# PLG

## Seminar

Aldous, D (California)
Wednesday 19 December 2007, 09:00-10:00

Seminar Room 1, Newton Institute

#### Abstract

Stepping away from technical issues in tree reconstruction from molecular data on extant species, I will describe broader questions that can be asked about the Tree of Life, and our attempts to devise a framework for their study. Here are three such questions. (i) It is appealing to say that any readily identifiable clade arose through adaptive radiation. Does data support this statement? What would trees look like if they didn't arise through adaptive radiation? (ii) For some clades (e.g. horse) the number $n$ of extant species is much smaller than the maximum (over past time) number $M$ of coexisting species. Is this remarkable? How large should we expect $M/n$ to be for a typical clade? (iii) Given the true phylogenetic tree on the extant species of a clade, but no information about extinct species, can one make any (even crude) estimates of past speciation and extinction rates?

More technical questions concern the likely shape of trees on higher-order taxa, or the likely size of fluctuation in time series of numbers of such taxa.

Based on joint work with Lea Popovic and Maxim Krikun.

#### Video

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