resembled a scale-free network in which the distribution of the number of links from each roost followed a power law. Despite being spread over a large geographic area (> 200 km(2)), each roost was connected to others by less than three links. One roost (the hub or communal roost) defined the architecture of the network because it had the most links. That the network showed scale-free properties has profound implications for the management of the habitat trees of this roosting group. Scale-free networks provide high tolerance against stochastic events such as random roost removals but are susceptible to the selective removal of hub nodes. Network analysis is a useful tool for understanding the structural organization of habitat tree usage and allows the informed judgment of the relative importance of individual trees and hence the derivation of appropriate management decisions, Conservation planners and managers should emphasize the differential importance of habitat trees and think of them as being analogous to vital service centers in human societies.

Ecologia de comunidades e comportamento reprodutivo de anfíbios anuros em savana amazônica

The Amazon savannas occur as isolated patches throughout extensive areas of forest in the states of Amapá, Amazonas, Pará, and Roraima. There is a considerable variation in the composition of anuran assemblages in the localities and phytophysiognomies of Amazon savannas and given the absence of studies on reproductive behavior, a systematic and geographically wide sampling has been carried out in the Amapá savanna, located in the Eastern Amazon. The study was conducted in a savanna area in the state of Amapá to examine the composition, ecology, and reproductive behavior of anuran amphibians. We carried out 24 field trips in each phytophysiognomy (gramineous-woody savana, gramineous-herbaceous-woody savana, park savana, and arboreal savanna); for analysis of reproductive behavior observations were made during the period January to December 2013, lasting four consecutive days. Samples were collected by active and acoustic search along 20 plots of 100x50 meters. Twenty-one anuran species were recorded, of which four are new records for the state of Amapá: Dendropsophus walfordi, Scinax fuscomarginatus, Pseudopaludicola boliviana e Elachistocleis helianneae. The KruskalWallis ANOVA revealed significant differences between richness and species diversity in the phytophysiognomies (p < 0.05). The Bray-Curtis similarity coefficient divided the phytophysiognomies into three groups: arboreal savana, gramineous-woody savanna and gramineous-herbaceous-woody savanna, and park savanna. According to the non-metric multidimensional scaling, the structure of the anuran community resulted in a separation into three phytophysiognomies, with significant differences in the structure of communities (ANOSIM, R = 0.823; p < 0.001). In the study of community ecology, the results obtained for spatial, temporal, and trophic niche breadth suggest that the assemblage of anurans of the Amapá savanna is not composed of predominantly generalist species. Also, the presence of other specialist anurans may explain the processes of speciation associated with the isolation of habitats, resulting in heterogeneity and spatial discontinuity in the phytophysiognomies with open formations. The null model analysis revealed that the community is structured based on temporal and trophic niche, indicating a significant influence of contemporary ecological factors on the assemblage. The absence of structure based on spatial niche might be explained by the spatial segregation in the distribution and occupation of anurans in the different phytophysiognomies of the Amapá savanna. Regarding the reproductive behavior of anurans, 11 species were classified as having a long breeding season, intrinsically associated with the rainy season and the reproductive mode of most species that lay egg clutches in lentic water bodies. Six reproductive modes were recorded and parental care was observed in Leptodactylus macrosternum and L. podicipinus, whose reproductive mode is characterized by foam nests. Regarding behavioral reproductive strategies, calling males were observed in all species of anurans, satellite males were recorded only for D. walfordi, Hypsiboas multifasciatus, S. nebulosus and S. fuscomarginatus; active search for females was observed for Phyllomedusa hypochondrialis and L. fuscus, and male displacement was recorded only for Rhinella major and R. margaritifera. Of the reproductive behaviors observed, throat and vocal sac display is associated with courtship and territorial behavior exhibited by males. In addition to courtship behavior, visual signals associated with courtship strategies were recorded for the anurans of the Amapá savanna.

Elevated CO2 affects predator-prey interactions through altered performance

Recent research has shown that exposure to elevated carbon dioxide (CO2) affects how fishes perceive their environment, affecting behavioral and cognitive processes leading to increased prey mortality. However, it is unclear if increased mortality results from changes in the dynamics of predator-prey interactions or due to prey increasing activity levels. Here we demonstrate that ocean pCO2 projected to occur by 2100 significantly effects the interactions of a predator-prey pair of common reef fish: the planktivorous damselfish Pomacentrus amboinensis and the piscivorous dottyback Pseudochromis fuscus. Prey exposed to elevated CO2 (880 µatm) or a present-day control (440 µatm) interacted with similarly exposed predators in a cross-factored design. Predators had the lowest capture success when exposed to elevated CO2 and interacting with prey exposed to present-day CO2. Prey exposed to elevated CO2 had reduced escape distances and longer reaction distances compared to prey exposed to present-day CO2 conditions, but this was dependent on whether the prey was paired with a CO2 exposed predator or not. This suggests that the dynamics of predator-prey interactions under future CO2 environments will depend on the extent to which the interacting species are affected and can adapt to the adverse effects of elevated CO2.

