http://hdl.handle.net/2262/12 Zoology 2013-06-18T22:44:01Z http://hdl.handle.net/2262/64936 Title: A common tendency for phylogenetic overdispersion in mammalian assemblages Author: COOPER, NATALIE; RODRIGUEZ, JESUS; PURVIS, ANDY Abstract: Competition has long been proposed as an important force in structuring mammalian communities. Although early work recognised that competition has a phylogenetic dimension, only with recent increases in the availability of phylogenies have true phylogenetic investigations of mammalian community structure become possible. We test whether the phylogenetic structure of 142 assemblages from three mammalian clades (New World monkeys, North American ground squirrels and Australasian possums) shows the imprint of competition. The full set of assemblages display a highly significant tendency for members to be more distantly-related than expected by chance (phylogenetic overdispersion). The overdispersion is also significant within two of the clades (monkeys and squirrels) separately. This is the first demonstration of widespread overdispersion in mammal assemblages and implies an important role for either competition between close relatives where traits are conserved, habitat filtering where distant relatives share convergent traits, or both. Description: PUBLISHED 2008-01-01T00:00:00Z http://hdl.handle.net/2262/64935 Title: Macroecology and extinction risk correlates of frogs Author: COOPER, NATALIE; BIELBY, JON; THOMAS, GAVIN H; PURVIS, ANDY Abstract: Aim Our aim was to test whether extinction risk in frogs could be predicted from their body size, fecundity or geographic range size. Because small geographic range size is a correlate of extinction risk in many taxa, we also tested hypotheses about correlates of range size in frogs. Methods Using a large comparative dataset (n = 527 species) compiled from the literature we performed bivariate and multiple regressions through the origin of independent contrasts, to test proposed macroecological patterns and correlates of extinction risk in frogs. We also created minimum adequate models to predict snout-vent length, clutch size, geographic range size and IUCN Red List status in frogs. Parallel non-phylogenetic analyses were also conducted. We verified the results of the phylogenetic analyses using gridded data accounting for spatial autocorrelation. Results The most threatened frogs tend to have small geographic ranges although the relationship between range and extinction risk is not linear. In addition, tropical frogs with small clutches have the smallest ranges. Clutch size was strongly positively correlated with geographic range size (r2 = 0.22) and body size (r2 = 0.28). Main conclusions Our results suggest that body size and fecundity only affect extinction risk indirectly through their effect on geographic range size. Thus, although large frogs with small clutches tend to be endangered, there is no comparative evidence that this relationship is direct. If correct, this inference has consequences for conservation strategy: it would be inefficient to allocate conservation resources on the basis of low fecundity or large body size; instead it would be better to protect areas which contain many, small geographic range frog species. Description: PUBLISHED 2008-01-01T00:00:00Z http://hdl.handle.net/2262/64934 Title: Body size evolution in mammals: complexity in tempo and mode Author: COOPER, NATALIE; PURVIS, ANDY Abstract: Body size correlates with virtually every aspect of species’ biology, so understanding the tempo and mode of its evolution is of key importance in macroecology and macroevolution. Here we use body-mass data from 3473 of 4510 extant mammalian species and an almost complete species-level phylogeny to determine the best model of log(body-mass) evolution across all mammals, split taxonomically and spatially. An early-burst model fits better across all mammals than models based on either Brownian motion or an Ornstein-Uhlenbeck process, suggesting that mammals experienced a burst of morphological evolution relatively early in their history followed by slower change subsequently. We also use spatial models to investigate rates of body-mass evolution within ecoregions. These models show that around 50% of the variation in rate can be explained by just a few predictors. High estimated rates are associated with cold, low lying, species-poor, high energy, mainland ecoregions. We conclude that the evolution of mammalian body size has been influenced by a complex interplay among geography, climate and history. Description: PUBLISHED 2010-01-01T00:00:00Z http://hdl.handle.net/2262/64932 Title: Specialization and the road to academic success Author: COOPER, NATALIE; BELMAKER, JONATHAN; LEE, TIEN MING; WILMAN, HAMISH Abstract: The relative merits of focusing research on few areas of science versus generalizing across topics have important implications for how academics