I am doing poorly at remembering to update this blog.
Last week we discussed the Smith et al, (2010) paper in Science on the evolution of maximum mammalian body size. The paper discussed the increase in maximum mammalian body size following the end Cretaceous extinction of the dinosaurs. The hypothesis is that the removal of the dinosaurs and thus openning of niches allowed the mammals to proliferate as well as to increase in body size. This is a traditional view of mammalian evolution (and by traditional I don't mean defunct, it is pretty clear that at least some (probably a lot) mammalian speciation occurred after the extinction of the dinosaurs. But if you want a different view consult Bininda-Edmonds et al, (2007)
http://www.nature.com/nature/journal/v446/n7135/abs/nature05634.html).
We found the Smith et al (2010) paper interesting and informative. The pattern of increasing maximum body size was apparent on all continents and was correlated with continental area (bigger animals need bigger home ranges) and temperature (18O; warmer means more primary productivity among other things). They implement the Gompertz model in their testing of the above parameters based on a less the 1.0 difference in AIC scores. In our opinion, this is not a big enough difference (< 2.0) to reject the use of the power law and would have liked to see delta AIC for each continent. We also found it interesting that the largest animals were generally hindgut fermenters and would like to see a discussion of the influences of other such factors on the observed patterns (of course we recognize the length limit on Science papers).
Tuesday, December 7, 2010
Wednesday, December 1, 2010
Discussion article for December 7
Lopez-Martinez, N., 2008. The lagomorph fossil record and the origin of the European rabbit. Lagomorph Biology: 27-46.
Abstract: Lagomorphs are very prolific mammals with a rich fossil record, which particularly increased over the last years by washing and screening techniques for microfossil recovery. Fossil remains of lagomorphs have been extensively documented in the Old World and North America from Early Paleogene onwards (around 45 Ma). Lagomorph diversity is much larger in the fossil record than in the biosphere. Only 12 genera and about 75 lagomorph species are still living in recent times, most of them almost devoid of paleontological record. In contrast, around 75 genera and more than 230 species, most of them already extinct, are represented in the fossil record of Lagomorpha. The local faunas today rarely contain more than three sympatric lagomorphs, frequently just one or two taxa. Instead, up to eight lagomorph species coexisted in local paleofaunas. This pattern constitutes a rare case in the recorded history of organisms, since the fossil record even in well-represented groups contains a lower number of species than the biosphere. Only declining groups, such as brachiopods or perissodactyl mammals, show higher diversity in the past than in the present, which denotes that lagomorph lineages are also declining in recent times.
I thought this would be a fun article to discuss since it deals with a clade that someone in the group works on, and also because it brings up some more generalized evo-palaeo topics like trying to make conclusions connecting the fossil record to extant diversity/distributions. I don't think there is a free .PDF of this, but you can access it through the Carleton Library site. Since it is more of a review chapter than an experimental report, it shouldn't take too long to read/skim the interesting parts (the density of text on each page is also lower than in a typical Science or Nature report as well).
Abstract: Lagomorphs are very prolific mammals with a rich fossil record, which particularly increased over the last years by washing and screening techniques for microfossil recovery. Fossil remains of lagomorphs have been extensively documented in the Old World and North America from Early Paleogene onwards (around 45 Ma). Lagomorph diversity is much larger in the fossil record than in the biosphere. Only 12 genera and about 75 lagomorph species are still living in recent times, most of them almost devoid of paleontological record. In contrast, around 75 genera and more than 230 species, most of them already extinct, are represented in the fossil record of Lagomorpha. The local faunas today rarely contain more than three sympatric lagomorphs, frequently just one or two taxa. Instead, up to eight lagomorph species coexisted in local paleofaunas. This pattern constitutes a rare case in the recorded history of organisms, since the fossil record even in well-represented groups contains a lower number of species than the biosphere. Only declining groups, such as brachiopods or perissodactyl mammals, show higher diversity in the past than in the present, which denotes that lagomorph lineages are also declining in recent times.
I thought this would be a fun article to discuss since it deals with a clade that someone in the group works on, and also because it brings up some more generalized evo-palaeo topics like trying to make conclusions connecting the fossil record to extant diversity/distributions. I don't think there is a free .PDF of this, but you can access it through the Carleton Library site. Since it is more of a review chapter than an experimental report, it shouldn't take too long to read/skim the interesting parts (the density of text on each page is also lower than in a typical Science or Nature report as well).
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