The leaf photosynthetic capacity, leaf N partitioning, non-structural carbohydrate content, C, N, and P contents of endangered U. elongata seedlings exposed to different light intensities were compared in this study. The most favorable light condition for the survival and growth of U. elongata seedlings in the present study was 100% full sunlight, as this induced higher Pn, PNUE, PC, PR, PB, and NSC content relative to shade-treated seedlings. PNUE, PR, PC, and PB in U. elongata seedling leaves decreased under 40% and 10% full sunlight, while PL increased, indicating that shade increased the light capture efficiency of photosystem (PS) II but decreased electron transfer from PSII to PSI. Furthermore, leaf N content increased with shade intensity, revealing an adaptive strategy for poor light environments. Additionally, the smallest leaf biomass, Pn, WUE, and CE values and C:N and C:P ratios in stems and leaves were observed under 10% full sunlight. These results indicate that seedlings growing under 40% full sunlight will benefit U. elongata conservation.
To explore the taxon‐dependent contribution of dispersal limitation versus environmental filters to bryophyte assemblages. We investigated bryophytes and six environmental variables on 168 islands in the Thousand Island Lake,China. We compared the observed beta diversity with the expected values based on six null models (EE, EF, FE, FF, PE, and PF), detected the partial correlation of beta diversity with geographical distances. We quantified the contributions of spatial versus environmental variables and island isolation per se to species composition (SC) using variance partitioning. We modeled the species‐area relationships (SARs) for bryophytes and the other eight biotas. To explore the taxon‐dependent effects of spatial versus environmental filters on bryophytes, 16 taxa including five categories (total bryophytes, total mosses, liverworts, acrocarpous, and pleurocarpous mosses) and 11 species‐richest families were included in the analyses. The observed beta diversity values were significantly different from the predicted values for all 16 taxa. For all five categories, the observed partial correlations between beta diversity and geographical distance after controlling environmental effects were not only positive, but also significantly different from the predicted values based on the null models. Spatial eigenvectors are more important in shaping SC than environmental variables for all 16 taxa except Brachytheciaceae and Anomodontaceae. Spatial eigenvectors contributed more to SC variation in liverworts than in mosses and in pleurocarpous mosses than in acrocarpous mosses. The effects of island isolation on SC were significant for all five categories, highly varied at the family level. The z values of the SARs for the five bryophyte categories were all larger than those of the other eight biotas. In subtropical fragmented forests, dispersal limitation exerted significant, taxon‐dependent effects on bryophyte assemblages. It was dispersal limitation rather than environmental filtering that predominantly regulated the SC patterns of bryophytes.
There exists an obvious gap in our knowledge of the nuclear DNA amount of bryophytes, not only in terms of the low number of species represented, but also in systematic and geographic representation. In order to increase our knowledge of nuclear DNA amounts and variation patterns in bryophytes, and their potential phylogenetic significances and influences on phenotypes, we used flow cytometry to determine the DNA 1C values of 209 bryophyte accessions, which belong to 145 mosses and 18 liverworts collected from China, by using Physcomitrella patens as a standard. We quantified the differences in DNA 1C values among different orders and families and constructed a phylogenetic tree of 112 mosses with four gene sequences (nad5, rbcL, trnL-F, and 18S-ITS1-5.8S-ITS2-26S). DNA 1C values were mapped onto the phylogenetic tree to test a potential phylogenetic signal. We also evaluated the correlations of the DNA 1C value with the sizes of individuals, leaves, cells, and spores by using a phylogenetically controlled analysis. New estimates of nuclear DNA amounts were reported for 145 species. The DNA 1C values of 209 bryophyte accessions ranged from 0.422 pg to 0.860 pg, with an average value of 0.561 pg, and a 2.04-fold variation covered the extremes of all the accessions. Although the values are not significantly different (p = 0.355) between mosses (0.528 pg) and liverworts (0.542 pg), there are variations to varying extents between some families and orders. The DNA 1C value size exerts a positive effect on the sizes of plants, leaves, and cells, but a negative effect on spore size. A weak phylogenetic signal is detected across most moss species. Phylogenetic signals are comparatively strong for some lineages. Our findings show that bryophytes have very small and highly constrained nuclear DNA amounts. There are nucleotype effects of nuclear DNA amounts for bryophytes at the individual, organ, and cell levels. We speculate that smaller nuclear DNA amounts are advantageous for bryophytes in dry environments. Significant differences in the DNA 1C values among some moss families and orders, as well as phylogenetic signals for some lineages, imply that nuclear DNA amount evolution in mosses seems to be unidirectional.
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