Model Systems in Ecology, Evolution, and Behavior: A Call for Diversity in Our Model Systems and Discipline

Embracing the diversity in diverse warning signals

Positive frequency-dependent selection should theoretically lead to monomorphic warning coloration. Instead, numerous examples of polymorphic warning signals exist. Biases - for example, in human perception - hinder our appreciation and research of understanding warning signal diversity. We propose strategies to counter such biases and objectively move our field forward.

Unhealthy herds and the predator–spreader: Understanding when predation increases disease incidence and prevalence

Disease ecologists now recognize the limitation behind examining host–parasite interactions in isolation: community members—especially predators—dramatically affect host–parasite dynamics. Although the initial paradigm was that predation should reduce disease in prey populations (“healthy herds hypothesis”), researchers have realized that predators sometimes increase disease in their prey. These “predator–spreaders” are now recognized as critical to disease dynamics, but empirical research on the topic remains fragmented. In a narrow sense, a “predator–spreader” would be defined as a predator that mechanically spreads parasites via feeding. However, predators affect their prey and, subsequently, disease transmission in many other ways such as altering prey population structure, behavior, and physiology. We review the existing evidence for these mechanisms and provide heuristics that incorporate features of the host, predator, parasite, and environment to understand whether or not a predator is likely to be a predator–spreader. We also provide guidance for targeted study of each mechanism and quantifying the effects of predators on parasitism in a way that yields more general insights into the factors that promote predator spreading. We aim to offer a better understanding of this important and underappreciated interaction and a path toward being able to predict how changes in predation will influence parasite dynamics.

Familia, Comunidad y Maestros: How I Became a Latina Science Professor

AbstractPeople of Mexican origin in the United States have long experienced discrimination in wages, housing, and schooling, which directly impacts their participation in the STEM (science, technology, engineering, and mathematics) workforce. Using interviews of Latina scientists and teachers, autoethnography, family and newspaper archives, and history and social science research, I reflect on key aspects of Mexican and Mexican American history that contribute to the challenges faced by Latinos in the US educational system today. Analysis of my own educational trajectory reveals the hidden part that teacher role models in my community and in my family played in my journey to becoming a scientist. Latina teachers and faculty, middle school science programs, and the provisioning of stipends for undergraduate researchers are emphasized as strategies for increasing student retention and success. The article concludes with several suggestions for how the ecology and evolutionary biology community can amplify the educational success of Latinos in STEM by supporting the training of Latino and other minoritized science, math, and computer science teachers.

Natural variation in host feeding behaviors impacts host disease and pathogen transmission potential

Animals ranging from mosquitoes to humans often vary their feeding behavior when infected or merely exposed to pathogens. These so-called "sickness behaviors" are part of the innate immune response with many consequences, including avoiding orally transmitted pathogens. Fully understanding the role of this ubiquitous behavior in host defense and pathogen evolution requires a quantitative account of its impact on host and pathogen fitness across environmentally relevant contexts. Here, we use a zooplankton host and fungal pathogen as a case study to ask if infection-mediated feeding behaviors vary across pathogen exposure levels and natural genetic variation in susceptibility to infection. Then, we connect these changes in behavior to pathogen transmission potential (spore yield) and fitness and growth costs to the host. Our results validate a protective effect of altered feeding behavior during pathogen exposure while also revealing significant variation in the magnitude of this response across host susceptibility and pathogen exposure levels. Across all four host genotypes, feeding rates were negatively correlated with susceptibility to infection and transmission potential. The most susceptible genotypes exhibited either strong anorexia, reducing food intake by 26%-42%, ("Standard") or pronounced hyperphagia, increasing food intake by 20%-54% ("A45"). Together, these results suggest that infection-mediated changes in host feeding behavior-which are traditionally interpreted as immunopathology- may in fact serve as crucial components of host defense strategies and warrant further investigation.

The overlooked complexity of avian brood parasite-host relationships

The relationships between avian brood parasites and their hosts are widely recognised as model systems for studying coevolution. However, while most brood parasites are known to parasitise multiple species of host and hosts are often subject to parasitism by multiple brood parasite species, the examination of multispecies interactions remains rare. Here, we compile data on all known brood parasite-host relationships and find that complex brood parasite-host systems, where multiple species of brood parasites and hosts coexist and interact, are globally commonplace. By examining patterns of past research, we outline the disparity between patterns of network complexity and past research emphases and discuss factors that may be associated with these patterns. Drawing on insights gained from other systems that have embraced a multispecies framework, we highlight the potential benefits of considering brood parasite-host interactions as ecological networks and brood parasitism as a model system for studying multispecies interactions. Overall, our results provide new insights into the diversity of these relationships, highlight the stark mismatch between past research efforts and global patterns of network complexity, and draw attention to the opportunities that more complex arrangements offer for examining how species interactions shape global patterns of biodiversity.

Exploring new genomic territories with emerging model insects

Improvements in reference genome generation for insects and across the tree of life are extending the concept and utility of model organisms beyond traditional laboratory-tractable supermodels. Species or groups of species with comprehensive genome resources can be developed into model systems for studying a large variety of biological phenomena. Advances in sequencing and assembly technologies are supporting these emerging genome-enabled model systems by producing resources that are increasingly accurate and complete. Nevertheless, quality controls including assessing gene content completeness are required to ensure that these data can be included in expanding catalogues of high-quality references that will greatly advance understanding of insect biology and evolution.

