Sensory cues of predation risk generate sex-specific changes in neural activity and behavior, but not hormones, in Trinidadian guppies.

How an organism responds to risk depends on how that individual perceives such risk. Integrating cues from multiple sensory modalities allows individuals to extract information from their environment, and whether and how the brain and body respond differently to different sensory cues can help reveal mechanistic decision-making processes. Here, we assessed neural, hormonal, and behavioral responses to different sensory cues of predation risk in Trinidadian guppies (Poecilia reticulata). Adult guppies were assigned to one of four treatment groups: control, visual, olfactory, and both sensory cues combined from a natural predator, the pike cichlid (Crenicichla alta), for 2 h. We found no difference in glucocorticoid response to any cue. However, we found behavioral and neural activation responses to olfactory-only cues. In addition, we found a sex by treatment effect, where males showed greater changes in neural activation in brain regions associated with avoidance behavior, while females showed greater changes in neural activation in regions associated with social behavior and memory, mirroring sex by treatment differences in behavioral antipredator responses. Altogether, our results demonstrate that single and combinatory cues may influence risk-taking behavior differently based on sex, suggesting that perception and integration of cues can cascade into sex differences in behavior.

How to Investigate the Origins of Novelty: Insights Gained from Genetic, Behavioral, and Fitness Perspectives.

Biologists are drawn to the most extraordinary adaptations in the natural world, often referred to as evolutionary novelties, yet rarely do we understand the microevolutionary context underlying the origins of novel traits, behaviors, or ecological niches. Here we discuss insights gained into the origins of novelty from a research program spanning biological levels of organization from genotype to fitness in Caribbean pupfishes. We focus on a case study of the origins of novel trophic specialists on San Salvador Island, Bahamas and place this radiation in the context of other rapid radiations. We highlight questions that can be addressed about the origins of novelty at different biological levels, such as measuring the isolation of novel phenotypes on the fitness landscape, locating the spatial and temporal origins of adaptive variation contributing to novelty, detecting dysfunctional gene regulation due to adaptive divergence, and connecting behaviors with novel traits. Evolutionary novelties are rare, almost by definition, and we conclude that integrative case studies can provide insights into this rarity relative to the dynamics of adaptation to more common ecological niches and repeated parallel speciation, such as the relative isolation of novel phenotypes on fitness landscapes and the transient availability of ecological, genetic, and behavioral opportunities.

Como Investigar as Origens da Novidade: Ideias Obtidas a Partir de Perspectivas da Genética, do Comportamento e de Fitness (How to Investigate the Origins of Novelty: Insights Gained from Genetic, Behavioral, and Fitness Perspectives) Biólogos são atraídos pelas adaptações mais extraordinárias do mundo natural, muitas vezes chamdas de novidades evolutivas, mas raramente entendemos o contexto microevolutivo subjacente às origens de novas características, novos comportamentos ou nichos ecológicos. Aqui discutimos ideias obtidas sobre as origens da novidade evolutiva a partir de um programa de pesquisa abrangendo níveis biológicos de organização de genótipo para fitness em pupas do Caribe. Nós nos concentramos em um estudo de caso sobre as origens de novos especialistas tróficos na ilha de São Salvador, Bahamas, e colocamos essa radiação no contexto de outras radiações rápidas. Destacamos questões que podem ser abordadas sobre as origens da novidade evolutiva em diferentes níveis biológicos, como medir o isolamento de novos fenótipos no cenário adaptativo, localizando as origens espaciais e temporais da variação adaptativa que contribuem para a novidade evolutiva, detectando a regulação gênica disfuncional devido à divergência adaptativa, e conectando comportamentos com novas características. As novidades evolutivas são raras, quase por definição, e concluímos que estudos de caso integrativos podem fornecer ideias sobre essa raridade em relação à dinâmica de adaptação a nichos ecológicos mais comuns e especiação paralela repetitiva, como o relativo isolamento de novos fenótipos em cenários adaptativos e a disponibilidade transitória de oportunidades ecológicas, genéticas, e comportamentais. Translated to Portuguese by G. Sobral (gabisobral@gmail.com).