| 1. |
- Lindenfors, Patrik, et al.
(author)
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Parasite species richness in carnivores : effects of host body mass, latitude, geographic range and population density
- 2007
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In: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 16, s. 496-509
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Journal article (peer-reviewed)abstract
- Aim: 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 area are the main determinants of the richness of parasites spread by close contact between hosts, and population density, geographical range size and distance from the equator account for the diversity of parasites that are not dependent on close contact. For generalist parasites, population density, geographical range size and latitude are the primary predictors of parasite species richness. We found no significant ecological correlates for the richness of specialist or vector-borne parasites. Main conclusions: Although we found that parasite species richness increases instead of decreases with distance from the equator, other comparative patterns in carnivores support previous findings in primates, suggesting that similar ecological factors operate in both these independent evolutionary lineages.
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| 2. |
- Altizer, Sonia, et al.
(author)
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Do threatened hosts have fewer parasites? : A comparative study in primates
- 2007
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In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745 .- 0021-8790 .- 1365-2656. ; 76, s. 304-314
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Journal article (peer-reviewed)abstract
- 1. Parasites and infectious diseases have become a major concern in conservation biology, in part because they can trigger or accelerate species or population declines. Focusing on primates as a well-studied host clade, we tested whether the species richness and prevalence of parasites differed between threatened and non-threatened host species. 2. We collated data on 386 species of parasites (including viruses, bacteria, protozoa, helminths and arthropods) reported to infect wild populations of 36 threatened and 81 non-threatened primate species. Analyses controlled for uneven sampling effort and host phylogeny. 3. Results showed that total parasite species richness was lower among threatened primates, supporting the prediction that small, isolated host populations harbour fewer parasite species. This trend was consistent across three major parasite groups found in primates (helminths, protozoa and viruses). Counter to our predictions, patterns of parasite species richness were independent of parasite transmission mode and the degree of host specificity. 4. We also examined the prevalence of selected parasite genera among primate sister-taxa that differed in their ranked threat categories, but found no significant differences in prevalence between threatened and non-threatened hosts. 5. This study is the first to demonstrate differences in parasite richness relative to host threat status. Results indicate that human activities and host characteristics that increase the extinction risk of wild animal species may lead simultaneously to the loss of parasites. Lower average parasite richness in threatened host taxa also points to the need for a better understanding of the cascading effects of host biodiversity loss for affiliated parasite species.
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| 3. |
- Lindenfors, Patrik, 1964-, et al.
(author)
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Females drive primate social evolution
- 2004
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In: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 271, s. S101-S103
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Journal article (peer-reviewed)abstract
- Within and across species of primates, the number of males in primate groups is correlated with the number of females. This correlation may arise owing to ecological forces operating on females, with subsequent competition among males for access to groups of females. The temporal relationship between changes in male and female group membership remains unexplored in primates and other mammalian groups. We used a phylogenetic comparative method for detecting evolutionary lag to test whether evolutionary change in the number of males lags behind change in the number of females. We found that change in male membership in primate groups is positively correlated with divergence time in pairwise comparisons. This result is consistent with male numbers adjusting to female group size and highlights the importance of focusing on females when studying primate social evolution
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| 4. |
- Lindenfors, Patrik, et al.
