Person: de Bivort, Benjamin
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de Bivort
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Benjamin
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de Bivort, Benjamin
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Publication Ethology as a physical science(Springer Science and Business Media LLC, 2018-04-09) Brown, André EX; de Bivort, BenjaminBehaviour is the ultimate output of an animal’s nervous system and choosing the right action at the right time can be critical for survival. The study of the organisation of behaviour in its natural context, ethology, has historically been a primarily qualitative science. A quantitative theory of behaviour would advance research in neuroscience as well as ecology and evolution. However, animal posture typically has many degrees of freedom and behavioural dynamics vary on timescales ranging from milliseconds to years, presenting both technical and conceptual challenges. Here we review 1) advances in imaging and computer vision that are making it possible to capture increasingly complete records of animal motion and 2) new approaches to understanding the resulting behavioural data sets. With the right analytical approaches, these data are allowing researchers to revisit longstanding questions about the structure and organisation of animal behaviour and to put unifying principles on a quantitative footing. Contributions from both experimentalists and theorists are leading to the emergence of a physics of behaviour and the prospect of discovering laws and developing theories with broad applicability. We believe that there now exists an opportunity to develop theories of behaviour which can be tested using these data sets leading to a deeper understanding of how and why animals behave.Publication Leg-tracking and automated behavioural classification in Drosophila(Nature Pub. Group, 2013) Kain, Jamey; Stokes, Chris; Gaudry, Quentin; Song, Xiangzhi; Foley, James; Wilson, Rachel; de Bivort, BenjaminMuch remains unknown about how the nervous system of an animal generates behaviour, and even less is known about the evolution of behaviour. How does evolution alter existing behaviours or invent novel ones? Progress in computational techniques and equipment will allow these broad, complex questions to be explored in great detail. Here we present a method for tracking each leg of a fruit fly behaving spontaneously upon a trackball, in real time. Legs were tracked with infrared-fluorescent dyes invisible to the fly, and compatible with two-photon microscopy and controlled visual stimuli. We developed machine-learning classifiers to identify instances of numerous behavioural features (for example, walking, turning and grooming), thus producing the highest-resolution ethological profiles for individual flies.Publication Asymmetric neurotransmitter release enables rapid odor lateralization in Drosophila(2012) Gaudry, Quentin; Hong, Elizabeth J.; Kain, Jamey; de Bivort, Benjamin; Wilson, RachelIn Drosophila, most individual olfactory receptor neurons (ORNs) project bilaterally to both sides of the brain1,2. Having bilateral rather than unilateral projections may represent a useful redundancy. However, bilateral ORN projections to the brain should also compromise the ability to lateralize odors. Nevertheless, walking or flying Drosophila reportedly turn toward their more strongly stimulated antenna3-5. Here we show that each ORN spike releases ~40% more neurotransmitter from the axon branch ipsilateral to the soma, as compared to the contralateral branch. As a result, when an odor activates the antennae asymmetrically, ipsilateral central neurons begin to spike a few milliseconds before contralateral neurons, and ipsilateral central neurons also fire at a 30-50% higher rate. We show that a walking fly can detect a 5% asymmetry in total ORN input to its left and right antennal lobes, and can turn toward the odor in less time than it requires the fly to complete a stride. These results demonstrate that neurotransmitter release properties can be tuned independently at output synapses formed by a single axon onto two target cells with identical functions and morphologies. Our data also show that small differences in spike timing and spike rate can produce reliable differences in olfactory behavior.Publication Evolutionary and Biogeographical History of an Ancient and Global Group of Arachnids (Arachnida: Opiliones: Cyphophthalmi) with a New Taxonomic Arrangement(Wiley-Blackwell, 2011) Giribet, Gonzalo; Sharma, Prashant Pradeep; Benavides, Ligia R.; Boyer, Sarah L.; Clouse, Ronald M.; de Bivort, Benjamin; Dimitrov, Dimitar; Kawauchi, Gisele Y.; Murienne, Jerome; Schwendinger, Peter J.We investigate the phylogeny, biogeography, time of origin and diversification, ancestral area reconstruction and large-scale distributional patterns of an ancient group of arachnids, the harvestman suborder Cyphophthalmi. Analysis of molecular and morphological data allow us to propose a new classification system for the group; Pettalidae constitutes the infraorder