Next Week

Note that discussion will be cancelled next week on account of SVP.

Great Discussion this Week!

This week we discussed the following paper:

Leslie, A.B. 2011. Predation and protection in the macroevolutionary history of conifer cones. Proc R. Soc. B. 278: 3003-3008.

The paper discussed morphological changes in conifer cones through time. In general, seed cones became "fatter" through the Jurassic and Cretaceous. Leslie (2011) suggests that increased selective pressure from herbivory may have resulted in such morphological changes.

In general we thought the paper was interesting and easy to read. However, we felt that several analyses would have been useful in terms of creating a tighter link between herbivory (dinosaur, bird, mammal) and conifer morphology. These may have included correlating diversity with conifer dimensions. 

We hope to see more on this subject and enjoyed discussing it.

Another Interesting Paper

McKenna and Sears. 2011. Limb specialization in living marsupial and eutherian mammals: constraint on limb evolution. Journal of Mammalogy 92: 1038-1049. (http://www.bioone.org/doi/abs/10.1644/10-MAMM-A-425.1)

McKenna and Sears (2011) use morphometric analyses to test the hypothesis that marsupials are limited in their degree of limb specialization compared to Eutherians. They found that marsupials have less specialized forelimbs but more specialized hindlimbs and suppose that the forelimbs are limited by the juvenile's need to crawl to the teat during development.

This Week's Paper - Conifer Cones

Julia will be presenting the following paper this week:

Leslie, A.B. 2011. Predation and protection in the macroevolutionary history of conifer cones. Proc R. Soc. B. 278: 3003-3008.

See you at Mike's this Thursday!

Reminder, discussion is cancelled next week due to SVP. I can't wait to see some of you in Vegas!

Interesting Recent Papers

This post is a long time coming. I have been extremely busy the last couple of weeks.

Sandel et al. 2011. The influence of late Quaternary climate-change velocity on species endemism. Science Early Online Publication DOI: 10.1126/science.1210173. (http://www.sciencemag.org/content/early/2011/10/05/science.1210173.abstract)

Sandel et al. (2011) link the velocity or rate of climate change to reduced levels of endemism among Quaternary animals. This means that in areas where climate change is occurring much more quickly endemic taxa are likely to go extinct. I imagine this to mean places like the Arctic but I have yet to read this paper (I will do so, however).

Gaillard et al. 2011. Atmospheric oxygenation caused by a change in volcanic degassing pressure. Science 478: 229-232. (http://www.nature.com/nature/journal/v478/n7368/full/nature10460.html?WT.ec_id=NATURE-20111013).

Gaillard et al. (2011) suggest that Precambrian oxygenation of the Earth's atmosphere was a result of a changes in volcanism, which led to the formation of the modern sulphur cycle. The formation of continents resulted in new terrestrial volcanoes that released SiO2 into the atmosphere, contributing to oxygenation.

Ungar and Sponheimer. 2011. The diets of early Hominins. Science 334: 190-193. (http://www.sciencemag.org/content/334/6053/190.short)

Ungar and Sponheimer (2011) review the diets of early Hominins, especially microwear and stable isotope evidence.

Venditti et al. 2011. Multiple routes to mammalian diversity. Nature Early Online Publication  doi:10.1038/nature10516. (http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10516.html?WT.ec_id=NATURE-20111020)

Venditti et al. (2011) investigate evolutionary rate shifts in the mammalia, finding that few clades show sustained increases in the velocity of evolution. They suggest that morphological diversification may vary much more freely than previously assumed.

Discussion paper for October 20

Here's a fairly new paper on a debate most people will already have heard of. It should be an interesting discussion with the mixture of palaeontology and biology people in our group.

Carbone, C., S.T. Turvey and J. Bielby. 2011. Intra-guild competition and its implications for one of the biggest terrestrial predators, Tyrannosaurus rex. Proc. R. Soc. B 278: 2682-2690.

