Frugivorous birds play an important role in the distribution of those plants on whose fruits they feed and affect species composition of plant communities. The fruiting phenology of Sambucus chinensis Lindl. in Wuhan ...Frugivorous birds play an important role in the distribution of those plants on whose fruits they feed and affect species composition of plant communities. The fruiting phenology of Sambucus chinensis Lindl. in Wuhan area ranges from July to November, while abundant fruits are available in July and August. Although other seven species of frugivores were found in the study area, only Pycnonotus sinensis (Gmelin), a resident bird endemic to China, was observed foraging in the fruits of this plant for the field. Pycnonotus sinensis shifts from eating fruits of Broussonetia papyrifera (L.) Vent. to those of S. chinensis from July to August. Identification of seeds in a total of 658 feces disseminated by P. sinensis which were collected in the field showed that most of the seeds came from S. chinensis and B. papyrifera . Seeds in those feces collected at the end of August were all of S. chinensis . Field investigation of the associations of S. chinensis shows that its frequent companion species are B. papyrifera, Cinnamomum camphora, Ligustrum lucidum and Rubus biflorus , whose fruits are also preferred by this frugivore in different seasons. The distribution of Pycnonotus sinensis is limited to the south of Qinling Mountain in China. The distribution of S. chinensis is basically consistent with that of Pycnonotus sinensis . The result indicates that seed dispersal of S. chinensis depends on the foraging of this frugivore. Likewise, the fruits of S. chinensis are the primary food for this frugivore in autumn. As the result suggests, conservationists and restoration biologists should highlight the study of plant_disperser mutualism in the future work.展开更多
Sex expression in Sagittaria guyanensis H.B.K. subsp. lappula (D. Don) Bojin is typically andromonoecious while the other species in the same genus are basically monoecious. The evolutionary advantages of male...Sex expression in Sagittaria guyanensis H.B.K. subsp. lappula (D. Don) Bojin is typically andromonoecious while the other species in the same genus are basically monoecious. The evolutionary advantages of male flowers and hermaphrodite flowers in S. guyanensis subsp. lappula were assessed by measuring sex allocation and pollen movements in two wild populations of the species. Two cultivated populations served as controls. The percentage of male flowers was very low in the two wild populations in Dongxiang, Jiangxi Province and Wuyishan, Fujian Province, viz., 2.48% and 0.96% respectively. In the two cultivated populations, male flower percentage significantly increased when the soil was of higher nutrient content. This indicates that the allocation to male versus female reproduction might change in response to environmental factors. Pollen production per male flower was 4.1 times higher than that of a hermaphrodite flower. The floral shape and size of male and hermaphrodite flowers were similar. No difference was observed between these dimorphological flowers in pollen germination rate in vitro and in the speed of pollen tube growth in vivo . Anthesis was only 4-5 h. Male flowers usually opened 0.5 h earlier than hermaphrodite flowers. An unexpected finding was that no pollen from the male flowers was found on the stigmas of the hermaphrodite flowers, in spite of the occasional visits by insects to both types of flowers in both wild and control populations. A consistent pattern of fruit development was found to exist in open pollinated flowers as well as in flowers that had been bagged. The sex ratios did not have significant influence on fruit set. Approximately 25% of the pistils in a gynoecium failed to develop into fruits because no pollen was deposited on them, indicating that the fruit set of this andromonoecious plant is mainly affected by pollen limitation rather than resource limitation. Reproduction in S. guyanensis subsp. lappula in the habitats was dependent on self_pollination in hermaphrodite flowers. The male flowers in this species might be a potential source of additional pollination and may facilitate cross_pollination. The fact that the flowers of monoecious species in Sagittaria pollinated by a wide diversity of insect visitors may contribute enormously to the diversification of sex expression in this genus.展开更多
文摘Frugivorous birds play an important role in the distribution of those plants on whose fruits they feed and affect species composition of plant communities. The fruiting phenology of Sambucus chinensis Lindl. in Wuhan area ranges from July to November, while abundant fruits are available in July and August. Although other seven species of frugivores were found in the study area, only Pycnonotus sinensis (Gmelin), a resident bird endemic to China, was observed foraging in the fruits of this plant for the field. Pycnonotus sinensis shifts from eating fruits of Broussonetia papyrifera (L.) Vent. to those of S. chinensis from July to August. Identification of seeds in a total of 658 feces disseminated by P. sinensis which were collected in the field showed that most of the seeds came from S. chinensis and B. papyrifera . Seeds in those feces collected at the end of August were all of S. chinensis . Field investigation of the associations of S. chinensis shows that its frequent companion species are B. papyrifera, Cinnamomum camphora, Ligustrum lucidum and Rubus biflorus , whose fruits are also preferred by this frugivore in different seasons. The distribution of Pycnonotus sinensis is limited to the south of Qinling Mountain in China. The distribution of S. chinensis is basically consistent with that of Pycnonotus sinensis . The result indicates that seed dispersal of S. chinensis depends on the foraging of this frugivore. Likewise, the fruits of S. chinensis are the primary food for this frugivore in autumn. As the result suggests, conservationists and restoration biologists should highlight the study of plant_disperser mutualism in the future work.
文摘Sex expression in Sagittaria guyanensis H.B.K. subsp. lappula (D. Don) Bojin is typically andromonoecious while the other species in the same genus are basically monoecious. The evolutionary advantages of male flowers and hermaphrodite flowers in S. guyanensis subsp. lappula were assessed by measuring sex allocation and pollen movements in two wild populations of the species. Two cultivated populations served as controls. The percentage of male flowers was very low in the two wild populations in Dongxiang, Jiangxi Province and Wuyishan, Fujian Province, viz., 2.48% and 0.96% respectively. In the two cultivated populations, male flower percentage significantly increased when the soil was of higher nutrient content. This indicates that the allocation to male versus female reproduction might change in response to environmental factors. Pollen production per male flower was 4.1 times higher than that of a hermaphrodite flower. The floral shape and size of male and hermaphrodite flowers were similar. No difference was observed between these dimorphological flowers in pollen germination rate in vitro and in the speed of pollen tube growth in vivo . Anthesis was only 4-5 h. Male flowers usually opened 0.5 h earlier than hermaphrodite flowers. An unexpected finding was that no pollen from the male flowers was found on the stigmas of the hermaphrodite flowers, in spite of the occasional visits by insects to both types of flowers in both wild and control populations. A consistent pattern of fruit development was found to exist in open pollinated flowers as well as in flowers that had been bagged. The sex ratios did not have significant influence on fruit set. Approximately 25% of the pistils in a gynoecium failed to develop into fruits because no pollen was deposited on them, indicating that the fruit set of this andromonoecious plant is mainly affected by pollen limitation rather than resource limitation. Reproduction in S. guyanensis subsp. lappula in the habitats was dependent on self_pollination in hermaphrodite flowers. The male flowers in this species might be a potential source of additional pollination and may facilitate cross_pollination. The fact that the flowers of monoecious species in Sagittaria pollinated by a wide diversity of insect visitors may contribute enormously to the diversification of sex expression in this genus.
