The Orchidaceae is a diverse and wide spread family of flowering plants that are of great value in ornamental, medical, conservation, and evolutionary research. The broad diversity in morphology,growth form, life hist...The Orchidaceae is a diverse and wide spread family of flowering plants that are of great value in ornamental, medical, conservation, and evolutionary research. The broad diversity in morphology,growth form, life history, and habitat mean that the members of Orchidaceae exhibit various physiological properties. Epiphytic orchids are often characterized by succulent leaves with thick cell walls,cuticles, and sunken stomata, whereas terrestrial orchids possess rhizomes, corms, or tubers. Most orchids have a long juvenile period, slow growth rate, and low photosynthetic capacity. This reduced photosynthetic potential can be largely explained by CO_2 diffusional conductance and leaf internal structure. The amount of light required for plant survival depends upon nutritional mode, growth form,and habitat. Most orchids can adapt to their light environments through morphological and physiological adjustments but are sensitive to sudden changes in irradiance. Orchids that originate from warm regions are susceptible to chilling temperatures, whereas alpine members are vulnerable to high temperatures.For epiphytic orchids, rapid water uptake by the velamen radicum, water storage in their pseudobulbs and leaves, slow water loss, and Crassulacean Acid Metabolism contribute to plant-water balance and tolerance to drought stress. The presence of the velamen radicum and mycorrhizal fungi may compensate for the lack of root hairs, helping with quick absorbance of nutrients from the atmosphere.Under cultivation conditions, the form and concentration of nitrogen affect orchid growth and flowering.However, the limitations of nitrogen and phosphorous on epiphytic orchids in the wild, which require these plants to depend on mycorrhizal fungi for nutrients throughout the entire life cycle, are not clearly understood. Because they lack endosperm, seed germination depends upon obtaining nutrients via mycorrhizal fungi. Adult plants of some autotrophic orchids also gain carbon, nitrogen, phosphorus, and other elements from their mycorrhizal partners. Future studies should examine the mechanisms that determine slow growth and flower induction, the physiological causes of variations in flowering behavior and floral lifespan, the effects of nutrients and atmospheric-nitrogen deposition, and practical applications of mycorrhizal fungi in orchid cultivation.展开更多
Nansi Lake and Hongze Lake are both water storage lakes along the East Route of the South-to-North Water Transfer project(ESNT).Frequent changes in hydrologic properties are responsible factors for controlling the zoo...Nansi Lake and Hongze Lake are both water storage lakes along the East Route of the South-to-North Water Transfer project(ESNT).Frequent changes in hydrologic properties are responsible factors for controlling the zooplankton community assemblages in both lakes,so we studied the possible influence of water transfer and environmental factors on zooplankton community structure and abundance.Zooplankton assemblages were investigated seasonally for one year in both lakes;a total of 133 and 122 zooplankton taxa were identified in Nansi Lake and Hongze Lake,respectively.The most dominant rotifer species were littoral,e.g.,Keratella tecta,Keratella valga and Lecane lunaris in Nansi Lake and Brachionus angularis,Brachionus forficula and Polyarthra vulgaris in Hongze Lake.Comparatively,Nansi Lake had a higher Shannon-Wiener diversity index value(5.13),while Hongze Lake had a higher species richness index(4.21).The average number of zooplankton across seasons in Nansi Lake(protozoa:774±63 ind./L,rotifers:4817±212 ind./L,cladocerans:896±14 ind./L,copepod:435±42 ind./L)was comparatively lower than Hongze Lake(protozoa:1238±63 ind./L,rotifers:6576±112 ind./L,cladocerans:1013±20 ind./L,copepod:534±25 ind./L).Canonical correspondence analysis identified differing environmental gradients that were most responsible for influencing zooplankton communities in the two lakes(Hongze Lake:NH4-N,total nitrogen,transparency and pH;Nansi:pH,temperature and total phosphorus).Frequent changes related to water transfer in lakes favoured the diversity of rotifers and protozoa communities.Zooplankton habitat preference,changes in community structure and opportunistic peaks and extinction of certain taxa were also observed in the study lakes.展开更多
