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.

INTERNATIONAL JOURNAL OF PLANT SCIENCES

UNIV CHICAGO PRESS

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

1058-5893

Premise of theresearch.Sexual functions in gymnosperms are mostly performed by separate reproductivestructures, which largely reduces sexual interference and sets the scene for morphologicaland functional sexual specialization. The evolutionary trajectories followed by traitsrelated to the male and female functions are therefore expected to beuncoupled. Studies on the fossil record of the coniferfamily Araucariaceae revealed important morphological changesoccurring in reproductive cones. Here, we explored the pattern of evolution ofmale and female cone sizes in Araucariaceae,with an special focus on Araucaria, the most variable andwidespread genus in the family. Methodology. We gathereddata on male and female cone sizes from fossils and extant Araucariaceaespecies. Focusing on Araucaria, we analysed whether cone sizes are phylogeneticallystructured. Furthermore, we compared the evolutionary trajectories of male andfemale cone sizes by evaluating the goodness of fit of different evolutionarymodels. Finally, we evaluated whether differentselective regimes across the phylogeny could have shaped conemorphology.Pivotal Results.Sizechanges in Araucariaceae occurred in both male and female cones, with thelargest cones appearing in extant Araucaria. In this genus, differentevolutionary models best describedcone size changes, with male cone evolution best described by a model not influencedby phylogeny, and female cone evolution by a stabilizing selection model with two optima.This resulted in contrasting phylogenetic signals, with female cone size beingmore phylogenetically structured than malecone size.Conclusions. Changes in conesize in Araucariaceae occurred in both male and female cones. The largest maleand female cones appeared in Araucaria through uncoupled evolutionary pathways,both involving a natural selection component as a driver of evolutionarychange. A contrasting pattern of phylogeneticsignal in male and female cone size reflected the uncoupled evolutionarytrajectories followed by these sexual structures.