conduct science. Little is known, however, about how research breadth and academic success are related. Drawing on data from more than 4000 ecologists and evolutionary biologists worldwide, we show that highest academic success is achieved at intermediate levels of research breadth. This suggests that being a "jack of all trades" or an overly narrow specialist could both be detrimental to long term academic success. Description: PUBLISHED 2011-01-01T00:00:00Z http://hdl.handle.net/2262/64929 Title: Host longevity and parasite species richness in mammals. Author: COOPER, NATALIE; KAMILAR, JASON M; NUNN, CHARLES L Abstract: Hosts and parasites co-evolve, with each lineage exerting selective pressures on the other. Thus, parasites may influence host life-history characteristics, such as longevity, and simultaneously host life-history may influence parasite diversity. If parasite burden causes increased mortality, we expect a negative association between host longevity and parasite species richness. Alternatively, if long-lived species represent a more stable environment for parasite establishment, host longevity and parasite species richness may show a positive association. We tested these two opposing predictions in carnivores, primates and terrestrial ungulates using phylogenetic comparative methods and controlling for the potentially confounding effects of sampling effort and body mass. We also tested whether increased host longevity is associated with increased immunity, using white blood cell counts as a proxy for immune investment. Our analyses revealed weak relationships between parasite species richness and longevity. We found a significant negative relationship between longevity and parasite species richness for ungulates, but no significant associations in carnivores or primates. We also found no evidence for a relationship between immune investment and host longevity in any of our three groups. Our results suggest that greater parasite burden is linked to higher host mortality in ungulates. Thus, shorter-lived ungulates may be more vulnerable to disease outbreaks, which has implications for ungulate conservation, and may be applicable to other short-lived mammals. Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/64927 Title: Phylogenetic conservatism of environmental niches in mammals Author: COOPER, NATALIE Abstract: Phylogenetic niche conservatism is the pattern where close relatives occupy similar niches, whereas distant relatives are more dissimilar. We suggest that niche conservatism will vary across clades in relation to their characteristics. Specifically, we investigate how conservatism of environmental niches varies among mammals according to their latitude, range size, body size and specialization. We use the Brownian rate parameter, s2, to measure the rate of evolution in key variables related to the ecological niche and define the more conserved group as the one with the slower rate of evolution. We find that tropical, small-ranged and specialized mammals have more conserved thermal niches than temperate, large-ranged or generalized mammals. Partitioning niche conservatism into its spatial and phylogenetic components, we find that spatial effects on niche variables are generally greater than phylogenetic effects. This suggests that recent evolution and dispersal have more influence on species’ niches than more distant evolutionary events. These results have implications for our understanding of the role of niche conservatism in species richness patterns and for gauging the potential for species to adapt to global change. Description: PUBLISHED 2011-01-01T00:00:00Z http://hdl.handle.net/2262/64204 Title: Cooperation and the evolution of intelligence Author: MCNALLY, Luke; BROWN, SAM P; JACKSON, ANDREW LLOYD Abstract: The high levels of intelligence seen in humans, other primates, certain cetaceans and birds remain a major puzzle for evolutionary biologists, anthropologists and psychologists. It has long been held that social interactions provide the selection pressures necessary for the evolution of advanced cognitive abilities (the ‘social intelligence hypothesis’), and in recent years decision-making in the context of cooperative social interactions has been conjectured to be of particular importance. Here we use an artificial neural network model to show that selection for efficient decision-making in cooperative dilemmas can give rise to selection pressures for greater cognitive abilities, and that intelligent strategies can themselves select for greater intelligence, leading to a Machiavellian arms race. Our results provide mechanistic support for the social intelligence hypothesis, highlight the potential importance of cooperative behaviour in the evolution of intelligence and may help us to explain the distribution of cooperation with intelligence across taxa. Description: PUBLISHED 2012-01-01T00:00:00Z http://hdl.handle.net/2262/64103 