Mixed-species assemblages and disease: the importance of differential vector and parasite attraction in transmission dynamics.

Individuals from multiple species often aggregate at resources, group to facilitate defense and foraging, or are brought together by human activity. While it is well-documented that host-seeking disease vectors and parasites show biases in their responses to cues from different hosts, the influence of mixed-species assemblages on disease dynamics has received limited attention. Here, we synthesize relevant research in host-specific vector and parasite bias. To better understand how vector and parasite biases influence infection, we provide a conceptual framework describing cue-oriented vector and parasite host-seeking behaviour as a two-stage process that encompasses attraction of these enemies to the assemblage and their choice of hosts once at the assemblage. We illustrate this framework, developing a case study of mixed-species frog assemblages, where frog-biting midges transmit trypanosomes. Finally, we present a mathematical model that investigates how host species composition and asymmetries in vector attraction modulate transmission dynamics in mixed-species assemblages. We argue that differential attraction of vectors by hosts can have important consequences for disease transmission within mixed-species assemblages, with implications for wildlife conservation and zoonotic disease. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

Expanding the landscape of opportunity: Professional societies support early-career researchers through community programming and peer coaching.

Weaving the future of the field of comparative psychology is dependent on the career advancement of early-career scientists. Despite concerted efforts to increase diversity in science, technology, engineering, and mathematics, scholars from marginalized groups are disproportionately underrepresented in the field-especially at advanced career stages. New approaches to sponsorship, mentoring, and community building are necessary to retain talent from marginalized communities and to create a culture and a system where all individuals can thrive. We describe the unique and supportive role of senior women scientists united through a professional society in initiating peer coaching circles to facilitate the success of a diverse cohort of early-career women scientists. We offer our experiences with the Weaving the Future of Animal Behavior program as a case study that illustrates the cascading impacts of professional societies investing in the success and career development of marginalized scholars. We focus on our peer coaching circle experience and share the products and outcomes after 2 years of meeting. Peer coaching transformed us from a group of loosely organized, anxious individuals into a collective of empowered agents of change with an enhanced sense of belonging. We end by presenting recommendations to institutions seeking to expand the landscape of opportunities to other marginalized scholars. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Adaptive changes in sexual signalling in response to urbanization.

Urbanization can cause species to adjust their sexual displays, because the effectiveness of mating signals is influenced by environmental conditions. Despite many examples that show that mating signals in urban conditions differ from those in rural conditions, we do not know whether these differences provide a combined reproductive and survival benefit to the urban phenotype. Here we show that male túngara frogs have increased the conspicuousness of their calls, which is under strong sexual and natural selection by signal receivers, as an adaptive response to city life. The urban phenotype consequently attracts more females than the forest phenotype, while avoiding the costs that are imposed by eavesdropping bats and midges, which we show are rare in urban areas. Finally, we show in a translocation experiment that urban frogs can reduce risk of predation and parasitism when moved to the forest, but that forest frogs do not increase their sexual attractiveness when moved to the city. Our findings thus reveal that urbanization can rapidly drive adaptive signal change via changes in both natural and sexual selection pressures.

Mating patterns and post-mating isolation in three cryptic species of the Engystomops petersi species complex.

Determining the extent of reproductive isolation in cryptic species with dynamic geographic ranges can yield important insights into the processes that generate and maintain genetic divergence in the absence of severe geographic barriers. We studied mating patterns, propensity to hybridize in nature and subsequent fertilization rates, as well as survival and development of hybrid F1 offspring for three nominal species of the Engystomops petersi species complex in Yasuní National Park, Ecuador. We found at least two species in four out of six locations sampled, and 14.3% of the wild pairs genotyped were mixed-species (heterospecific) crosses. We also found reduced fertilization rates in hybrid crosses between E. petersi females and E. "magnus" males, and between E. "magnus" females and E. "selva" males but not in the reciprocal crosses, suggesting asymmetric reproductive isolation for these species. Larval development times decreased in F1 hybrid crosses compared to same species (conspecific) crosses, but we did not find significant reduction in larval survival or early metamorph survival. Our results show evidence of post-mating isolation for at least two hybrid crosses of the cryptic species we studied. The general decrease in fertilization rates in heterospecific crosses suggests that sexual selection and reinforcement might have not only contributed to the pattern of call variation and behavioral isolation we see between species today, but they may also contribute to further signal divergence and behavioral evolution, especially in locations where hybridization is common and fertilization success is diminished.

Collateral damage or a shadow of safety? The effects of signalling heterospecific neighbours on the risks of parasitism and predation.

Although males often display from mixed-species aggregations, the influence of nearby heterospecifics on risks associated with sexual signalling has not been previously examined. We tested whether predation and parasitism risks depend on proximity to heterospecific signallers. Using field playback experiments with calls of two species that often display from the same ponds, túngara frogs and hourglass treefrogs, we tested two hypotheses: (1) calling near heterospecific signallers attractive to eavesdroppers results in increased attention from predatory bats and parasitic midges (collateral damage hypothesis) or (2) calling near heterospecific signallers reduces an individual's predation and parasitism risks, as eavesdroppers are drawn to the heterospecifics (shadow of safety hypothesis). Bat visitation was not affected by calling neighbours. The number of frog-biting midges attracted to hourglass treefrog calls, however, rose threefold when played near túngara calls, supporting the collateral damage hypothesis. We thus show that proximity to heterospecific signallers can drastically alter both the absolute risks of signalling and the relative strengths of pressures from predation and parasitism. Through these mechanisms, interactions between heterospecific guild members are likely to influence the evolution of signalling strategies and the distribution of species at both local and larger scales.