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Session Schedule & Abstracts
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|Wednesday 29th June, 2016|
|Moderator(s): J. M. Hoyos & R. Diogo|
CHA2-1 4:30 pm Major challenges in vertebrate morphology, ecology and biophysics: Hummingbirds as a case study. Rico-Guevara A*, University of Connecticut firstname.lastname@example.org |
Abstract: A central challenge of biology is to describe the links among structures (e.g. organismal morphology), underlying biophysical mechanisms, and emergent phenomena (e.g. performance, ecological and evolutionary patterns) in live organisms. Because morphology varies among individuals, performance and the adaptive value of behaviors vary accordingly. Hence, a complete understanding of the evolutionary and ecological implications of phenotypical variability, the fuel of natural selection, requires us to quantify the causal link between variation in traits and the performance capabilities of their possessors. A major challenge in the study of vertebrate morphology is to explicitly link biomechanics to ecological determinants of species interactions at several levels. To tackle this challenge, I will show how I use hummingbirds as a study model to bridge the gap between our knowledge of coevolutionary and pollination patterns, and underlying foraging behavior and feeding apparatus morphology. I employ the induction-deduction method to gain a complete understanding of how the physics of nectar feeding mechanisms in hummingbirds shape their ecology and evolution. The last challenge I will address corresponds to the necessity to take advantage of multidisciplinary approaches and cutting-edge technology in the study of functional morphology. I propose mechanistic explanations based on electron microscopy, mircroCT scans, high-speed videos, and experiments under controlled conditions, that we use to develop biophysical models of each step of the feeding process. Then, we test the model predictions using data from birds feeding at wild flowers collected through customized camera traps. I will present how we can establish the way in which the biophysics of the tongue-nectar interaction, and thus the mechanics of the entire drinking process, creates boundary conditions for the energetics of feeding on flowers, and thereby the ecological and co-evolutionary patterns in hummingbirds.
CHA2-2 4:45 pm Major challenges in vertebrate morphology: 2D, 3D, and 4D visualization and network tools applied to study the origin and evolution of tetrapod limbs. Molnar JL*, Howard University; Esteve-Altava B, Royal Veterinary College & Howard University; Johnston PS, University of Auckland; Diogo R, Howard University email@example.com |
Abstract: Innovations in imaging and computing are making great contributions to vertebrate morphology. Complex virtual models allow us to estimate physiological properties that are difficult to measure experimentally and compare vast amounts of data among species. Meanwhile, technologies such as micro-computed tomography, magnetic resonance imaging (MRI), iodine staining, and 3D printing give us new and more detailed anatomical information about both extant and extinct animals, and they make it possible for researchers to share rare specimens with colleagues across the globe. In our lab, we are applying some of these techniques, in combination with traditional anatomical methods and molecular data, to make progress on the puzzle of how musculoskeletal anatomy and function changed over the transition from fish fins to tetrapod limbs. The origin of tetrapods has been the subject of intense debate for more than a century, but little is known about the soft tissue anatomy or locomotion of the first terrestrial vertebrates. We used MRI scans of lungfish and coelacanths, the closest living relatives of tetrapods, to identify homologous appendicular muscles among the two lobe-finned fish and salamanders. Then, we used anatomical networks to quantify topological organization within the appendages of each animal. Finally, we built 3D biomechanical models to compare the leverage of various muscle groups over the step cycle. These methods allow us for the first time to compare functionally important parameters across morphologically disparate species. In the future, we plan to use similar methods in conjunction with fossil specimens to reconstruct and analyze changes in limb muscle anatomy and function in early tetrapods and their close relatives. This case study illustrates how 2D, 3D, and 4D visualization and network tools can provide new ways to approach old problems in vertebrate morphology.
