| Corydalis DC. is one of the largest genus distributed in China, with many species endemic to China. The morphological characters are very complicated and floral structures are variable. The divergences in breeding systems and reproductive characters among species or within species provide an ideal study system for pollination and evolutionary study. We carried out researches on morphology, reproductive investment and mating system of sympatric Corydalis species, in order to explore the evolutionary trends and the adaptive significance.We conducted measurements of floral and inflorescence traits, pollinator observations, tests of mating system on9species distributed in Hubei province. The flowers of Corydalis are bilateral and has spur, and distributed in similar environment and share pollinators. But the floral traits, pollination system and mating systems diverge among species. According to the morphology of stigma, the9study species were classified into5sections. All sections share a same branch in the phylogeny evolutionary trends. The section Asterostigmata Fedde is considered to be ancient groups, and the species of this section are relatively large in size, purple, rich in nectar and self-incompatible. The section Fumarioides Liden is considered to be latter groups, and species of this section are small in size, yellow, autogamous, with a low pollinator visitation rate. This indicated that evolutionary changes from xenogamy to self-pollination occurred in this genius. Deficiency in pollinator service or interference among sympatric species on pollination may enhance these evolutionary changes. The mixed mating system is common in these species.The successive visits in the inflorescences mediate the pollen flow among flowers of the same inflorescence. As the relative success though male or female function differs among flowers of different positions within the inflorescence, the reproductive investment in male and female function may vary among flowers of different positions. In Corydalis species, pollen is secondarily presented on the stigma before the flowers open, so female and male functions are not spatially separated. The pollen is presented before the stigma become receptive. The flowers at the base of the inflorescence open before flowers above, so when the lower (older) flowers presented female function, the upper (younger) flowers are at male phase. Pollinators usually visit the inflorescences upwards, so lower flowers may receive more pollen carried by pollinators from other plants, by contrast, the pollen of upper flowers may be better removed by the pollinators and disperse to other plants. So increasing investments on the female functions in lower flowers and on the male functions in upper flowers may enhance the fitness of the whole plant. The pollination system and mating system may affect the male and female success, as well as the sex allocation within the inflorescence. To test the association between mating system and intra-inflorescence sex allocation, we examined the differences of pollen, ovule and seed production among flowers of different position for C. edulis and C. sheareri, which is self-compatible and self-incompatible, respectively. We found differences in sex allocation among these two species, because the pattern of investment in male function differs. We concluded that pollination systems and mating systems may affect the mating environment of individual flowers, and select for the evolution of sex allocation. Other factors, such as resource condition may limit the resource investment to upper (lateral) flowers or fruits.Sympatric sister species usually suffer from pollination interference caused by interspecific pollen deposition. The Corydalis species usually form mixed population by two or more species and their flowering periods often overlaps. Sharing pollinators also make the interspecific pollen deposition possible. We studied the isolation system among sister species in Sandouping and Muyu, both with three species. The pollinators remain constantly in foraging bouts, as most successive visits are among flower of the same species. In addition, the cross pollen can't elongate and fertilize the ovules. So we think the prezygotic isolation (including ethological isolation and pollen competition) play the most important role in the maintenance of species boundary. Moreover, some species reproduce though autogamy, functioning to avoid the competition and interference by other species.Vertical raceme or spike inflorescences that are bee-pollinated tend to present their flowers horizontally. Horizontal presentation of flowers is hypothesized to enhance pollinator recognition and pollination precision, and it may also ensure greater consistency of pollinator movement on inflorescences. We tested the hypotheses using bee-pollinated C. sheareri which has erect inflorescences consisting of flowers with horizontal orientation. We altered the orientation of individual flowers and prepared three types of inflorescences:unmanipulated inflorescences with horizontal-facing flowers, inflorescences with flowers turned upward, and inflorescences with flowers turned downward. We compared number of inflorescences approached and visited, number of successive probes within an inflorescence, the direction percentage of vertical movement on inflorescences, efficiency of pollen removal and seed production per inflorescence. Deviation from horizontal orientation decreased both approaches and visits by leafcutter bees and bumble bees to inflorescences. Changes in floral orientation increased the proportion of downward movements by leafcutter bees and decreased the consistency of pollinator movement on inflorescences. In addition, pollen removal per visit and seed production per inflorescence also declined with changes of floral orientation. In conclusion, floral orientation seems more or less optimal as regards bee behavior and pollen transfer for C. sheareri. A horizontal orientation may be under selection of pollinators and co-adapt with other aspects of the inflorescence and floral traits. |
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