Distribución y taxonomía de mamíferos (clase mammalia) en el Cerro El Potosí Galeana, Nuevo León, México

El Cerro El Potosí es un área prioritaria para la Comisión Nacional para la Biodiversidad (CONABIO) y un Área Natural Protegida por el estado (Anónimo, 2000), debido a la existencia de una gran diversidad de tipos de vegetación y de especies de importancia fitogeografica o su orografía y altitud (3715 msnm) se considera un área promotora de procesos de especiación, registrándose especies endémicas y relictuales como el caso del Pinus culminicola y Nucifraga columbiana , es una de las montañas más altas del noroeste del país, está enclavada en la Sierra Madre Oriental. Con base en la información previa disponible, se presume que esta área ostente una mayor diversidad de flora y fauna. El objetivo principal fue el análisis de la diversidad y distribución de los mamíferos en los diferentes estratos vegetativos y altitudes dentro de los límites del Cerro El Potosí. Con el propósito de realizar las comparaciones de las diversidades de las especies en forma altitudinal, por vegetación, estacional; Se seleccionó la prueba de Chi-cuadrada para determinar dependencia entre especies y la altitud, tipo de muestreo o tipo de vegetación. Se efectuaron 24 salidas (mensuales) de campo, de noviembre del 2006 a octubre del 2008, de 3 a 4 días por salida. Se registraron 27 especies (14 Familias, 24 géneros, 27 especies, y 14 especies no reportadas previamente). De acuerdo al tipo de vegetación la riqueza se concentro en el bosque de pino seguido por el bosque de encino, las especies se distribuyeron en uno, en dos o más estratos de vegetación (patrones), para los diferentes tipos de vegetación se distribuyeron las especies de Silvilagus floridanus, Thomomys bottae, Peromyscus melanotis, Peromyscus levipes ambiguus, Canis latrans y Lynx rufus. Las especies que sólo se encontraron en un solo tipo de vegetación fueron Bassariscus astutus, Conepatus mesoleucus, Corynorhinus townsendii, Didelphis virginiana, Eptesicus fuscus, Puma yagouaroundi, Lasiurus cinereus, Lasiurus ega, Leptonycteris nivalis, Mustela frenata y Sorex milleri, por lo que se aprecia la diversidad encontrada en el sitio, esto en gran medida por la asociación de la vegetación y la altura marcado por la temperatura reportada para el sitio. Las especies que se localizaron en dos o más estratos o patrones de vegetación fueron Myotis thysanodes, Sciurus alleni, Otospermophilus variegatus, Microtus mexicanus, Urocyon cinereoargenteus, Procyon lotor, Puma concolor, Pecari tajacu y Odocoileus virginianus.

Floods and famine: climate-induced collapse of a tropical predator-prey community

Will climate change threaten wildlife populations by gradual shifts in mean conditions, or by increased frequency of extreme weather events? Based on long-term data (from 1991 to 2014), the aim of the present study was to analyse and compare the sensitivity of predator-prey demography to extreme climatic events versus normal, albeit highly variable, annual deviations in climatic conditions in the Australian wet-dry tropics. From 1991 to 2005, predators (water pythons, Liasis fuscus) and their main prey (dusky rats, Rattus colletti) showed significant climate-driven fluctuations in numbers. These fluctuations were, however, trivial compared to the impact of two massive but brief deluges in 2007 and 2011, which virtually eliminated the dusky rats. The two floods resulted in the pythons experiencing an unprecedented famine in seven out of the last 8 years causing a massive shift in python demography, that is a significant reduction in feeding rates, reproductive output, growth rates, relative body mass, survival, mean body length and numbers (from 3173 in 1992 to 96 in 2013). Our results demonstrate that attempts to predict faunal responses to climate change, even if based on long-term studies, may be doomed to failure. Consequently, biologists may need to confront the uncomfortable truth that increased frequency of brief unpredictable bouts of extreme weather can influence populations far more than gradual deviations in mean climatic conditions.