Serotiny and the Evolution of Seed Cone Size in Cupressaceae Conifers

• Published in: International journal of plant sciences Vol. 182; no. 1; pp. 9 - 18
• Main Authors: Swarup, Karishma, Contreras, Dori, Leslie, Andrew B.
• Format: Journal Article
• Language: English
• Published: Chicago The University of Chicago Press 01.01.2021; University of Chicago, acting through its Press
• Subjects: Adaptation; Branching; Cones; Conifers; Correlation; Cupressaceae; Dispersal; Evolution; Morphology; Phylogeny; Seed dispersal; Seeds; Taxa; serotiny; conifers; seed dispersal; cone evolution; wildfire
• ISSN: 1058-5893; 1537-5315
• DOI: 10.1086/711470

Premise of research. Serotiny is a specialized dispersal mechanism in which seeds are retained on the parent plant and released following a disturbance event. This strategy has evolved repeatedly in plants inhabiting fire-prone regions and typically requires adaptations for the protection and release of seeds. We explore the relationship between serotiny and reproductive morphology in the Cupressaceae conifer clade, asking whether serotiny is associated with the evolution of larger, more protective seed cones. Methodology. We compiled cone volume data from 72 extant Cupressaceae species, with detailed cone and seed mass measurements from 19. Using phylogenetic regressions and a previously published phylogeny, we reconstructed how many times serotiny evolved in Cupressaceae and asked whether its appearance was correlated with larger seed cones. We also tested whether cones from serotinous taxa produced proportionally more sterile tissues than those from nonserotinous taxa. Pivotal results. Serotiny has likely evolved five times within extant Cupressaceae, and each time it is correlated with the evolution of larger seed cones. The larger cones of serotinous taxa do not show proportionally more investment in sterile tissues, however. Conclusions. The relationship between cone size and serotiny is particularly strong in Cupressaceae because their branching architecture favors the production of small cones; fire regimes can then exert a strong selective pressure favoring larger ones. Conifers that produce generally larger seed cones may be less likely to show a correlation with serotiny. Considering seed cone size and branching architecture together, however, may allow for the interpretation of serotiny in the conifer fossil record.