A new genus of fossil Cycads, Yixianophyllum gen. nov., is reported here. The specimens were collected from the southern hill of Jinjiagou village, Toudaohezi Town, Yixian County, western Liaoning Province, China. The...A new genus of fossil Cycads, Yixianophyllum gen. nov., is reported here. The specimens were collected from the southern hill of Jinjiagou village, Toudaohezi Town, Yixian County, western Liaoning Province, China. The fossil plant-beating bed belongs to the lower part, the Zhuanchengzi bed, of the Upper Jurassic Yixian Formation （Yixianian）. The new genus in leaf shape, venation and epidermal structure shows a transitional form between Mesozoic Cycads （Ctenis, Nilssonia） and modem Cycads （Stangeria and Encephalartos）. Since the features of these specimens differ from any known genera of Cycads, a new generic name Yixianophyllum is proposed for these leaves. Typical species, Yixianophyllum jinjiagouense gen. et sp. nov. is described here. A supposed evolutionary tendency of Cycadean leaf-forms with Taeniopteris-type is discussed.展开更多
<i><span style="font-family:"">Cycas angulata, Cycas armstrongii </span></i><span style="font-family:"">and<i> Cycas conferta </i>that are<i&g...<i><span style="font-family:"">Cycas angulata, Cycas armstrongii </span></i><span style="font-family:"">and<i> Cycas conferta </i>that are<i> </i>native species of Australia were collected in Darwin city of tropical region, <i>Zamia </i><i>erosa </i>and angiosperm <i>Guaiacum officinale</i> of Zygophyllaceae which are introduced collected in the Darwin Botanic Gardens, and were carried out light microscope and electron microscope observed research to tracheary element and parenchyma tissue cells of leaflet, rachis and stem. The results showed that there are more vessel elements in their xylems;the length of vessel element of Cycadaceae with Zamiaceae are not obvious difference, the length of vessel element of angiosperm <i>Guaiacum officinale</i> is shorter, but their diameter is smaller, we thought that the characteristics which the length of vessel element is longer and the diameter is bigger are more evolutionary, because thus vessel, their number which interconnected points of possessed perforations’ end walls of vessel element is fewer, and the passageway space is larger so that the conduction speed and quantity are faster and more in unit length range and unit time. These vessels are annular vessels, spiral vessels, scalariform vessels, reticular vessels, pitted vessels and scalariform-pitted vessels, etc. In the transverse section, the vessel elements of Cycadaceae and Zamiaceae are circular, polygonous, more similar to vessel characteristics of <a name="OLE_LINK73"></a>leaf and stem of some angiosperms;however, the number of circular vessel of <a name="OLE_LINK21"></a><i>Guaiacum </i><i>officinale</i> is more, about occupy 35%, others are polygonous. The diameter of vessel is that annular vessel, spiral vessel is least, scalariform vessel or scalariform-reticular vessel is medium, reticular vessel and pitted vessel are the biggest, the characteristic is same as angiosperm. In <i>Cycas conferta</i>, etc. plants often can see several large perforations in the end walls, some species are several big scalariform or pitted perforations formed multiple perforation plates, in many vessel element lateral walls, there are some perforations formed a horizontal transport avenue of aqueous solution. The scale of diameter of <i>Cycas</i> vessel element is similar to that of <i>Zamia</i>, but the diameter of more vessel elements of <i>Cycas angulata </i>and<i> Cycas conferta</i> is bigger than the latter, and is bigger than that of <i>Guaiacum officinale</i>, although <i>Cycas</i> plants are more primitive than <i>Zamia</i><i> </i>plants, and <i>Guaiacum officinale</i> is more evolutionary, but the scale of vessel diameter of <i>Cycas</i> plants is similar to <i>Zamia </i>or bigger than the latter, even larger than <i>Guaiacum officinale</i>, these showed that cycads have evolutionary and more developed characteristics in aqueous solution transport system. In <i>Guaiacum officinale</i>, more vessel element has been not seen the ridges in the different directions of side walls which can make vessel has more mechanical supportability, but some possessed the ridges;however, more vessel elements are twist shape and can twist together each other, thus the state can increase their mechanical supportability, and their synergy with fiber elements which is longer with a twist shape, therefore their capability of xylem conduction and the combine mechanical support capability with mechanical tissue are also stronger. In the respect of observed parenchyma tissue, any parenchyma tissue cells are without perforation, all cell walls are smoothed and like a membrane. Aimed at only one or two people pointed the query about Jeffery’s method, some scholars have made comparative researches, their research used as following methods: 1) The fresh materials were cut sections 1 - 2 mm thick by hand (the query person provided and thought right method), were examined with SEM. 2) The materials were treated by Jeffrey’s Fluid and observed