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Acrorumohra subreflexipinna, an endemic fern of Taiwan, has been suspected to be a hybrid species. The aims of this study were to detect possible multiple origins of this species, determine the genetic variation in different populations, and clarify their lineages. One nuclear and three organellar DNA fragments were sequenced to determine parentage of this putative hybrid and to examine genetic differentiation among populations. Sequence data support the conclusion that A. subreflexipinna arose from the hybridization of A. hasseltii and A. diffracta, and the hybridization was uni-directional, i.e., based on the assumption of maternal inheritance in organellar DNA, the former was its maternal species while the latter was its paternal source. A convincing interpretation is that the female gametes of A. hasseltii gametophyte could be fertilized by the male gametes from apogamous A. diffracta. Unique nuclear alleles present in different populations of A. subreflexipinna and A. hasseltii demonstrated that hybridization occurred many times independently. The nuclear haplotypes present in A. subreflexipinna were subsets of those found in the parental species, and A. subreflexipinna always had lower haplotype diversity than A. hasseltii at sympatric sites. Our results show that any genetic variation of A. subreflexipinna came from its parents and that it maintains this significant genetic variability because of recurrent hybridization.
A new full-length genomic DNA, encoding a member of the cyanovirin-N (CV-N) homologous protein family, has been cloned from the fern species Ceratopteris thalictroides by chromosome walking. It is 1993 bp long, contains a 723 bp open reading frame (ORF) that encodes a deduced protein (named CtCVNH) with 150 amino acid residues. CtCVNH has a predicted isoelectric point (PI) of 4.47 and a calculated molecular mass 15.9556 kDa. It possesses the conserved anti-HIV (human immunodeficiency virus) CV-N domain, which is the same as the cyanovirin-N homology (CVNH) members that were isolated from filamentous ascomycetes and C. richardii. Modeling of the tertiary structure indicated that CtCVNH is an elongated, largely β-sheet protein that displays internal two-fold pseudosymmetry. Comparative structure analysis of the predicted CtCVNH with native CV-N revealed that the major evolutionary changes occurring during the evolution of plant CVNHs were: 1) a length increase at N- and C-terminal regions; and 2) a loop to helix transition at the helical-turn regions. Phylogenetic analysis showed that CtCVNH was grouped together with the two CVNHs from C. richardii.
Adiantum alomae is described from eastern Cuba. It is characterized by pubescence on all parts of the leaves and its small size. Its habitat is also distinctive, occurring on limestone cliffs and walls, usually facing and very near the sea, receiving salt spray. A key is given to differentiate it from the related Cuban endemic Adiantum sericeum, and illustrations of the distinctive characteristics of both species are presented.
Asplenium truncorum, a new asplenioid fern from the Brazilian Atlantic Rain Forest, is described, illustrated and compared to the most similar species. So far, it seems to be restricted to the montane moist forests of southern Bahia and Espírito Santo States, at elevations of 750 to 950 m. Field observations suggest that this species grows exclusively as an epiphyte on the trunks of tree ferns, especially Alsophila setosa Kaulf. (Cyatheaceae).
From taxonomic studies of Pleopeltis from southeastern Brazil, some new combinations are made: Pleopeltis alborufula (Brade) Salino, P. bradei (de la Sota) Salino, P. desvauxii (Klotzsch) Salino, P. minarum (Weath.) Salino, P. monoides (Weath.) Salino, and P. trindadensis (Brade) Salino.
The fern genus Phlebodium is traditionally described as having a row of costal areoles lacking included veins, with the sori located in extra-costal areoles and each sorus served by two veinlets. The discovery of a hybrid between Phlebodium pseudoaureum and Polypodium pleurosorum raises questions about the limits of Phlebodium and necessitates a revised taxonomic circumscription of the genus.