Abstract Detail

Macroevolution

Bilbao, Gonzalo [1], Joly, Simon [2], Bruneau, Anne [3].

The winning strategy: pollinator-mediated convergent floral shape evolution in tropical legumes of the genus Erythrina.

Pollinators are believed to be a major driver of angiosperm evolution, exerting selective pressures on the plants they visit, which can result in convergent evolution in distantly related angiosperm taxa. The example posed by flower shape illustrates well this principle, with similar morphologies having arisen multiple independent times. However, it is unclear how these pressures drive the appearance of specific flower shapes. The pantropical genus Erythrina (Leguminosae), with 131 species pollinated mainly by birds (including hummingbirds, passerines and sunbirds) but also by bees, offers an ideal model to better understand pollinator-mediated flower shape evolution. Phylogenetic studies indicate that hummingbird pollination has evolved several times in this genus, each time with the appearance of a prominent standard petal, that gives the flower an overall tubular shape. The shape of the standard petal plays a key role in the plant-pollinator relationship in Erythrina, and it is believed to be a target of pollinator-mediated selective pressures. The keel and wing petals are usually much smaller than the standard, and they are often hidden within the calyx, although a strong interspecific variance in size and shape can be observed. In the present study, we use geometric morphometrics and a molecular phylogenetic analysis of 90 Erythrina species (including representatives of most clades and of all the pollination modes) to explore morphological changes in the standard, keel and wing petals. The outlines for each kind of petal were digitized using three landmarks and 40 semilandmarks. Species were grouped according to their petal shape using a Procrustes PCA. Our results show that the standard petal in hummingbird-pollinated Erythrina species has repeatedly converged to a specific recurrent shape, suggesting a strong selection pressure imposed by hummingbirds on flower shape. These findings also suggest that the standard petal has a key mechanical role in mediating plant-pollinator interactions in hummingbird-pollinated Erythrina. Keel petal shape and size are more variable, ranging from 3-4 millimetres to a few centimetres, depending on the species. Our findings are in line with similar studies performed in other angiosperm families, and confirm the importance of pollinator-induced selective pressures in the evolution of legumes.

1 - Université de Montréal, Dept. of Biological Sciences , Institut de Recherche en Biologie Végétale, 4101 Sherbrooke St. East, Montréal, QC, H1X2B2, Canada
2 - Institut De Recherche En Biologie Végétale, 4101 CUE SHERBROOKE EST, Montréal, QC, H1X 2B2, Canada
3 - INSTI DE RECHERCHE BIO VEGETAL, 4101 CUE SHERBROOKE EST, Montréal, QC, H1X 2B2, Canada

Keywords:
floral evolution
pollination
Leguminosae
Geometric morphometrics.

Presentation Type: Oral Paper
Session: 2, Macroevolution
Location: Fort Worth Ballroom 5/Omni Hotel
Date: Monday, June 26th, 2017
Time: 9:15 AM
Number: 2006
Abstract ID:362
Candidate for Awards:None