with SEM and so on. The results showed that the pit membrane, the remnants in the perforation and the structural characteristics of perforations were not different;and the results of our comparative research in past time and this research all justified that Jeffrey’s method is reliable and reasonable. Meanwhile, our research results showed that only vessel element can form perforation, in other all parenchyma tissue cells cannot form perforation are also proved that the perforations of vessel element are naturally inherited character. Analyzed from the structural characteristics, although they distributed so far apart from each other, they are a well and unified taxonomy system;we thought that Australia’ most species or all species of Cycadaceae came from Asia, and it is impossible from Africa, because the latter only has one more evolutionary species and lack of fossil of Cycadaceae, these species of Cycadaceae are the descendants of ancestor species;America possessed more genera of Zamiaceae, this family is mutual with Africa and Australia, we thought that these genera of Zamiaceae in Australia and America came from Pangea before continental drift in Jurassic Period, this family is also maybe one of the proofs to Australia drifted from Pangea to present position after Jurassic Period. The characteristics of tracheary element of several different genera of cycads and angiosperm further showed that more primary species or taxon, their more tissue characteristics are not also more primary, because of the need to adapt the environment, they are also constantly evolving. The research is important significant and theory reference to understand cycads evolutionary aqueous solution transport system, and understand the ecological adaptation mechanism which why present cycads of 3 families in world major distributed in tropical or subtropical regions, even many drought and barren areas.展开更多
The evolution of the latitudinal diversity gradient(LDG),characterized by a peak in diversity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mec...The evolution of the latitudinal diversity gradient(LDG),characterized by a peak in diversity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mechanism,wherein species richness increases toward the poles,remains inadequately explored.Cycads are among one of the oldest lineages of extant seed plants and have undergone extensive diversification in the tropics.Intriguingly,the extant cycad abundance exhibits an i-LDG pattern,and the underlying causes for this phenomenon remain largely elusive.Here,using 1,843 nuclear genes from a nearly complete sampling,we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas,the largest genus within cycads.We then reconstructed the spatial-temporal dynamics and integrated global environmental data to evaluate the roles of species ages,diversification rates,contemporary environment,and conservatism to ancestral niches in shaping the i-LDG pattern.We found Cycas experienced decreased diversification rates,coupled with the cooling temperature since its origin in the Eocene from continental Asia.Different regions have distinctively contributed to the formation of i-LDG for Cycas,with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cradles.Moreover,water-related climate variables,specifically precipitation seasonality and potential evapotranspiration,were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator.Notably,the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern.This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms underpinning global biodiversity patterns.展开更多
A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved ...A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved intact on a sandstone slab, 89 cm long and 130 cm wide, including leaves up to 82 cm long and a male cone physically attached to the stem apex. Analysis on the morphology, arrangement and venation of leaf and pinna, male cone and its relationship with other parts indicates that the fossil is closely related to living Zamiaceae in Cycadales. This cycad fossil is hitherto most completely preserved cycad specimen including both vegetative and reproductive organs. Its discovery contributes much to our understanding of the morphology and evolution of cycads, palaeoclimate as well as palaeoenvironment.展开更多
文摘A new genus of fossil Cycads, Yixianophyllum gen. nov., is reported here. The specimens were collected from the southern hill of Jinjiagou village, Toudaohezi Town, Yixian County, western Liaoning Province, China. The fossil plant-beating bed belongs to the lower part, the Zhuanchengzi bed, of the Upper Jurassic Yixian Formation （Yixianian）. The new genus in leaf shape, venation and epidermal structure shows a transitional form between Mesozoic Cycads （Ctenis, Nilssonia） and modem Cycads （Stangeria and Encephalartos）. Since the features of these specimens differ from any known genera of Cycads, a new generic name Yixianophyllum is proposed for these leaves. Typical species, Yixianophyllum jinjiagouense gen. et sp. nov. is described here. A supposed evolutionary tendency of Cycadean leaf-forms with Taeniopteris-type is discussed.
