http://hdl.handle.net/2262/102 Zoology (Scholarly Publications) Sun, 12 May 2013 21:16:15 GMT 2013-05-12T21:16:15Z 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 Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/2262/64936 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 Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/2262/64935 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 Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2262/64934 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 Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2262/64932 2011-01-01T00:00:00Z 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 Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2262/64932 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 Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/64929 2012-01-01T00:00:00Z 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 Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/64929 2012-01-01T00:00:00Z 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 Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/64929 2012-01-01T00:00:00Z 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 Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2262/64929 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 Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2262/64927 2011-01-01T00:00:00Z