Scopulophthalmi new clade, sister group to all other families, which are divided into the infraorders Sternophthalmi new clade and Boreophthalmi new clade. Sternophthalmi includes the families Troglosironidae, Ogoveidae, and Neogoveidae; Boreophthalmi includes Stylocellidae and Sironidae, the latter family of questionable monophyly. The internal resolution of each family is discussed and traced back to its geological time origin, as well as to its original landmass, using methods for estimating divergence times and ancestral area reconstruction. The origin of Cyphophthalmi can be traced back to the Carboniferous, whereas the diversification time of most families ranges between the Carboniferous and the Jurassic, with the exception of Troglosironidae, whose current diversity originates in the Cretaceous/Tertiary. Ancestral area reconstruction is ambiguous in most cases. Sternophthalmi is traced back to an ancestral land mass that contained New Caledonia and West Africa in the Permian, whereas the ancestral landmass for Neogoveidae included the south-eastern USA and West Africa, dating back to the Triassic. For Pettalidae, most results include South Africa, or a combination of South Africa with the Australian plate of New Zealand or Sri Lanka, as the most likely ancestral landmass, back in the Jurassic. Stylocellidae is reconstructed to the Thai-Malay Penisula during the Jurassic. Combination of the molecular and morphological data results in a hypothesis for all the cyphophthalmid genera, although the limited data available for some taxa represented only in the morphological partition negatively affects the phylogenetic reconstruction by decreasing nodal support in most clades. However, it resolves the position of many monotypic genera not available for molecular analysis, such as Iberosiro, Odontosiro, Speleosiro, Managotria or Marwe, although it does not place Shearogovea or Ankaratra within any existing family. The biogeographical data show a strong correlation between relatedness and formerly adjacent landmasses, and oceanic dispersal does not need to be postulated to explain disjunct distributions, especially when considering the time of divergence. The data also allow testing of the hypotheses of the supposed total submersion of New Zealand and New Caledonia, clearly falsifying submersion of the former, although the data cannot reject the latter.Publication A Systematic Revision of the South African Pettalidae (Arachnida : Opiliones : Cyphophthalmi) Based on a Combined Analysis of Discrete and Continuous Morphological Characters with the Description of Seven New Species(CSIRO Publishing, 2010) de Bivort, Benjamin; Giribet, GonzaloThe cyphophthalmid family Pettalidae in South Africa is revised and seven new species are described from museum material collected between 1939 and 1985. Two of these are placed in the genus Purcellia and five in Parapurcellia, bringing the total number of described South African cyphophthalmids to 15. In addition, Purcellia peregrinator is transferred to the genus Parapurcellia. Phylogenetic analyses of discrete morphological and continuous morphometric characters, both separately and in combination, support the generic assignments and contribute towards a more detailed understanding of the systematics of the group in South Africa. In order to assess the stability of our phylogenetic results, the different morphological datasets were analysed under equal and implied weighting, as well as under several weighting schemes that varied the respective contribution to tree length of the discrete and continuous data partitions. These variations generated two phylogenetic hypotheses: (1) monophyly of the South African pettalids + Austropurcellia from north-eastern Australia as a derived clade within Pettalidae; and (2) polyphyly of the South African pettalids with Parapurcellia basal within Pettalidae. The latter hypothesis is congruent with previous molecular phylogenies of Cyphophthalmi, and has moderate bootstrap support. The sisterhood of Purcellia griswoldi, sp. nov. and P. lawrencei, sp. nov. receives high nodal support across analytic methods. New combination: Parapurcellia peregrinator (Lawrence, 1963).Publication A Morphometrics-Based Phylogeny of the Temperate Gondwanan Mite Harvestmen (Opiliones, Cyphophthalmi, Pettalidae)(Wiley-Blackwell, 2010) de Bivort, Benjamin; Clouse, Ronald M.; Giribet, GonzaloA phylogenetic estimation of the temperate Gondwanan mite harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi) was conducted using 143 morphological variables (59 raw and 84 scaled measurements) from 37 ingroup and 15 outgroup terminals. We used custom algorithms to do pairwise comparisons between characters and identify sets of dependent characters, which were collapsed using principal components analysis. We analysed the resulting data without discretization under the parsimony criterion. Monophyly or paraphyly of most groups suspected from previous molecular and morphological phylogenetic studies were recovered. Trees were optimized for monophyly of 20 different focus clades by