Abstract
Angiosperms are highly diverse in their reproductive systems, including predominantly selfing, exclusive outcrossing, and mixed mating systems. Even though selfing can have negative consequences on natural populations, it has been proposed that plants having a predominantly selfing strategy are also associated with fast development strategies through time limitation mechanisms that allow them to complete their life cycle before the onset of severe drought. This relationship might be affected by the challenges imposed by global change, such as a decrease in pollinator availability and the earlier and more severe onset of droughts. In this work, our aim was to investigate whether selfing is correlated with a dehydration avoidance strategy, and how this could affect drought resistance and survival in two species with different types of selfing: pollinator-independent delayed selfing (Schizanthus grahamii) and pollinator-dependent selfing (Schizanthus hookeri), representing a gradient in selfing rates. We hypothesize that delayed selfing species and highly selfing populations will show “fast” plant traits whereas we will find no pattern in more outcrossed populations of the pollinator-dependent species. However, we predicted that high selfing populations would have lower survival rates when exposed to chronic drought early in their development since fast traits imply physiological compromises that will affect their drought survival. To evaluate these hypotheses, we characterized different physiological and morphological traits in response to two contrasting treatments (moist and dry) in a total of six populations of the two species. We found a relationship between the delayed selfing species and a dehydration avoidance strategy and also with low drought survival. Our work offers evidence to support the importance of abiotic factors, such as drought, on the possible variation in selfing rates on natural populations, and the effect that this mating system could have in their ability to face new environmental conditions such as those imposed by climate change.
Highlights
We studied six populations of S. hookeri and S. grahamii with contrasting selfing rates and conducted a greenhouse experiment to compare these species and assess how populations respond to drought conditions
We found a somewhat consistent linear relationship between selfing and key traits associated with dehydration avoidance, providing some evidence to support the hypothesis that it is associated with a specific physiological profile
We found that the differences appeared between species for most traits, indicating a stronger association of the delayed selfing species (S. grahamii) with a dehydration avoidance strategy than the geitonogamous species (S. hookeri)
Summary
Mating system variation is common within and among angiosperms (Stebbins, 1974; Barrett, 1990), including alternative extremes of predominant outcrossing, or selfing, and "mixed mating" systems present in ~40% of flowering plants (Goodwillie et al, 2005; Dudley et al, 2012; Moeller et al, 2017).Within the 60% of potentially selfing species (Goodwillie et al, 2005; Jordan and Otto, 2012), there is pollinator independent (autonomous) selfing, such as delayed selfing, where the anthers touch the stigma at the end of the season assuring reproduction when crossed pollination is not possible. It leads to lower adaptive potential, increase the probability of inbreeding depression (Herlihy and Eckert, 2002), and lower genetic variability in natural populations, reducing their evolutionary potential and increasing extinction risks (Herlihy and Eckert, 2002; Moeller and Geber, 2005; Dierks et al, 2012; Dudley et al, 2012) These outcomes have led biologists to ask whether selfing is an evolutionary dead end (Dobzhansky, 1950; Stebbins, 1957; Stebbins, 1974; Schemske and Lande, 1985; Igic and Busch, 2013). The importance of these advantages and disadvantages in the maintenance of natural populations might be altered by the new challenges imposed by global change, which can modify several aspects on their environment
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