Data on spore morphology of Cerosora microphylla ( Anogramma microphylla ) ( Pteridaceae )

We used the method of scanning electron microscopy (SEM) to study the representatives of the genus Anogramma from South-West Asia and the Himalayas. To confirm the presence of Cerosora microphylla (Hook.) R.M. Tryon in China (hence, the absence of Anogramma microphylla (Hook.) Diels), we revealed the features of external morphology of spores that are not inherent in representatives of the genus Anogramma: absence of an equatorial ridge, roundishtriangular shape of the spores in the proximal-polar and distal-polar positions; absence of roller-like bulges extending upward in the form of ridges along the contour of the distal side of the spore; roller-like folds extending upward in the form of ridges both on the proximal and distal sides of the spore. In addition, one feature revealed for C. microphylla – spherical tubercles between the proximal and distal roller-like folds located along the spore equator – indicates its high species-specificity.


Introduction
The genus Anogramma includes about five species widespread in the American tropics from Mexico to Argentina, from the Azores towards the south to the Cape Verde islands, Africa and Madagascar, southwestern and southern Europe, northern India (including Ceylon), southern Taiwan, Australia and New Zealand (Tryon, 1990).
For the flora of China, Zhang Gangmin and Tom A. Ranker report on two types: A. leptophylla (Linn.) Link and A. microphylla (Hook.) Diels . The main species diversity of the representatives of Anogramma occurs in tropical and subtropical America, excluding A. leptophylla, which is found throughout the tropical and subtropical belts in all floristic realms (Gastony and Baroutsis, 1975).
According to the latest data, the genus Anogramma is part of the subfamily Pteridoideae C. Chr. ex Crabbe, the family Pteridaceae E. D. M. Kirchn. (Smith et al., 2006;Christenhusz, 2011). The results on the phylogeny of ferns obtained by independent research groups using molecular genetics show that the representatives of the genus Anogramma can be unambiguously united in the Pteridoid clade, the group of taenitioid (Zhang et al., 2005;Schuettpelz et al., 2007) and hemionitid ferns (Liu et al., 2008).
The representatives of the Pteridoid clade are referred to the ferns of the taenitioids group based on the data on the Taenitidoideae subfamily reported by Roll Trion (Tryon, , 1990. However, in the research devoted to the most complete reconstruction of the molecular phylogenetic relationships of the representatives of the Pteridaceae family of Chinese-Himalayan and Afro-Madagascar origin, Harald Schneider and his colleagues referred the representatives of the genera Anogramma, Cerosora, Cosentinia and Pityrogramma to the Anogramma clade (Schneider et al., 2013).
The representatives of the genus Cerosora exhibit a sufficiently wide disjunct distribution in Borneo, Sumatra and the Himalayas (Tryon, 1990). In 1986, Rolla Trion brought a new combination and singled out the Chinese-Himalayan representative -C.microphylla Schneider et al., 2013).
Despite this, in the Flora of China A. microphylla is distinguished as a representative of the predominantly neotropical genus Anogramma. In this case, the features of the external morphology of A. microphylla, including an obovate form of the final lobes of the frond and the location of the soruses along the central vein of the final frond, are not common to other representatives of the genus Anogramma.
In the relevant research conducted in 2017 that considers the phylogeny of the subfamily Pteridoideae C. Chr. ex Crabbe, the family Pteridaceae, C. microphylla takes an isolated position in the subfamily system (Zhang et al., 2017). At the same time, the group Cerosora, which includes a single representative of the genus, is closely related to the group of the representatives of Pityrogramma and Gastoniella -a new genus, which comprises three species, previously considered in Anogramma (Gastoniella Li Bing Zhang a. Liang Zhang, gen. nov., Zhang et al., 2017).
It should be noted that Rolla Trion transferred the species A. microphylla to Cerosora despite the absence of glandular hairs on the leaf surface common to all representatives of the genus Anogramma (Schneider et al., 2013). This fact testifies to the species-specific features of the external morphology of C. (A.) microphylla.
To confirm the autonomy of the Chinese-Himalayan C. (A.) microphylla, we performed scanning electron microscopy of spores of ferns collected in the Himalayas. In addition, original photographs of the A. leptophylla spore were obtained for specimens from South-West Asia.

Material and methods
Spores for the study were selected from the herbarium material deposited in the Herbarium of the Komarov Botanical Institute of the Russian Academy of Sciences (St. Petersburg). Three specimens collected in South-West and East Asia were investigated. The spores were fixed on a slide with an electrically conductive adhesive tape, sputtered with gold using a sputter coater Quorum Q150R S, and examined under a scanning electron microscope Mini-SEM SNE-4500M (Korea) located in the laboratory of structural and molecular analysis of plants, TSU. The spores surface was scanned in high vacuum at a voltage of 10-30 kV and magnified from 2,500 to 10,000 times. The spore dimensions and the element ornamentation were determined using photographs taken with a scanning microscope.

Results and discussion
The description and original electron micrographs of the representatives of the genus Anogramma are presented below.
A specimen of A. microphylla (Hook.) Diels from Guizhou province was investigated in thesis by Zhang Gangmin "A systematic study on the Chinese cheilanthoid ferns and their related taxa" in 2003 (unpublished). In contrast to our SEM image, the image presented in the thesis exhibits distinctly expressed tubercles on the proximal surface of the spore between the laesura and roller-like folds.
The analysis of the obtained electron micrographs and comparison of the descriptions of external morphology of spores of the representatives of the genus Anogramma from South America, C. sumatrana Holtt. from the island of Sumatra, as well as the distinctive features of the external morphology of representatives of these genera (Tryon and Lugardon, 1991;Giacosa et al., 2004), show that the species A. microphylla can be considered separately from the genus Anogramma. The features typical of the representatives of the genus Anogramma but not of the species A. microphylla are as follows: absence of the equatorial fold, roundish-triangular spores in the proximal-polar and distal-polar positions; absence of roller-like bulges rising in the form of ridges along the contour of the distal side of the spore; highly risen roller-like folds on both the proximal and distal sides of the spore.
The analysis of the clades of the phylogenetic trees obtained for the representatives of the family Pteridaceae (Schneider et al., 2013;Zhang et al., 2017) and the data obtained in the study of morphology of fern spores of this group have shown that the species A. microphylla (Hook.) is Sino-Himalayan C. microphylla (Hook.) R. M. Tryon. In contrast to the external morphology of spores of C. sumatrana (Tryon and Lugardon, 1991), the feature revealed for C. microphylla -spherical tubercles between the proximal and distal roller-like folds located along the spore equator -indicates its high species-specificity.