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The ferns of Adiantum Series Gravesiana (Pteridaceae) consist of species that occur exclusively on Danxia (A. juxtapositum) and Karst (A. mariesii, A. longzhouensis, A. dentatum, A. obovatum, and A. gravesii) landforms. We cultured representatives of these six species from 20 different populations on both agar and soil to investigate and compare their gametophyte development. All species had the Vittaria-type pattern of spore germination except A. obovatum, for which we missed the best time to observe this developmental phase. However, two different patterns of subsequent development were observed: the Adiantum-type (i.e., naked, cordate mature gametophyte thallus) in A. mariesii, A. longzhouensis, A. juxtapositum, and A. gravesii and the Kaulinia-type (i.e., naked, ribbon-shaped mature gametophyte thallus) in A. dentatum and A. obovatum. All populations from A. juxtapositum and A. gravesii possess the same Adiantum-type, suggesting that Karst and Danxia soils were not the main factor causing the differences in gametophyte development. The Kaulinia-type adult thallus has not been observed previously in Adiantum and may be an adaptive strategy for survival within the relatively harsh micro-habitats experienced by A. dentatum and A. obovatum compared to other members of this series. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium spp.) is a vital global source of renewable fiber and ranks among the world's most important cash crops. While extensive nuclear genomic data of Gossypium has been explored, the organellar genomic resources of allotetraploid cotton, remain largely untapped at the population level. The plastid genome (plastome) is well suited for studying plant species relationships and diversity due to its nonrecombinant uniparental inheritance. Here, we conducted de novo assembly of 336 Gossypium plastomes, mainly from domesticated cultivars, and generated a pan‐plastome level resource for population structure and genetic diversity analyses. The assembled plastomes exhibited a typical quadripartite structure and varied in length from 160 103 to 160 597 bp. At the species level, seven allotetraploid species were resolved into three clades, where Gossypium tomentosum and Gossypium mustelinum formed an early diverging clade rooted by diploids, followed by splitting two sister clades of Gossypium darwinii–Gossypium barbadense and Gossypium hirsutum–Gossypium ekmanianum–Gossypium stephensii. Within the G. hirsutum clade the resolution of cultivated accessions was less polyphyletic with landrace and wild accessions than in G. barbadense suggesting some selection on plastome in the domestication of this adaptable species of cotton. The nucleotide diversity of G. hirsutum was higher than that of G. barbadense. We specifically compared the plastomes of G. hirsutum and G. barbadense to find mutational hotspots within each species as potential molecular markers. These findings contribute a valuable resource for exploring cotton evolution as well as in the breeding of new cotton cultivars and the preservation of wild and cultivated germplasm. [ABSTRACT FROM AUTHOR]