Research | Phylogenetics
Phylogenetics and the timing of species divergences
Knut Finstermeier | Michael Knapp | Nadin Rohland | Mathias Stiller
We are currently working on two mammalian species groups, bears and Afrotherians. Despite many attempts, the phylogenetic relationships of the extant bear species could not be fully resolved to date. What is especially difficult is to illuminate the relationships within the ursine bears, i.e. all the large bear species except the giant panda and the spectacled bear, most likely because separation of the various lineages happened within a short time span. To resolve this issue, we have sequenced complete mitochondrial genomes from all living bear species for which no such information is available. Moreover, we included the sequences from two extinct species, the European cave bear and the American short faced bear. We also dated the divergence events to put speciation into a meaningful ecological context. Our results clearly indicate that climatic change played a major role in bear evolution.
- Proboscidean phylogeny
In addition to bears, we are studying a number of Afrotherian species. We recently showed that the mammoth is more closely related to the Asian elephant than to the African elephant, an issue that had been controversial for a long time. This analysis was much facilitated by using a two-step multiplex PCR, an approach that allows rapid amplification of large DNA sequence data sets even from samples with fragmented DNA as it is normally the case for DNA from fossils. We have now extended our analysis to another Proboscidean species, the American mastodon. Inclusion of this species allowed us not only to resolve the phylogenetic relationship between mammoth and the living elephant species with more confidence; it also enabled us to date the divergence events. Intriguingly, the divergence of mammoth and the elephants in Africa occurred at the same time as the divergence of humans, chimpanzees and gorillas, hinting to a possible common environmental change that may have triggered these speciations. Currently we are working on an extension of these studies, including more extinct species as well as several individuals from each species. We are especially interested in the phylogenetic relationship of the various island dwarf forms to their normal-sized mainland relatives.
- Multiplex PCR and results
Finally, we are also investigating the phylogenetic relationships within extant Afrotherian groups in collaboration with Dr. Robert Asher from the University of Cambridge. Using a method for non-destructive analyses of museum specimens we were able to resolve the phylogenetic relationships within the African tenrecs. As many tenrec species are rare and endangered the use of museum specimens has been, as in other projects, extremely helpful. To this end, we often collaborate with the Natural History Museum in Berlin. The tenrec analysis also included morphological data from extant and long-extinct species bringing together molecular and morphological analyses. Our long-term goal is to provide a phylogeny, including estimates for divergence dates for all extinct and extant Afrotheria, for which sufficient molecular and / or morphological data can be obtained.
