Reproductive strategy of an invasive buzz-pollinated plant (Solanum rostratum)

Some plants that invade environments outside their native range of distribution often face reproductive challenges such as limited pollinators and mates. Thus, the capacity to reproduce autonomously in the absence of pollinators or mates can facilitate establishment and spread of invasive plants. Here, we study the capacity of Solanum rostratum to reproduce through autonomous self-pollination. Although this plant is self-compatible, it strongly depends on visitation of buzzing bees to reproduce in its native range. We compared floral morphology, pollen: ovule ratios, reproductive phenology, and capacity for autonomous self-pollination of two populations of native distribution (Mexico) and another two populations of the invasive range (USA). We found a reduction in anther-stigma distance, pollen: ovule ratio, and plant height in invasive populations, as well as a shift to increased resource allocation to floral vs. vegetative structures and faster flowering compared to native populations. Importantly, invasive populations show a marked increase in the capacity to produce fruits autonomously (without pollen vectors). Our results suggest that the northern invasion of S. rostratum could have been facilitated by a shift in reproductive strategy from outcrossing to autonomous self-pollination.