Heterostyly is an adaptation found in numerous families that enables outbreeding in dioecious flowers, complementing self-incompatibility mechanisms. However, an evolutionary transition to homostyly with high levels of self-fertilization is frequently seen, with consequences for the genetic structure, evolution and adaptation of the species. These are found in population studies and can be understood with theoretical modelling. Identifying the environmental conditions favouring transitions to selfing and determining their population genetic consequences can provide insights into how often and why selfing evolves in heterostylous lineages.
Researchers of South China Botanical Garden, CAS formulate three critical questions about ecological correlates and genetic consequences of evolutionary transitions from distyly to homostyly. (1) What are the frequencies, geographical distribution and reproductive characteristics of floral morphs in distylous and homostylous populations? (2) Does increased elevation influence pollinator
service and the likelihood of inbreeding in populations? (3) How often has homostyly originated and what are the consequences of the breakdown of distyly for the amounts and distribution of genetic diversity in populations? We address these questions using 14 populations of Primula oreodoxa, finding that homostyles set more seeds than distylous morphs following open pollination, although there are fewer long-tongued pollinator visits. Despite the lower genetic diversity in the homostylous populations, these populations benefited from reproductive certainty through self-pollination allowed by loss of heterostyly.
With the guiding of Professor Dianxiang Zhang, Dr. Shuai Yuan and Dr. Miaomiao Shi performed the study during three years. This study was financially supported by the National Natural Science Foundation of China (grants U1202261, U1603231 to D.X.Z., 31400209 to M.M.S.). The paper was finally published in Annals of Botany (2017, 120:775-789) with a title of ‘Ecological correlates and genetic consequences of evolutionary transitions from distyly to homostyly’.