Mycorrhizal fungi are essential for the growth and development of both epiphytic(growing on trees)and lithophytic(growing on rocks)orchids.Previous studies indicate that in lowland tropical areas,orchid mycorrhizal fu...Mycorrhizal fungi are essential for the growth and development of both epiphytic(growing on trees)and lithophytic(growing on rocks)orchids.Previous studies indicate that in lowland tropical areas,orchid mycorrhizal fungal compositions are correlated with the life form(i.e.,epiphytic,lithophytic,or terrestrial)of their host plants.We therefore tested if a similar correlation exists in an orchid distributed at higher elevations.Coelogyne corymbosa is an endangered ornamental orchid species that can be found as a lithophyte and epiphyte in subtropical to subalpine areas.Based on high-throughput sequencing of the fungal internal transcribed spacer 2(ITS2)-rDNA region of mycorrhizae of C.corymbosa,we detected 73 putative mycorrhizal fungal Operational Taxonomic Units(OTUs).The OTUs of two dominant lineages(Cantharellales and Sebacinales)detected from C.corymbosa are phylogenetically different from those of other species within the genus Coelogyne,indicating that different orchid species prefer specific mycorrhizal fungi.We also found that the Non-metric multidimensional scaling(NMDS)plots of orchid mycorrhizal fungi were not clustered with life form,the variations among orchid mycorrhizal fungal communities of different life forms were not significant,and most of the OTUs detected from epiphytic individuals were shared by the lithophytic plants,suggesting that orchid mycorrhizal associations of C.corymbosa were not affected by life form.These findings provide novel insights into mycorrhizal associations with endangered ornamental orchids.展开更多
Interbasin water transfer projects(IBWT's)have emerged as dispersal corridors for aquatic species.However,little is known about how water transfer affects regional spread dynamics,or shapes the genetic diversity p...Interbasin water transfer projects(IBWT's)have emerged as dispersal corridors for aquatic species.However,little is known about how water transfer affects regional spread dynamics,or shapes the genetic diversity patterns of non-native populations.Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many wellestablished populations in IBWT's.Here,we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China.Our objectives were to(1)reveal the genetic diversity patterns of the Shimofuri Goby during regional spread,and(2)identify its mode of spreading in water transfer systems.We observed(1)a high level of genetic diversity in non-native populations without evidence of bottleneck effects,(2)that non-native populations with a longer water transfer times had a higher private allele richness,and(3)that non-native populations showed a highly mixed genetic structure,low level of genetic differentiation,and no significant relationship between geographical and genetic distances.Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae,and are probably related to propagule pressure caused by the construction of water transfer.To manage the non-native populations of T.bifasciatus,preventive actions and physical removal should be implemented in IBWT's.展开更多
基金supported by the National Natural Science Foundation of China(31670342,31370362)the Natural Science Foundation of Yunnan Province(2018FA016)
文摘The Orchidaceae is a diverse and wide spread family of flowering plants that are of great value in ornamental, medical, conservation, and evolutionary research. The broad diversity in morphology,growth form, life history, and habitat mean that the members of Orchidaceae exhibit various physiological properties. Epiphytic orchids are often characterized by succulent leaves with thick cell walls,cuticles, and sunken stomata, whereas terrestrial orchids possess rhizomes, corms, or tubers. Most orchids have a long juvenile period, slow growth rate, and low photosynthetic capacity. This reduced photosynthetic potential can be largely explained by CO_2 diffusional conductance and leaf internal structure. The amount of light required for plant survival depends upon nutritional mode, growth form,and habitat. Most orchids can adapt to their light environments through morphological and physiological adjustments but are sensitive to sudden changes in irradiance. Orchids that originate from warm regions are susceptible to chilling temperatures, whereas alpine members are vulnerable to high temperatures.For epiphytic orchids, rapid water uptake by the velamen radicum, water storage in their pseudobulbs and leaves, slow water loss, and Crassulacean Acid Metabolism contribute to plant-water balance and tolerance to drought stress. The presence of the velamen radicum and mycorrhizal fungi may compensate for the lack of root hairs, helping with quick absorbance of nutrients from the atmosphere.Under cultivation conditions, the form and concentration of nitrogen affect orchid growth and flowering.However, the limitations of nitrogen and phosphorous on epiphytic orchids in the wild, which require these plants to depend on mycorrhizal fungi for nutrients throughout the entire life cycle, are not clearly understood. Because they lack endosperm, seed germination depends upon obtaining nutrients via mycorrhizal fungi. Adult plants of some autotrophic orchids also gain carbon, nitrogen, phosphorus, and other elements from their mycorrhizal partners. Future studies should examine the mechanisms that determine slow growth and flower induction, the physiological causes of variations in flowering behavior and floral lifespan, the effects of nutrients and atmospheric-nitrogen deposition, and practical applications of mycorrhizal fungi in orchid cultivation.
