John Gittleman - Academia.edu (original) (raw)

Papers by John Gittleman

Blackwell Science, LtdFlippers versus feet: comparative trends in aquatic and non-aquatic carnivores

Ecology letters, Sep 28, 2016

Identifying drivers of infectious disease patterns and impacts at the broadest scales of organisa... more Identifying drivers of infectious disease patterns and impacts at the broadest scales of organisation is one of the most crucial challenges for modern science, yet answers to many fundamental questions remain elusive. These include what factors commonly facilitate transmission of pathogens to novel host species, what drives variation in immune investment among host species, and more generally what drives global patterns of parasite diversity and distribution? Here we consider how the perspectives and tools of macroecology, a field that investigates patterns and processes at broad spatial, temporal and taxonomic scales, are expanding scientific understanding of global infectious disease ecology. In particular, emerging approaches are providing new insights about scaling properties across all living taxa, and new strategies for mapping pathogen biodiversity and infection risk. Ultimately, macroecology is establishing a framework to more accurately predict global patterns of infectious...

Evolution; international journal of organic evolution, 2015

Evolutionarily distinctive host lineages might harbor fewer parasite species because they have fe... more Evolutionarily distinctive host lineages might harbor fewer parasite species because they have fewer opportunities for parasite sharing than hosts having extant close relatives, or because diverse parasite assemblages promote host diversification. We evaluate these hypotheses using data from 930 species of parasites reported to infect free-living carnivores. We applied nonparametric richness estimators to estimate parasite diversity among well-sampled carnivore species and assessed how well host evolutionary distinctiveness, relative to other biological and environmental factors, explained variation in estimated parasite diversity. Species richness estimates indicate that the current published literature captures less than 50% of the true parasite diversity for most carnivores. Parasite species richness declined with evolutionary distinctiveness of carnivore hosts (i.e., length of terminal ranches of the phylogeny) and increased with host species body mass and geographic range area....

Journal of Animal Ecology, 2015

1. Host extinction can alter disease transmission dynamics, influence parasite extinction and ult... more 1. Host extinction can alter disease transmission dynamics, influence parasite extinction and ultimately change the nature of host-parasite systems. While theory predicts that single-host parasites are among the parasite species most susceptible to extinction following declines in their hosts, documented parasite extinctions are rare. 2. Using a comparative approach, we investigate how the richness of single-host and multihost parasites is influenced by extinction risk among ungulate and carnivore hosts. Host-parasite associations for free-living carnivores (order Carnivora) and terrestrial ungulates (orders Perissodactyla + Cetartiodactyla minus cetaceans) were merged with host trait data and IUCN Red List status to explore the distribution of single-host and multi-host parasites among threatened and non-threatened hosts. 3. We find that threatened ungulates harbour a higher proportion of single-host parasites compared to non-threatened ungulates, which is explained by decreases in the richness of multi-host parasites. However, among carnivores threat status is not a significant predictor of the proportion of single-host parasites, or the richness of single-host or multi-host parasites. 4. The loss of multi-host parasites from threatened ungulates may be explained by decreased cross-species contact as hosts decline and habitats become fragmented. Among carnivores, threat status may not be important in predicting patterns of parasite specificity because host decline results in equal losses of both single-host parasites and multi-host parasites through reduction in average population density and frequency of cross-species contact. 5. Our results contrast with current models of parasite coextinction and highlight the need for updated theories that are applicable across host groups and account for both inter-and intraspecific contact.

Science, 2000

The hierarchical nature of phylogenies means that random extinction of species affects a smaller ... more The hierarchical nature of phylogenies means that random extinction of species affects a smaller fraction of higher taxa, and so the total amount of evolutionary history lost may be comparatively slight. However, current extinction risk is not phylogenetically random. We show the potentially severe implications of the clumped nature of threat for the loss of biodiversity. An additional 120 avian and mammalian genera are at risk compared with the number predicted under random extinction. We estimate that the prospective extra loss of mammalian evolutionary history alone would be equivalent to losing a monotypic phylum.

