| Sambucus javanica is a perennial herb of the genus Sambucus Linn.of Caprifoliaceae.It is mainly distributed in central and southern China,and also in Japan,Myanmar and Vietnam.The extrafloral nectaries of Sambucus javanica are scattered on inflorescence,which are yellow or orange-red in the initial stage.With the opening of white bisexual flowers,the extrafloral nectaries gradually grow and secrete a large amount of extrafloral nectar,attracting a large number of ants to visit.In this paper,two natural populations of Sambucus javanica were selected in Yucheng District of Ya'an City,Sichuan Province to conduct two-factor experiments(blocking ants and removing nectaries).The number of ants attracted by the nectaries of two populations of Sambucus javanica,the species of ants,the number of active extrafloral nectaries and the leaf area of Sambucus javanica under different treatments,the insect feeding rate,the visits of extrafloral nectaries and ants to pollinating insects were studied.In order to understand the ecological significance of the extrafloral nectary of Sambucus javanica and lay a foundation for further research on the reproductive ecology of Sambucus javanica,the effects of bee and fly visiting frequency and reproductive fitness(seed setting rate)and the pollination effect of ant visiting on Sambucus javanica were studied.The results show as follows:1.There were significant differences in the number of extrafloral nectaries among different populations(population 1 P < 0.001,population 2 P < 0.05).The number of active extrafloral nectaries of Sambucus javanica was the highest in the middle flowering stage,and the number of extrafloral nectaries of the two populations were 41.70 ± 11.05 and 24.80 ± 9.95 per plant,respectively.In the same population,the number of ants attracted by Sambucus javanica was significantly different in different periods,and the number of active extrafloral nectaries was different.The difference was significant(population 1 P < 0.001,population 2 P < 0.05).The number of ants attracted by the extrafloral nectary of Sambucus javanica was the highest in the middle flowering stage,and the number of extrafloral nectaries of was the highest in the middle flowering stage.The number of ants attracted by the two populations was 4.57 ± 2.86 and 1.49 ± 1.15,respectively.Population 1 mainly attracted 4 species of ants,and population 2 mainly attracted 6 species of ants.2.Population 1 did not remove the extrafloral nectary,did not block the ants;did not remove the extrafloral nectary,blocked the ants;removed the extrafloral nectary,did not block the ants and the extrafloral nectary,blocked the four treatments of ants,the leaf insect feeding rates were 0.18 ± 0.09,0.17 ± 0.12,0.16 ± 0.07,0.17 ± 0.07,respectively,and the population 2 were 0.08 ± 0.06,0.09 ± 0.07,0.09 ± 0.07,0.09 ± 0.07.During the experiment,the extrafloral nectaries and ants had no effect on the insect-feeding rate of the leaf area of Sambucus javanica(P > 0.13).3.Population 2 did not remove the extrafloral nectaries,did not block the ants;did not remove the extrafloral nectaries,blocked the ants;removed the extrafloral nectaries,did not block the ants and the extrafloral nectaries,blocked the ants.The visiting frequencies of Sambucus javanica were 1.82 ± 1.12,1.84 ± 1.75,1.32 ± 0.89,1.07 ± 0.82 times per 15 minutes,and syrphid flies were 0.30 ± 0.47,0.15 ± 0.21,0.15 ± 0.20,0.21 ± 0.23 times per15 minutes respectively,respectively.The total pollinating insect visits were 2.15 ± 1.23,2.01 ± 1.77,1.48 ± 0.92 and 1.31 ± 0.77 times per 15 minutes.Removal of extrafloral nectaries had a significant effect on the frequency of bee insect visits(P < 0.05).The frequency of total pollinating insects was significantly different(P < 0.001).The frequency of fly insect visits was nearly significant(P = 0.076).Ants had no significant effect on the frequency of different pollinating insects and the frequency of total pollinating insects visits of Sambucus javanica(all P > 0.42).4.Population 1 did not remove the extrafloral nectary,did not block the ants;did not remove the extrafloral nectary,blocked the ants;removed the extrafloral nectary,did not block the ants and the extrafloral nectary,blocked the ants,and blocked the four treatments,the average seed setting rate per plant was 0.65 ± 0.13,0.70 ± 0.12,0.50 ± 0.18,0.52 ± 0.15,the number of flowers was 2657 ± 1862,2663 ± 1637,2510 ± 1364,2472 ± 952 per plant,respectively.The average seed setting rates of the four treatments were 0.56 ± 0.12,0.58 ± 0.10,0.39 ± 0.12,respectively.The number of flowers were 1201 ± 952,1282 ± 454,1342 ± 554,1366 ± 631 per plant,respectively.There was a significant difference in seed setting rate between non-removal of extrafloral nectary and non-removal of extrafloral nectary(P < 0.001);there was no effect on the number of flowers(all P > 0.10);there was no effect on the seed setting rate of Ants(P > 0.21);there was a significant difference in seed setting rate between populations(P < 0.001).5.Population 1 did not block pollinating insects,does not block ants;does not block pollinating insects,obstructs ants;obstructs pollinating insects,does not block ants;obstructs pollinating insects,obstructs the ant;obstructs pollinating insects,obstructs the ant's Sambucus javanica branch setting rate average values are 0.68 ± 0.22,0.67 ± 0.25,0.15 ± 0.10,14 ± 0.09,respectively.After blocking pollinating insects by bagging,the seed setting rate of Sambucus javanica decreased significantly(P < 0.001),but the ant had no significant effect on the seed setting rate of Sambucus javanica(P > 0.82).In conclusion,the extrafloral nectary of elderweed attracts a large number of ant visits,which have no effect on the insect-feeding rate of leaf area.It does not support the generally accepted protection hypothesis,which may be related to the species,abundance and time of the attracted ants.The extrafloral nectary of Sambucus javanica can attract pollinating insects and improve the reproductive fitness of Sambucus javanica.The visiting frequency of pollinating insects is not significantly affected by ants.The extrafloral nectary can improve flower display.Ants do not pollinate in the process of visiting the extrafloral nectary.Sambucus javanica mainly relies on honeybees,flies and insects to pollinate.When pollinating insects are insufficient,there may be self-pollinator autonomously. |
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