Martin Stervander: "Speciation in finches on isolated islands"
Jan 15, 2019
14:00 - 15:00
Martin Stervander from the Institute of Ecology and Evolution (IE²) at University of Oregon, USA
For more information on the speaker, please check here: http://www.stervander.com/
You are all familiar with the rock stars of
speciation, the Darwin’s finches of Galápagos. But did you
know of the world’s largest seedeater, or of Inaccessible
Island? I will tell the tale of two insular finch systems that
are not so well-known, but rather interesting to anyone with a
flair for resource-driven selection, gene flow, and isolation.
Via a short stop in the Gulf of Guinea off West Africa, home
to the enigmatic São Tomé Grosbeak, I will take you on a
journey to the middle of the South Atlantic. Here,
Inaccessible Island and Nightingale Island are neighbours to
the officially most remote human settlement on earth Tristan
da Cunha. The former islands are home to a peculiar avifauna,
including a pair each of small-billed and large-billed finch
taxa, stemming from a South American colonization. On each
island, the small-billed finches are feeding generalists,
whereas the large-billed finches specialize on the fruits of
the only tree species growing on the islands. Smaller and
older Nightingale Island harbours the most divergent
phenotypes, with small-billed finches being smaller than those
on Inaccessible Island and large-billed finches being larger.
The species do not hybridize. On Inaccessible Island, the
small- and large-billed taxa mate entirely assortatively in
the lowlands, whereas there is full hybridization in the
woodland of the high plateau. And this on an island that is 14
square kilometers! With the help of genetic and genomic tools,
we can establish that the constant gene flow erodes
genome-wide differentiation between Inaccessible Island taxa,
but one autosomal region differentiates body size and one
region on a sex chromosome differentiates bill morphology.
Using the genomic landscape of this miniature radiation, we
aim at understanding the speciation mechanisms and the
evolutionary history of the system.