Effects Of Floral Size Variation On Male Reproductive Fitness In Herpetospermum Pedunculosum (Cucurbitaceae)

Flowers are the agents in communications between plants and their pollinators,and changes of floral size can usually result in the difference in visitation preference of pollinators.In dioecious plants,male flowers are usually larger than female ones,which might be related to the differences in gender function,but it still needs to be clarified on how variations of floral size among male flowers affect the male fitness.Herpetospermum pedunculosum(Ser.)C.B.Clarke is a dioecious plant in Cucurbitaceae,and the ratio of male to female in natural population is usually strong male-biased(about 7:3),indicating the competition among male flowers.Therefore,in this thesis,I performed transcriptome sequencing to develop SSR primers that could be used in paternal analysis of H.pedunculosum.Then,based on different male plants and seed DNA,male reproductive success was analyzed.At the same time,the relationship between male floral size and male reproductive success was analyzed.Our results provided experimental evidence for the effect of floral size variation on male fitness in a dioecious plant.The main results are as follows:1.Through the transcriptome data of male and female plants of H.pedunculosum,131 pairs of SSR primers were designed,and polymorphism of these SSRs was validated based on PCR amplification using two population materials from Yunnan and Tibet.Finally,15 pairs of polymorphic SSR primers were obtained for further paternity analysis.2.The paternity analysis results showed that the potential paternity could be identified for 242 offspring at the 80% confidence level.In the 33 male plants that could be the potential paternity in the same population,25 male plants(75.76%)might produce the potential offspring.The contribution rate of male reproduction ranged from 0.41%-9.09%,and the male reproduction fitness ranged from 0.05-1.3.In the bee color space,the region absorbing ultraviolet was within the visual range,but the region reflecting ultraviolet was included in the 0.1 hexagon unit center,indicating that the region absorbing ultraviolet was visible but the region reflecting ultraviolet was invisible to bee.There was a positive correlation between the size of male flower(area and length of petal)and the size of the absorbing ultraviolet region.In the natural population,the frequencies of flower size in both visible light and ultraviolet light showed a bias to small flower size.The regression analysis showed a negative relationship between number of offspring and the male flower size in both visible light and ultraviolet.Conclusively,15 pairs of polymorphic SSR primers were validated for paternity analysis based on transcriptome sequencing,and a negative relationship was found between male reproductive fitness and floral size under visible and ultraviolet light,which could result from the low number of male flower with large size in the study population and extensive pollen flow from other populations into the study population.In addition,other pollinators(such as butterflies)may visit flowers of H.pedunculosum using olfactory signals instead of visual signals.However,I cannot present the exact reasons leading to the negative correlation between floral size and male reproductive fitness in H.pedunculosum,and field observations and pollination experiments are still needed in further researches.