Journey beyond the embryo: The beauty of Pristina and naidine annelids for studying regeneration and agametic reproduction

Regeneration, asexual agametic reproduction, and other forms of postembryonic development are ecologically important and widely variable across animals, yet our understanding of this important aspect of animal diversity remains limited. A significant limitation has been the dearth of adequate study systems for exploring the mechanisms and evolution of these processes. Here I describe key parts of our journey in developing naid annelids as a study system for investigating the evolution and development of regeneration and fission. Naids are small freshwater annelids that provide numerous advantages for studying postembryonic development: they are small and reproduce readily by fission, they include species with diverse regenerative abilities, and many species are easy to culture. Among the naids, Pristina leidyi is a particularly useful study species, being largely transparent and quite robust to a variety of experimental manipulations. Building on a sparse but long history of past research on these animals, we have developed this system by establishing methods and generating resources for working with them. Naids are yielding novel insights into the evolution of regeneration and fission, providing one of many examples of the value of developing new study species to enable the exploration of fundamental and understudied questions in biology. Establishing new study systems comes with challenges but is exciting and rewarding, and I provide perspectives from my own experiences with the hope of encouraging the further expansion of study systems in biology.

Increasing the spatial and temporal impact of ecological research: A roadmap for integrating a novel terrestrial process into an Earth system model

Terrestrial ecosystems regulate Earth's climate through water, energy, and biogeochemical transformations. Despite a key role in regulating the Earth system, terrestrial ecology has historically been underrepresented in the Earth system models (ESMs) that are used to understand and project global environmental change. Ecology and Earth system modeling must be integrated for scientists to fully comprehend the role of ecological systems in driving and responding to global change. Ecological insights can improve ESM realism and reduce process uncertainty, while ESMs offer ecologists an opportunity to broadly test ecological theory and increase the impact of their work by scaling concepts through time and space. Despite this mutualism, meaningfully integrating the two remains a persistent challenge, in part because of logistical obstacles in translating processes into mathematical formulas and identifying ways to integrate new theories and code into large, complex model structures. To help overcome this interdisciplinary challenge, we present a framework consisting of a series of interconnected stages for integrating a new ecological process or insight into an ESM. First, we highlight the multiple ways that ecological observations and modeling iteratively strengthen one another, dispelling the illusion that the ecologist's role ends with initial provision of data. Second, we show that many valuable insights, products, and theoretical developments are produced through sustained interdisciplinary collaborations between empiricists and modelers, regardless of eventual inclusion of a process in an ESM. Finally, we provide concrete actions and resources to facilitate learning and collaboration at every stage of data-model integration. This framework will create synergies that will transform our understanding of ecology within the Earth system, ultimately improving our understanding of global environmental change, and broadening the impact of ecological research.

Building on 150 Years of Knowledge: The Freshwater Isopod Asellus aquaticus as an Integrative Eco-Evolutionary Model System

Interactions between organisms and their environments are central to how biological diversity arises and how natural populations and ecosystems respond to environmental change. These interactions involve processes by which phenotypes are affected by or respond to external conditions (e.g., via phenotypic plasticity or natural selection) as well as processes by which organisms reciprocally interact with the environment (e.g., via eco-evolutionary feedbacks). Organism-environment interactions can be highly dynamic and operate on different hierarchical levels, from genes and phenotypes to populations, communities, and ecosystems. Therefore, the study of organism-environment interactions requires integrative approaches and model systems that are suitable for studies across different hierarchical levels. Here, we introduce the freshwater isopod Asellus aquaticus, a keystone species and an emerging invertebrate model system, as a prime candidate to address fundamental questions in ecology and evolution, and the interfaces therein. We review relevant fields of research that have used A. aquaticus and draft a set of specific scientific questions that can be answered using this species. Specifically, we propose that studies on A. aquaticus can help understanding (i) the influence of host-microbiome interactions on organismal and ecosystem function, (ii) the relevance of biotic interactions in ecosystem processes, and (iii) how ecological conditions and evolutionary forces facilitate phenotypic diversification.

Positive genetic covariance and limited thermal tolerance constrain tropical insect responses to global warming

Tropical ectotherms are particularly vulnerable to global warming because their physiologies are assumed to be adapted to narrow temperature ranges. This study explores three mechanisms potentially constraining thermal adaptation to global warming in tropical insects: (a) Trade-offs in genotypic performance at different temperatures (the jack-of-all-trades hypothesis), (b) positive genetic covariance in performance, with some genotypes performing better than others at viable temperatures (the 'winner' and 'loser' genotypes hypothesis), or (c) limited genetic variation as the potential result of relaxed selection and the loss of genes associated with responses to extreme temperatures (the gene decay hypothesis). We estimated changes in growth and survival rates at multiple temperatures for three tropical rain forest insect herbivores (Cephaloleia rolled-leaf beetles, Chrysomelidae). We reared 2,746 individuals in a full sibling experimental design, at temperatures known to be experienced by this genus of beetles in nature (i.e. 10-35°C). Significant genetic covariance was positive for 16 traits, supporting the 'winner' and 'loser' genotypes hypothesis. Only two traits displayed negative cross-temperature performance correlations. We detected a substantial contribution of genetic variance in traits associated with size and mass (0%-44%), but low heritability in plastic traits such as development time (0%-6%) or survival (0%-4%). Lowland insect populations will most likely decline if current temperatures increase between 2 and 5°C. It is concerning that local adaption is already lagging behind current temperatures. The consequences of maintaining the current global warming trajectory would be devastating for tropical insects. However, if humans can limit or slow warming, many tropical ectotherms might persist in their current locations and potentially adapt to warmer temperatures.