Real-time divergent evolution in plants driven by pollinators

Abstract

Pollinator-driven diversification is thought to be a major source of floral variation in plants. Our knowledge of this process is, however, limited to indirect assessments of evolutionary changes. Here, we employ experimental evolution with fast cycling Brassica rapa plants to demonstrate adaptive evolution driven by different pollinators. Our study shows pollinator-driven divergent selection as well as divergent evolution in plant traits. Plants pollinated by bumblebees evolved taller size and more fragrant flowers with increased ultraviolet reflection. Bumblebees preferred bumblebee-pollinated plants over hoverfly-pollinated plants at the end of the experiment, showing that plants had adapted to the bumblebees' preferences. Plants with hoverfly pollination became shorter, had reduced emission of some floral volatiles, but increased fitness through augmented autonomous self-pollination. Our study demonstrates that changes in pollinator communities can have rapid consequences on the evolution of plant traits and mating system.

Differences in sex expression and mating systems in three pollination morphs of Cimicifuga simplex

“…On the other hand, intraspecific variation of mating systems (i.e., outcrossing vs. self‐fertilization) has been well studied. Gervasi and Schiestl () showed experimentally that Brassica rapa plants with hoverfly pollination increased fitness through augmented autonomous self‐pollination, demonstrating that changes in pollinator communities can have rapid consequences for the evolution of plant mating systems. Similar to Gervasi and Schiestl (), we suggest that different pollinator environments affect the selfing rate of C. simplex , but more importantly, we suggest that different pollinator environments also affect flower sex expressions of C. simplex .…”

Should I stay or should I go? Pollinator shifts rather than cospeciation dominate the evolutionary history of South African Rediviva bees and their Diascia host plants

“…Thus, in systems with multiple interaction partners that exhibit diffuse co‐evolution like the Rediviva – Diascia mutualism, there may be little opportunity for a tight evolutionary coupling between 2 partners, which subsequently reduces the opportunity for cospeciation (Chacoff, Resasco, & Vázquez, ; Vázquez et al, ). Specifically, while pollinators are often thought to exert strong selective pressures on their hosts, thereby spurring plant diversification (Gervasi & Schiestl, ; Johnson, ; van der Niet & Johnson, ; van der Niet, Peakall, & Johnson, ), the reverse seems to occur much less frequently (Suchan & Alvarez, ). Such a pattern potentially explains the lack of cospeciation in the Diascia–Rediviva system and supports the notion of unilateral evolution, such as pollinator shifts.…”

The role of breeding system in community dynamics: Growth and mortality in forests of different successional stages

“…Ecological variables that are associated with resources available for pollinators (e.g., quantity of inflorescence) have a great impact on population structure through their effect on the pollinator behavior and plant mating (Case & Ashman, 2009; Gervasi & Schiestl, 2017; Iwata, Nagasaki, Ishii, & Ushimaru,2012). In addition, the sex ratio of species can vary considerably in response to tree size, density and stand age if the plants are growing in a stressful environment (Charlesworth, 2006; Lloyd & Bawa, 1984; Ortiz, Arista, & Talavera, 2002), which likely explains the frequency and role changing of hermaphrodite over succession.…”