title: Evolutionary stasis in pollen morphogenesis due to natural selection.
abstract: The contribution of developmental constraints and selective forces to the determination of evolutionary patterns is an important and unsolved question. We test whether the long-term evolutionary stasis observed for pollen morphogenesis (microsporogenesis) in eudicots is due to developmental constraints or to selection on a morphological trait shaped by microsporogenesis: the equatorial aperture pattern. Most eudicots have three equatorial apertures but several taxa have independently lost the equatorial pattern and have microsporogenesis decoupled from aperture pattern determination. If selection on the equatorial pattern limits variation, we expect to see increased variation in microsporogenesis in the nonequatorial clades. Variation of microsporogenesis was studied using phylogenetic comparative analyses in 83 species dispersed throughout eudicots including species with and without equatorial apertures. The species that have lost the equatorial pattern have highly variable microsporogenesis at the intra-individual and inter-specific levels regardless of their pollen morphology, whereas microsporogenesis remains stable in species with the equatorial pattern. The observed burst of variation upon loss of equatorial apertures shows that there are no strong developmental constraints precluding variation in microsporogenesis, and that the stasis is likely to be due principally to selective pressure acting on pollen morphogenesis because of its implication in the determination of the equatorial aperture pattern.
authors.affiliation: Institut de Systématique, Évolution, Biodiversité, UMR 7205 - CNRS, MNHN, UPMC, EPHE Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, CP39 F-75005, Paris, France.|Laboratoire Ecologie Systématique et Evolution, UMR 8079 CNRS-AgroParisTech-Université Paris-Sud, 11, F-91405, Orsay, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Matamoro-Vidal
authors.affiliation: Institut de Systématique, Évolution, Biodiversité, UMR 7205 - CNRS, MNHN, UPMC, EPHE Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, CP39 F-75005, Paris, France.|Laboratoire Ecologie Systématique et Evolution, UMR 8079 CNRS-AgroParisTech-Université Paris-Sud, 11, F-91405, Orsay, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Prieu
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, UK.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Furness
authors.affiliation: Laboratoire Ecologie Systématique et Evolution, UMR 8079 CNRS-AgroParisTech-Université Paris-Sud, 11, F-91405, Orsay, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Albert
authors.affiliation: Institut de Systématique, Évolution, Biodiversité, UMR 7205 - CNRS, MNHN, UPMC, EPHE Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, CP39 F-75005, Paris, France.
authors.forename: Pierre-Henri
authors.initials: PH
authors.lastname: Gouyon
mesh_terms: D005075:Biological Evolution; D056130:Gametogenesis, Plant; D019684:Magnoliopsida / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D010802:Phylogeny; D011058:Pollen / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D012641:Selection, Genetic; D013045:Species Specificity
keywords: comparative analyses; constraints; macroevolution; microsporogenesis; morphological evolution; morphospace; pollen aperture pattern