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Non-native species invading habitats often cause ecosystem damage and biodiversity losses. Elevating temperature and CO2concentrations promote the invasiveness that is highly associated with the nitrogen fixation rates and traits that foster the adaptation of the non-native species, resulting in invasive plants as a cosmopolitan problem. Nevertheless, recent studies revealed a high carbon sequestration capacity of invasive plants in land and coastal habitats, arousing a question if invasive plants always a notorious invader. Badlands are characterized with poor soil development and nutrition, which restrict the growth of plants and soil microbes. Interestingly, leguminous plant with symbiotic nitrogen-fixation bacteria help them explore habitats with low nutrition. Leucaenawith high seed yields and deep roots acts as a pioneer in badland ecosystems, usually forming a dominant vegetation with bamboos. Roots exudates likely attract microbes beneficial to the plant growth. Even so, microbial metabolism and respiration tend to increase the CO2emission from the soils. Nevertheless, biologists discovered that carbon precipitated by roots is more effective in forming mineral-associated soil organic carbon than leaf and root litter inputs. Soil microbial biomass ultimately transforms into necromass with specific properties, constituting an important source of soil organic matter, which compensates largely the CO2from microbial metabolism. Furthermore, deep roots of Leucaenalikely interact with soil microbes through various biogeochemical processes, promoting soil formation, altering rocks and soil minerals, and providing carbon to deeper layers. From the viewpoint of carbon sequestration, invasive Leucaenacan make more significant contribution to the badland ecosystem than native species.

Ludwigia, a genus with rampant interspecific hybridization, is an ideal model for examining the impact of gene introgression and polyploidization on species diversification. We examined the evolution of the Ludwigiasect. Isnardia, which is a polyploid complex (x= 8) of five species distributed in North America. The phylogeny of L. sect. Isnardiawas reconstructed based on sequences of cpDNA atpB­rbcLintergenic spacer and nrITS (internal transcribed spacer). Most L. sect. Isnardiaspecies are polyphyletic at both loci, indicating possible recurrent hybridization, based on maximum likelihood trees rooted at L. sect. Microcarpium. A minimum spanning network was also constructed to examine genealogical relationships among haplotypes. In the cpDNA network, haplotypes of tetraploid L. spathulataare nested at the most interior nodes, suggesting a parental genome origin of an extinct diploid or an unsampled extant diploid with a DD cytotype. Allopolyploid L. arcuata contributed its cpDNA to hexaploid L. repens and L. brevipes. ITS haplotypes of diploid L. palustris were clustered with L. spathulata, suggesting L. palustrisas the paternal genome donor. Ludwigia brevipesmay have arisen via bi3directional hybridization between L. palustrisand L. arcuatafollowed by polyploidy. Genetic and phylogenetic analyses using molecular markers with different inheritance modes provided sufficient insights into the reticulate evolution of the species of L. sect. Isnardia. Interspecific hybridization and polyploidy play a key role in the species evolution in L. sect. Isnardia.

Miscanthus, a genus of the Poaceae, has attracted biologists' attention because of its high biomass and fast growth, traits that make this grass potentially useful as a biofuel. Miscanthus, is morphologically diverse and widespread across various habitats along altitude and latitude, providing a perfect model for investigating adaptation and speciation. Nevertheless, big genome sizes and rampant gene flow cause challenges in the genomic analysis of species swarms of Miscanthus. Here, we illustrate genetic and genomic analyses of divergence and adaptive differentiation among Miscanthusspecies. Outlier and linkage disequilibrium analyses are suggested for the identification of genes under diversifying selection.