| 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. |
- Evans, Alistair R., et al.
(author)
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The maximum rate of mammal evolution
- 2012
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:11, s. 4187-4190
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Journal article (peer-reviewed)abstract
- How fast can a mammal evolve from the size of a mouse to the size of an elephant? Achieving such a large transformation calls for major biological reorganization. Thus, the speed at which this occurs has important implications for extensive faunal changes, including adaptive radiations and recovery from mass extinctions. To quantify the pace of large-scale evolution we developed a metric, clade maximum rate, which represents the maximum evolutionary rate of a trait within a clade. We applied this metric to body mass evolution in mammals over the last 70 million years, during which multiple large evolutionary transitions occurred in oceans and on continents and islands. Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. When differences in generation time are considered, we find an exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous-Paleogene (K-Pg) extinction event. Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases. Our findings allow more rigorous comparisons of microevolutionary and macroevolutionary patterns and processes.
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| 3. |
- Lindenfors, Patrik, 1964-, et al.
(author)
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Sexual size dimorphism in mammals
- 2007
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In: Sex, size and gender roles. - New York : Oxford University Press. - 9780199208784 ; , s. 16-26
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Book chapter (peer-reviewed)abstract
- This chapter explores the pattern of sexual size dimorphism in mammals and the processes that underly its evolution. We find that, on average, male mammals are the larger sex (average male/female mass ratio 1.184), with males being at least 10% larger than females in over 45% of species. Most mammalian orders are also have male-biased sexual dimorphism, although some orders do not show any bias or are significantly female-biased (Lagomorpha). Sexual size dimorphism increases with body size across mammals (Rensch’s rule), suggesting that there are parallel selection pressures on both male and female size. We found support for the hypothesis that male-biased dimorphism relates to sexual selection on males through male–male competition for females. We draw this conclusion from a positive correlation between the degree of sexual selection, as indicated by mating systems and the degree of male biased size dimorphism. The degree of sexual selection was also positively correlated with male and female size across mammals. Further, a parallel selection pressure on female mass is identified in that age at weaning is significantly higher in more polygynous species, even when correcting for body mass. We also explore the processes maintaining smaller female size in sexually dimorphic species and confirm that reproductive rate is lower for larger females, indicating that fecundity selection selects for smaller females in mammals. Although the patterns we discuss hold across mammals as a whole, there is considerable variation across orders and many of these relationships are not significant. Further work is still needed to more closely investigate the pattern of sexual dimorphism and processes driving sexual dimorphism in different clades.
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| 4. |
- Smith, Felisa A, et al.
(author)
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The evolution of maximum body size of terrestrial mammals
- 2010
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 330:6008, s. 1216-1219
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Journal article (peer-reviewed)abstract
- The extinction of dinosaurs at the Cretaceous/Paleogene (K/Pg) boundary was the seminal event that opened the door for the subsequent diversification of terrestrial mammals. Our compilation of maximum body size at the ordinal level by sub-epoch shows a near-exponential increase after the K/Pg. On each continent, the maximum size of mammals leveled off after 40 million years ago and thereafter remained approximately constant. There was remarkable congruence in the rate, trajectory, and upper limit across continents, orders, and trophic guilds, despite differences in geological and climatic history, turnover of lineages, and ecological variation. Our analysis suggests that although the primary driver for the evolution of giant mammals was diversification to fill ecological niches, environmental temperature and land area may have ultimately constrained the maximum size achieved.
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