Statistics Seminars: Evolutionary links between multiple species
10 December 2012 14:00 in CM221
Phylogenetics studies how species have evolved and how they are related to each other. Cospeciation is the joint evolution of two or more lineages that are ecologically associated, the standard example being a host and its parasite. Hommola et al. (2009) introduced a permutation test to detect cospeciation in closely related host-parasite systems by testing the null hypothesis that hosts and their associated parasites evolved independently. To determine whether the correlation between host distances and parasite distances is significantly high, one permutes the labels in the host and parasite phylogenies retaining the observed interactions.
However, evolutionary relationships are often more complicated than a simple host-parasite pairing. Thus we want investigate whether cospeciation is reflected across three (or more) associated phylogenies. This involves finding a test-statistic capable to capture correlation in a multivariate setting, and implementing a suitable randomisation scheme coping with multiple phylogenies. It is relatively easy to answer the simple question of "is there evidence of cospeciation somewhere in this system?" By carefully considering how to randomise the trees, we are able to address more subtle questions such as "do plant A and bird C show more cospeciation than can be explained by their common links with insect B?"
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