INTRODUCTION
The cosmopolitan genus, Porina (Porinaceae: Ostropales), with more than 320 species worldwide, is most diverse in rather shaded habitats of tropical and subtropical regions [1-10]. The tropical climate of Vietnam is supported by prolonged humid conditions because of the large coastline surrounded by the South China Sea in the east and the Pacific Ocean in the south. These conditions are favorable to the growth of Porina on a range of substrates in tropical rainforests, seasonal forests, and wet lands in the country. The present study on this genus is a continuation of previous studies [11-16] and was conducted in Nam Cat Tien National Park (Fig. 1). The national park includes one of the largest areas of lowland tropical rainforests in southern Vietnam. Tree layer of the forest is comprised mainly of Dipterocarpus alatus, D. intricatus, Dalbergia alata, D. mammosa, Afzelia xylocarpa, Pterocarpus macrocarpus, Lagerstroemia calyculata, Tetrameles nudiflora, Anogeissus acuminata, Bambusa procera, and Gigantochloa sp. Subtree layer is composed of Actinodaphne pilosa, Beilschmiedia micranthopsis, and Illigera rhodantha. Amaranthus spinosu, Acanthus leucostachyus, Celosia argentea, Cyclacanthus coccineus and Ruellia repens compose the shrub layer of the forest.
The checklist and preceding works on Vietnamese lichens reflect the great diversity of foliicolous species of Porina in the country (ca. 25 species), while a few were also reported on rock and bark [17,18]. Two species stated in the earlier account have now been accommodated in the genus Strigula as S. phyllogena (Müll. Arg.) R. C. Harris (=Porina phyllogena Müll. Arg.) and S. platypoda (Müll. Arg.) R. C. Harris (=Porina platypoda Müll. Arg.), whereas the previous report of Porina consanguinea Müll. Arg. from the country was uncertain in subsequent studies [17]; hence, it was not included in the current account.
The salient taxonomic features of Porina species are mostly shiny (corticate or ecorticate) thallus in different shades of greenish grey to olivaceous grey, containing algae either Trentepohlia (for bark and rock inhabiting species) or Phycopeltis (for leaf inhabiting species); perithecia present on thallus or immersed in thallus-dominated verrucae (H arada [6] proposed the term 'prominent thalloid exciple' replacing the 'thallus-dominated verrucae', applied previously to categorize the perithecial morphology by McCarthy [1]); pale brown to reddish brown or black, vestigial to well-developed involucrellum and hyaline, transversely three or more septate to muriform ascospores [1]. The genus is usually devoid of chemical compounds, but some species can give a K+ reddish or yellowish reaction on the thallus or on the fruiting bodies.
The present study was carried out in order to evaluate and enrich the diversity of Vietnamese lichens. The conducted work not only provides the noteworthy species of Porina, but also indicates the scope of nonlichenized fungi in unexplored areas of the country.
MATERIALS AND METHODS
The interesting samples were selected from the lichen collection made by one of the authors (JSH) in December 2015 from the three provinces (Dong Nai, Lam Dong and Binh Phuoc) that circumscribed the national park. The field trip was organized by Dr. Nguyen Thi Thanh at Tay Nguyen University, Vietnam. The trip was conducted in the frame of internal joint program between Korea and Vietnam, supported by Korea National Research Foundation. The field studies did not involve any endangered or protected species. The material was preserved in the herbarium of the Korea National Arboretum, Korea (KH). The material was made available for taxonomic treatment in the Lichenology laboratory of CSIR-National Botanical Research Institute, Lucknow, India. The standard protocols were followed for identification. The morphological and anatomical characters were studied using a Leica S8APO stereo-zoom microscope and Leica DM500 compound microscope, respectively. Thin, hand-cut sections (10-15 sections) of perithecia, initially mounted in water, were studied for a range of structures and measurements. Cotton blue, 5% KOH and Lugols iodine solution were used wherever required. Thin layer chromatography was performed in solvent system A according to the report by Orange et al. [19]. Illustrations were prepared using Corel Draw (ver. 12).
