Females commonly exhibit directional preferences for males that produce more exaggerated, elaborate, or energetic signals. Key questions remain regarding individual variation in the expression of such preferences, particularly when performance related trade-offs in signaling occur in social environments (e.g., leks and choruses) where males dynamically compete for females. In this study of Cope’s gray treefrog (Hyla chrysoscelis), we investigated directional female preferences for longer calls and faster call rates, two performance-related traits that negatively covary. Subjects repeatedly chose between two simulated males with different call durations and call rates, but with equal overall calling efforts (pulses per unit time). In half of tests, call duration and rate were dynamically swapped between the two simulated males prior to females reaching a speaker. Females chose randomly with respect to differences in call duration and call rate and ignored dynamic shifts in calling behavior. The repeatability of female choice was not different from zero, and females were highly committed to choosing the simulated male they initially approached, even when stimuli differing in call duration and rate were dynamically swapped between speakers as she approached. There was no evidence that subpopulations of females differentially weighted call duration or rate in making their choices. Individual differences in body size, condition, and corticosterone levels had no effects on female responses. Together, these results support an inter-signal interaction hypothesis in showing that females choose mates by attending to the emergent signal property of calling effort instead of its constituent components of call duration and rate. Mate choice can impose selection on communication signals and signaling behaviors, but key questions remain regarding the expression of mate preferences, particularly when multiple signals or signal components related to a signaler’s overall performance potentially interact to influence mating decisions. In this study of a treefrog, we used two-alternative choice tests to investigate female preferences for higher values of two performance-related traits in male advertisement signals (call duration and call rate) that negatively covary but together determine a male’s overall signaling output (calling effort). We found that females chose randomly with respect to differences in both traits, suggesting they integrate temporal information across multiple signals to choose mates based on differences in their overall signaling output and not its constituent components. These results highlight the potential importance of inter-signal interactions in mating decisions.
Students in high school and college are expected to take on greater responsibility for regulating their own learning. As they navigate course demands and explore potential career paths, students are making decisions about what to attend to, how to engage, how much effort to invest, and how long to persist. Motivation and its regulation is key to this process (Sansone et al., 2019). We integrate insights about the importance of task value from situated expectancy-value theory (Eccles Wigfield, 2020) and research on utility-value interventions (UVIs) that target task value with insights from the four-phase model of interest development (Renninger Hidi, 2022) to identify ways to support students as they manage motivational challenges. Value and interest are often closely related, and, when considered separately, each positively predicts student effort. Rather than considering them in isolation, we consider how they may work together over time. UVIs can help students think about and articulate the usefulness of course topics, which has been found to enhance perceived task value and motivate engagement with course content (Harackiewicz Priniski, 2018; Wigfield Eccles, 2020). UVIs may be especially helpful when students have little interest in learning the content, but this effect may become more nuanced as students develop interest. We suggest a framework for integrating these perspectives, identify self-regulation challenges, and discuss possible ways to support this self-regulatory process. We also highlight future directions for research that emerge from this integration.
Exposure to organophosphorus pesticides (OPs) during pregnancy has been suggested to cause adverse outcomes on neural development of the fetus but the mechanisms underlying developmental neurotoxicity of OPs remain unclear. While OPs share acetylcholinesterase (AChE) as the primary molecular target, different OPs have been shown to induce different effects in laboratory studies. Previously, we found that OPs differentially affect regenerating planarians when applied on the first day of regeneration. To determine if the timing of OP exposure affects adverse outcomes, here, we performed a comparative study of 5 OPs—chlorpyrifos (17.8 μM), diazinon (16.2 μM), dichlorvos (1 μM), profenofos (10 μM), and malathion (56.2 μM)—in the planarian Dugesia japonica. We evaluated how effects on behavior and nervous system morphology changed with OP exposure starting on different days of regeneration/development. We found that some toxic effects were dependent on the developmental stage during exposure. For example, profenofos impaired brain development when exposure started on day 1 of development but caused lethality when exposure started during later stages. Inhibition of the enzymatic activity of AChE on day 12 of exposure was not affected by the different exposure paradigms, suggesting that the differential effects were either due to effects on the non-enzymatic functions of AChE or on other targets during neurodevelopment. This work provides insight into which neurodevelopmental key events are affected by OP exposure, enabling future mechanistic work to identify the targets underlying OP developmental neurotoxicity.
Climate change is one of the main drivers of a global insect decline. Stoneflies (Insecta: Plecoptera) have one of the highest local extinction rates among insects, in part due to their requirements for cold, highly oxygenated, unpolluted water. Investigating the population structure of stonefly species is integral to their conservation as it can identify populations at risk of localized extinction. In this study, we extracted DNA from Nemoura arctica (Esben-Petersen, 1910), Nemoura cinerea (Retzius, 1783) and Nemurella pictetii (Klap & aacute;lek, 1900) specimens collected across Arctic Alaska, Sweden and Finland. We sequenced the mitochondrial COI gene and the nuclear 28S gene of 96 specimens from 9 locations and constructed haplotype networks for these three species by combining our sequences with publicly available sequences of circumboreal stoneflies from the Barcode of Life Database (BOLD) and the National Center for Biotechnology Information (NCBI) GenBank. Haplotype networks suggest that N. arctica and N. cinerea have higher COI genetic diversity than N. pictetii, with potential evidence for the description of new species. We modeled past, present and future habitat suitability using species distribution models (SDMs) in the program Wallace v2.1.3. Our models predict that all three species will lose most or all of their current suitable habitat by 2070, no matter the climate scenario.
Acoustic signals in anurans are classic models for understanding how endocrine mechanisms regulate courtship behavior. However, our understanding of how steroids influence male calling performance remains limited because most studies examine single hormones or isolated call traits. Here we quantified three plasma steroids-testosterone (T), estradiol (E2), and corticosterone (CORT)-from male Cope's gray treefrogs (Hyla chrysoscelis) recorded in natural male-male calling pairs, relating these concentrations to multiple calling components including call rate, duration, and effort. We used principal components analysis to describe a male's overall calling performance and his calling strategy, defined here as a male's allocation along the tradeoff between producing longer calls versus faster call rates at similar overall effort. We analyzed these relationships at the population level and within male pairs using multiple regressions including all three hormones as predictors. At the population level, T and E2 positively correlated with calling performance, whereas calling strategy was unrelated to hormones. Within male pairs, differences in T also positively correlated with differences in calling performance. Despite their positive covariance, both T and E2 retained independent partial associations with calling performance. CORT showed no association with calling performance or strategy at either level. These results show that gonadal steroid state predicts asymmetries in calling performance between competitors while remaining unrelated to performance-related tradeoffs. By revealing strong positive correlations between gonadal hormones and energetic investment in calling, this study demonstrates how female preferences for high-performing callers can impose sexual selection on endocrine mechanisms regulating courtship behavior.