文摘<i><span style="font-family:"">Cycas angulata, Cycas armstrongii </span></i><span style="font-family:"">and<i> Cycas conferta </i>that are<i> </i>native species of Australia were collected in Darwin city of tropical region, <i>Zamia </i><i>erosa </i>and angiosperm <i>Guaiacum officinale</i> of Zygophyllaceae which are introduced collected in the Darwin Botanic Gardens, and were carried out light microscope and electron microscope observed research to tracheary element and parenchyma tissue cells of leaflet, rachis and stem. The results showed that there are more vessel elements in their xylems;the length of vessel element of Cycadaceae with Zamiaceae are not obvious difference, the length of vessel element of angiosperm <i>Guaiacum officinale</i> is shorter, but their diameter is smaller, we thought that the characteristics which the length of vessel element is longer and the diameter is bigger are more evolutionary, because thus vessel, their number which interconnected points of possessed perforations’ end walls of vessel element is fewer, and the passageway space is larger so that the conduction speed and quantity are faster and more in unit length range and unit time. These vessels are annular vessels, spiral vessels, scalariform vessels, reticular vessels, pitted vessels and scalariform-pitted vessels, etc. In the transverse section, the vessel elements of Cycadaceae and Zamiaceae are circular, polygonous, more similar to vessel characteristics of <a name="OLE_LINK73"></a>leaf and stem of some angiosperms;however, the number of circular vessel of <a name="OLE_LINK21"></a><i>Guaiacum </i><i>officinale</i> is more, about occupy 35%, others are polygonous. The diameter of vessel is that annular vessel, spiral vessel is least, scalariform vessel or scalariform-reticular vessel is medium, reticular vessel and pitted vessel are the biggest, the characteristic is same as angiosperm. In <i>Cycas conferta</i>, etc. plants often can see several large perforations in the end walls, some species are several big scalariform or pitted perforations formed multiple perforation plates, in many vessel element lateral walls, there are some perforations formed a horizontal transport avenue of aqueous solution. The scale of diameter of <i>Cycas</i> vessel element is similar to that of <i>Zamia</i>, but the diameter of more vessel elements of <i>Cycas angulata </i>and<i> Cycas conferta</i> is bigger than the latter, and is bigger than that of <i>Guaiacum officinale</i>, although <i>Cycas</i> plants are more primitive than <i>Zamia</i><i> </i>plants, and <i>Guaiacum officinale</i> is more evolutionary, but the scale of vessel diameter of <i>Cycas</i> plants is similar to <i>Zamia </i>or bigger than the latter, even larger than <i>Guaiacum officinale</i>, these showed that cycads have evolutionary and more developed characteristics in aqueous solution transport system. In <i>Guaiacum officinale</i>, more vessel element has been not seen the ridges in the different directions of side walls which can make vessel has more mechanical supportability, but some possessed the ridges;however, more vessel elements are twist shape and can twist together each other, thus the state can increase their mechanical supportability, and their synergy with fiber elements which is longer with a twist shape, therefore their capability of xylem conduction and the combine mechanical support capability with mechanical tissue are also stronger. In the respect of observed parenchyma tissue, any parenchyma tissue cells are without perforation, all cell walls are smoothed and like a membrane. Aimed at only one or two people pointed the query about Jeffery’s method, some scholars have made comparative researches, their research used as following methods: 1) The fresh materials were cut sections 1 - 2 mm thick by hand (the query person provided and thought right method), were examined with SEM. 2) The materials were treated by Jeffrey’s Fluid and observed with SEM and so on. The results showed that the pit membrane, the remnants in the perforation and the structural characteristics of perforations were not different;and the results of our comparative research in past time and this research all justified that Jeffrey’s method is reliable and reasonable. Meanwhile, our research results showed that only vessel element can form perforation, in other all parenchyma tissue cells cannot form perforation are also proved that the perforations of vessel element are