RESULTS AND DISCUSSION
Porina eminentior (Nyl.) P. M. McCarthy (Fig. 2A, 2B and 2C)
Lichenologist 32: 42 (2000).
Thallus epiperidermal, greenish grey to pale greenish grey, smooth to slightly verruculose, ± glossy, continuous, sometimes cracked (due to bark texture), ≤150 μm thick, corticate; algal layer Trentepohlioid, ≤100 μm thick, medulla indistinct to endoperidermal; ascomata perithecioid, emergent, subglobose to hemispherical, 0.3-0.6 mm in diam.; ostiolar region pale brown to brown, 0.04-0.08 mm in diam.; involucrellum covered completely by a prominent thalloid exciple; proper exciple hyaline to pale brown, 15-20 μm thick; centrum clear, 0.2-0.4 mm wide; asci 8-spored, 100-170×25-35 μm; ascospores hyaline, broadly ellipsoidal, muriform, 40-70×15-25 μm, multi-septate, perispore 3-5 μm.
Chemistry: No lichen substances detected by thin layer chromatography.
Known distribution: In Vietnam, this species was found growing on tree twigs and most commonly associated with some sterile Porinaceae members in the wet tropical complex of the national park. Porina eminentior is also found in the Neotropics, East Africa, SE Asia, New Caledonia and the South Pacific [1].
Material examined: Vietnam, Dong Nai Province, Tan Phu district, Nam Cat Tien National Park, 11°26′ 35″N 107°24′19″E, 150 m elevation, on bark, 18 December 2015, Hur & Woo VN150213 (KH).
Notes: The species with muriform ascospores was assigned previously to the genus Clathro Porina Müll. Arg, but later following the conservative concept outlined by Santesson [20] and McCarthy & Malcolm [21], Lücking & Vězda [22] included them in Porina. The Vietnamese specimen closely matches the original description of Porina eminentior, except that the examined sample has cracked rather than rimose thallus as described in McCarthy [1]. The thallus texture of our sample is somewhat similar to P. nuculastrum, but differs in ascospores with multi-sepation.
Porina meridionalis P. M. McCarthy (Fig. 2D, 2E)
Nova Hedwigia 58: 397 (1994).
Thallus epiperidermal, pale greenish grey, smooth, matt, continuous in large patches of ≤10 cm, flaking away from the bark in the middle part, delimited by brownish black prothallus, ecorticate, 50-70 μm thick; algal layer Trentepohlioid, 20-40 μm thick; medulla not apparent; ascomata perithecioid, semi-immersed to slightly emergent, hemispherical to subglobose, 0.1-0.3 mm in diam.; ostiole black, 0.01-0.03 mm in diam.; involucrellum dimidiate, covered mostly by a prominent thalloid exciple, 60-70 μm thick; proper exciple hyaline to pale brown, 20-30 μm thick; centrum clear, 0.25-0.27 mm thick; asci 8-spored, 90-130 × 10-17 μm; ascospores hyaline, elongate fusiform to subacicular, transversely 10-14-septate, 25-52×5-8 μm, perispore absent.
Chemistry: No lichen substances detected by thin layer chromatography.
Known distribution: This species appears to grow luxuriantly in large patches near coastal areas or mangroves in Vietnam and is collected from the thick and smooth trunk of trees in the protected forests of the park. The species was previously described in Tasmania [1].
Material examined: Vietnam, Dong Nai Province, Tan Phu district, Nam Cat Tien National Park, 11°27′ 27″N 107°22′11″E, 174 m elevation, on bark, 19 February 2015, Hur & Woo VN150389 (KH).
Notes: This species is distinct in producing elongate fusiform transversely 11-17(-21)-septate ascospores usually broader towards the distal end. McCarthy [1] reported the species with an inconspicuous ostiolar region, which is slightly conspicuous (0.01-0.03 mm in diam.) in this specimen. The Vietnamese sample is close to Porina rhaphidiophora (Nyl.) Müll. Arg., which differs mainly in the size of the perithecia and ascospores [1]. Although such minor variations may be acceptable within the broad concept of species delimitation, more collection is needed to observe the actual variations between the Vietnamese sample and the only report of this species from Tasmania, or more collection is prerequisite to describe the sample as noval.
