Water availability and temperature as modifiers of evaporative water loss in tropical frogs.

Water plays a notable role in the ecology of most terrestrial organisms due to the risks associated with water loss. Specifically, water loss in terrestrial animals happens through evaporation across respiratory tissues or epidermis. Amphibians are ideal systems for studying how abiotic factors impact water loss since their bodies often respond quickly to environmental changes. While the effect of temperature on water loss is well known across many taxa, we are still learning how temperature in combination with humidity or water availability affects water loss. Here, we tested how standing water sources (availability) and temperature (26 and 36°C) together affect water loss in anuran amphibians using a Bayesian framework. We also present a conceptual model for considering how water availability and temperature may interact, resulting in body mass changes. After accounting for phylogenetic and time autocorrelation, we determined how different variables (water loss and uptake rates, temperature, and body size) affect body mass in three species of tropical frogs (Rhinella marina, Phyllobates terribilis, and Xenopus tropicalis). We found that all variables impacted body mass changes with greater similarities between P. terribilis and X. tropicalis, but only temperature showed a notable effect in P. terribilis. Furthermore, we describe how the behavior of P. terribilis might affect its water budget. This study shows how organisms might manage water budgets across different environments and is important for developing our models of evaporative water loss and species distributions.

Pavement ant extract is a chemotaxis repellent for C. elegans.

Ant behavior relies on a collection of natural products, from following trail pheromones during foraging to warding off potential predators. How nervous systems sense these compounds to initiate a behavioral response remains unclear. Here, we used Caenorhabditis elegans chemotaxis assays to investigate how ant compounds are detected by heterospecific nervous systems. We found that C. elegans avoid extracts of the pavement ant ( Tetramorium immigrans ) and either osm-9 or tax-4 ion channels are required for this response. These experiments were conducted in an undergraduate laboratory course, demonstrating that new insights into interspecies interactions can be generated through genuine research experiences in a classroom setting.

Ecology, sexual dimorphism, and jumping evolution in anurans.

Sexual dimorphism (SD) is a common feature of animals, and selection for sexually dimorphic traits may affect both functional morphological traits and organismal performance. Trait evolution through natural selection can also vary across environments. However, whether the evolution of organismal performance is distinct between the sexes is rarely tested in a phylogenetic comparative context. Anurans commonly exhibit sexual size dimorphism, which may affect jumping performance given the effects of body size on locomotion. They also live in a wide variety of microhabitats. Yet the relationships among dimorphism, performance, and ecology remain underexamined in anurans. Here, we explore relationships between microhabitat use, body size, and jumping performance in males and females to determine the drivers of dimorphic patterns in jumping performance. Using methods for predicting jumping performance through anatomical measurements, we describe how fecundity selection and natural selection associated with body size and microhabitat have likely shaped female jumping performance. We found that the magnitude of sexual size dimorphism (where females are about 14% larger than males) was much lower than dimorphism in muscle volume, where females had 42% more muscle than males (after accounting for body size). Despite these sometimes-large averages, phylogenetic t-tests failed to show the statistical significance of SD for any variable, indicating sexually dimorphic species tend to be closely related. While SD of jumping performance did not vary among microhabitats, we found female jumping velocity and energy differed across microhabitats. Overall, our findings indicate that differences in sex-specific reproductive roles, size, jumping-related morphology, and performance are all important determinants in how selection has led to the incredible ecophenotypic diversity of anurans.

Context-dependent evolution of ostracod morphology along the ecogeographical gradient of ocean depth.

Ecogeographical rules inform our understanding of biodiversity by seeking reliable associations between organismal phenotypes and environmental factors. Reminiscent of classic ecogeographical rules, environmental factors vary in predictable ways with ocean depth, leading to predictions about organismal phenotypes. A valuable group for studying associations between habitat depth and phenotype is cylindroleberidid ostracods (Crustacea) because of previous phylogenetic analyses and their enormous depth range. Using phylogenetic comparative methods, we asked how habitat depth relates to body size and eye morphology in 232 cylindroleberidid species measured from museum specimens and literature descriptions. For each species, we recorded maximum habitat depth, body size, absolute eye size, number of ommatidia (facets) per eye, and diameter of the largest ommatidium. We find that the relationship between morphology and habitat depth in cylindroleberidids depends on pelagic zone: as depth increases in the photic zone, body size increases and eyes have fewer ommatidia; as depth increases in the disphotic zone, body size does not change and eyes have more ommatidia. We did not find a relationship between absolute eye size and depth in either pelagic zone. Overall, we find that associations between phenotypes and ecogeographical gradients depend on interactions between contexts such as pelagic zone, character state, and evolutionary history.