Abstract Detail



Systematics

Spriggs, Elizabeth [1], Schlutius, Caroline [2], Eaton, Deren [3], Park, Brian [2], Sweeney, Patrick [4], Edwards, Erika [5], Donoghue, Michael [6].

Differences in flowering time maintain species boundaries in a continental radiation of Viburnum.

With extensive RADseq data we assessed the diversification of the Lentago clade of Viburnum. This lineage includes five species of shrubs and small trees that radiated in eastern North America over the past 15-20 million years. All five are clearly differentiated, and although we infer a history of introgression between multiple species pairs, there is little evidence of hybridization today. We tested whether differences in flowering time are responsible for species isolation by comparing historical flowering dates documented in herbarium specimens. In each species, we found a strong relationship between flowering date and latitude such that southern populations flower earlier than northern ones. Within areas of sympatry, the species flower in sequence rather than simultaneously, with flowering dates offset by at least nine days for all species pairs. In some cases, it appears that the offset in flowering times is an incidental consequence of adaptation to differing climates, but in the recently diverged sister species V. prunifolium and V. rufidulum, we find evidence that reinforcement led to reproductive character displacement. Long-term trends in flowering time suggest that the two northern-most species are flowering earlier in response to recent climate change. However, given the direction of these shifts and the particular sequence of flowering among the species, it appears unlikely that climate change will disrupt the existing reproductive barriers in this case. We argue that speciation in the Lentago clade has primarily occurred through ecological divergence of allopatric populations, but differences in flowering time were essential to maintain separation of incipient species when they came into secondary contact. This same combination of factors may underlie diversification in many other plant clades.


1 - Arnold Arboretum, 125 Arborway, Boston, MA, 02130, United States
2 - Yale University, Ecology and Evolutionary Bioloy, PO Box 208106, New Haven, CT, 06520, USA
3 - Columbia University, Ecology, Evolution, And Environmental Biology, 1200 Amsterdam Ave. , Schermerhorn Ext. Office 1007, New York, NY, 10027, United States
4 - Yale University, Peabody Museum Of Natural History, P.O. Box 208118, New Haven, CT, 06520, United States
5 - Yale University, Ecology and Evolutionary Biology, PO Box 208106, New Haven, CT, 06520, USA
6 - Yale University, Department Of Ecology And Evolutionary Biology, Po Box 208106, New Haven, CT, 06511, United States

Keywords:
Viburnum
phenology
phylogeny
RADseq
Speciation
Reinforcement.

Presentation Type: Oral Paper
Number:
Abstract ID:338
Candidate for Awards:None


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