The mixed mating system of a widespread weed: the case of Argemone ochroleuca Sweet (Papaveraceae)

Abstract

Background: Argemone ochroleuca is a worldwide invasive weed but is also highly valuable for their chemical compounds. Knowledge about its reproduction will help create plans for its control or its propagation. Questions: Does A. ochroleuca has an incompatibility system like other Papaveraceae species? Which are the reproductive strategies that favor the seed formation in A. ochroleuca? Studied species: A. ochroleuca is an annual species with bisexual flowers. Study site and dates: Mexico City, Mexico. The fieldwork was performed from February to May in 2013, 2014, and 2017. Methods: Direct observations were made to describe the flower cycle of A. ochroleuca. We used self-pollinated flowers to analyze if this species is self-incompatible by following the pollen tube growth through gynoecium. Controlled pollinations were made to quantify and compare the number of seeds produced per treatment to know the mating system and explore if the species presents a mechanism of reproductive assurance through autogamy, or exhibits inbreeding depression. Results: A. ochroleuca is self-compatible and exhibits a mixed mating system. Although outcrossing is how more seeds are produced, both autogamy and pseudocleistogamy are present as reproductive assurance mechanisms. Naturally pollinated flowers produce the maximum number of seeds, but inbreeding depression is present in the population. Thus, the number of seeds will be affected by continuous selfing. Conclusions: This study highlights the mixed mating system and reproductive assurance mechanisms as successful strategies for A. ochroleuca, a common pattern in invasive weeds.