Is there room for punctuated equilibrium and species selection in macroevolution?

Posted by Erik Svensson

Next week (Tuesday November 5, 2013 at 10.30) I want to discuss a classical question in macroevolution that was originally suggested by paleontologists Niles Eldredge and Stephen Jay Gould in 1973, but which has gained increased interested with the explosion of molecular phylogenetic information and improved comparative methods: punctuated equilbrium and species selection. A recent TREE-article take a critical look at the evidence, and it should hopefully be an interesting read and stimulate discussion.

The first TREE-article seems critical towards the prospects for punctuated equilibrium, so as a complement (optional reading) I also post a link to an empirical study on extant mammalian body size variation by Folmer Bokma, which is suggestive of punctuated equilbrium. Enjoy that too!

 

Is there room for punctuated equilibrium in macroevolution?

• Matthew W. Pennell ,
• Luke J. Harmon,
• Josef C. Uyeda

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Highlights

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The theory of punctuated equilibrium is a mix of conceptually distinct parts.

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We identify and disentangle four questions that are often associated with the theory.

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We review recent progress towards each of these four questions.

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Lumping these four questions together as ‘punctuated equilibrium’ is problematic.

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The long-controversial theory of punctuated equilibrium (PE) asserts that speciation causes rapid evolution against a backdrop of stasis. PE is currently undergoing a resurgence driven by new developments in statistical methods. However, we argue that PE is actually a tangle of four unnecessarily conflated questions: (i) is evolution gradualistic or pulsed? (ii) does trait evolution occur mainly at speciation or within a lineage? (iii) are changes at speciation adaptive or neutral? and (iv) how important is species selection in shaping patterns of diversity? We discuss progress towards answering these four questions but argue that combining these conceptually distinct ideas under the single framework of PE is distracting and confusing, and more likely to hinder progress than to spur it.

Extant mammal body masses suggest

punctuated equilibrium

Tiina M. Mattila and Folmer Bokma

Is gradual microevolutionary change within species simultaneously the source of 

macroevolutionary differentiation between species? Since its first publication, Darwin’s original idea that 

phenotypicdifferences between species develop gradually over time, as the accumulation of small selection-induced

changes in successive generations has been challenged by palaeontologists claiming that, instead, new

species quickly acquire their phenotypes to remain virtually unchanged until going extinct again. This

controversy, widely known as the ‘punctuated equilibrium’ debate, remained unresolved, largely owing to

the difficulty of distinguishing biological species from fossil remains. We analysed body masses of 2143

existing mammal species on a phylogeny comprising 4510 (i.e. nearly all) extant species to estimate rates of

gradual (anagenetic) and speciational (cladogenetic) evolution. Our Bayesian estimates from mammals as

well as separate sub-clades such as primates and carnivores suggest that gradual evolution is responsible for

only a small part of body size variation between mammal species.

Minisymposium May 24 2012: "Biogeography and Evolution"

We are happy to announce an exciting Minisymposium entitled "Biogeography and Evolution" on May 24 2012 that will take place on the afternoon the day preceeding Anna Runemarks PhD-thesis defence (May 25). We have four excellent speakers that will present some exciting talks this afternoon. This symposium is open for everyone, whether from the Biology Department of from elsewhere. Full details of the programme and the titles of the talks are presented below:

Minisymposium on Biogeography and 

Evolution

                 

May 24, 13.00 - 16.00                               

"Blue Hall", Ecology Building, Department of Biology, Lund

13.00-13.40 Scott V. Edwards (Harvard University, USA)  “The phylogeography-phylogenetics continuum: a look to the future”

13.50-14.20 Jessica Ware (Rutgers University, USA) "Here be dragons: biodgeography and age of Petaluridae, the petaltail dragonflies"

14.30-14.50 Coffee

14.50 - 15.20 Alexandre Antonelli (Gothenburg University, Sweden) "Ecology meets Biogeography: A Multi-Disciplinary Approach to Study Neotropical Diversification"

15.30- 15.50 Folmer Bokma (Umeå University, Sweden) ”Why species may not adapt”

15.50 - 16.00 Discussion and concluding remarks

Symposium open for all interested. No registration required.

Welcome!


Bengt Hansson, Anna Runemark & Erik Svensson

New PhD-thesis from the lab: Anna Runemark and evolution on islands

Posted by Erik Svensson

Some of the proudest moments in the careers and life of advisors come when their students successfully finish their PhD-theses. Now it is time again, this time for Anna Runemark, who will defend her PhD-thesis on Friday May 25 in the "Blue Hall" (Ecology Building, Department of Biology) at 09.30. The thesis defence is open to all interested, as with all PhD-thesis defences at our university.

The Science Faculty's external opponent is Professor Scott Edwards from Harvard University. The examination committé consists of Drs. Alexandre Antonelli (Gothenburg University, Sweden), Folmer Bokma (Umeå University, Sweden) and Jessica Ware (Rutgers University, USA). On May 24 (Thursday, the day before Anna's thesis defence), we will have a small and informal research symposium with the opponent and the members of the thesis-committé entitled "Island Biology and Evolution", which will start at 13.00 in the "Blue Hall" (Ecology Building).

The title of the thesis is "Island biogeography and population divergence in the Skyros wall lizard". You can find a Swedish summary of the thesis here, and here is the link to the entire thesis, for those of you work at Lund University.

On a more personal note, Anna Runemark is my fifth PhD-student, preceeded by Jessica Abbott (2006), Thomas Gosden (2008), Fabrice Eroukhmanoff (2009) and Kristina ("Tina") Karlsson-Green (2010). I am proud of all these students, and I have learnt tremendously much from being an advisor of these five PhD-theses. Above all, I have learnt that there is not one way of being a good advisor or a good student - but many. 

There is thus no single "magic formula" to do an excellent PhD-thesis, but many different avenues. In a way, one could compare the writing of a thesis with the hill-climbing process on Sewall Wright's Adaptive Landscape: there are multiple adaptive peaks (excellent theses) and many different combinations of skills that make a good thesis. There are also many different kinds of students, each with different social and intellectual backgrounds, personalities, skills and interests. 

Equally, there are many different ways of a being a good advisor, and being a good advisor or a good student is, in itself, no guarantee for success. It is rather the combination of advisor and student that is crucial. One could perhaps compare this with the concept of genetic compatability in sexual selection: some combinations are less fit than others, even if the component parts (genes, advisors, students) do not differ and are excellent in isolation. 


The ideal student-advisor relationship is one of complementarity and mutual respect for each other's skills: The advisor provides the broader overview, theoretical and conceptual background and helps the student to see "the Big Picture" of the work, and forces the student to keep looking at the horizon, rather than dwelling in to methodological details. The student, on the other hand, should develop his/her methodological and technical skills and become "good" at it, and work to build his/her understanding of scientific concepts and how the thesis work can contribute to increased understanding of the natural world. I feel that Anna's thesis about a classical topic in evolutionary biology (evolution on islands) exemplifies this type of advisor-student collaboration that characterizes an excellent PhD-thesis.