CHA2-3 5:00 pm Major challenges in vertebrate morphology, muscle evolution and evolutionary change via heterochrony. Ziermann Janine*, Howard University College of Medicine; Diogo Rui, Howard University College of Medicine firstname.lastname@example.org |
Abstract: Evolutionary developmental biology (Evo-Devo) aims to unravel changes in development or developmental mechanism that led to evolutionary change. In other words, which developmental modifications and processes led to morphological changes and/or to novel features of species? By comparing developmental processes between different organisms the developmental basis of homoplasy and homology, as well as changes in developmental timing, i.e. heterochrony, might be revealed. In recent years Evo-Devo studies tended to address the more developmental part of Evo-Devo focusing mainly on genetic/molecular analysis. This led to a shift of attention towards the genomic basis for developmental processes instead of addressing older and/or broader evolutionary concepts and theories. One striking example for the application of Evo-Devo studies to analyze evolutionary theories comes from our myological studies of muscle development and morphology in the head, neck, heart, and pectoral and pelvic appendages in vertebrates. The comparison of developmental patterns of cephalic muscles revealed general developmental gradients that seem to be conserved throughout vertebrates (e.g. an anterior to posterior gradient during the differentiation). Furthermore, amphibians and bony fishes, show a parallel in phylogeny and ontogeny of cephalic muscles. However, those large scale comparative studies reveal also heterochronies that might be responsible for species specific morphologies. Including the analysis of development in species without a cranium, e.g. the Cephalochordate Amphioxus, and with only cartilaginous craniums, e.g. sharks, unravels the early evolution and origin of cephalic muscles in vertebrates. Finally, we can include ourselves, Homo sapiens, a species seen by many as highly neotenic for some features, in Evo-Devo studies in order to understand the importance of heterochrony, the links between phylogeny and ontogeny, birth defects, and other broader evolutionary topics.
CHA2-4 5:15 pm Major challenges in vertebrate morphology: bridging the gap between genotypes and musculo-skeletal phenotypes in primates using functional genomics and developmental genetics. Capellini TD*, Harvard University; Dingwall H, Harvard University; Willen J, Harvard University; Wohns A, Harvard University email@example.com |
Abstract: Primates exhibit remarkable diversity in musculo-skeletal morphology, much of which is apparent in skeletal appendages that interact with substrates during locomotion and positional behavior. Differences in the lengths, shapes, and proportions of the major long bones of the forelimb (scapula/humerus/radius/ulna) and hindlimb (pelvis/femur/tibia/fibula) reflect the myriad of skeletal adaptations primates have evolved to occupy diverse ecological niches. This diversity is not only observable at the level of the entire appendage or individual limb segment, but at specific functional zones, such as growth plates, joints, and muscle-attachment sites. From an evolutionary perspective, this striking morphological diversity reflects the actions of natural selection on variation in pre- and postnatal developmental processes. Yet despite many decades of research relatively little is known about the molecular mechanisms that control the specific shapes of bones, let alone how modifications to pre- and postnatal developmental programs influence the morphological variation within and between species. We use a modern synthetic approach, one that integrates experimental findings from developmental biology, genetics, functional genomics, and bioinformatics to improve the connections between genotype to phenotype and reveal the causative mutations that underlie adaptive morphological evolution. Given the complex relationship between genotypes and phenotypes, we explore how to identify functionally important loci and gauge how much variation they control, how to sift through the numerous genetic variants within an identified locus to find the variants responsible for species-specific phenotypes, and how to functionally test these sequences to reveal molecular mechanism and their impacts on development. We address these challenges in the context of comparative appendage skeletal development, genetics, and evolution in primates.
CHA2-5 5:30 pm Biomechanics as part of the evo-devo-morphology synthesis, and the challenges of including fossil taxa. Hutchinson John*, The Royal Veterinary College, Univ. London firstname.lastname@example.org |
Abstract: A relatively complete characterization of a major evolutionary transformation would integrate data from microscopic and macroscopic morphological levels across ontogeny (including genetic and environmental influences) with biomechanical analyses of function, performance and behaviour across phylogeny, and thence on to evaluations of potential links to fitness and thereby adaptation. This of course is no simple task, but here I explain, using examples from my team's research, how biomechanical data in particular can add value to the "evo-devo synthesis" by making function part of that synthesis, moving closer to inferences about natural selection and other evolutionary processes by demonstrating rather than assuming how form, function and behaviour are linked. A principal challenge in such a synthesis is to reconstruct how intermediate (or uniquely derived) morphologies in extinct taxa functioned. In this challenge, science needs to escape from constraints on identifying function, such as relying solely on studies of extant descendants of those major evolutionary transformations, crude analogues of ancestral form and function, or 'functional traits' (e.g. body mass, limb lengths) that may be correlated with actual function but often simply are reiterations of morphology. Computer modelling and simulation offer one solution to this challenge, but themselves recursively depend on studies of living animals to refine and test them in order to maximize confidence in their application to extinct taxa. However, I paint an optimistic picture of how these multi-pronged avenues of research could be advanced, by finding and exploiting synergy and common ground between them, to gradually build a more robust synthesis of the evolution of the morphological and developmental bases underlying the greatest transitions in organismal history. I focus on examples from our research on dinosaurs, early tetrapods and sesamoid bones but the concepts are transferrable to any clade of life.
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