Paper 8: Community Evolution and the Origin of Mammals (1996)
Blog Author: Lam Le
Blurb Author:
Mark D. Uhen
-Assistant Professor and Associate Chair in the Department of Atmospheric, Oceanic, and Earth Sciences at George Mason University in Fairfax, Virginia
-Chair of the Executive Committee of the Paleobiology Database (paleobiodb.org), the largest repository of fossil distribution and taxonomic data in the world.
-vertebrate paleontologist who studies the evolution of whales and other marine mammals
Jessica Theodor
-Professor of Ecology and Evolutionary Biology at University of Calgary
-research focuses on understanding the causes of organismal diversity patterns found over geologic time
Paper Author: Everett C. Olson
-zoologist, paleontologist, and geologistnoted for his seminal research of origin and evolution of vertebrate animals extinction that occurred 270 million years ago and which now carries his name - Olson's Extinction, also termed "Olson's Gap"
-former chair of the department of Biology at the UCLA
-Recipient of Romer-Simpson Medalof the Society of Vertebrate Paleontology
-National Academy of Science said that he ranked "among the great vertebrate paleontologists of the twentieth century".
Background:Studies of vertebrate evolution with the concept of fauna modifications have constituted a major field of interest of the writer for a long time. The framework that has been established for evolution of mammals is based on less than sufficient evidence at many levels. This paper presents an extension for the topic of changes in communities through geological time.
Assumptions:2 aspects of the system are most important:
-The contribution by its vertebrates to the community
-The paths of flow of food-derived energy through the community.
Methods:
-Use data in previous studies, but this paper synthesizes it in a more general and ecological way.
Results:
-The nature of the communities: The pattern of interaction expressed in the structure of the community and the flow of food-derived energy provide the continuity of existence.
-Community evolution: Community types are limited in their possible spectra of development by the conditions during the time they exist. The evolution of a complex of communities involves changes of each component because their modifications alter living conditions of communities.
-Community types of Permian and Triassic: 3 types:
-Type I: Food chain based primarily in aquatic plants consumed by invertebrates and vertebrates
-Type II: Food chain based in terrestrial plants consumed directly by terrestrial, vertebrate herbivores.
-Types III: Food chain based in terrestrial plants consumed by terrestrial invertebrates which in turn are food source for terrestrial vertebrates.
-Evolution of communities leading to mammals: The early Permian communities that contained terrestrial vertebrate elements were all Type I. The Wichita community of Type I led to the Clear Fork community of Type I and to the community Type II of Hennessey formation. This in turn led to San Angelo-Flowerpot Type II community. Several places in Soviet Union have community Type III.
Conclusions:
-Communities had a temporal as well as spatial extent
-Emphasis on the idea of reconstructing the food web of entire assemblages
-Define communities by ecological interactions of the organisms and the flow of energy that these interactions facilitate
-Different Permian communities gave rise to different radiations of vertebrates.
Comments/Questions:
-This is a really interesting paper. I had to read it many times to understand the details but once I got the hang of it the paper made more sense. The paper goes a lot deeper into the concept of community in ecology, which is useful knowledge for another Ecology class that I’m taking.
While the material was interesting, I did not particularly like how it was presented. There was a lot of extra text that wasn't necessary ("fluff") and made following the author's points a bit tedious. The figures were useful. Overall, I feel like the takeaway was: there was a shift in community away from aquatic habitats, which allowed the emergence of different types of food chains.
ReplyDeleteThe paper as a whole is very interesting and I can see foundations of modern topics in paleo, such as ecometrics and taxon-free approaches, in this research. However, I think the title is misleading. Olsen talks about Permian and Triassic community structure and is able to reconstruct food webs, but I did not see much about how that research and the evolution of mammals linked together. I think there is a potential for an interesting discussion on the effects of mass extinctions on food webs and community ecology that wasn't discussed by Olsen here. I also agree with Maria that there is a lot of extra sections in the paper that bogs down the readability. There didn't seem to be a distinction between results and discussion in the organization.
ReplyDeleteI thoroughly enjoyed this paper and felt it covered a lot of ground to sum up his applicable knowledge on the subject, as this was not a well known or understood topic at the time. I find the structures of the mammal-like-reptiles or proto-mammal communities is fascinating.
ReplyDeleteI liked the paper and doing some web browsing at how animals from these old groups looked like.
ReplyDeleteI´m puzzled about why type III communities didn´t have herbivorous vertebrates if by the time they appear in the fossil record, the other type of faunas already show this guild. I would have liked to read about this in the discussion.
What is a synthetic, taxon-free community structure? I appreciated that he broke down and defined the terms and ideas he was exploring. Figure 2 is probably the most complex web I've seen, and definitely the first to sort by habitat, so that was interesting.
ReplyDeleteSame as mentioned before, the way this paper is written has lots of text that just made it unclear to follow his ideas. However, the ideas he presented seem very interesting. I specially found interesting the idea of how community structure might be kept over time, even if the species within the community change. Has that been looked in more detail?
ReplyDeleteWhat a relevant paper since Devra, Dr Lyons, and I just returned from the latest annual SVP meeting! It was neat to see an early discussion of paleo communities as it’s something so fundamental to a lot of our work, yet often misunderstood. I often have trouble conceptualizing time averaging occurring within my communities and thinking about communities I work with representing both snapshots and long lengths of time and what that actually means for my research. I enjoyed the introduction/discussion of the terms he planned to use in his paper.
ReplyDeleteWell, this kind of research is very important to tell us what happened in the past and the community structure assessment is a clever way to look at it. I have visited Ashfall preservation a few years ago and we learned about the story. Determining the true species community structure in the fossil is challenging because it is complex to find and extract all the parts. This is hard to do because of its work effort to collect specimen. The paper was interesting to read and fascinating. Few terms were challenging but figured it out.
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ReplyDeleteThere was a lot of stuff going on in the paper, but I actually thought it was still a decent paper. I thought it was cool learning about the community structure and he goes way more in depth about it than we do in any other class I've taken so far.
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