176 research outputs found

    Extant diversity of bryophytes emerged from successive post-Mesozoic diversification bursts

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    Unraveling the macroevolutionary history of bryophytes, which arose soon after the origin of land plants but exhibit substantially lower species richness than the more recently derived angiosperms, has been challenged by the scarce fossil record. Here we demonstrate that overall estimates of net species diversification are approximately half those reported in ferns and similar to 30% those described for angiosperms. Nevertheless, statistical rate analyses on time-calibrated large-scale phylogenies reveal that mosses and liverworts underwent bursts of diversification since the mid-Mesozoic. The diversification rates further increase in specific lineages towards the Cenozoic to reach, in the most recently derived lineages, values that are comparable to those reported in angiosperms. This suggests that low diversification rates do not fully account for current patterns of bryophyte species richness, and we hypothesize that, as in gymnosperms, the low extant bryophyte species richness also results from massive extinctions.Assembling the Tree of Life programme at NSF; NSF [EF-0531730-002, EF-0531680, EF-0531750]; Scottish Government's Rural and Environment Science and Analytical Services Division; BeiPD-cofund Marie Curie fellowshipinfo:eu-repo/semantics/publishedVersio

    Factors influencing epiphytic bryophyte and lichen species richness at different spatial scales in managed temperate forests

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    The effect of management related factors on species richness of epiphytic bryophytes and lichens was studied in managed deciduous-coniferous mixed forests in Western-Hungary. At the stand level, the potential explanatory variables were tree species composition, stand structure, microclimate and light conditions, landscape and historical variables; while at tree level host tree species, tree size and light were studied. Species richness of the two epiphyte groups was positively correlated. Both for lichen and bryophyte plot level richness, the composition and diversity of tree species and the abundance of shrub layer were the most influential positive factors. Besides, for bryophytes the presence of large trees, while for lichens amount and heterogeneity of light were important. Tree level richness was mainly determined by host tree species for both groups. For bryophytes oaks, while for lichens oaks and hornbeam turned out the most favourable hosts. Tree size generally increased tree level species richness, except on pine for bryophytes and on hornbeam for lichens. The key variables for epiphytic diversity of the region were directly influenced by recent forest management; historical and landscape variables were not influential. Forest management oriented to the conservation of epiphyte s should focus on: (i) the maintenance of tree species diversity in mixed stands; (ii) increment the proportion of deciduous trees (mainly oaks); (iii) conserving large trees within the stands; (iv) providing the presence of shrub and regeneration layer; (v) creating heterogeneous light conditions. For these purposes tree selection and selective cutting management seem more appropriate than shelterwood system

    Choosing and Using a Plant DNA Barcode

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    The main aim of DNA barcoding is to establish a shared community resource of DNA sequences that can be used for organismal identification and taxonomic clarification. This approach was successfully pioneered in animals using a portion of the cytochrome oxidase 1 (CO1) mitochondrial gene. In plants, establishing a standardized DNA barcoding system has been more challenging. In this paper, we review the process of selecting and refining a plant barcode; evaluate the factors which influence the discriminatory power of the approach; describe some early applications of plant barcoding and summarise major emerging projects; and outline tool development that will be necessary for plant DNA barcoding to advance

    Evolution of Stress-Regulated Gene Expression in Duplicate Genes of Arabidopsis thaliana

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    Due to the selection pressure imposed by highly variable environmental conditions, stress sensing and regulatory response mechanisms in plants are expected to evolve rapidly. One potential source of innovation in plant stress response mechanisms is gene duplication. In this study, we examined the evolution of stress-regulated gene expression among duplicated genes in the model plant Arabidopsis thaliana. Key to this analysis was reconstructing the putative ancestral stress regulation pattern. By comparing the expression patterns of duplicated genes with the patterns of their ancestors, duplicated genes likely lost and gained stress responses at a rapid rate initially, but the rate is close to zero when the synonymous substitution rate (a proxy for time) is >∼0.8. When considering duplicated gene pairs, we found that partitioning of putative ancestral stress responses occurred more frequently compared to cases of parallel retention and loss. Furthermore, the pattern of stress response partitioning was extremely asymmetric. An analysis of putative cis-acting DNA regulatory elements in the promoters of the duplicated stress-regulated genes indicated that the asymmetric partitioning of ancestral stress responses are likely due, at least in part, to differential loss of DNA regulatory elements; the duplicated genes losing most of their stress responses were those that had lost more of the putative cis-acting elements. Finally, duplicate genes that lost most or all of the ancestral responses are more likely to have gained responses to other stresses. Therefore, the retention of duplicates that inherit few or no functions seems to be coupled to neofunctionalization. Taken together, our findings provide new insight into the patterns of evolutionary changes in gene stress responses after duplication and lay the foundation for testing the adaptive significance of stress regulatory changes under highly variable biotic and abiotic environments
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