Science, 2010

How Mammals Grew in Size Mammals diversified greatly after the end-Cretaceous extinction, which e... more How Mammals Grew in Size Mammals diversified greatly after the end-Cretaceous extinction, which eliminated the dominant land animals (dinosaurs). Smith et al. (p. 1216 ) examined how the maximum size of mammals increased during their radiation in each continent. Overall, mammal size increased rapidly, then leveled off after about 25 million years. This pattern holds true on most of the continents—even though data are sparse for South America—and implies that mammals grew to fill available niches before other environmental and biological limits took hold.

Proceedings of the Royal Society of London. Series B: Biological Sciences, 1998

We use complete species-level phylogenies of extant Carnivora and Primates to perform the ¢rst th... more We use complete species-level phylogenies of extant Carnivora and Primates to perform the ¢rst thorough phylogenetic tests, in mammals, of the hypothesis that small body size is associated with species-richness. Our overall results, based on comparisons between sister clades, indicate a weak tendency for lineages with smaller bodies to contain more species. The tendency is much stronger within caniform carnivores (canids, procyonids, pinnipeds, ursids and mustelids), perhaps relating to the dietary £exibility and hence lower extinction rates in small, meat-eating species. We ¢nd signi¢cant heterogeneity in the size^diversity relationship within and among carnivore families. There is no signi¢cant association between body mass and species-richness in primates or feliform carnivores. Although body size is implicated as a correlate of species-richness in mammals, much of the variation in diversity cannot be attributed to size di¡erences.

Molecular Ecology, 2000

Kinkajou social groups generally consist of one adult female, two males, one subadult and one juv... more Kinkajou social groups generally consist of one adult female, two males, one subadult and one juvenile. Based on analysis of variation in 11 microsatellite loci, we assess the degree of kinship within and between four social groups totaling 25 kinkajous. We use exclusion and likelihood analyses to assign parents for seven of the eight offspring sampled, five with ≥ 95% certainty, and two with ≥ 80% certainty. Five of six identified sires of group offspring came from the same social group as the mother and pup. Adult males and females within a group were unrelated and subadults and juveniles were offspring of the group adults, suggesting a family structure. All five identified paternities within a social group were by the dominant male of the group. However, this copulation asymmetry does not necessarily reflect cooperation due to kinship ties between the two adult males within a group as one of two adult male pairs sampled was unrelated. Neighbouring male kinkajous were more closely...

Organochlorine residues in maternal blubber, milk, and pup blubber from grey seals (Halichoerus g... more Organochlorine residues in maternal blubber, milk, and pup blubber from grey seals (Halichoerus grypus) from Sable Island, Nova Scotia. Journal of the Fisheries Research Board Canada 34: 937-941. Addison, R. F. & Brodie, P. F. (1987b). Transfer of organochlorine residues from blubber through the circulatory system to milk in the lactating grey seal Hali-choC/'us grypus.

The American naturalist, 2003

We investigated patterns and processes of extinction and threat in bats using a multivariate phyl... more We investigated patterns and processes of extinction and threat in bats using a multivariate phylogenetic comparative approach. Of nearly 1,000 species worldwide, 239 are considered threatened by the International Union for Conservation of Nature and Natural Resources (IUCN) and 12 are extinct. Small geographic ranges and low wing aspect ratios are independently found to predict extinction risk in bats, which explains 48% of the total variance in IUCN assessments of threat. The pattern and correlates of extinction risk in the two bat suborders are significantly different. A higher proportion (4%) of megachiropteran species have gone extinct in the last 500 years than microchiropteran bats (0.3%), and a higher proportion is currently at risk of extinction (Megachiroptera: 34%; Microchiroptera: 22%). While correlates of microchiropteran extinction risk are the same as in the order as a whole, megachiropteran extinction is correlated more with reproductive rate and less with wing morph...