naturally inherited character. Analyzed from the structural characteristics, although they distributed so far apart from each other, they are a well and unified taxonomy system;we thought that Australia’ most species or all species of Cycadaceae came from Asia, and it is impossible from Africa, because the latter only has one more evolutionary species and lack of fossil of Cycadaceae, these species of Cycadaceae are the descendants of ancestor species;America possessed more genera of Zamiaceae, this family is mutual with Africa and Australia, we thought that these genera of Zamiaceae in Australia and America came from Pangea before continental drift in Jurassic Period, this family is also maybe one of the proofs to Australia drifted from Pangea to present position after Jurassic Period. The characteristics of tracheary element of several different genera of cycads and angiosperm further showed that more primary species or taxon, their more tissue characteristics are not also more primary, because of the need to adapt the environment, they are also constantly evolving. The research is important significant and theory reference to understand cycads evolutionary aqueous solution transport system, and understand the ecological adaptation mechanism which why present cycads of 3 families in world major distributed in tropical or subtropical regions, even many drought and barren areas.
基金There are 8 projects supported by National Natural Science Foundation of China which Dr. Y.Y. Huang have taken charge of and/or taken part in Dr. Y.Y. Huang have published 5 bookmakings and more than 100 papers.
基金funded by the National Natural Science Foundation of China(Nos.32270246 and 31900184 to J.L.)the Scientific Foundation of Urban Management Bureau of Shenzhen(Nos.202019 and 202208 to S.Z.)+1 种基金the Youth Innovation Promotion Association CAS,China(Grant No.:2023410)the Yunnan Fundamental Research Projects(Grant Nos.:202001AT070072 and 2019FD057 to J.L.)。
文摘The evolution of the latitudinal diversity gradient(LDG),characterized by a peak in diversity toward the tropics,has captured significant attention in evolutionary biology and ecology.However,the inverse LDG(i-LDG)mechanism,wherein species richness increases toward the poles,remains inadequately explored.Cycads are among one of the oldest lineages of extant seed plants and have undergone extensive diversification in the tropics.Intriguingly,the extant cycad abundance exhibits an i-LDG pattern,and the underlying causes for this phenomenon remain largely elusive.Here,using 1,843 nuclear genes from a nearly complete sampling,we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas,the largest genus within cycads.We then reconstructed the spatial-temporal dynamics and integrated global environmental data to evaluate the roles of species ages,diversification rates,contemporary environment,and conservatism to ancestral niches in shaping the i-LDG pattern.We found Cycas experienced decreased diversification rates,coupled with the cooling temperature since its origin in the Eocene from continental Asia.Different regions have distinctively contributed to the formation of i-LDG for Cycas,with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cradles.Moreover,water-related climate variables,specifically precipitation seasonality and potential evapotranspiration,were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator.Notably,the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern.This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms underpinning global biodiversity patterns.
基金Supported by the National Natursl Science Foundation of China (Grant Nos. 40772006, 40372008, 40632010 and J0630967)Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-154)National Basic Research Program of China (Grant No. 2006CB701401)
文摘A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved intact on a sandstone slab, 89 cm long and 130 cm wide, including leaves up to 82 cm long and a male cone physically attached to the stem apex. Analysis on the morphology, arrangement and venation of leaf and pinna, male cone and its relationship with other parts indicates that the fossil is closely related to living Zamiaceae in Cycadales. This cycad fossil is hitherto most completely preserved cycad specimen including both vegetative and reproductive organs. Its discovery contributes much to our understanding of the morphology and evolution of cycads, palaeoclimate as well as palaeoenvironment.