Porina nuculastrum (Müll. Arg.) R. C. Harris (Fig. 2F, 2G)
More Florida Lichens: 174 (1995).
Thallus epiperidermal, pale grey, smooth to verruculose due to emerging ascomata, glossy, continuous with black prothallus, <100 μm thick; cortex 5-10 μm thick; algal layer Trentepohlioid, 10-20 μm thick; medulla white, crystalline, <60 μm thick; ascomata perithecioid, scattered, distinctly emergent, convex to subglobose, 0.3-0.5 mm in diam., ostiole pale brown to dark brown, 0.1-0.3 mm; involucrellum apical to dimidiate, pale brown, covered completely by a prominent thalloid exciple; proper exciple hyaline to yellowish brown, 25-30 μm thick; centrum clear, 0.3-0.5 mm wide; asci 8-spored, 200-250 × 30-35 μm; ascospores hyaline, narrowly to broadly fusiform, muriform (12-15 transverse septa and 1-3 longitudinal septa), 50-76 × 12-20 μm, perispore 2-3 μm thick.
Chemistry: No lichen substances detected by thin layer chromatography.
Known distribution: This species was found growing in small and irregular patches on rough barked trees of the protected rainforests in Vietnam. The species has a common occurrence on tree bark as well as on rocks. Worldwide, it is distributed in the Neotropics, Madagascar, the Philippines, Hong Kong, and neighboring countries [1].
Material examined: Vietnam, Dong Nai Province, Tan Phu district, Nam Cat Tien National Park, 11°26′ 35″N 107°24′19″E, 150 m elevation, on bark, 18 December 2015, Hur & Woo VN150198 (KH).
Notes: McCarthy [1] described this species with an inconspicuous ostiolar region. The examined material could be placed in P. eminentior, but multiple optical sections of perithecia showed very less septation in the measured ascospores. In contrast to the Australian specimens with an inconspicuous ostiole, the Vietnamese sample contains perithecia with a rather conspicuous ostiolar region. The ostiole conspicuity in the present sample may be the result of over maturity because only a single specimen from Vietnam was observed.
Fig. 2. New records from Vietnam. A, Habitus of Porina eminentior ; B-C, Ascospores of Porina eminentior ; D, Habitus of P. meridionalis ; E, Asci and ascospores of P. meridionalis ; F, Habitus of Porina nuculastrum ; G, Ascospores of Porina nuculastrum (Scale bars: A, D, F = 1 mm; B, C, E, G = 50 μm).
Key to Porina species recorded from Vietnam
The taxonomic key characters of twenty-nine species are discussed. The previously known taxa were characterized following the descriptions provided by McCarthy [1], Upreti [19], Lücking & Vězda [22] and Pinokiyo & Singh [23] and presented below with some modifications.