Title: Validation and use of a parametric model for projecting cystic fibrosis survivorship beyond observed data: a birth cohort analysis Author: JACKSON, Abaigeal; Daly, Leslie; Jackson, Andrew; Marshall, Bruce; Quinton, Hebe; Fletcher, Godfrey; Harrington, Mary; Zhou, Shijun; McKone, Edward; Gallagher, Charles; Foley, Linda; Fitzpatrick, Patricia; Kelleher, Cecily Abstract: Background: The current lifetable approach to survival estimation is favoured by CF registries. Recognising the limitation of this approach, we examined the utility of a parametric survival model to project birth cohort survival estimates beyond the follow-up period, where short duration of follow-up meant median survival estimates were indeterminable. Methods: Parametric models were fitted to observed survivorship data from the US CF Foundation (CFF) Patient Registry 1980–1994 birth cohort. Model-predicted median survival was estimated. The best fitting model was applied to a Cystic Fibrosis Registry of Ireland dataset to allow an evaluation of the model's ability to estimate predicted median survival. This involved a comparison of birth cohort lifetable predicted and observed (Kaplan–Meier) median survival estimates. Results: A Weibull model with main effects of gender and birth cohort was developed using a US CFF dataset (n=13 115) for which median survival was not directly estimable. Birth cohort lifetable predicted median survival for male and female patients born between 1985 and 1994 and surviving their first birthday was 50.9 and 42.4 years respectively. To evaluate the accuracy of a Weibull model in predicting median survival, a model was developed for the 1980–1984 Cystic Fibrosis Registry of Ireland birth cohort (n=243), which had an observed (Kaplan–Meier) median survival of 27.7 years. Model-predicted median survival estimates were calculated using data censored at different follow-up periods. The estimates converged to the true value as length of follow-up increased. Conclusions: Accurate prognostic information that is clinically critical for care of patients affected by rare, life-limiting disorders can be provided by parametric survival models. Problems associated with short duration of follow-up for recent birth cohorts can be overcome using this approach, providing better opportunities to monitor survival and plan services locally. Description: PUBLISHED 2011-07-21T23:00:00Z http://hdl.handle.net/2262/61969 Title: The role of Intelectin-2 in resistance to Ascaris suum lung larval burdens in susceptible and resistant mouse strains Author: STAFFORD, PETER; HOLLAND, CELIA Abstract: The underlying mechanism of predisposition to Ascaris infection is not yet understood but host genetics are thought to play a fundamental role. We investigated the association between the Intelectin-2 gene and resistance in F2 mice derived from mouse strains known to be susceptible and resistant to infection. Ascaris larvae were isolated from murine lungs and the number of copies of the Intelectin-2 gene was determined in F2 mice. Intelectin-2 gene copy number was not significantly linked to larval burden. In a pilot experiment, the response to infection in parental mice of both sexes was observed in order to address the suitablity of female F2 mice. No overall significant sex effect was detected. However, a divergence in resistance/susceptibility status was observed between male and, female hybrid offspring. The responsiveness to Ascaris in mice is likely to be controlled by multiple genes and, despite a unique absence from the susceptible C57BL/6j strain, the Intelectin-2 gene does not play a significant role in resistance. The observed intra-strain variation in larval burden requires further investigation but we hypothesize that it stems from social/dominance hierarchies created by the presence of female mice and possibly subsequent hormonal perturbations that modify the intensity of the immune response. Description: PUBLISHED 2011-01-01T00:00:00Z http://hdl.handle.net/2262/61579 Title: The effects of season, habitat, hydroperiod and water chemistry on the distribution of turlough aquatic invertebrate communities Author: PORST, GWENDOLIN Abstract: The aim of this study was to investigate the effects of season, habitat, hydroperiod and water chemistry on the distribution of turlough aquatic invertebrate communities. Twenty-two turloughs, selected as representative of geographical distribution and hydrological conditions were included in the study. A comparative study of eight turloughs representing a nutrient gradient determined macroinvertebrate community distinctiveness in a stratified sampling design and related assemblage structures to environmental variables. Assessment of macroinvertebrate temporal and spatial variation was the objective of separate studies conducted in a subset of four turloughs, varying in hydrological and nutrient regimes. The influence of disturbance