DIVERSITY-DEPENDENT CLADOGENESIS AND TRAIT EVOLUTION IN THE ADAPTIVE RADIATION OF THE AUKS (AVES: ALCIDAE)
Article first published online: 27 SEP 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 67, Issue 2, pages 403–416, February 2013
How to Cite
Weir, J. T. and Mursleen, S. (2013), DIVERSITY-DEPENDENT CLADOGENESIS AND TRAIT EVOLUTION IN THE ADAPTIVE RADIATION OF THE AUKS (AVES: ALCIDAE). Evolution, 67: 403–416. doi: 10.1111/j.1558-5646.2012.01786.x
- Issue published online: 28 JAN 2013
- Article first published online: 27 SEP 2012
- Accepted manuscript online: 3 SEP 2012 11:55AM EST
- Received January 18, 2012, Accepted August 6, 2012
- Adaptive radiation;
- diversity-dependent diversification;
- ecological opportunity;
Through the course of an adaptive radiation, the evolutionary speed of cladogenesis and ecologically relevant trait evolution are expected to slow as species diversity increases, niches become occupied, and ecological opportunity declines. We develop new likelihood-based models to test diversity-dependent evolution in the auks, one of only a few families of seabirds adapted to underwater “flight,” and which exhibit a large variety of bill sizes and shapes. Consistent with the expectations of adaptive radiation, we find both a decline in rates of cladogenesis (a sixfold decline) and bill shape (a 64-fold decline) evolution as diversity increased. Bill shape diverged into two clades at the basal cladogenesis event with one clade possessing mostly long, narrow bills used to forage primarily on fish, and the other with short thick bills used to forage primarily on plankton. Following this initial divergence in bill shape, size, a known correlate of both prey size and maximum diving depth, diverged rapidly within each of these clades. These results suggest that adaptive radiation in foraging traits underwent initial divergence in bill shape to occupy different food resources, followed by size differentiation to subdivide each niche along the depth axis of the water column.