The effect of the environment may result in different developmental outcomes. Extrinsic signals can modify developmental pathways and result in alternative phenotypes (phenotypic plasticity). The environment can also be interpreted as a stressor and increase developmental instability (developmental noise). Directional and fluctuating asymmetry provide a conceptual background to discriminate between these results. This study aims at assessing whether variation in dentition and shape of pharyngeal arches of the clonal fish Chrosomus eos-neogaeus results from developmental instability or environmentally induced changes. A total of 262 specimens of the Chrosomus eos-neogaeus complex from 12 natural sites were analysed. X-ray microcomputed tomography (X-ray micro-CT) was used to visualize the pharyngeal arches in situ with high resolution. Variation in the number of pharyngeal teeth is high in hybrids in contrast to the relative stability observed in both parental species. The basal dental formula is symmetric while the most frequent alternative dental formula is asymmetric. Within one lineage, large variation in the proportion of individuals bearing basal or alternative dental formulae was observed among sites in the absence of genetic difference. Both dentition and arch shape of this hybrid lineage were explained significantly by environmental differences. Only individuals bearing asymmetric dental formula displayed fluctuating asymmetry as well as directional left-right asymmetry for the arches. The hybrids appeared sensitive to environmental signals and intraspecific variation on pharyngeal teeth was not random but reflects phenotypic plasticity. Altogether, these results support the influence of the environment as a trigger for an alternative developmental pathway resulting in left-right asymmetry in dentition and shape of pharyngeal arches.

Biological complexity is a key component of evolvability, yet its study has been hampered by a focus on evolutionary trends of complexification and inconsistent definitions. Here, we demonstrate the utility of bringing complexity into the framework of epigenetics to better investigate its utility as a concept in evolutionary biology. We first analyze the existing metrics of complexity and explore the link between complexity and adaptation. Although recently developed metrics allow for a unified framework, they omit developmental mechanisms. We argue that a better approach to the empirical study of complexity and its evolution includes developmental mechanisms. We then consider epigenetic mechanisms and their role in shaping developmental and evolutionary trajectories, as well as the development and organization of complexity. We argue that epigenetics itself could have emerged from complexity because of a need to self‐regulate. Finally, we explore hybridization complexes and hybrid organisms as potential models for studying the association between epigenetics and complexity. Our goal is not to explain trends in biological complexity but to help develop and elucidate novel questions in the investigation of biological complexity and its evolution.

Animal behaviour courses integrate concepts across biological disciplines and are particularly well suited for collaborative, student-focused teaching strategies. Case Studies can positively impact students by placing their learning in context while providing an opportunity to do quick research and have rich discussions with both their peers and instructional team. Case Studies can also enrich the learning environment and help to produce a safe, collaborative space for asking questions and developing critical thinking skills. Here we describe three Case Study lesson plans using the Jigsaw approach that allows students to explore animal communication, migration, and parental care. Each Case Study includes 16 primary literature summaries on four different animal groups. In the Jigsaw approach, students are first sorted into four "expert groups" where they receive primary literature summaries exploring proximate and ultimate approaches to a specific animal's behaviour (e.g., neurobiology, physiology, genetics, and evolution). One student from each "expert group" (e.g., ants, birds, etc.) then joins and shares their group's knowledge in a "jigsaw group." By the end of each lesson, students will have read one primary literature article summary, prepared and delivered an oral brief, and summarized and then presented their expert group's findings to the new Jigsaw group members. Through this collaborative peer-to-peer learning activity, students gain skills in interpreting, analyzing and synthesizing scientific literature. They also have the opportunity to practice communicating scientific findings effectively and concisely, sharing how animal behaviour is studied, and explaining how behaviour is influenced by both proximate and ultimate factors