PLoS biology, 2004

Understanding why some species are at high risk of extinction, while others remain relatively saf... more Understanding why some species are at high risk of extinction, while others remain relatively safe, is central to the development of a predictive conservation science. Recent studies have shown that a species' extinction risk may be determined by two types of factors: intrinsic biological traits and exposure to external anthropogenic threats. However, little is known about the relative and interacting effects of intrinsic and external variables on extinction risk. Using phylogenetic comparative methods, we show that extinction risk in the mammal order Carnivora is predicted more strongly by biology than exposure to high-density human populations. However, biology interacts with human population density to determine extinction risk: biological traits explain 80% of variation in risk for carnivore species with high levels of exposure to human populations, compared to 45% for carnivores generally. The results suggest that biology will become a more critical determinant of risk as ...

The American naturalist, 2005

We present the most extensive examination to date of proposed correlates of species richness. We ... more We present the most extensive examination to date of proposed correlates of species richness. We use rigorous phylogenetic comparative techniques, data for 1,692 mammal species in four clades, and multivariate statistics to test four hypotheses about species richness and compare the evidence for each. Overall, we find strong support for the life-history model of diversification. Species richness is significantly correlated with shorter gestation period in the carnivores and large litter size in marsupials. These traits and short interbirth intervals are also associated with species richness in a pooled analysis of all four clades. Additionally, we find some support for the abundance hypotheses in different clades of mammals: abundance correlates positively with species richness in primates but negatively in microchiropterans. Our analyses provide no evidence that mammalian species richness is associated with body size or degree of sexual dimorphism.

Proceedings of the National Academy of Sciences of the United States of America, 2006

Global conservation prioritization usually emphasizes areas with highest species richness or wher... more Global conservation prioritization usually emphasizes areas with highest species richness or where many species are thought to be at imminent risk of extinction. However, these strategies may overlook areas where many species have biological traits that make them particularly sensitive to future human impact but are not yet threatened because such impact is currently low. In this article, we identify such areas for the world's mammals using latent extinction risk, the discrepancy between a species' current extinction risk and that predicted from models on the basis of biological traits. Species with positive latent risk are currently less threatened than their biology would suggest, usually because they inhabit regions or habitats still comparatively unmodified by human activity. Using large new geographic, biological, and phylogenetic databases for nearly 4,000 mammal species, we map the global geographic distribution of latent risk to reveal areas where the mammal fauna ...

Proceedings. Biological sciences / The Royal Society, Jan 22, 2008

Extinction risk varies among species, and comparative analyses can help clarify the causes of thi... more Extinction risk varies among species, and comparative analyses can help clarify the causes of this variation. Here we present a phylogenetic comparative analysis of species-level extinction risk across nearly the whole of the class Mammalia. Our aims were to examine systematically the degree to which general predictors of extinction risk can be identified, and to investigate the relative importance of different types of predictors (life history, ecological, human impact and environmental) in determining extinction risk. A single global model explained 27.3% of variation in mammal extinction risk, but explanatory power was lower for region-specific models (median R2=0.248) and usually higher for taxon-specific models (median R2=0.383). Geographical range size, human population density and latitude were the most consistently significant predictors of extinction risk, but otherwise there was little evidence for general, prescriptive indicators of high extinction risk across mammals. Ou...

Proceedings. Biological sciences / The Royal Society, Jan 7, 2008

Assemblage-level phylogenies carry the signature of ecological and evolutionary processes, which ... more Assemblage-level phylogenies carry the signature of ecological and evolutionary processes, which may provide useful information on modes of assemblage formation. We present a global-scale analysis of the emergent phylogenetic properties of mammal assemblages on islands, in which we compared the structure of 595 island assemblages with null models constructed under four alternative definitions of regional source pools. Although most assemblages had a structure indistinguishable from random samples, for some mammal taxa, up to 40% of island assemblages were phylogenetically overdispersed. This suggests that in at least some cases, the processes that shape island faunas are not independent of phylogeny. Furthermore, measures of phylogenetic structure were associated in some cases with island geographical features (size, maximum elevation and habitat diversity). Our results suggest that part of the signal of assemblage formation processes is detectable in the phylogenies of contemporary...

