Bee-pollination promotes rapid divergent evolution in plants growing in different soils

Area of Science:

• Plant evolutionary biology
• Ecology
• Experimental evolution

Background:

• Divergent evolution drives diversification, with ecological factors like soil, pollinators, and herbivores hypothesized as key drivers in plants.
• Experimental evidence for these drivers, especially their interactions, is limited.

Purpose of the Study:

• To experimentally investigate the impact of soil type, pollination method, and aphid herbivory on adaptive divergence in Brassica rapa.
• To identify the relative contributions and interactions of these ecological factors in shaping plant evolution.

Main Methods:

• Utilized fast-cycling Brassica rapa in an eight-generation experimental evolution study.
• Manipulated soil types, pollination (bumblebee vs. hand-pollination), and introduced aphid herbivory.
• Assessed evolutionary changes in various plant phenotypic traits.

Main Results:

• Soil, pollination, and herbivory, along with their interactions, caused significant evolutionary changes in plant phenotypes.
• Richer soil and bumblebee pollination accelerated evolutionary rates, leading to increased plant attractiveness to bumblebees.
• Aphid herbivory reduced plant attractiveness, while the strongest divergence occurred under different soils with bee-pollination.

Conclusions:

• The interaction between soil conditions and biotic pollination is a crucial factor promoting divergent evolution in plants across different soil types.
• This "soil-pollinator effect" influences a wide range of traits, including leaf size, flowering time, and floral characteristics, even without pollinator guild shifts.