Uncoupled evolution of male and female cone sizes in an ancient conifer lineage

GLEISER, G.; SPEZIALE, K. L.; LAMBERTUCCI, S. A.; HIRALDO, F.; TELLA, J. L.; AIZEN, M. A.

INTERNATIONAL JOURNAL OF PLANT SCIENCES

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 2019 vol. 180 p. 72 - 80

1058-5893

Premise of the research. Sexual functions in gymnosperms are mostly performed byseparate reproductive structures, which largely reduces sexual interference and setsthe scene for morphological and functional sexual specialization. The evolutionarytrajectories followed by traits related to the male and female functions are thereforeexpected to be uncoupled. Studies on the fossil record of the conifer familyAraucariaceae revealed important morphological changes occurring in reproductivecones. Here, we explored the pattern of evolution of male and female cone sizes inAraucariaceae, with an special focus on Araucaria, the most variable and widespreadgenus in the family.Methodology. We gathered data on male and female cone sizes from fossils andextant Araucariaceae species. Focusing on Araucaria, we analysed whether conesizes are phylogenetically structured. Furthermore, we compared the evolutionarytrajectories of male and female cone sizes by evaluating the goodness of fit of differentevolutionary models. Finally, we evaluated whether different selective regimes acrossthe phylogeny could have shaped cone morphology.Pivotal Results. Size changes in Araucariaceae occurred in both male and femalecones, with the largest cones appearing in extant Araucaria. In this genus, differentevolutionary models best described cone size changes, with male cone evolution bestdescribed by a model not influenced by phylogeny, and female cone evolution by astabilizing selection model with two optima. This resulted in contrasting phylogeneticsignals, with female cone size being more phylogenetically structured than male conesize.Conclusions. Changes in cone size in Araucariaceae occurred in both male and femalecones. The largest male and female cones appeared in Araucaria through uncoupledevolutionary pathways, both involving a natural selection component as a driver ofevolutionary change. A contrasting pattern of phylogenetic signal in male and femalecone size reflected the uncoupled evolutionary trajectories followed by these sexualstructures.