varying character phylogenetic independence. This yielded a final tree with monophyly of 15 out of 20 focus clades, including the South African pettalids, which contains the troglomorphic species Speleosiro argasiformis Lawrence, 1931. Two of the remaining five clades were found paraphyletic, with the genera Aoraki, Rakaia, and Siro always being found polyphyeletic.Publication Phylogenetic Signal in Morphometric Data(Wiley-Blackwell, 2011) Clouse, Ronald M.; de Bivort, Benjamin; Giribet, GonzaloPublication Variability in thermal and phototactic preferences in Drosophila may reflect an adaptive bet‐hedging strategy(John Wiley and Sons Inc., 2015) Kain, Jamey S.; Zhang, Sarah; Akhund‐Zade, Jamilla; Samuel, Aravi; Klein, Mason; de Bivort, BenjaminOrganisms use various strategies to cope with fluctuating environmental conditions. In diversified bet‐hedging, a single genotype exhibits phenotypic heterogeneity with the expectation that some individuals will survive transient selective pressures. To date, empirical evidence for bet‐hedging is scarce. Here, we observe that individual Drosophila melanogaster flies exhibit striking variation in light‐ and temperature‐preference behaviors. With a modeling approach that combines real world weather and climate data to simulate temperature preference‐dependent survival and reproduction, we find that a bet‐hedging strategy may underlie the observed interindividual behavioral diversity. Specifically, bet‐hedging outcompetes strategies in which individual thermal preferences are heritable. Animals employing bet‐hedging refrain from adapting to the coolness of spring with increased warm‐seeking that inevitably becomes counterproductive in the hot summer. This strategy is particularly valuable when mean seasonal temperatures are typical, or when there is considerable fluctuation in temperature within the season. The model predicts, and we experimentally verify, that the behaviors of individual flies are not heritable. Finally, we model the effects of historical weather data, climate change, and geographic seasonal variation on the optimal strategies underlying behavioral variation between individuals, characterizing the regimes in which bet‐hedging is advantageous.Publication Bet-hedging, seasons and the evolution of behavioral diversity in Drosophila(2015) Kain, Jamey; Zhang, Sarah; Klein, Mason; Samuel, Aravi; de Bivort, BenjaminOrganisms use various strategies to cope with fluctuating environmental conditions. In diversified bet-hedging, a single genotype exhibits phenotypic heterogeneity with the expectation that some individuals will survive transient selective pressures. To date, empirical evidence for bet-hedging is scarce. Here, we observe that individual Drosophila melanogaster flies exhibit striking variation in light- and temperature-preference behaviors. With a modeling approach that combines real world weather and climate data to simulate temperature preference-dependent survival and reproduction, we find that a bet-hedging strategy may underlie the observed inter-individual behavioral diversity. Specifically, bet-hedging outcompetes strategies in which individual thermal preferences are heritable. Animals employing bet-hedging refrain from adapting to the coolness of spring with increased warm seeking that inevitably becomes counterproductive in the hot summer. This strategy is particularly valuable when mean seasonal temperatures are typical, or when there is considerable fluctuation in temperature within the season. The model predicts, and we experimentally verify, that the behaviors of individual flies are not heritable. Finally, we model the effects of historical weather data, climate change, and geographic seasonal variation on the optimal strategies underlying behavioral variation between individuals, characterizing the regimes in which bet-hedging is advantageous.Publication Sensorimotor structure of Drosophila larva phototaxis(Proceedings of the National Academy of Sciences, 2013) Kane, E. A.; Gershow, Marc; Afonso, Bruno; Larderet, I.; Klein, Mason; Carter, A. R.; de Bivort, Benjamin; Sprecher, S. G.; Samuel, AraviThe avoidance of light by fly larvae is a classic paradigm for sensorimotor behavior. Here, we use behavioral assays and video microscopy to quantify the sensorimotor structure of phototaxis using the Drosophila larva. Larval locomotion is composed of sequences of runs (periods of forward movement) that are interrupted by abrupt turns, during which the larva pauses and sweeps its head back and forth, probing local light information to determine the direction of the successive run. All phototactic responses are mediated by the same set of sensorimotor transformations that require temporal processing of sensory inputs. Through functional imaging and genetic inactivation of specific neurons downstream of the sensory periphery, we have begun to map these sensorimotor circuits into the larval central brain. We find that specific sensorimotor pathways that govern distinct light-evoked responses begin to segregate at the first relay after the photosensory neurons.