New Report on Tetraploid Cytotype of Thelypteris Papilio (C. Hope) K. Iwats. (Thelypteridaceae: Pteridophyta) from India Along With a Taxonomic Note on Thelypteris Sledgei Fraser-Jenk
- 1. Botanical Survey of India, Western Regional Centre, Pune, India-411001
- 2. Department of Botany, S. P. Pune University, Pune, India
- 3. Department of Botany, St. Xavier’s College (Autonomous), Palayamkottai, India, 627 002
The thelypteroid fern Thelypteris Papilio (C. Hope) K. Iwats. (Thelypteridaceae) is widely distributed in tropical, subtropical and warm temperate regions. The chromosome counts made so far from India are diploid sexual (n=36) (Loyal 1961, Khullar et al. 1988, Manickam 1984, Manickam & Irudyayaraj 1988, Raj & Manickam, 1987). Tetraploid sexual cytotype has been reported only from Sri Lanka (Manton & Sledge, 1954). In the present study Octoploid cytotype (n=144) of this plant collected from Kolli Hills, Tamilnadu, was observed for the first time Thelypteris papilio (C. Hope) K. Iwats, the tropical Asian thelypteroid fern, is cytologically known from India and Sri Lanka only with the presence of diploid sexual in India (Western Ghats and Western Himalayas) and the tetraploid sexual in Sri Lanka. The Sri Lankan tetraploid plant, Christella papilio var. repens Sledge, has also been treated as Thelypteris sledgei FraserJenk. In India, this species is distributed in Eastern/Western Himalayas and Western Ghats. During the recent exploration of pteridophytes on the Western Ghats of Goa, India, the tetraploid cytotype of Thelypteris papilio with erect rhizome has been cytologically confirmed with the presence of 72 regular bivalents in Spore Mother Cells. The cytological data from North India, South India and Sri Lanka shows the latitudinal pattern of distribution of the diploid and tetraploid cytotypes. Thus, tetraploid cytotype is present in Sri Lanka towards the equator with tropical climate in contrast to the diploid cytotype which is present in the Western Himalayas, little away from the equator with temperate climate. Interestingly, on the Western Ghats, the diploid cytotype is present on Southern Western Ghats (Tamilnadu) in contrast to the tetraploid cytotype on the Northern Western Ghats (Goa). Since the cytomorphological characters (rhizome and ploidy) are not consistent with the discovery of the present tetraploid cytotype with erect rhizome, the treatment of tetraploid cytotype with creeping rhizome as distinct species is not valuable.
• Thelypteris papilio • Thelypteridaceae • Tetraploid cytotype • India
Thelypteridaceae is one of the fern families that have a subcosmopolitan distribution and great species richness, with approximately 1000 species, of which most occur in tropical and subtropical regions [1,2] Of the 81 Indian thelypteroid ferns , 27 (33%) species have been reported from the Western Ghats . Thelypteroid ferns are cytologically diversified with the presence of different base numbers (x=31, 35, 36)  along with intraspecific cytological variation in some species complexes like Thelypteris tenera (Roxb.) C.V.Mortan ex Fraser-Jenk.,T. interrupta (Willd.) K. Iwats. etc. Thelypteris papilio (C.Hope) K.Iwats. is one of the threatened fern in India and it is usually growing in semi ever green forests along road sides above 1000m. Cytological report for this Asian species is available from India (2x) and Sri Lanka (4x) only [5,6]. Usually the diploid plants of this species are with erect rhizome with several pairs of gradually reduced basal pinna [7,8]. The tetraploid cytotype of this species from Sri Lanka with long creeping rhizome has been described as a variety repens of C. papilio  and later on Fraser-Jenkins  considered it as a distinct endemic species Thelypteris sledgei which is treated as synonym of Christella papilio var. repens . With an aim to search the presence of tetraploid cytotype of T. papilio (C. Hope) Holttum, Irudayaraj  compared all the specimens in St. Xavier’s college Herbarium for rhizome and spore size and concluded that there is possibility for the presence of tetraploid cytotype in South India, but the presence of tetraploid cytotype has not yet been confirmed cytlogically from India. This species, in the present study, collected from Netravathi Wildlife Sanctuary, Goa, Western Ghats, India (N15? 04N and ’14.16’ N latitudes and 074? 14’ E and 06?.48 E Longitude) was cytologically worked out and it has been proved to be of tetraploid new cytotype (n=72) for this species from India
MATERIAL AND METHODS
Wild population of Thelypteris papilio (C. Hope) K. Iwats fern grows in Netravathi Wildlife Sanctuary, Goa, Western Ghats, India. The young sporophylls were collected early morning and fixed in Carnoy’s fluid (absolute Alcohol, Chloroform and Glacial acetic acid in the ratio of 12:3:1). For meiotic chromosome studies, the acetocarmine squash technique was followed . The material gave good results after 10 days. The voucher specimen has been deposited in the Botanical Survey of India, Western Regional Centre, Pune.
