EVOLUTION & DEVELOPMENT 9:5, 460–471 (2007) Constraints and selection: insights from microsporogenesis in Asparagales Laurent Penet,a,1,Ã Michel Laurin,b Pierre-Henri Gouyon,a,c and Sophie Nadota aLaboratoire Ecologie, Syste´matique et Evolution, Batiment 360, Universite´ Paris-Sud, 91405 Orsay Ce´dex, France bUMR CNRS 7179, Universite´ Paris 6FPierre & Marie Curie, 2 place Jussieu, Case 7077, 75005 Paris, France cMuse´um National d’Histoire Naturelle, De´partement de Syste´matique et Evolution Botanique, 12 rue Buffon, 75005 Paris CP 39, France ÃAuthor for correspondence (email:
[email protected]) 1Current address: Department of Biological Sciences, University of Pittsburgh, 4249 Fifth & Ruskin, Pittsburgh, PA 15260, USA. SUMMARY Developmental constraints have been proposed different characteristics of microsporogenesis, only cell to interfere with natural selection in limiting the available wall formation appeared as constrained. We show that set of potential adaptations. Whereas this concept has constraints may also result from biases in the correlated long been debated on theoretical grounds, it has been occurrence of developmental steps (e.g., lack of successive investigated empirically only in a few studies. In this article, cytokinesis when wall formation is centripetal). We document we evaluate the importance of developmental constraints such biases and their potential outcomes, notably the during microsporogenesis (male meiosis in plants), with an establishment of intermediate stages, which allow emphasis on phylogenetic patterns in Asparagales. Different development to bypass such constraints. These insights are developmental constraints were tested by character discussed with regard to potential selection on pollen reshuffling or by simulated distributions. Among the morphology. INTRODUCTION 1991) also hindered tests using the concept (Pigliucci and Kaplan 2000).