Robin M. Tinghitella

Novel antagonistic interactions between species are expected to drive especially rapid coevolution. However, little is known about the genomic basis of such coevolution in nature because novel inter-specific interactions are rarely observed. Here, we study two species that recently came into first contact in Hawaii, the parasitoid fly Ormia ochracea and its cricket host Teleogryllus oceanicus. The fly locates crickets acoustically using their song, and parasitism usually results in host death. In response, protective male-silencing mutations have rapidly spread through cricket populations over the last ~25 years, imposing novel selective pressure on flies. By integrating population genomic analyses of 358 re-sequenced flies with field surveys of selection imposed by host adaptations, we discover genomic signatures of recent selective sweeps driven by host adaptations, indicative of escalating arms-race dynamics. This evolutionary response is occurring despite severely depleted genetic variation after bottlenecks in Hawaiian fly populations. Comparative analyses suggest that the genomic substrate of modern-day, rapid counter-adaptation in O. ochracea has been under positive selection on intermediate and long-term timescales across parasitoid flies. Our findings thus support predictions of influential arms race coevolution models and illustrate the current and ancient genomic bases of counteradaptation in nature.

The evolution of novel animal signals is critical to the generation of biodiversity. Here, we explore how new sexual signals become established. This process is challenging to explain because if receiver preferences are coupled with existing signals, then most receivers should discriminate against new signals. We investigated an underappreciated hypothesis: relaxed receiver preferences facilitate novel signal evolution by allowing new signals to establish a foothold. Further, we probed the mechanistic underpinnings of relaxed preferences by combining field-based and common garden approaches, allowing us to investigate evolution and plasticity as mechanisms. We capitalized on the Pacific field cricket, Teleogryllus oceanicus, a species that has recently evolved multiple novel acoustic signals (e.g., purring and rattling) in response to an eavesdropping parasitoid fly only found in the crickets’ introduced range in Hawaii. To test the hypothesis that selection associated with high search costs in introduced populations leads to relaxed mating preferences and determine whether such relaxation is plastic, we conducted sound preference (phonotaxis) trials with females from the cricket’s native range (Australia and French Polynesia, where the fly is absent) and its introduced range (Hawaii, where the fly is present). We presented females with novel songs plus the typical, ancestral song. Differences in phonotactic behavior between the lab and field settings would indicate plasticity in preferences. We found that Australian and French Polynesian females were quite plastic; they discriminated strongly against most songs in the field, but were much more phonotactic to rattling and the typical song in the lab. However, Hawaiian females exhibited little plasticity and were consistently highly responsive to the rattling and typical songs in the lab and field. This pattern points to a loss of ancestral plasticity in female preferences sometime after colonizing Hawaii, resulting in heightened responsiveness to all songs—allowing novel signals to establish.

Science communication (scicomm) shapes our world by helping people use science to make societal and personal decisions. Supporting and doing ethical scicomm requires valuing diverse perspectives and the people who do scicomm. Unfortunately, institutional hurdles ingrained in academia impede and undermine ethical scicomm. The injustices impeding scicomm stem from the prestige paradigm of academia (articulated in the present article), which reinforces hierarchical relationships in an exclusionary and exploitative system. To move academia forward, we name and review these injustices through the lens of five realms of scicomm (scientific communication, teaching scicomm, academics engaging in scicomm, scicomm research, and scicomm careers beyond academia). We then provide a novel framework, helping readers identify axes of influence and how they can leverage their intersectional, academic capital to take concrete action to remove the hurdles impeding ethical scicomm in academia.

Competition for mates can play a critical role in determining reproductive success, shaping phenotypic variation within populations, and influencing divergence. Yet, studies of the role of sexual selection in divergence and speciation have focused disproportionately on mate choice. Here, we synthesize the literature on how mate competition may contribute to speciation and integrate concepts from work on sexual selection within populations—mating systems, ecology, and mate choice. Using this synthesis, we generate testable predictions for how mate competition may contribute to divergence. Then, we identify the extent of existing support for these predictions in the literature with a systematic review of the consequences of mate competition for population divergence across a range of evolutionary, ecological, and geographic contexts. We broadly evaluate current evidence, identify gaps in available data and hypotheses that need testing, and outline promising directions for future work. A major finding is that mate competition may commonly facilitate further divergence after initial divergence has occurred, e.g., upon secondary contact and between allopatric populations. Importantly, current hypotheses for how mate competition contributes to divergence do not fully explain observed patterns. While results from many studies fit predictions of negative frequency-dependent selection, agonistic character displacement, and ecological selection, results from ~30% of studies did not fit existing conceptual models. This review identifies future research aims for scenarios in which mate competition is likely important but has been understudied, including how ecological context and interactions between mate choice and mate competition can facilitate or hinder divergence and speciation.

Sensory drive can lead to the evolution of signals that are optimized to the environment in which they are perceived. However, when environmental conditions change, the interactions between signal, environment, and receiver may also shift, leading to the evolution of a new signal optimum or more categorical shifts in sexual signals (gains or losses). We evaluated how visual systems have evolved following a change in environment and male signal, and whether visual system divergence contributes to reproductive isolation between ancestral and derived types in red and black morphs of Pacific Northwest freshwater threespine stickleback. We found that opsin sequence was tuned to enhance the perceived contrast of black fish on a red-shifted light background, whereas opsin expression was not. Further, we found no evidence for homotypic preferences or assortative mating between colour morphs; males of both morphs were equally successful in no-choice mating contexts, perhaps because black males are more vigorous courters. Together, our results suggest that habitat transitions in black stickleback have led to a shift in sensory-drive dynamics with some aspects of the visual system and behaviour evolving in response to other factors (foraging or predation) or lagging behind the evolution of opsin sequences in red-shifted environments.

