Abstract
Since plant mating choices are flexible and responsive to the environment, rates of spontaneous hybridization may vary across ecological clines. Developing a robust and predictive framework for rates of plant gene flow requires assessing the role of environmental sensitivity on plant reproductive traits, relative abundance, and pollen vectors. Therefore, across a soil moisture gradient, we quantified pollinator movement, life-history trait variation, and unidirectional hybridization rates from crop (Raphanus sativus) to wild (Raphanus raphanistrum) radish populations. Both radish species were grown together in relatively dry (no rain), relatively wet (double rain), or control soil moisture conditions in Ohio, USA. We measured wild and crop radish life-history, phenology and pollinator visitation patterns. To quantify hybridization rates from crop-to-wild species, we used a simply inherited morphological marker to detect F1 hybrid progeny. Although crop-to-wild hybridization did not respond to watering treatments, the abundance of hybrid offspring was higher in fruits produced late in the period of phenological overlap, when both species had roughly equal numbers of open flowers. Therefore, the timing of fruit production and its relationship to flowering overlap may be more important to hybrid zone formation in Raphanus spp. than soil moisture or pollen vector movements.
Highlights
As climate change transforms environments [1], it can profoundly affect biotic processes occurring within those environments, such as species coexistence, migration and evolutionary trajectories [2–4]
Hybridization was rare across all plots; of the 8110 progeny genotyped, only 114 total hybrids were produced (3.4% hybridization rate) by 55 maternal plants
The frequency of hybrid offspring produced could be predicted by the date on which seeds were produced (Table 1, Fig 1)
Summary
As climate change transforms environments [1], it can profoundly affect biotic processes occurring within those environments, such as species coexistence, migration and evolutionary trajectories [2–4]. If mating processes are affected by environmental variation [5], this can have numerous and cascading effects on fecundity [6, 7], the organization of genetic diversity within versus among populations [8, 9], and, population persistence [10]. Plant populations with more genetic diversity may be able to more rapidly adapt in response to environmental change than those with less diversity. Hybridization and Climate Change systems are perhaps the most influential in structuring genetic diversity within and among populations by both transmitting diversity across generations and determining rates of diversity loss [11]. Environmentally-induced changes in plant mating patterns may alter the organization of intra- and inter-specific genetic diversity and could further magnify or dampen biotic responses to anthropogenic climate change [12]. To develop a robust and predictive framework for the science of mating systems and gene flow, it is critical to understand how plant mating systems respond to environmental variation
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