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Abstract Phenological synchrony enables species to occur when conditions are optimal for survival. While phenological synchrony between butterflies and their host plants has been extensively documented, the importance of phenology in maintaining interspecies interactions, such as mimicry, is less understood. Mimicry occurs when a species (i.e. the mimic) evolves a phenotypic resemblance to an unpalatable species (i.e. the model), resulting in protection against predation for the mimic. Theory predicts that in Batesian mimicry systems, models should appear seasonally before their mimics to give predators sufficient time to learn, recognize, and avoid their aposematic signal (i.e. model-first hypothesis). Here, we use citizen science data from iNaturalist to test these long-standing predictions. To understand how mimicry influences the evolution of different phenological strategies, we estimate onset phenology in two systems: the defended model species Battus philenor and its classic Batesian mimic Limenitis arthemis astyanax, and the more complex system consisting of Mullerian co-mimics Danaus plexippus and Limenitis archippus. Our results support the model-first hypothesis and demonstrate that unpalatable models appear significantly before their mimics across large geographical scales. This research highlights a new avenue for utilizing large-scale citizen science datasets to address long-standing questions about how phenology impacts complex ecological interactions. 

Ants have remarkably diverse diets and extraordinary species richness, making them an excellent model system to study the evolution of taste. In this entirely eusocial clade, food choice and the mechanisms that regulate feeding have both individual and social dimensions. How taste receptors and sensory processing drive food preferences to generate dietary breadth in ants is poorly understood. It is additionally unclear how elements of colony organization such as division of labor and social food flow impact the mechanistic basis and evolution of taste. Previous work on dipteran, lepidopteran, and hymenopteran gustatory systems, while foundational, provide limited insights into ant dietary specialization. Here we synthesize and analyze research on ant gustation to identify mechanisms, sociobiological correlates, and phylogenetic patterns. We discuss the current state of genomic analyses of taste and future research. We propose that strikingly polymorphic species of Pheidole , Cephalotes , Camponotus , and leafcutter ants ( Atta and Acromyrmex ) offer compelling social systems to explore adaptive variation in gustation because of their pronounced division of labor in which morphologically, behaviorally, and neurally differentiated workers vary in feeding behavior. Research on ant gustation within and among species will advance our understanding of sensory systems and provide insight into the impact of taste on the evolution of species diversity and how social organization influences gustation. 

Abstract Reproductive isolation is the heuristic basis of the biological species concept, but what is it? Westram et al. (this issue) propose that it is a measurable quantity, “barrier strength,” that prevents gene flow among populations. However, their attempt to make the concept of reproductive isolation more scientific is unlikely to satisfy the diverse opinions of all evolutionary biologists. There are many different opinions about the nature of species, even under the biological species concept. Complete reproductive isolation, where gene flow is effectively zero, is regarded by some biologists as an important end point of speciation. Others, including Westram et al., argue for a more nuanced approach, and they also suggest that reproductive isolation may differ in different parts of the genome due to variation in genetic linkage to divergently selected loci. In contrast to both these approaches, we favour as a key criterion of speciation the stable coexistence of divergent populations in sympatry. Obviously, such populations must be reproductively isolated in some sense, but neither the fraction of the genome that is exchanged, nor measures of overall barrier strength acting on neutral variation will yield very precise predictions as to species status. Although an overall measure of reproductive isolation is virtually unattainable for these reasons, its early generation components, such as assortative mating, divergent selection, or hybrid inviability and sterility are readily measurable and remain informative. For example, we can make the prediction that to remain divergent in sympatry, almost all sexual species will require strong assortative mating, as well as some sort of ecological or intrinsic selection against hybrids and introgressed variants.