基金Supported by the Service Project of Special Institute of Chinese Academy of Sciences(No.Y55Z06)the Key Project in Frontier Science of Chinese Academy of Sciences(No.QYZDB-SSW-SMC041)+1 种基金the National Science Foundation of Jiangsu Province,China(No.BK20141268)the National Natural Science Foundation of China(No.31400486a)。
文摘Nansi Lake and Hongze Lake are both water storage lakes along the East Route of the South-to-North Water Transfer project(ESNT).Frequent changes in hydrologic properties are responsible factors for controlling the zooplankton community assemblages in both lakes,so we studied the possible influence of water transfer and environmental factors on zooplankton community structure and abundance.Zooplankton assemblages were investigated seasonally for one year in both lakes;a total of 133 and 122 zooplankton taxa were identified in Nansi Lake and Hongze Lake,respectively.The most dominant rotifer species were littoral,e.g.,Keratella tecta,Keratella valga and Lecane lunaris in Nansi Lake and Brachionus angularis,Brachionus forficula and Polyarthra vulgaris in Hongze Lake.Comparatively,Nansi Lake had a higher Shannon-Wiener diversity index value(5.13),while Hongze Lake had a higher species richness index(4.21).The average number of zooplankton across seasons in Nansi Lake(protozoa:774±63 ind./L,rotifers:4817±212 ind./L,cladocerans:896±14 ind./L,copepod:435±42 ind./L)was comparatively lower than Hongze Lake(protozoa:1238±63 ind./L,rotifers:6576±112 ind./L,cladocerans:1013±20 ind./L,copepod:534±25 ind./L).Canonical correspondence analysis identified differing environmental gradients that were most responsible for influencing zooplankton communities in the two lakes(Hongze Lake:NH4-N,total nitrogen,transparency and pH;Nansi:pH,temperature and total phosphorus).Frequent changes related to water transfer in lakes favoured the diversity of rotifers and protozoa communities.Zooplankton habitat preference,changes in community structure and opportunistic peaks and extinction of certain taxa were also observed in the study lakes.
基金We thank Jia-Lin Huang and Jia-Wei Li for their kind help with field work.John Meadows and Raymond Porter are acknowledged for improvements of the manuscript.This study was supported by the National Natural Science Foundation of China(Nos.31670342 and 31700026)Yunnan Applied Basic Research Project(2019FB019)+1 种基金the Science and Technology Plan of Yunnan(2018BB010)the Scientific and Technological Leading Talent Project of Yunnan Province(2016HA005).
文摘Mycorrhizal fungi are essential for the growth and development of both epiphytic(growing on trees)and lithophytic(growing on rocks)orchids.Previous studies indicate that in lowland tropical areas,orchid mycorrhizal fungal compositions are correlated with the life form(i.e.,epiphytic,lithophytic,or terrestrial)of their host plants.We therefore tested if a similar correlation exists in an orchid distributed at higher elevations.Coelogyne corymbosa is an endangered ornamental orchid species that can be found as a lithophyte and epiphyte in subtropical to subalpine areas.Based on high-throughput sequencing of the fungal internal transcribed spacer 2(ITS2)-rDNA region of mycorrhizae of C.corymbosa,we detected 73 putative mycorrhizal fungal Operational Taxonomic Units(OTUs).The OTUs of two dominant lineages(Cantharellales and Sebacinales)detected from C.corymbosa are phylogenetically different from those of other species within the genus Coelogyne,indicating that different orchid species prefer specific mycorrhizal fungi.We also found that the Non-metric multidimensional scaling(NMDS)plots of orchid mycorrhizal fungi were not clustered with life form,the variations among orchid mycorrhizal fungal communities of different life forms were not significant,and most of the OTUs detected from epiphytic individuals were shared by the lithophytic plants,suggesting that orchid mycorrhizal associations of C.corymbosa were not affected by life form.These findings provide novel insights into mycorrhizal associations with endangered ornamental orchids.
基金funded by the Key Project in Frontier Science of Chinese Academy of Sciences(Grant No.QYZDB-SSW-SMC041)the National Natural Science Foundation of China(Grant No.31870398).
文摘Interbasin water transfer projects(IBWT's)have emerged as dispersal corridors for aquatic species.However,little is known about how water transfer affects regional spread dynamics,or shapes the genetic diversity patterns of non-native populations.Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many wellestablished populations in IBWT's.Here,we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China.Our objectives were to(1)reveal the genetic diversity patterns of the Shimofuri Goby during regional spread,and(2)identify its mode of spreading in water transfer systems.We observed(1)a high level of genetic diversity in non-native populations without evidence of bottleneck effects,(2)that non-native populations with a longer water transfer times had a higher private allele richness,and(3)that non-native populations showed a highly mixed genetic structure,low level of genetic differentiation,and no significant relationship between geographical and genetic distances.Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae,and are probably related to propagule pressure caused by the construction of water transfer.To manage the non-native populations of T.bifasciatus,preventive actions and physical removal should be implemented in IBWT's.
