The 75 species of Australian honeyeaters (Meliphagidae) are morphologically and ecologically diverse, with species feeding on nectar, insects, fruit, and other resources. We investigated ecomorphology and community structure of honeyeaters across Australia. First, we asked to what degree morphology and ecology (foraging behavior) are concordant. Second, we estimated rates of trait evolution. Third, we compared phylogenetic and trait community structure across the broad environmental gradients of continental Australia. We found that morphology explained 37% of the variance in ecology (and 62% vice versa), and that recovered multivariate ecomorphological relationships incorporated well-known bivariate relationships. Clades of large-bodied species exhibited elevated rates of morphological trait evolution, while members of Melithreptus showed slightly faster rates of ecological trait evolution. Finally, ecological trait diversity did not decline in parallel with phylogenetic diversity along a gradient of decreasing precipitation. We employ a new method (trait fields) and extend another (phylogenetic fields) to show that while species from phylogenetically clustered assemblages co-occur with morphologically similar species, these species are as varied in foraging behavior as those from more diverse assemblages. Thus, although closely related, these arid-adapted species have diverged in ecological space to a similar degree as their mesic counterparts, perhaps mediated by competition. [more]

Animals, from fruit flies and cockroaches to birds and humans, display consistent individual variation in behavior (i.e. animal personality). However, the role of individual variation in group behavior is not well understood in animals, particularly in insects where tracking many individuals simultaneously has traditionally been difficult or impossible. Recent technological developments, particularly in computer vision, are making this problem increasingly tractable, however, and are opening the door for understanding the nuances of individual variation and its role in collective behavior. Here, I use a low-cost, image-based automated tracking system (BEEtag) to investigate the extent, origins, and function of individual behavioral variation in two insects with varying level of social behavior: cockroaches (Blaberus discoidalis) and bumblebees (Bombus impatiens). In cockroaches, we find that individuals display strong and stable differences during collective light avoidance. These differences are robust to changes in group composition, but fascinatingly disappear when individuals are tested in isolation, suggesting that group context plays a key role in modulating personality in this species. In bumblebees, we find that individual workers vary substantially in both foraging activity and nest behavior. Interestingly, the distribution of behaviors appears to be regulated at the colony level, and behavioral idiosyncrasy plays an important role in determining patterns of task switching when colony labor demands shift. Finally, we use this trackingtechnology to examine the effects of individual pesticide exposure on social behavior in colonies. Overall, these studies underscore the importance of individual variation in social insects, but also highlight the complex interplay between behavior at the individual and the group level. [more]

Understanding how brains vary across species or during disease necessitates defining and comparing cell types, the building blocks of neural circuits. Single-cell measurements of gene expression take advantage of the fact that cellular specialization is controlled transcriptionally, allowing an unbiased picture of intra- and inter-cell type variation. Due to the experimental noise, analyses with only hundreds or even thousands of measurements can be hard to interpret. Here we apply a system developed in our lab for massively high-throughput single-cell transcriptomics („Drop-seq“) to mouse and marmoset brains. Our first project has generated an atlas of cellular variation from the adult mice. This dataset consists of >750K single-cell transcriptomes from n=9 different brain regions. We illustrate this single-cell approach by comparing 28K interneurons and describe our ongoing efforts to compare brains across species and throughout development. [more]

The traditional view of evolution is that mutations create variation, natural selection and drift reduces variation either randomly or by selecting alleles that confer some fitness effect. However, genomes have taught us that a significant agent of change in evolutionary biology is the process of merging evolving objects with one another. In this talk, I will elaborate on how evolutionary history is like a global economy, where DNA sequences act as “public goods” and the creation of new products (genes, proteins, gene clusters, cell types, genomes) is very likely to occur by the merging of evolving objects. Obviously this is balanced by the loss of whole genes, parts of genes, large tracts of DNA and sometimes the majority of a genome. This “goods thinking” alternative to “tree-thinking” is necessary in order to fully explain evolutionary history. Dr O’Connell’s research group combine computational biology and genome scale analyses with molecular/biochemical assays. She is interested in the tipping point that can occur between purifying selection which preserves function and positive selection that switches function. In essence, she is interested in understanding when protein function changes, where it changes, and how it changes. In this talk Dr O’Connell will summarise work her group have carried out to explore the emergence of novel function and the relationship between genotype and phenotype. [more]

