Cytological and taxonomic observations on some members of the Cyclosorus parasiticus complex.1

The role of deep hybridization in fern speciation: Examples from the Thelypteridaceae

PREMISE

Hybridization is recognized as an important mechanism in fern speciation, with many allopolyploids known among congeners, as well as evidence of ancient genome duplications. Several contemporary instances of deep (intergeneric) hybridization have been noted, invariably resulting in sterile progeny. We chose the christelloid lineage of the family Thelypteridaceae, recognized for its high frequency of both intra- and intergeneric hybrids, to investigate recent hybrid speciation between deeply diverged lineages. We also seek to understand the ecological and evolutionary outcomes of resulting lineages across the landscape.

METHODS

By phasing captured reads within a phylogenomic data set of GoFlag 408 nuclear loci using HybPhaser, we investigated candidate hybrids to identify parental lineages. We estimated divergence ages by inferring a dated phylogeny using fossil calibrations with treePL. We investigated ecological niche conservatism between one confirmed intergeneric allotetraploid and its diploid progenitors using the centroid, overlap, unfilling, and expansion (COUE) framework.

RESULTS

We provide evidence for at least six instances of intergeneric hybrid speciation within the christelloid clade and estimate up to 45 million years of divergence between progenitors. The niche quantification analysis showed moderate niche overlap between an allopolyploid species and its progenitors, with significant divergence from the niche of one progenitor and conservatism to the other.

CONCLUSIONS

The examples provided here highlight the overlooked role that allopolyploidization following intergeneric hybridization may play in fern diversification and range and niche expansions. Applying this approach to other fern taxa may reveal a similar pattern of deep hybridization resulting in highly successful novel lineages.

Phytochemical and anti-bacterial activity of epidermal glands extract of Christella parasitica (L.) H. Lev

OBJECTIVE

To study the morphology, biochemistry and bioactivity of the epidermal glands of the glandular morphotype of Christella parasitica (C. parasitica) (L.) H. Lev.

METHODS

Morphological studies on epidermal glands were carried out by using light microscope and scanning electron microscope. To prepare the extract, the shade-dried fronds of glandular morphotype were soaked in acetone. For antibacterial studies paper disc method was followed by using various pathogenic bacteria.

RESULTS

Detailed micromorphological, phytochemical and bioactivity studies on a medicinal fern C. parasitica (L.) H. Lev. showed its intraspecific variation in antibacterial activity. The presence or absence of the epidermal glands was the key factor for antibacterial activity in the morphovariants of this species. The epidermal glands were orange-coloured, stalked and elongated ones of about 84.2 µm × 45 µm, and distributed on the undersurface of costa, costules and veins in croziers, young and mature leaves. Frequency of glands varied from 15/cm on costa in mature leaves to 140/cm on costules in croziers. The acetone extract of the glands showed antibacterial activities and also toxic effect against mosquito larvae and tadpoles of frog. Preliminary phytochemical analysis and HPLC studies of the gland extract showed the presence of various kinds of terpenoids, alkaloids, tannins, saponins and flavonoids in it.

CONCLUSIONS

The present study shows that epidermal glands of the glandular morphotype of C. parasitica (L.) H. Lev. have several bioactive compounds and such rare morphovariant should be conserved in nature. The next step is to isolate the pure compounds and to screen the bioactivity of individual compounds of the epidermal glands.

IX.—A Cytotaxonomic Survey of the Pteridophytes of Jamaica

Results are presented of a cytological survey of the Pteridophyte flora of Jamaica. Approximately 270 species or cytotypes were investigated, only a few of which have previously been investigated from other parts of the world. Several genera have been cytologically examined for the first time and their phylogeny has been discussed in the light of these findings. A number of species complexes and interspecific hybrids have been revealed. The overall statistics of the survey are compared with those compiled from an investigation of the Pteridophyte flora of Ceylon, by Manton and Sledge (1954). Finally, endemic species are discussed in the light of the cytological results and the time known to have been available for their establishment in Jamaica.