Proceedings of the National Academy of Sciences of the United States of America, Jan 12, 2008

Phylogenies describe the origins and history of species. However, they can also help to predict s... more Phylogenies describe the origins and history of species. However, they can also help to predict species' fates and so can be useful tools for managing the future of biodiversity. This article starts by sketching how phylogenetic, geographic, and trait information can be combined to elucidate present mammalian diversity patterns and how they arose. Recent diversification rates and standing diversity show different geographic patterns, indicating that cradles of diversity have moved over time. Patterns in extinction risk reflect both biological differences among mammalian lineages and differences in threat intensity among regions. Phylogenetic comparative analyses indicate that for small-bodied mammals, extinction risk is governed mostly by where the species live and the intensity of the threats, whereas for large-bodied mammals, ecological differences also play an important role. This modeling approach identifies species whose intrinsic biology renders them particularly vulnerab...

Journal of Evolutionary Biology, 2003

Journal of Animal Ecology, 2001

1. It is commonly accepted that many adaptations characterize carnivores that live in water. Howe... more 1. It is commonly accepted that many adaptations characterize carnivores that live in water. However, no comparative tests have ever shown systematic differences between aquatic and terrestrial carnivore species as a whole. We examine numerous hypotheses that purport to distinguish aquatic and terrestrial carnivores using 20 morphological, life history, physiological and ecological traits. 2. Using the method of independent contrasts with a complete species-level phylogeny of extant carnivores, we found few differences between aquatic and terrestrial species. Compared to terrestrial sister taxa, aquatic carnivores are streamlined (increased head and body length for a given body weight), have larger brains, smaller litter sizes, shorter interbirth intervals, and shorter lifespans. 3. Some of these differences are important functionally. Larger brain size may be related to increased cognitive and sensory needs required for an amphibious lifestyle; smaller litters are likely associated with increased neonatal survival amidst competition for suitable breeding sites and advantages accruing to increased precociality. 4. We conclude that broad differentiation of carnivores into aquatic and terrestrial ecotypes is not useful given that adaptive differences between these groups are limited and seemingly no more numerous than those that occur within each ecological group.

Global Ecology and Biogeography, 2004

ABSTRACTAim To examine which aspects of primates and carnivore biology can be used to predict at... more ABSTRACTAim To examine which aspects of primates and carnivore biology can be used to predict attributes of species yet to be discovered.Location Global.Methods Multiple regressions of phylogenetically independent contrasts and non‐phylogenetic species date of description, on multiple biological predictor variables, formed from previous hypotheses tested in the literature.Results Orders differ, but both carnivore and primate species with a large geographical range tend to have been discovered earlier. When geographical range is controlled for, body mass is also significantly correlated with description date in carnivores, but remains a poor predictor in primates. No multiple‐predictor model is apparent in the primates, but diurnal species are on average more likely to be described first. Carnivores not endemic to the tropics are more likely to be discovered earlier, reflecting a northern bias in description patterns.Main conclusions Geographical range is by far the most importa...

Global Ecology and Biogeography, 2007

ABSTRACTAim Comparative studies have revealed strong links between ecological factors and the nu... more ABSTRACTAim Comparative studies have revealed strong links between ecological factors and the number of parasite species harboured by different hosts, but studies of different taxonomic host groups have produced inconsistent results. As a step towards understanding the general patterns of parasite species richness, we present results from a new comprehensive data base of over 7000 host–parasite combinations representing 146 species of carnivores (Mammalia: Carnivora) and 980 species of parasites.Methods We used both phylogenetic and non‐phylogenetic comparative methods while controlling for unequal sampling effort within a multivariate framework to ascertain the main determinants of parasite species richness in carnivores.Results We found that body mass, population density, geographical range size and distance from the equator are correlated with overall parasite species richness in fissiped carnivores. When parasites are classified by transmission mode, body mass and home range ...