Origin of earliest land plants from ancestral algae dramatically accelerated the evolution of Earth's terrestrial ecosystems, in which microbial symbioses have played key roles. Recent molecular ...diversification analyses identify the rare, geographically-limited moss Takakia as Earth's most archaic modern land plant. Despite occupying a phylogenetic position pivotal for understanding earliest plants, Takakia microbial associations are poorly known. Here, we describe symbiosis-related structural features and contig-based metagenomic data that illuminate the evolutionary transition from streptophyte algae to early embryophytes. We observed that T. lepidozioides shares with streptophyte algae secretion of microbe-harboring mucilage and bacterial taxa such as Rhizobium and genes indicating nitrogen fixation. We find that Takakia root-analogs produce lateral mucilage organs that are more complex than generally understood, having structural analogies to angiosperm lateral roots adapted for N-fixation symbioses, including presence of intracellular microbes. We also find structural and metagenomic evidence for mycorrhiza-like species of glomalean fungi (including Rhizophagus irregularis) not previously known for mosses, as well as ascomycete fungi (e.g. Rhizoscyphus ericae) that associate with other early-diverging plants. Because Takakia is the oldest known modern plant genus, this study of plants of a remote locale not strongly influenced by human activities may indicate microbiome features of early land plants.
A relative of the African species described by Brotherus as
Bryum perspinidens
, has been discovered in Guyana with erect capsules and a short inner peristome. The Guyana material is recognized as a ...new species, and both species are placed in the genus
Brachymenium
. The characteristics that distinquish the genus are discussed with reference to the Guyana specimens of
Brachymenium speciosum
.
Aim: Arctic plant species are often characterized by a complex genetic structure because of changes in their population size, the fragmentation of metapopulation systems, extensive hybridization and ...allopolyploidization, and survival in disjunct refugia, historical features associated with Pleistocene glaciation. We assessed the biogeographical and genetic patterns in three closely related northern species of peat-moss (Sphagnum inexspectatum, S. orientale and S. miyabeanum), especially interspecific hybridization, infraspecific geographical differentiation and Pleistocene survival in one or more refiigial areas. We tested alternative hypotheses of refugiai survival in three widely disjunct regions: eastern Asia, Alaska and Greenland. Location: North America (Canada, western USA and Greenland), China, Japan and Russia. Methods: Four hundred and forty-three plants were genotyped at 12 microsatellite loci. Nucleotide sequences from 130 accessions for two plastid and two nuclear loci were used to reconstruct haplotype relationships. Population genetic analyses produced estimates of genetic diversity, levels of interspecific gene flow and rates of infraspecific intercontinental migration. Approximate Bayesian computation was used to test alternative biogeographical scenarios. Results: We found evidence of hybridization between two of the three species, but phylogenetic patterns are predominantly divergent rather than reticulate. Disjunct populations of one species, S. orientale, in Greenland, Alaska and China are genetically differentiated, but migration has occurred among all three metapopulation systems. Divergence-time analyses strongly support the hypothesis that S. orientale survived the Last Glacial Maximum in Beringia and also in Greenland. Main conclusions: Our results indicate that Beringia served as a rerugium for peat-mosses, and therefore peatlands, which are currently extensive at high latitudes of the Northern Hemisphere. Sphagnum orientale also appears to have survived the Last Glacial Maximum in Greenland, indicating that the species persisted in multiple Pleistocene réfugia. Phylogenetic patterns are relatively simple in these mosses compared with those commonly encountered in Arctic angiosperms.
Linear infrastructure such as pipelines and power lines is ubiquitous and responsible for loss of habitats and disruption of landscape connectivity. We reviewed published research to answer the ...following questions: (1) Which organisms are commonly used to indicate impacts of pipelines and power lines to biodiversity? (2) How do pipelines and power lines impact biodiversity? and (3) How are these impacts mitigated? Studies of pipelines most often used mammals and plants as bioindicators, whereas studies of power lines focused largely on birds and plants. A myriad of impacts were identified, including the mortality of plants during construction, changes to the structure and composition of plant and animal communities that resulted from construction, the creation of open and shrubby corridors within intact forests, and collisions and electrocutions of birds with power lines. However, in most studies baseline data were not collected, so magnitudes of the impacts are often unknown. Mitigation in many studies was mentioned only in the discussion as a way to reduce impacts, but mitigation techniques were rarely tested directly. We outline considerations when selecting bioindicators—research that takes a community- or ecosystem-level approach will more fully determine the scope of impacts of linear infrastructure than the historical approach of focusing on populations of select bioindicators. Mitigation strategies must ultimately result from appropriate baseline studies, scientific data collection and analyses, and be implemented within an adaptive management strategy.
Holocene climate, vegetation, and fire history were reconstructed using pollen, molluscs, and charcoal from two lake sediment records (Scum and Norma lakes) collected from the Chilcotin Plateau, ...British Columbia, Canada. In the late-glacial period, cold steppe prevailed and fire was limited. Artemisia steppe expanded in the earliest Holocene as climate warmed and conditions became dry, with shallow basins drying out. High-frequency surface fires maintained the steppe. An increase in Pinus after 10 200 cal BP signals moistening and the establishment of Pinus ponderosa P. & C. Lawson and Pinus contorta Dougl. ex Loud. stands, with surface fires in the former and higher severity fires in the latter. Cooling around 8500 cal BP favored P. contorta, and a crown fire regime likely prevailed, with intermittent surface fires. Shallow basins began to fill with water. In the mid-Holocene, basins filled further and Picea increased slightly in abundance. Fire frequency decreased, though severity increased. In the last three millennia, modern P. contorta dominated forests were established, with mixed-severity fire disturbance. Considering the future, the results of this study align well with ecosystem climate niche simulations, indicating that non-arboreal and open-forest communities may again prevail widely on the plateau, together with surface fires. Land managers need to develop strategies to manage the upcoming transformation.
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