*New Paper*: Flower Size and Shape Evolution Following the Transition to Separate Sexes

The main results of my undergraduate honours thesis are now published (open access) in the American Journal of Botany! A few thoughts about it below, and then, because I wanted an excuse to look through my photos, some pictures from the trip to Baja California with my wonderful undergrad advisors, Jill Miller and Rachel Levin, on which we collected the flowers for this work.

• Lycium is a genus of poky, shrubby plants in the tomato family (Solanaceae) that’s distributed near-globally, in drier environments. Research on these plants has focussed primarily on their systematics, biogeography, and reproductive systems. Most species in the genus have hermaphroditic flowers, with a genetic way of preventing self-fertilization. But in some species, changes in the genome lead to the breakdown of this genetic mechanism, and this change is accompanied by the evolution of separate sexes. Lycium californicum is particularly interesting, because populations of this monophyletic species can have either hermaphroditic flowers or male and female flowers (see  the companion paper to this one, published last year in Annals of Botany for more details). This lets us examine, in the new paper, how selection may have acted on males and females to change the shape and size of their flowers from the ancestral hermaphroditic condition, using present day hermaphrodites from nearby populations as a close proxy for the hermaphroditic ancestor. 
• To this end, we collected hundreds of flowers, and I spent many hours hunched over a microscope listening to This American Life and measuring tiny floral traits. In making these comparisons, we had to take into account a stark environmental gradient in rainfall and temperature across central Baja California. 
• We found that while these abiotic environmental gradients influenced both overall flower size and shape, flower size dimorphism in L. californicum appeared to arise through selection for larger flowers in males but not smaller flowers in females. Axes of flower shape were related to sex (male/female/hermaphrodite) and sexual system (hermaproditic populations vs. separate sex populations). 
• Someday I will use this paper as a jumping off point for writing more about differences between botantists’ and zoologists’ approaches to studying reproduction, and specifically how the people studying plants do a much better job of quantifying both sex and mating systems continuously as opposed to categorically. But those thoughts are still forming…in the meanwhile, check out the paper if you want to learn more details about this study, and here are some picture from fieldwork! This trip is when I learnt to love fish tacos, tidepools, and the West Coast light.