and habitat characteristics on macroinvertebrate community dynamics was tested. Across twenty-two turloughs macroinvertebrate and cladoceran zooplankton communities were analysed and their relation to varying trophic, hydrological and morphological regimes identified. For a comparative study of macroinvertebrates eight turloughs were selected to represent a gradient of total phosphorus (TP) concentrations. To allow comparability of turlough macroinvertebrate communities, samples were collected from one habitat type (submerged grassland) in April 2007 using a simple box sampler. Five replicates were collected in every turlough by rapidly lowering the box to the substratum and removing trapped organisms with a net. Community analysis identified highly distinct macroinvertebrate assemblages, indicating that a single or pooled sample can provide a reliable description of turlough macroinvertebrate communities. Hydroperiod influenced mean taxon richness and abundance of macroinvertebrates but no correlation was found between nutrient status and either mean taxon richness or abundance. In order to study temporal dynamics of macroinvertebrates in turloughs, littoral faunal samples were collected over a one to two year period in four turloughs with differing hydrological and nutrient regimes. Sampling was carried out using a standardised sampling approach. Five replicate samples were collected every month using a box sampler from the dominant turlough habitat, submerged grassland. Macroinvertebrate biodiversity and community structure varied monthly and interannually. A two-phased hydrocycle was identified with permanent residents dominating during the start of the hydrocycle, with an increase of ephemeral taxa over time. Disturbance, as demonstrated by short hydroperiod and high areal reduction rate had an important effect on macroinvertebrate community structure in turloughs, with high disturbance generally supporting lower faunal diversity. Influence of disturbance generally decreased over time leading to a stabilization of macroinvertebrate communities. For the study of spatial variation of macroinvertebrates in turloughs two habitats were sampled in two turloughs during sampling season 2006/2007 using a box sampler and five replicates were collected in each habitat. Within-habitat variability was assessed by collecting five replicate macroinvertebrate samples from four different submerged grassland habitat sites in four turloughs in sampling season 2007/2008 using the box sampler. While habitat specific preferences were found for some taxa of conservation concern variability of macroinvertebrates within turloughs was nevertheless identified to be smaller than among turloughs. Macroinvertebrate samples collected in any location of the dominant turlough habitat (submerged grassland) were identified as reliable indicators of ecological change of turloughs. A comparative study of macroinvertebrates and cladoceran zooplankton communities was conducted across twenty-two turloughs, representing a wide hydromorphological and geographical range. Macroinvertebrate samples were collected in November 2006 and April 2007 using a stratified sampling approach. All available habitats in a turlough were sampled proportional to their availability using sweeps with a standard FBA pond net. Three minute sampling time was subdivided proportionally to each habitat’s availability. Cladoceran zooplankton and separate chydorid samples were collected from twenty turloughs in April 2007 by horizontal hauls with a zooplankton net from the shore and a perspex tube, respectively. Varying associations of macroinvertebrate as well as zooplankton communities to environmental variables season, TP concentrations, number of habitats sampled and hydroperiod of turloughs were detected. Some macroinvertebrate orders and zooplankton species showed significant relationships with chemical descriptors of nutrient enrichment. Turlough macroinvertebrate communities are highly distinct and conducive to time and cost-effective monitoring. Collection of a single submerged grassland sample reduces inherent ‘noise’ and is suited for the detection of pressure gradients. The number of habitats sampled should, however, depend on the objective of the sampling. Sampling for more holistic purposes should be carried out using a multi-habitat sampling approach to obtain a more comprehensive survey of turlough biodiversity. Season had an important influence on macroinvertebrate community structures. Turlough sampling regimes need a flexible approach with timing and frequency of sampling depending on sampling protocol objectives and should be geared towards the start of the flooding season and variable hydrocycles. Turloughs are inherently variable systems which might negate the development of simple type-specific reference conditions as required for lakes under the WFD. Description: PUBLISHED 2012-01-09T00:00:00Z