(author)
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Primate brain architecture and selection in relation to sex
- 2007
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In: BMC Biology. - : Springer Science and Business Media LLC. - 1741-7007. ; 5:20
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Journal article (peer-reviewed)abstract
- Background: Social and competitive demands often differ between the sexes in mammals. These differing demands should be expected to produce variation in the relative sizes of various brain structures. Sexual selection on males can be predicted to influence brain components handling sensory-motor skills that are important for physical competition or neural pathways involving aggression. Conversely, because female fitness is more closely linked to ecological factors and social interactions that enable better acquisition of resources, social selection on females should select for brain components important for navigating social networks. Sexual and social selection acting on one sex could produce sexual dimorphism in brain structures, which would result in larger species averages for those same brain structures. Alternatively, sex-specific selection pressures could produce correlated effects in the other sex, resulting in larger brain structures for both males and females of a species. Data are presently unavailable for the sex-specific sizes of brain structures for anthropoid primates, but under either scenario, the effects of sexual and social selection should leave a detectable signal in average sizes of brain structures for different species. Results: The degree of male intra-sexual selection was positively correlated with several structures involved in autonomic functions and sensory-motor skills, and in pathways relating to aggression and aggression control. The degree of male intra-sexual selection was not correlated with relative neocortex size, which instead was significantly positively correlated with female social group size, but negatively correlated with male group size. Conclusion: Sexual selection on males and social selection on females have exerted different effects on primate brain architecture. Species with a higher degree of male intra-sexual selection carry a neural signature of an evolutionary history centered on physical conflicts, but no traces of increased demands on sociocognitive tasks. Conversely, female sociality is indicated to have driven the evolution of socio-cognitive skills. Primate brain architecture is therefore likely to be a product of ecological and species-specific social factors as well as different sex-specific selection pressures. Our results also highlight the need for acquisition and analysis of sex-specific brain components in mammals.
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| 5. |
- Lindenfors, Patrik, 1964-, et al.
(author)
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Sexual dimorphism in primate aerobic capacity : a phylogenetic test
- 2010
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In: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 23:6, s. 1183-1194
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Journal article (peer-reviewed)abstract
- Male intrasexual competition should favour increased male physical prowess.This should in turn result in greater aerobic capacity in males than in females(i.e. sexual dimorphism) and a correlation between sexual dimorphism inaerobic capacity and the strength of sexual selection among species. However,physiological scaling laws predict that aerobic capacity should be lower perunit body mass in larger than in smaller animals, potentially reducing orreversing the sex difference and its association with measures of sexualselection. We used measures of haematocrit and red blood cell (RBC) countsfrom 45 species of primates to test four predictions related to sexual selectionand body mass: (i) on average, males should have higher aerobic capacity thanfemales, (ii) aerobic capacity should be higher in adult than juvenile males,(iii) aerobic capacity should increase with increasing sexual selection, but alsothat (iv) measures of aerobic capacity should co-vary negatively with bodymass. For the first two predictions, we used a phylogenetic paired t-testdeveloped for this study. We found support for predictions (i) and (ii). For prediction (iii), however, we found a negative correlation between the degreeof sexual selection and aerobic capacity, which was opposite to our prediction.Prediction (iv) was generally supported. We also investigated whethersubstrate use, basal metabolic rate and agility influenced physiologicalmeasures of oxygen transport, but we found only weak evidence for acorrelation between RBC count and agility.
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| 6. |
- Nunn, Charles L, et al.
(author)
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On sexual dimorphism in immune function
- 2009
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In: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 364:1513, s. 61-69
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Journal article (peer-reviewed)abstract
- Sexual dimorphism in immune function is a common pattern in vertebrates and also in a number of invertebrates. Most often, females are more ‘immunocompetent’ than males. The underlying causes are explained by either the role of immunosuppressive substances, such as testosterone, or by fundamental differences in male and female life histories. Here, we investigate some of the main predictions of the immunocompetence handicap hypothesis (ICHH) in a comparative framework using mammals. We focus specifically on the prediction that measures of sexual competition across species explain the observed patterns of variation in sex-specific immunocompetence within species. Our results are not consistent with the ICHH, but we do find that female mammals tend to have higher white blood cell counts (WBC), with some further associations between cell counts and longevity in females. We also document positive covariance between sexual dimorphism in immunity, as measured by a subset of WBC, and dimorphism in the duration of effective breeding. This is consistent with the application of ‘Bateman's principle’ to immunity, with females maximizing fitness by lengthening lifespan through greater investment in immune defences. Moreover, we present a meta-analysis of insect immunity, as the lack of testosterone in insects provides a means to investigate Bateman's principle for immunity independently of the ICHH. Here, we also find a systematic female bias in the expression of one of the two components of insect immune function that we investigated (phenoloxidase). From these analyses, we conclude that the mechanistic explanations of the ICHH lack empirical support. Instead, fitness-related differences between the sexes are potentially sufficient to explain many natural patterns in immunocompetence.
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