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Threat of predation often requires animals to seek refuge in unusual or suboptimal habitats. While aquatic refugia are thought to be used by many terrestrial animal species, there are challenges associated with aquatic refugia that could preclude their actual usefulness, particularly to air‐breathing ectotherms. Consequently, observations that can shed light on the evolution of antipredator strategies that cross the air–water interface are particularly valuable. “Semi‐aquatic” spiders in the family Trechaleidae have not been documented using diving as part of their antipredator behavior and, indeed, they are rarely known to submerge themselves at all, as their aquatic foraging occurs from a terrestrial location. The lack of diving behavior is hypothesized to be due to the high potential costs (e.g., thermal and respiratory) of submergence. Despite this, we document the prolonged underwater refuge use (>30 min) ofTrechalea extensafollowing pursuit by a perceived threat (humans). We also identify some morphological adaptations that may potentially help counterbalance these costs and permit underwater antipredator behavior, specifically the ability of cuticular hairs to provide a hydrophobic surface, allowing the formation of a plastron that, in turn, may facilitate respiratory function and reduce heat loss. These observations expand our overall understanding of habitat use in this genus and, more generally, antipredator adaptations of spiders.

 

Disturbances can alter the structure and function of ecosystems. In stream ecosystems, changes in discharge and physicochemistry at short, intermediate, and long recurrence intervals can affect food webs and ecosystem processes. In this paper, we compare pH regimes in streams at La Selva Biological Station, Costa Rica, where episodic acidification frequency across the stream network varies widely due to buffering from inputs of bicarbonate‐rich interbasin groundwater. To examine the effects of acidification on ecosystem structure and function, we experimentally increased the buffering capacity of a headwater stream reach and compared it to an unbuffered upstream reach. We compared these reaches to a naturally buffered and unbuffered reaches of a second headwater stream. We quantified ecosystem structural (macroinvertebrate assemblages on leaf litter and coarse woody debris) and functional responses (leaf litter and coarse woody debris decomposition rates, and growth rates of a focal insect taxon [Diptera: Chironomidae]). Non‐metric multidimensional scaling and analysis of similarity revealed that macroinvertebrate assemblages were relatively homogenous across the four study reaches, although the naturally buffered reach was the most dissimilar. Ecosystem function, as measured by chironomid growth rates, was greater in the naturally buffered reach, while decomposition rates did not differ across the four reaches. Our results indicate that biological assemblages are adapted to pH regimes of frequently acidified stream reaches. Our experiment informs the effects on structure and function at short time scales in streams that experience moderate acidification, but larger magnitude acidification events in response to hydroclimatic change, as projected under climate change scenarios, may induce stronger responses in streams.

 

The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog,Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (T_b), preferred body temperatures (T_pref), critical thermal maxima (CT_max), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater meanT_bandT_prefthan those from forests. In contrast,CT_maxandTSMdid not differ significantly between habitats. However,CT_maxdid increase moderately with increasingT_b, suggesting that changes inCT_maxmay be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. AlthoughO. pumilioexhibited moderate divergence inT_pref,CT_maxappears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain theirT_bbelow air temperatures that reach or exceedCT_max. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming.

Abstract in Spanish is available with online material.

 

Pesticide use can impact not only cultivated land, but also protected ecosystems that receive pesticide inputs due to aquatic connectivity or atmospheric transport from agricultural regions. In Costa Rica's Caribbean lowlands, pesticides applied to banana and pineapple plantations are a potential source of pollution to ecological reserves. Macroinvertebrates and fish are both potentially useful bioindicators of agrochemical pollution in aquatic systems, and our goal was to determine whether three common stream consumer species (one fish and two aquatic insect species) could serve as bioindicators for the organophosphate pesticide ethoprophos. We identified thresholds at which ethoprophos impacts the survival (LC50) and observed behavior (LOEC – lowest observed effect concentration) for each species. The LC50 of the guppy Priapichthys annectens was 1530 µg/L, with observable behavioral changes occurring at 1000 µg/L. Insects were more sensitive: the mayfly Traverella holzenthali had an LC50 of 15 µg/L and an LOEC of 2.5 µg/L, and the caddisfly Leptonema sp. had an LC50 of approximately 30 µg/L and an LOEC of 5 µg/L. The LC50 values are notably higher than ambient concentrations recorded from polluted Costa Rican streams and suggest that these taxa are not ideal indicator species. However, the lower LOEC values (in the same order of magnitude as ambient concentrations) highlight the potential ecological importance of behavioral modification due to pesticides. Quantifying the thresholds at which common pesticides impact ecosystems is a key step in identifying bioindicator species and protecting tropical biodiversity. 

Global climate change has profound effects on species, especially those in habitats already altered by humans. Tropical ectotherms are predicted to be at high risk from global temperature increases, particularly those adapted to cooler temperatures at higher altitudes. We investigated how one such species, the water anole (Anolis aquaticus), is affected by temperature stress similar to that of a warming climate across a gradient of human-altered habitats at high elevation sites. We conducted a field survey on thermal traits and measured lizard critical thermal maxima across the sites. From the field survey, we found that (1) lizards from the least disturbed site and (2) operative temperature models of lizards placed in the least disturbed site had lower temperatures than those from sites with histories of human disturbance. Individuals from the least disturbed site also demonstrated greater tolerance to high temperatures than those from the more disturbed sites, in both their critical thermal maxima and the time spent at high temperatures prior to reaching critical thermal maxima. Our results demonstrate within-species variability in responses to high temperatures, depending on habitat type, and provide insight into how tropical reptiles may fare in a warming world. 

In species with parental care behaviors, parents may adjust the intensity and duration of their care if fluctuation in factors such as environmental variables or body condition affects offspring survival. In the face of environmental changes, many egg-laying species remain with their clutch for extended periods if this behavioral adjustment provides tangible benefits to the offspring. However, the length of time parents stay with the offspring may also differ depending on the individual’s body condition. In the glass frog family (Centrolenidae), several species exhibit long-term egg attendance in which they remain with their clutch for several days after oviposition takes place. For some of them, changes in environmental variables lead to increased parental care efforts. For the species in which parents remain with their offspring for a short period (less than 24 hours), it is less clear if this constitutes parenting behavior, and whether parents adjust their efforts as a function of environmental change or the parent’s body condition remains unexplored. We studied a population of the Emerald Glass Frog,Espadarana prosoblepon, a species that exhibits a short period of quiescence after oviposition (less than three hours). Our study aimed to determine whether females alter the length of their post-oviposition quiescence period in response to changes in environmental variables (i.e., temperature, humidity, rainfall, and mean wind speed) or female body condition. Pairs in amplexus were captured in the field and transported to semi-natural enclosures to record the duration of post-oviposition quiescence using infrared cameras. Females’ post-oviposition quiescence lasted an average of 67.4 ± 26.6 min (range = 22.7–158.3 min). We did not find a significant relationship between the duration of the post-oviposition quiescence and any of the environmental variables tested. Similarly, post-oviposition quiescence duration was not influenced by female body condition. Because the variation observed in the duration of post-oviposition quiescence was not related to changes in extrinsic (environmental) or intrinsic (body condition) factors, we found no evidence that females ofE. prosobleponmodify their post-oviposition behavior in response to any of the variables examined in this study. Future research investigating the adaptive significance of the post-oviposition quiescence observed in this species is needed to understand how this behavior is related to parental care efforts.