Abstract: Identifying tradeoffs between hunting and scavenging in an ecological context is important for understanding predatory guilds. In the past century, the feeding strategy of one of the largest and best-known terrestrial carnivores, Tyrannosaurus rex, has been the subject of much debate: was it an active predator or an obligate scavenger? Here we look at the feasibility of an adult T. rex being an obligate scavenger in the environmental conditions of Late Cretaceous North America, given the size distributions of sympatric herbivorous dinosaurs and likely competition with more abundant small-bodied theropods. We predict that nearly 50 per cent of herbivores would have been within a 55 – 85 kg range, and calculate based on expected encounter rates that carcasses from these individuals would have been quickly consumed by smaller theropods. Larger carcasses would have been very rare and heavily competed for, making them an unreliable food source. The potential carcass search rates of smaller theropods are predicted to be 14 – 60 times that of an adult T. rex. Our results suggest that T. rex and other extremely large carnivorous dinosaurs would have been unable to compete as obligate scavengers and would have primarily hunted large vertebrate prey, similar to many large mammalian carnivores in modern-day ecosystems.

Carboniferous Vegetation

This week Thomas Cullen will be introducing the following paper:

Davies, N. S. and Gibling, M. R. 2011. Evolution of fixed-channel alluvial plains in response to Carboniferous vegetation. Nature Geoscience 4(9): 629-633.

I hope to see everyone at Mike's Place tomorrow!

Is Evolutionary History Rewritten with New Fossil Discoveries?

This week we discussed the following paper:

Tarver, J. E., P. C. J. Donoghue, and M. J. Benton. 2011. Is evolutionary history repeatedly rewritten in light of new fossil discoveries? Proceedings of the Royal Society B 278, 599–604.

Tarver et al. (2011) compared the catarrhine and non-avian dinosaur phylogenetic trees in terms of balance (do we know more about one part of the tree than the other?), completeness (how congruent the tree is with the stratigraphic context), and perception of macroevolutionary trends (do bursts of origination remain after new fossil discoveries?). They compared the trees through time to determine how new fossil discoveries changed these parameters. Tarver et al. (2011) conclude that the catarrhine tree is currently more complete and more robust to new fossil discoveries than the non-avian dinosaur tree. The non-avian tree is continually being altered by new, dramatic fossil discoveries.

We thought these results had important implications for those of us who want to use phylogenetic trees to study macroevolutionary trends. The paper provided us with three methods to analyze our trees before drawing grand conclusions from analyses of evolutionary rates or of correlation among traits. We, however, found that the comparison between catarrhines and non-avian dinosaurs was not appropriate. We felt that the two trees represent very different levels of diversity and that the non-avian dinosaur tree should have been compared to a larger group of mammals (one hopefully containing a similar level of morphological and ecological diversity). We also felt that analyzing two groups with living members may have improved the comparison. The phylogenetic relationships of catarrhines are likely better understood due to the extant forms. 

In general, the paper will be useful in shaping our future analyses. We felt that the title of the paper was misleading as it did not provide an answer to the question besides "in some groups and not others."

Thanks to everyone who showed up! See you next week.

Thomas Cullen will be presenting next week's paper.

Google Calendar for Scheduling Presenters

Please use the link below to view upcoming presenters. I can only share the calendar with people who have a Gmail account (you can view but cannot add events). You can create a Gmail account (which I recommend given that many of you need to have your Carleton mail forwarded) and send it to me so I can share the calendar with you or you can contact me to be scheduled. Remember we are only meeting Thursday at 5pm. Putting your name on the calendar is sufficient.

https://www.google.com/calendar/embed?src=da6f72fsp1hebsr8nhem333ejg%40group.calendar.google.com&ctz=America/Toronto

Additionally...

Several of your email addresses are over quota, which means I cannot send you the paper. Please empty your inbox or have it forwarded to Gmail. You can also provide me with an alternative email address.

dfraser1@connect.carleton.ca

Thursday October 6 Paper

I have chosen the paper for this week's discussion. There have been many excellent papers this year but I wanted to set the tone. Since we will likely be discussing many new fossil and evolutionary discoveries this semester, I have chosen the following:

Tarver, J. E., P. C. J. Donoghue, and M. J. Benton. 2011. Is evolutionary history repeatedly rewritten in light of new fossil discoveries? Proceedings of the Royal Society B 278, 599–604.

I think this is an important question but I will leave the discussing for Thursday. See you at Mike's between 5pm and 5:30pm.