Paper 22- Jablonski 1986
Jablonski, D. 1986. Background and mass extinctions: the alternation of macroevolutionary regimes. Science 231:129-133.
Blog Author: Angel Sumpter
Blurb Author: Michael Foote
● A.B.,: 1985 Geological Sciences, Harvard University
● S.M.: 1988 Evolutionary Biology, University of Chicago
● Department of the Geophysical Sciences at the University of Chicago
● Current research focuses on biogeography, evolutionary paleoecology and macroevolution
Paper Author: David Jablonski
● American professor of geophysical sciences at the University of Chicago.
● Research Focus: Evolution, paleontology
● “Research emphasizes the combining of data from living and fossil organisms to study the origins and fates of lineages and adaptations within three major areas. The dynamics of the latitudinal diversity gradient; the role of geographic range, larval development, and other biological factors in determining speciation rates and patterns in mollusks; Along with comparing patterns of extinction and survival during mass extinction s to gain a better picture of the evolutionary significance of extinction events.”
Main Question
● Background
○ For many of years, the numerous amounts of data and hypotheses on mass extinction has focused on extraterrestrial impacts and whether or not they can be considered forcing mechanisms. Current evolutionary theory is derived based almost entirely in terms of pattern and process during background times. However, when comparing evolutionary patterns the same time periods, background levels of extinctions and mass extinction indicate that mass extinctions cannot be due to random selection of the biota or raised intensity of background patterns.
● Question
○ Does the alternation of background and mass extinction regimes
shape large-scale evolutionary patterns in the history of life?
Methods
● Larval development, geographic range, and the number of species within a taxonomic group was tested for its effects on background and mass extinction in Late Cretaceous mollusks of the Gulf and Atlantic Coastal Plain of North America by comparing the data to other extinctions and itself across time.
Results/Conclusion
● The alteration of the macroevolutionary regimes makes it difficult for any smooth observations of evolutionary processes during that specific time frame. The end-Cretaceous mass extinction wasn't just simply intensifying trends seen during background times. Instead of doing that, the mass extinction was characterized by qualitative as well as quantitative changes in patterns of extinction and survival. With this observation, it shows that long term adaptation of the biota was not promoted during mass extinction making it difficult for species-rich clades and permit radiation of taxa.
Comments
● Between the paper itself and the graphs, this was a pretty easy paper to read.
My main takeaway was that mass extinctions can totally change the evolutionary path of life on Earth, through "nonconstructive selectivity" which works completely differently from background extinction. The idea that beneficial adaptations can be lost because the species with these adaptations may succumb to mass extinctions... Wow, I hadn't really thought about it.
ReplyDeleteThere are few graphs that are very interesting: Fig 2. A. and Fig 3. A. The figure A. support the idea of current conservation approach of conserving larger habitat would give more chance to sustain little longer. Figure 3. A. more endemic species gone extinct faster in species-poor genera than species-rich genera. I wonder if this pattern is comparable to current species composition in the same group of organisms. This paper is very cool and has lots of interesting points.
ReplyDeleteI liked this paper and think Maria´s takeaway is a very good synopsis of it. I guess many further questions came from that paper. For example, I´m curious if there are consistent clade survival predictors (as clade range in K-T) under all mass extinctions.
ReplyDeleteThis paper was well written and straight to the point, I enjoyed reading it. This paper makes me think about mass extinctions differently, like Maria said, to consider that many well-adapted traits have a been lost due to mass extinctions is interesting. This paper triggers my interest in the different characteristics of of all mass extinctions. I am interested in the type of qualitative and quantitative of a mass extinction and how that may change the recovery patterns.
ReplyDeleteI thought it was interesting that Jablonski brought up biological hierarchy in respect to evolution. Particularly, his argument that evolutionary processes do not stop during these extinction events, but rather certain selective processes at higher levels were more important and cascaded down. I think it's an important point to recognize that evolutionary processes such as speciation do not stop during extinctions, but there's higher pressure that causes more species to go extinct.
ReplyDeleteI really like this paper. This paper is very straight to the point. Traits that make species last longer during normal times do not guarantee their survival during mass extinctions. And mass extinctions create faunal change, remove dominant taxa and enable survival of other species. These are super interesting ideas I never thought of before!
ReplyDeleteThis paper reminded me of paper 35 where the author hypothesized that evolution=optimization. We didn’t get a chance to talk about it, but this made me it honk about how scale dependent that is. On one hand, you can super specialize in a specific habitat, become sort of optimized for that, but then a mass extinction comes and changes the situation and you aren’t optimized for those conditions anymore. On scales of species durations, are thins actually getting optimized? In the long run over many environmental changes nothing is really optimized.
ReplyDeleteThis paper also sort of makes a case for generic level niche conservatism, but flat out says there is no evidence for that. Has this changed?
I also enjoyed the paper's clear and concise writing. Easy to follow and understand. I was also interested in Raup's idea of nonconstructive selectivity, curious how much different things would look like now if the beneficial traits had been selected for.
ReplyDeleteAnother vote for Maria's comment. I found this paper very interesting. The fact that mass extinctions could change the whole evolutionary process surprised me in a good way. I haven't thought much about the past history/challenges of current living organisms, as my research focuses more in behaviours that are perceivable now and their function in the organisms life at the present time. Of course one thinks of evolution, but I haven't addressed the real role that events such as these night have in the species present now.
ReplyDelete