RESULTS AND DISCUSSION
The threatened fern Thelypteris papilio (C. Hope) K. Iwats was collected from Northern Western Ghats Goa (Fig. i), India and it has been found to grow in semi evergreen forest along roadside of Netravathi Wildlife Sanctuary in Goa (A. Benniamin, BSI, 206068, 01.11.2019). This species is distributed in the states of Tamil Nadu, Kerala, Karnataka, Goa, Arunachal Pradesh, Himachal Pradesh, Jammu-Kashmir, Sikkim, Uttarkhand, West Bengal in India (Fig. i) and Bhutan, China, Malaysia, Nepal, Sri Lanka, Taiwan, Thailand, Tibet and Vietnam (Fig. ii) in Asia [3,4]. The plant is with erect rhizome and simply pinnate lamina with several pairs of gradually reduced basal pinnae (Figs A-C). The lower surface of costa, costule and intervenal area are sparsely covered by short rigid acicular hairs (Figs. D, E). Sori submarginal with reniform indusium (Fig. F). The forked soral placenta is with short and stout tracheids (Fig. G, H). The sporangial stalk is with glandular hair (Fig. I) and each sporangium is filled with 64 uniform normal spores (Fig. O). The behaviour of chromosomes is normal throughout the stages of meiosis with the formation of 72 regular bivalents in spore mother cells (Figs. J, K) during meiosis I. Equal size of daughter two and four nuclei are formed after I and II meiosis respectively (Figs. L-N). Basic chromosome numbers of the family thelypteridaceae are x= 27, 29-39 . Walker  found that chromosome numbers supported Holttum’s generic delimitation of thelypteroid ferns from Old World. Bir and Verma  suggested the existence of strong isolation barriers between various chromosomal lines.
The Asian thelypteroid fern, Thelypteris papilio, is cytologically known from India and Sri Lanka only (Fig. i). So far, only diploid sexual cytotype (n=36) with erect rhizome has been reported from India [7,8,16-18] with the indication for the presence of tetraploid cytotype . In the meantime, only tetraploid sexual cytotype has been reported from Sri Lanka  where the plant is with creeping rhizome  and it has been described  as a variety (C. palilio (C. Hope) Holttum var. repens Sledge). Later, Fraser-Jenkins  considered this fern as a distinct endemic Sri Lankan species, Thelypteris sledgei Fraser-Jenk. (= Christella sledgei (Fraser-Jenk.) Ranil). Thelypteris sledgei Fraser-Jenk. is an unresolved name (http://www.theplantlist.org/1.1/browse/P/ Thelypteridaceae/Thelypteris) and it has been treated as Christella papilio (C. Hope) Hottum var. repens Sledge  and this species/ taxon. Interestingly in India, both diploid [7,8] and tetraploid (present study) cytotypes are with erect rhizome. Thus, there is an indication for the cytomorphological evolution in this species with the occurrence of erect rhizome-plants with both diploid and tetraploid cytotypes in India [7,8,17] and creeping rhizometetraploid plants in Sri Lanka . The evolutionary trend is from erect rhizome-diploid taxon to creeping rhizome-tetraploid taxon with the presence of intermediate erect rhizome-tetraploid plants. The diploid plants from Tamilnadu (Palni Hills) is with 30 x 25 µm sized spores [7,8] in contrast to the present tetraploid cytotype with 40 x 25 µm spores.
The presence of both dipoid and tetraploid cytotypes with erect rhizome in India supports the view of keeping both the cytotypes of this species as single species, unlike the opinion of Fraser-Jenkins  who treated the tetraploid cytotype of Sri Lanka as a distinct species (T. sledgei Fraser-Jenk.). As considered Hassler (11), the unresolved name T. sledgei Fraser-Jenk. is treated as synonym of C. papilio (C. Hope) Holttum (=T. papilio (C. Hope) K. Iwats). In general, T. papilio is a rare species with varied cytotypes and morphotypes and so there is less chance for the presence of natural hybrid between these different cytotypes and morphotypes. But with the sympatric growth of tetraploid T. parasitica (L.) Tardieu and tetraploid T. dentata (Forssk.) E.P.St. John in South India, natural hybrids are common [7,8]. In Southern and Northern India diploids are present, while in Western India (Goa) tetraploid is present. Thus India with varied climate and habitats is not only with high number of species, but also with intraspecific morphotypes, cytotypes and genotypes which prefers to grow in specific ecological nich in different regions of India.
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