Niche and phenotypic differentiation in fern hybrid speciation, a case study of Pteris fauriei (Pteridaceae).

BACKGROUND AND AIMS: Niche differentiation is a crucial issue in speciation. Although it has a well-known role in adaptive processes of hybrid angiosperms, it is less understood in hybrid ferns. Here, we investigate whether an intermediate ecological niche of a fern hybrid is a novel adaptation that provides insights into fern hybrid speciation. METHODS: Pteris fauriei (Pteridaceae) is a natural hybrid fern, occurring in environments between its parent species. The maternal Pteris minor is found in sunny areas, but the habitat of the paternal Pteris latipinna is shady. We combined data from morphology, leaf anatomy and photosynthetic traits to explore adaptation and differentiation, along with measuring the environmental features of their niches. We also performed experiments in a common garden to understand ecological plasticity. KEY RESULTS: The hybrid P. fauriei was intermediate between the parent species in stomatal density, leaf anatomical features and photosynthetic characteristics in both natural habitats and a common garden. Interestingly, the maternal P. minor showed significant environmental plasticity and was more similar to the hybrid P. fauriei in the common garden, suggesting that the maternal species experiences stress in its natural habitats but thrives in environments similar to those of the hybrid. CONCLUSIONS: Based on the similar niche preferences of the hybrid and parents, we propose hybrid superiority. Our results indicate that the hybrid P. fauriei exhibits greater fitness and can compete with and occupy the initial niches of the maternal P. minor. Consequently, we suggest that the maternal P. minor has experienced a niche shift, elucidating the pattern of niche differentiation in this hybrid group. These findings offer a potential explanation for the frequent occurrence of hybridization in ferns and provide new insights into fern hybrid speciation, enhancing our understanding of fern diversity.

Spore morphology and its systematic implication in Pteris (Pteridaceae).

Pteris (Pteridaceae) spores are usually trilete and can be distinguished by the perine ornamentation. The systematic value of spore morphology in Pteris is unclear, especially based on the renewed infrageneric classification of Pteris. In the present study, we used scanning electron microscopy (SEM) to understand spore characters in 57 Pteris species, one Onychium species, and two Astrolepis species; 40 species are reported here for the first time. The observed spore characters combined with published spore data, totaling 100 species from 16 sections of Pteris, were mapped onto a reconstructed phylogenetic tree. Seven characters (five proposed in previous studies), including an equatorial flange, laesural ridges, proximal ridges, distal ridges, tubercula on distal faces, coarse reticula on distal faces, and a row of extervermiculi between the distal face and equatorial flange, were analyzed to investigate spore morphology evolution in Pteris. However, the results showed no synapomorphies with other genera in Pteridaceae. Most of the characters were found to have arisen independently several times in different lineages or were even frequently reversed. Equatorial flanges and tubercula on distal faces are plesiomorphies and present in most Pteris species. Overall, the application of spore morphology in section circumscription is limited. Thus, we suggest combining spore morphology with leaf characters for Pteris infrageneric classification.

Effect of arsenate on endogenous levels of cytokinins with different existing forms in two Pteris species.

Our previous results showed that content of trans-zeatin (tZ) increases in leaves of heavy metal hyperaccumulators but decreases in non-hyperaccumulators growing in multiple heavy metal polluted soils. However, the relationship between arsenic (As) accumulation and endogenous forms of cytokinins (CTKs) in As hyperaccumulators remains unknown. Here a hydroponic experiment was conducted to compare the CTK forms in the As hyperaccumulator Pteris cretica var. nervosa and non-hyperaccumulator Pteris ensiformis under arsenate stress (0, 2, 5, and 10 mg L-1). A simple and cost-effective procedure for the determination of CTK forms in plants was established, and a stepwise regression analysis was used to study the relationship among total As contents and different forms of endogenous CTKs in fronds of two plants. The results showed that the optimized chromatographic parameters were Zobax SB-C18 column (5 µm × 4.6 mm × 250 mm), UV detection detector at 269 nm, a flow rate of 0.6 mL min-1, constant temperature of 45 °C and gradient elution with methanol-acetonitrile-1% acetic acid. Contents of chlorophylls in the fronds of P. ensiformis were significantly decreased with addition of As compared to P. cretica var. nervosa. Furthermore, the total As content in fronds of P. cretica var. nervosa was positively correlated to the contents of N6-(2-isopentenyl) adenine-7-ß-D-glucoside (iP7G) and N6-(2-isopentenyl) adenosine (iPR). However, the total As content in fronds of P. ensiformis was negatively correlated to its trans-zeatin riboside (ZR) content. Therefore, iP7G and iPR could positively improve As accumulation by P. cretica var. nervosa.

