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Allometric relationships better explains seed coat microsculpture traits in Mentzelia section Bartonia (Loasaceae) than ecology or dispersal Actions

Topic: Allometric relationships better explains seed coat microsculpture traits in Mentzelia section Bartonia (Loasaceae) than ecology or dispersal
Presenter: John J. Schenk

Variation in seed coat microsculpture traits provide reliable characters for species delimitation as well as synapomorphies that support phylogenetic hypotheses; however, botanists have not yet identified the ecological or evolutionary reasons why closely related species differ in microsculpture traits. A statistical phylogenetic approach was applied to seed variation in Mentzelia section Bartonia (Loasaceae) to determine whether seed traits are correlated with ecological variation, dispersal strategies, and/or each other. Fifty-six taxa were measured for capsule, whole seed, and seed-coat microsculpture-traits (cell area, cell shape, sinus depth, papillae number, and papillae length) and compared to each other and to bioclimate variation. We determined that seed coat traits covary with each other; specifically, seeds with larger cells have more sinuate walls and more numerous, small papillae. The hypothesis that seed coat microsculpture traits directly covary with climate or with dispersal strategy was unsupported. We conclude that bioclimate variation does not directly select for seed microsculpture traits in Mentzelia section Bartonia, but rather indirectly selects for larger seeds that, in turn, are correlated with larger cells. Cell sizes are ultimately responsible for the variation in microsculpture traits, such as sinus depth, papillae number, and papillae length.

Keywords: character evolution, morphology, phylogenetic comparative methods, phylogenetic independent contrasts, Seed, testa

Allometric relationships better explains seed coat microsculpture traits in Mentzelia section Bartonia (Loasaceae) than ecology or dispersal

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