Many animals use venoms or toxins to protect themselves against predators or to obtain prey. Thus, there is strong selection pressure to evolve resistance to these toxins on the part of the targeted animal and, in the case of alkaloid toxins that may diffuse throughout the body, in the animal that possess the toxins. I will first describe a situation in which a predator—the grasshopper mouse—has evolved resistance to voltage-gated sodium channel-targeting peptide components in the venom of their scorpion prey. This allows these carnivorous mice to exploit an abundant food resource in the Sonoran Desert in America. Then, I will show how poison arrow frogs from South America have evolved resistance to the acetylcholine receptor agonist epibatidine which is found in different independently evolved lineages of frogs. In both examples, resistance is conferred by a single, or at most a few, amino acid substitutions in key parts of the target molecule. [more]

Lek mating systems are arenas of intense sexual selection, in which mate choice is unfettered by male-female pair bonds or the requirements of offspring care. Current selective pressures from female choice are widely assumed to dictate the elaborate phenotypes and social systems of lekking males. To investigate the process of female choice and the patterns of male fitness it produces, I’ve collected 20 years of behavioral, morphological, and fitness data from a population of lance-tailed manakins, a cooperatively lekking tropical bird. In this species, breeding alpha males have distinctive morphological and behavioral phenotypes, males team up to perform complicated two-male dances for visiting females, and females search extensively to choose their mates. Tracking individual females’ movements during mate assessment reveals a hierarchical process of mate choice, and females receive indirect genetic benefits from choosing particular sires. I’ll discuss my progress in understanding this fascinating system, what we do and don’t know about the mechanisms of sexual selection in manakins, and what it suggests more broadly for the study of sexual selection. [more]

The external appearance of an organism reflects selection from multiple drivers, including abiotic factors such as climate and substrate, and potentially biotic factors such as sexual selection and mimicry. Woodpeckers are an excellent group to examine how external phenotypes evolve because they occupy a broad range of climates across many habitats, and display patterns of rapid divergence and striking convergence. Here we show that both habitat and climate profoundly shape plumage evolution. However, we also find a strong signal that many species exhibit remarkable convergence not explained by these factors or shared ancestry. Instead, this convergence is associated with geographic overlap between species, suggesting occasional, strong selection for interspecific mimicry. Consequently, both abiotic and biotic factors, including interspecific interactions, are potent drivers of phenotypic evolution. [more]

Animals rely on an internal sense of body position and movement to effectively control motor behavior. This sense of proprioception is mediated by diverse populations of internal mechanosensory neurons distributed throughout the body. My lab is trying to understand how proprioceptive stimuli are detected by sensory neurons, integrated and transformed in the brain, and used to guide motor output. We approach these questions using genetic tools, in vivo two-photon imaging, and patch-clamp electrophysiology in the fruit fly, Drosophila. We recently found that fly leg proprioceptors are organized into distinct functional projections that contain topographic representations of specific kinematic features: one group of axons encodes tibia position, another encodes movement direction, and a third encodes bidirectional movement and vibration frequency. Overall, our findings reveal how a low-dimensional stimulus – the angle of a single leg joint – is encoded by a diverse population of mechanosensory neurons. This architecture may help to maximize information transmission, processing speed, and robustness, which are critical for feedback control of the limbs during adaptive locomotion. [more]

When interacting with their environment animals constantly make decisions. These decisions frequently aim at maximizingreward while avoiding negative consequences such as energy costs, pain, or long-term disadvantages. Faced with a choice,animals consider and integrate several parameters such as their internal and behavioral state as well as external stimuli.Often decisions are shaped by prior experiences such as exposure to a given stimulus in a certain condition. But preferencesand aversions can be innate, and an instinctive reaction can be essential to secure survival. Nevertheless, even these innatepreferences need to be evaluated in a context-dependent manner and hence, context strongly impinges on behavior. Whileit is generally accepted that context influences behavior, our knowledge of the neural mechanisms of how internal state andexternal conditions alter ongoing behavior is scarce. The goal of my research is to provide a comprehensive understandingof the neural and molecular basis of context-specific behavior. To this end, my group studies how internal states shapechemosensory processing and behavior of the fly. [more]

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