Heterostyly accelerates diversification via reduced extinction in primroses

Area of Science:

• Evolutionary biology
• Plant sciences
• Ecology

Background:

• Flowering plant (angiosperm) diversity is exceptionally high, driven by floral innovations and mating systems.
• The link between floral evolution, speciation, and extinction dynamics is not fully understood.
• Heterostyly, a floral syndrome promoting outcrossing, evolved independently multiple times in angiosperms.

Purpose of the Study:

• Investigate the impact of heterostyly on species diversification trajectories.
• Determine whether heterostyly influences speciation or extinction rates.
• Examine the role of heterostyly in the context of evolutionary time scales.

Main Methods:

• Utilized Darwin's model for heterostyly in the primrose family (Primulaceae).
• Analyzed species diversification rates in relation to the evolution and loss of heterostyly.
• Compared short-term and long-term effects of heterostyly on lineage diversification.

Main Results:

• Heterostyly accelerates angiosperm diversification primarily by decreasing extinction rates, likely by avoiding inbreeding depression.
• The diversification-accelerating effect of heterostyly is evident over long evolutionary time scales.
• Recent losses of heterostyly may lead to short-lived increases in speciation rates.

Conclusions:

• Heterostyly promotes long-term lineage diversification by enhancing survival rather than generating new species.
• The net effect of heterostyly on diversification depends on temporal and clade-specific factors.
• Understanding trait-driven diversification requires considering evolutionary time and specific ecological contexts.