Abstract
Revealing the environmental pressures determining the frequency of females amongst populations of sexually dimorphic plants is a key research question. Analyses of sex ratio variation have been mainly done in dioecious plants, which misses key plant sexual systems that might represent intermediate stages in the evolution of dioecy from hermaphroditism. We investigated female frequency across populations of sexually dimorphic plant species in relation to environmental stressors (temperature, precipitation), totaling 342 species, 2011 populations, representing 40 orders and three different sexual systems (dioecy, gynodioecy and subdioecy). We also included the biome where the population was located to test how female frequency may vary more broadly with climate conditions. After correcting for phylogeny, our results for gynodioecious systems showed a positive relationship between female frequency and increased environmental stress, with the main effects being temperature-related. Subdioecious systems also showed strong positive relationships with temperature, and positive and negative relationships related to precipitation, while no significant effects on sex ratio in dioecious plants were detected. Combined, we show that female frequencies in an intermediate sexual system on the pathway from hermaphroditism to dioecy respond strongly to environmental stressors and have different selective agents driving female frequency.
Highlights
The evolution and maintenance of plant sexual systems has been fascinating evolutionary ecologists for decades
We investigated female frequency across populations of sexually dimorphic plant species in relation to environmental stressors, totaling 342 species, 2011 populations, representing 40 orders and 3 different sexual systems
We show that female frequencies in intermediate sexual system on the pathway from hermaphroditism to dioecy respond strongly to environmental stressors and have different selective agents driving female frequency
Summary
The evolution and maintenance of plant sexual systems has been fascinating evolutionary ecologists for decades. Most plant species are hermaphroditic, with individuals having perfect or bisexual flowers possessing both the female (i.e. seed production) and male (i.e. pollen production) sexual functions within the same flower. Physical separation of the female and male sexual functions in different individuals (i.e. dioecy) has independently evolved repeatedly (Charlesworth 2002, Renner 2014). Dioecy evolves with the spread of monoecious (i.e. plants bearing pistillate and staminate flowers) individuals first and the evolution of unisexual individuals (see Käfer et al 2017 for more details). The macroevolutionary pathways in plant sexual system evolution are complex with support for transitions both towards and away from sexual differentiation (Goldberg et al 2017; Käfer et al 2017). There are potentially multiple underlying gene and pathways underpinning sexual differentiation (Henry et al 2018), highlighting the complex nature of plant sexual system evolution
Sign-in/Register to view highlights & summary 
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call