The effect of arbuscular mycorrhizal fungi and phosphate amendement on arsenic uptake, accumulation and growth of Pteris vittata in As-contaminated soil.

This study investigated the contributions of mixed arbuscular mycorrhizal fungi (AMF) inoculum-i.e., mixed populations of indigenous mycorrhiza (Glomus intraradices, Glomus geosporum, Glomus mosseae) (IM) isolated from arsenic (As) contaminated soil and non-indigenous mycorrhiza such as G. mosseae (GM), which possess metal tolerance characteristics-and the addition of phosphate rock (PR) towards the uptake and accumulation of As by Pteris vittata (As hyperaccumlator) grown in As-contaminated soil. Regardless of As levels added to soil, plant growth was substantially improved in amended treatments when compared with the control. In addition, root surface area (0 mg/kg As: 15.2 cm2; 150 mg/kg As: 16.9 cm2; 300 mg/kg As: 20.7 cm2), chlorophyll contents (0 mg/kg As: 1.16 mg/g; 150 mg/kg As: 1.46 mg/g; 300 mg/kg As: 1.81 mg/g) and As translocation factor (0 mg/kg As: 0; 150 mg/kg As: 4.29; 300 mg/kg As: 5.22) in P. vittata of PR+IM/GM were also increased. Such combination could further enhance plant growth (indicated by higher N, P and chlorophyll contents) and As uptake by P. vittata.

Una especie nueva de helecho del género Pteris (Pteridaceae) endémica de Costa Rica / A new species of fern of the genus Pteris (Filicales: Pteridaceae) endemic to Costa Rica

The new fern species Pteris herrerae A. Rojas & M. Palacios, endemic to Costa Rica, is described. It differs from P. decurrens C. Presl in basal segments reduced to 1/5-1/2 of the next segment (vs. 2/3-3/4), basal pinnae not bifurcated (vs. bifurcated), pinnae apex mucronate (vs. acuminate) and segment apex undulate (vs. dentate). It differs from Pteris consanguinea in the elliptic pinnae (vs. oblong), two segments reduced on the base (vs. lack), segments entire to undulate (vs. dentate), basal pinnae without basiscopic lobes (vs. with basiscopic lobes) and segment apex entire to undulate (vs. dentate).

Se describe Pteris herrerae A. Rojas & M. Palacios, endémica de Costa Rica. Esta es diferente de P. decurrens C. Presl por segmentos basales reducidos a 1/5-1/2 del tamaño de los siguientes (vs. 2/3-3/4), pinnas basales no bifurcadas (vs. bifurcadas), ápice de las pinnas mucronado (vs. acuminado) y ápice de los segmentos ondulado (vs. dentado). También es diferente de Pteris consanguinea Mett. ex Kuhn por pinnas deltado-lanceoladas (vs. oblongas), con un par de segmentos reducidos en la base (vs. sin ellos), pinnas basales sin lóbulos basicópicos alargados (vs. con lóbulos basiscópicos) y segmentos enteros a ondulados (vs. dentados).

[A new species of fern of the genus Pteris (Filicales: Pteridaceae) endemic to Costa Rica]. / Una especie nueva de helecho del género Pteris (Pteridaceae) endémica de Costa Rica.

The new fern species Pteris herrerae A. Rojas & M. Palacios, endemic to Costa Rica, is described. It differs from P. decurrens C. Presl in basal segments reduced to 1/5-1/2 of the next segment (vs. 2/3-3/4), basal pinnae not bifurcated (vs. bifurcated), pinnae apex mucronate (vs. acuminate) and segment apex undulate (vs. dentate). It differs from Pteris consanguinea in the elliptic pinnae (vs. oblong), two segments reduced on the base (vs. lack), segments entire to undulate (vs. dentate), basal pinnae without basiscopic lobes (vs. with basiscopic lobes) and segment apex entire to undulate (vs. dentate).

[Morphological and histological study on Pteris multifida].

The thesis studies on the pharmacognostical characteristics of Pteris multifida were carried out in this paper. The blade has special vein-like cell. The stomas in dorsal epidermis are regular. The petiol has V-shaped amphicribral bundles. The rhizome has 6-8 meristeles. The triangle-form spore has tumor-shaped or pellet-shaped decorations on its surface.