Compound-specific δD and its hydrological and environmental implication in the lakes on the Tibetan Plateau

The hydrogen isotopic composition(δD) of n-alkanes in lacustrine sediments is widely used in palaeoenvironmental studies, but the heterogeneous origins and relative contributions of these lipids provide challenges for the interpretation of the increasing dataset as an environment and climatic proxy. We systematically investigated n-alkane δD values from 51 submerged plants(39 Potamogeton, 1 Myriophyllum, and 11 Ruppia), 13 algae(5 Chara, 3 Cladophora, and 5 Spirogyra) and 20 terrestrial plants(10 grasses and 10 shrubs) in and around 15 lakes on the Tibetan Plateau. Our results demonstrate that δD values of C_(29) nalkane are correlated significantly with the lake water δD values both for algae(R^2=0.85, p<0.01, n=9) and submerged plants(R^2=0.90, p<0.01, n=25), indicating that δD values of these algae and submerged plants reflect the δD variation of lake water. We find that apparent hydrogen isotope fractionation factors between individual n-alkanes and water(εa/w) are not constant among different algae and submerged plants, as well as in a single genus under different liminological conditions, indicating that the biosynthesis or environmental conditions(e.g. salinity) may affect their δD values. The δD values of submerged plant Ruppia in the Xiligou Lake(a closed lake) are significant enriched in D than those of terrestrial grasses around the lake(one-way ANOVA,p<0.01), but the algae Chara in the Keluke Lake(an open lake) display similar δD values with grasses around the lake(one-way ANOVA, p=0.826>0.05), suggesting that the n-alkane δD values of the algae and submerged plants record the signal of D enrichment in lake water relative to precipitation only in closed lakes in arid and semi-arid area. For each algae and submerged plant sample, we find uniformed δD values of different chain length n-alkanes, implying that, in combination with other proxies such as Paq and Average Chain Length, the offset between the δD values of different chain length n-alkanes can help determine the source of sedimentary n-alkanes as well as inferring the hydrological characteristics of an ancient lake basin(open vs closed lake).

Dismantling Marchandiomphalina into Agonimia(Verrucariaceae)and Lawreymyces gen.nov.(Corticiaceae):setting a precedent to the formal recognition of thousands of voucherless fungi based on type sequences

Based on an unexpected result of obtaining molecular sequence data from tropical representatives of the genus Normandina,we revised the biological concept of the neotropical taxon Marchandiomphalina foliacea.The obtained data let us conclude that M.foliacea is not a basidiomycete,as originally proposed,but belongs in Verrucariaceae,in the genus Agonimia,including its perithecia which had been identified with the lichenicolous Norrlinia peltigericola.The ITS(and nuLSU)sequences previously obtained from M.foliacea,seemingly confirming its status as a basidiomycete,are from an unmanifested lichenicolous fungus,present also in numerous specimens of Normandina.ITS data suggest the presence of seven lineages that can be recognized at the species level,forming two clusters:one cluster of three lineages found in thalli of M.foliacea,and a second cluster of four lineages found in thalli of Normandina.This pattern is similar to what has recently been found in the basidiomycete genus Cyphobasidium occurring predominantly in Parmeliaceae lichens.We propose the combination of Omphalina foliacea into the genus Agonimia,as Agonimia foliacea(P.M.Jørg.)Lucking&Moncada,comb.nov.,and place Marchandiomphalina in synonymy with Agonimia.To formally recognize the unnamed lichenicolous basidiomycete present in Agonimia and Normandina thalli,we take advantage of provision ICN Art.40.5 in the Code and describe the unmanifested fungus as a new genus,with seven new species,even if no physical type specimens can be preserved(except for the corresponding host lichens which,however,do not show the features of the fungus):Lawreymyces Lucking&Moncada,gen.nov.(Type:L.palicei),with L.bogotensis Lucking&Moncada,sp.nov.,L.columbiensis Lucking&Moncada,sp.nov.,L.confusus Lucking&Moncada,sp.nov.,L,foliaceae Lucking&Moncada,sp.nov.,L.palicei Lucking&Moncada,sp.nov.,L.pulchellae Lucking&Moncada,sp.nov.,and L.spribillei Lucking&Moncada,sp.nov.This opens the door to the formal recognition of thousands of species of voucherless fungi detected through environmental sequencing techniques under the current Code.