Understanding how the early stages of sexual signal diversification proceed is critically important because these microevolutionary dynamics directly shape species trajectories and impact macroevolutionary patterns. Unfortunately, studying this is challenging because signals involve complex interactions between behavior, morphology, and physiology, much of which can only be measured in real-time. In Hawaii, male Pacific field cricket song attracts both females and a deadly parasitoid fly. Over the past two decades, there has been a marked increase in signal variation in Hawaiian populations of these crickets, including novel male morphs with distinct mating songs. We capitalize on this rare opportunity to track changes in morph composition over time in a population with three novel morphs, investigating how mate and parasitoid attraction (components of sexual and natural selection) may shape signal evolution. We find dramatic fluctuation in morph proportions over the three years of the study, including the arrival and rapid increase of one novel morph. Natural and sexual selection pressures act differently among morphs, with some more attractive to mates and others more protected from parasitism. Collectively, our results suggest that differential protection from parasitism among morphs, rather than mate attraction, aligns with recent patterns of phenotypic change in the wild.

Divergence of sexual signals between populations can lead to speciation, yet opportunities to study the immediate aftermath of novel signal evolution are rare. The recent emergence and spread of a new mating song, purring, in Hawaiian populations of the Pacific field cricket (Teleogryllus oceanicus) allows us to investigate population divergence soon after the origin of a new signal. Male crickets produce songs with specialized wing structures to attract mates from afar (calling) and entice them to mate when found (courtship). However, in Hawaii, these songs also attract an eavesdropping parasitoid fly (Ormia ochracea) that kills singing males. The novel purring song, produced with heavily modified wing morphology, attracts female crickets but not the parasitoid fly, acting as a solution to this conflict between natural and sexual selection. We've recently observed increasing numbers of purring males across Hawaii. In this integrative field study, we investigated the distribution of purring and the proportion of purring males relative to other morphs in six populations on four islands and compared a suite of phenotypic traits (wing morphology, calling song and courtship song) that make up this novel signal across populations of purring males. We show that purring is found in varying proportions across five, and is locally dominant in four, Hawaiian populations. We also show that calling songs, courtship songs and wing morphology of purring males differ geographically. Our findings demonstrate the rapid pace of evolution in island populations and provide insights into the emergence and divergence of new sexual signals over time. Abstract What occurs immediately following the emergence of a successful new sexual signal? The fleeting nature of these evolutionary events makes them difficult to study, yet they have important implications for our understanding of speciation. Several years ago, a new male cricket morph arose in Hawaii that produced a novel sexual signal (song) using altered wing morphology. This novel ‘purring’ song is attractive to female crickets but protective against a deadly, eavesdropping parasitoid fly, serving as a new private mode of communication among crickets. In this study, we show that despite arising very recently, purring males are now found in multiple populations across Hawaii and have even reached fixation in one. Perhaps surprisingly, we also find that the wings and songs of purring males now differ geographically. The accelerated timeframe in which these changes have occurred provides new insights into how sexual signals can diverge in small island populations.

Women and racially and ethnically minoritized populations are underrepresented in science, technology, engineering, and mathematics (STEM). Out-of-school time programs like summer camps can provide positive science experiences that may increase self-efficacy and awareness of STEM opportunities. Such programs often use the same high-impact practices used in K–12 classrooms including relating concepts to real-world examples, engaging students as active participants in inquiry-driven projects, and facilitating learning in a cooperative context. They additionally provide opportunities for engaging in STEM without fear of failure, offer a community of mentors, and allow families to become more involved. We designed a summer camp for middle schoolers who identified as girls, low-income, and as a minoritized race or ethnicity. We describe the design of the camp as well as the results from a simple pre- and post-camp questionnaire that examined each camper’s relationship to science, scientific self-efficacy, and interest in having a job in STEM. We found an increase in self-efficacy in camp participants, which is important because high scientific self-efficacy predicts student performance and persistence in STEM, especially for girls. We did not detect an increase in interest in pursuing a STEM job, likely because of already high values for this question on the pre-camp survey. We add to the growing body of work recognizing the potential of out-of-school time STEM programs to increase scientific self-efficacy for girls and racially minoritized students.Tweet: Summer camp for minoritized middle-school girls increases scientific self-efficacy, a characteristic that may be important for removing barriers to participation in STEM.

Sexual signals are often transmitted through multiple modalities (e.g., visual and chemical) and under selection from both intended and unintended receivers. Each component of a multimodal signal may be more or less conspicuous to receivers, and signals may evolve to take advantage of available private channels. We recently documented percussive substrate-borne vibrations in the Pacific field cricket (Teleogryllus oceanicus), a species that uses airborne acoustic and chemical signals to attract and secure mates. The airborne signals of Hawaiian T. oceanicus are currently undergoing rapid evolution; at least five novel male morphs have arisen in the past 20 years. Nothing is yet known about the newly discovered percussive substrate-borne vibrations, so we ask “how” they are produced, “who” produces them (e.g., population, morph), “when” they produce them (e.g., whether they are plastic), and “why” (e.g., do they play a role in mating). We show that the vibrations are produced exclusively by males during courtship via foreleg drumming. One novel morph, purring, produces quieter airborne songs and is more likely to drum than the ancestral morph. However, drumming behavior is also contextually plastic for some males; when we removed the ability of males to produce airborne song, ancestral males became more likely to drum, whereas two novel morphs were equally likely to drum regardless of their ability to produce song. Opposite our prediction, females were less likely to mate with males who drummed. We discuss why that might be and describe what we can learn about complex signal evolution from this newly discovered behavior.