The inXuence of stimulus direction and eccentricity on pro-and anti-saccades in humans

Abstract We examined the sensory and motor inXuences of stimulus eccentricity and direction on saccadic reaction times (SRTs), direction-of-movement errors, and saccade amplitude for stimulus-driven (prosaccade) and volitional (antisaccade) oculomotor responses in humans. Stimuli were presented at Wve eccentricities, ranging from 0.5° to 8°, and in eight radial directions around a central Wxation point. At 0.5° eccentricity, participants showed delayed SRT and increased direction-of-movement errors consistent with misidentiWcation of the target and Wxation points. For the remaining eccentricities, horizontal saccades had shorter mean SRT than vertical saccades. Stimuli in the upper visual Weld trigger overt shifts in gaze more easily and faster than in the lower visual Weld: prosaccades to the upper hemiWeld had shorter SRT than to the lower hemiWeld, and more anti-saccade direction-of-movement errors were made into the upper hemiWeld. With the exception of the 0.5° stimuli, SRT was independent of eccentricity. Saccade amplitude was dependent on target eccentricity for prosaccades, but not for antisaccades within the range we tested. Performance matched behavioral measures described previously for monkeys performing the same tasks, conWrming that the monkey is a good model for the human oculomotor function. We conclude that an upper hemiWeld bias lead to a decrease in SRT and an increase in direction errors

Consequences Matter : Compassion in Conservation Means Caring for Individuals, Populations and Species

Funding This research received no external funding. Acknowledgments The manuscript benefitted from significant input from Dan Brockington, J.B. Callicott, Peter Coals, Tim Hodgetts, David Macdonald and Jeremy Wilson. Conflicts of Interest The authors declare no conflict of interest.Peer reviewedPublisher PD

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Some aspects of the economics of territoriality in North American hummingbirds

Territoriality of post-breeding North American hummingbirds is one of the clearest examples of energy-based feeding territoriality, and has played an important role in the formulation and testing of theories on territoriality. This thesis follows two lines of inquiry. First, what special foraging strategies are used by hummingbirds holding energy-based feeding territories? Second, are energy-based models applicable to territoriality of breeding as well as non-breeding hummingbirds? I use a simulation model to examine the possible benefits for a non-breeding territorial hummingbird of avoiding recently visited locations while foraging. The simulation results suggest that while birds might benefit by avoiding flowers visited recently during a foraging bout, they would not benefit significantly by avoiding patches of flowers visited on previous bouts. An important benefit of short-term avoidance of flowers for model birds is that they can empty all or nearly all flowers in each patch visited. They therefore create coarse-grained patterns of nectar availability that are easy to exploit later on. Results of a field study on breeding territoriality of male Calliope Hummingbirds indicate that a solely energy-based model of territoriality cannot account for the behavior of these males. Throughout the 2 month breeding season, flower sampling indicated that males could have obtained energy faster by foraging on nearby undefended areas than by foraging on their territories. During June, flowers blooming on the territories were sparse and/or contained very little nectar, and males could not have obtained enough energy from them even to compensate for the cost of hovering while foraging. Consequently, they did virtually all their foraging away from their territories at that time. During May, when nectar availability on the territories was at its peak, males did not leave, expand, or shift their territories in response to experimental exclosure of all flowers blooming on them. I develop a model of optimal territory size for a promiscuously breeding male that defends a breeding territory containing no energy sources, as did the Calliope males during June at my study site. This model is analogous in design to existing models of energy-based feeding territoriality, but is based on the premise that a male's optimal territory size is that which maximizes his immediate reproductive success. A prediction of this model is that a male's territory size will be limited by the rate at which he can obtain energy while foraging away from his territory. An experiment performed on a Calliope male's territory did not support this prediction, and suggested that the size of his territory may have been limited only by his ability to detect intruders.Science, Faculty ofZoology, Department ofGraduat

Using reintroduction to compensate for isolation in fragmented landscapes

The rationale for most reintroductions is that: (1) habitat at the reintroduction site has been adequately restored through management or natural regeneration; and (2) natural colonisation is unlikely due to isolation from potential source populations. Therefore, reintroduction is usually preceded by restorative actions such as revegetation or control of exotic predators. However, where habitat has become fragmented, metapopulation theory suggests that absences of species from some sites could be due to isolation alone. That is, local extinctions may occur by chance in habitat fragments, and these are not recolonised if isolated. Therefore, in theory, reintroductions could be used to reverse declines of some species in fragmented landscapes without accompanying habitat restoration. We discuss the evidence necessary to assess whether this is a sensible strategy, noting that it will usually be impossible to obtain such evidence without doing the reintroductions. We then review three Australasian case studies where experimental reintroductions were done for this purpose. In all cases, isolation among fragments was found to be a significant barrier to dispersal, and reintroductions led to establishment and breeding in at least some fragments. However, these subpopulations ultimately declined to extinction. In the most extensive study, monitoring throughout the landscape revealed inter-fragment variation in adult survival that could account for fragments being unoccupied. This variation in habitat quality was subtle, because it was not associated with measures of vegetation structure or predator density. Metapopulation modelling suggested that improving connectivity (through reintroduction or corridors) would actually negatively impact the metapopulation by facilitating movement from source to sink fragments. Long-term research from the other case studies also suggested that absences from fragments followed declines due to habitat degradation, with isolation only being important in the final stages. Given the challenges involved in demonstrating that reintroduction to unrestored habitat fragments is a sensible strategy, we suggest that habitat restoration such as predator control should continue to be considered a necessary prerequisite for reintroduction in most circumstances

Big Decisions and Sparse Data: Adapting Scientific Publishing to the Needs of Practical Conservation

The biggest challenge in conservation biology is breaking down the gap between research and practical management. A major obstacle is the fact that many researchers are unwilling to tackle projects likely to produce sparse or messy data because the results would be difficult to publish in refereed journals. The obvious solution to sparse data is to build up results from multiple studies. Consequently, we suggest that there needs to be greater emphasis in conservation biology on publishing papers that can be built on by subsequent research rather than on papers that produce clear results individually. This building approach requires: (1) a stronger theoretical framework, in which researchers attempt to anticipate models that will be relevant in future studies and incorporate expected differences among studies into those models; (2) use of modern methods for model selection and multi-model inference, and publication of parameter estimates under a range of plausible models; (3) explicit incorporation of prior information into each case study; and (4) planning management treatments in an adaptive framework that considers treatments applied in other studies. We encourage journals to publish papers that promote this building approach rather than expecting papers to conform to traditional standards of rigor as stand-alone papers, and believe that this shift in publishing philosophy would better encourage researchers to tackle the most urgent conservation problems