An ontogenetic framework for functional studies in the model fern Ceratopteris richardii.

As the sister group to seed plants, ferns are a phylogenetically informative lineage. Functional studies in representatives of the fern lineage are helping bridge the knowledge gap in developmental mechanisms between angiosperms and non-vascular plants. The fern life cycle has the advantage of combining a sizable free-living haploid gametophyte, more amenable for developmental studies than the reduced seed plant gametophyte, with an indeterminate and complex diploid sporophyte. Ceratopteris richardii has long been proposed as a model fern and has recently become tractable due to stable transgenesis and increasing genomic resources, allowing researchers to test explicit questions about gene function in a fern for the first time. As with any model system, a detailed understanding of wild-type morphology and a staged ontogeny are indispensable for the characterization of mutant phenotypes resulting from genetic manipulations. Therefore, the goal of this study is to provide a unified reference ontogeny for this emerging model fern as a tool for comparative evolutionary and developmental studies. It complements earlier research by filling gaps in major stages of development of the haploid gametophyte and diploid sporophyte generations, and provides additional descriptions of the shoot apical meristem and early leaf development. This resource is meant to facilitate not only studies of candidate genes within C. richardii, but also broader ontogenetic comparisons to other model plants.

Leaf epidermal micromorphology and its implications in systematics of certain taxa of the fern family Pteridaceae from Northern Pakistan.

The present study is insights into foliar epidermal anatomy for characterizing clades, and their utility in taxonomic segregation of certain species of Pteridaceae from Northern Pakistan. The leaf epidermal anatomy of 10 species of Pteridaceae representing four genera were examined using light and scanning electron microscope. A micromorphological matrix was constructed for eight qualitative and 12 quantitative characters. unweighted pair group method with arithmetic means and principal components analysis statistical analysis were performed to test the validity of foliar epidermal anatomical features as method of separating species and genera, and phylogenetic clusters among species are constructed using qualitative and quantitative traits. The qualitative characters described here are shape of epidermal cells, stomata, guard cell and subsidiary cells, anticlinal wall pattern, and trichomes types which is helpful in defining groups within Pteridaceae. In addition, the size of stomata, guard cells, subsidiary cells, stomatal pore epidermal cells, and trichomes are quantitatively analyzed. All species have hypostomatic leaves. Two types of stomata were observed in studied species, anomocytic and polocytic. Anomocytic stomata were observed in three genera namely: Adiantum, Onychium, and Chielanthes whereas Pteris can be discriminated from other genera by its polocytic stomata. On the basis of multivariate analysis present study does provides sufficient information on the taxonomic importance of foliar anatomy which validate its efficacy in species and genera discrimination. From result obtained here it is further possible to use leaf micromorphologic data in ferns phylogeny and providing basis for future taxonomic delimitation in other taxa.

Adaptation and convergent evolution within the Jamesonia-Eriosorus complex in high-elevation biodiverse Andean hotspots.

The recent uplift of the tropical Andes (since the late Pliocene or early Pleistocene) provided extensive ecological opportunity for evolutionary radiations. We test for phylogenetic and morphological evidence of adaptive radiation and convergent evolution to novel habitats (exposed, high-altitude páramo habitats) in the Andean fern genera Jamesonia and Eriosorus. We construct time-calibrated phylogenies for the Jamesonia-Eriosorus clade. We then use recent phylogenetic comparative methods to test for evolutionary transitions among habitats, associations between habitat and leaf morphology, and ecologically driven variation in the rate of morphological evolution. Páramo species (Jamesonia) display morphological adaptations consistent with convergent evolution in response to the demands of a highly exposed environment but these adaptations are associated with microhabitat use rather than the páramo per se. Species that are associated with exposed microhabitats (including Jamesonia and Eriorsorus) are characterized by many but short pinnae per frond whereas species occupying sheltered microhabitats (primarily Eriosorus) have few but long pinnae per frond. Pinnae length declines more rapidly with altitude in sheltered species. Rates of speciation are significantly higher among páramo than non-páramo lineages supporting the hypothesis of adaptation and divergence in the unique Páramo biodiversity hotspot.