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Abstract Detail


Reyes, Elisabeth [1], Nadot, Sophie [2], Sauquet, Herve [3].

Floral symmetry shifted 198 times in angiosperms.

The number of species in families of flowering plants ranges from 1 to more than 20,000, which is one of the symptoms of a highly uneven distribution of diversity in angiosperms. One of the commonly proposed factors in shaping this uneven distribution is the origin of key innovations, which are traits that give the clades possessing them a significant advantage over close relatives lacking them. Clades possessing such an advantage are assumed to produce more species per unit of time, with a consequence of being more speciose than their close relatives in present day. One generally accepted key innovation is floral zygomorphy (bilateral symmetry), which is considered advantageous over actinomorphy (radial symmetry) because flowers have more efficient pollen transfer via limiting pollinator approach angles. The presumed influence of zygomorphy on diversification rates has been argued mostly through the comparison of closely related clades with contrasting floral symmetry. This approach has ignored the broader picture in which many speciose angiosperm families are completely actinomorphic and the finer pattern of changes in floral symmetry. This observation has led us to question the extent to which floral zygomorphy can be considered a key innovation in angiosperms as a whole. To begin answering this question, we need to know where and how many times zygomorphy has originated in the angiosperm phylogeny. Using the same database and general approach as the eFLOWER project (see Fifteen clues to the early diversification of flowers: first results from the eFLOWER initiative), we recorded perianth symmetry from more than 700 species, selected to represent all 61 orders and 422 currently accepted families of angiosperms and to include all presumed origins of perianth zygomorphy. We then reconstructed the evolution of perianth symmetry on a consensus backbone tree, using parsimony. We found perianth zygomorphy in 31 orders and 107 families. There was a minimum of 125 origins, almost the double of what was previously estimated, and 73 reversals to actinomorphy. Among the origins, two were in magnoliids, 27 in monocots, 17 in basal eudicots, 34 in superrosids and 45 in superasterids. Among the reversals, 9 were in monocots, 4 in basal eudicots, 22 in superrosids and 38 in superasterids. Our next step will be to test the extent to which these shifts in floral symmetry are linked to shifts in species diversification.

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1 - Universite Paris-Sud, Lab. Ecologie, Systematique, Evolution (ESE), CNRS UMR 8079, Bat. 360, Orsay, 91405, France
2 - Université Paris-Sud, Ecologie, Systematique Et Evolution, Batiment 360, Orsay, N/A, 91405, France
3 - Universite Paris-Sud, CNRS UMR 8079, Bat. 360, Orsay, N/A, 91405, France

bilateral flower symmetry
floral evolution
radial flower symmetry

Presentation Type: Oral Paper:Papers for Topics
Session: 3
Location: Salon 3/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 10:45 AM
Number: 3011
Abstract ID:297
Candidate for Awards:None

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