1. Thallus foliicolous; algae Trentepohlia or Phycopeltis ······························································ 2
1a. Thallus corticolous or saxicolous; algae Trentepohlia ···························································· 23
2. Algae Trentepohlia; prothallus broad bluish black to grey black; thallus sterile or fertile ···················· 3
2a. Algae Phycopeltis; prothallus if present translucent or whitish; thallus fertile ································· 4
3. Thallus sterile, isidiate; isidia abundant, cylindrical to coralloid ·································· Porina distans
3a. Thallus fertile; perithecia applanate, large, 0.6-1 mm in diam.; ascospores broadly fusiform, transversely
7(-9)-septate, 38-64 × 6.5-10 μm ······························································· Porina imitatrix
4. Perithecia immersed in thallus-dominated verrucae (thalloid exciple), mainly pale grey green, pale yellowish green or pale greyish brown ·············································································· 5
4a. Perithecia ± superficial, not immersed in thallus dominated verrucae (thalloid exciple), yellowish white, in shades of brown or black ·························································································· 11
5. Ascospores 3-septate, 12-18 × 2-3.5 μm (13-25 × 2-4 μm vide Lücking & Vězda, 1998); perithecia 0.15-0.2 mm in diam. ················································································ Porina albicera
5a. Ascospores 7- or more septate ························································································· 6
6. Thallus and perithecia furnished with dense cushions of soft hairs; perithecia convex to hemispherical; ascospores 7-15-septate, 45-74 × 4-7 μm ···················································· Porina virescens
6a. Thallus and perithecia glabrous; perithecia variously shaped; ascospores exclusively 7-septate (with a few exceptions), mostly less than 50 μm long ···································································· 7
7. Perithecia subconical to conical; apex with a short flat-topped cylindrical extension; ascospores 28-46 × 3-5 μm ·································································································· Porina conica
7a. Perithecia lens-shaped, hemispherical, or wart-shaped; if conical then apex lacking short flat-topped extension ················································································································· 8
8. Perithecia applanately lens-shaped; thallus with whitish short-stalked deeply concave disciform isidia, 0.1(-0.15) mm in diam. (0.4-0.7 mm in diam. vide Lücking & Vězda, 1998); ascospores 35-48 × 3-4.5 μm [(35-)40-45 × 3-4.5 μm vide Lücking & Vězda, 1998] ······························ Porina mirabilis
8a. Perithecia lens-shaped to hemispherical; thallus lacking isidia ·················································· 9
9. Perithecia lens-shaped, 0.2-0.35(-0.4) mm in diam., with a blackish apical spot or a brownish apical cap; ascospores 23-33 × 3-4 μm (27-35 × 3-4.5 μm vide Lücking & Vězda 1998) ······ Porina atriceps
9a. Perithecia hemispherical, concolorous or pale reddish brown at apices ······································ 10
10. Perithecia 0.2-0.3 mm in diam.; phycobiont cell rectangular, arranged in radiating rows; ascospores 21- 27 × 3 μm ····················································································· Porina epiphylloides
10a. Perithecia 0.25-0.4(-0.5) mm in diam.; phycobiont cells round to angular, irregularly arranged; ascospores 25-35 × 3-4.5 μm ·································································· Porina epiphylla
11. Perithecia very small, 0.08-0.1 mm in diam., yellowish white; ascospores bacillar, 1-septate, 10-12 × 2-2.2 μm ···························································································· Porina diaphana
11a. Perithecia comparatively, brown to black, larger; ascospores 3- or more septate ·························· 12
12. Perithecia in shades of brown; involucrellum often containing algae ········································· 13
12a. Perithecia ± black; involucrellum not or rarely containing algae ············································ 16
13. Perithecia finely and sparsely furnished with cushions of soft hairs, 0.2-0.26 mm in diam.; ascospores 7-septate, 25-33 × 3-5 μm ······································································ Porina octomera
13a. Perithecia not pilose; ascospores 3-septate ······································································· 14
14. Perithecia subglobose, 0.17-0.26 mm in diam., constricted at the base; sides often with a slightly rough covering of thallus material; ascospores 17-26 × 3-6 μm ································ Porina semecarpi
14a. Perithecia convex to subconical ···················································································· 15
15. Perithecia 0.2-0.4 mm in diam.; ascospores 18-28 × 2.5-4.5 μm ························· Porina limbulata
15a. Perithecia 0.13-0.21 mm in diam.; ascospores 13-21 × 2-3 μm ························· Porina rubentior
16. Ascospores muriform, 85-110 × 17-22 μm; perithecia 0.35-0.50 mm in diam. ········· Porina foliicola
16a. Ascospores transversely 3- or more septate ······································································ 17
17. Ascospores 3-septate, 15-24 × 3-4.5 μm; perithecia applanate towards the margins, but usually with a conical to hemispherical centre, 0.2-0.41 mm in diam. ·································· Porina chrysophora
17a. Ascospores more than 3-septate ···················································································· 18
18. Perithecia convex to hemispherical; base usually spreading ···················································· 19
18a. Perithecia subglobose to globose and attenuated at the base ·················································· 22
19. Perithecia overgrown almost to the apex by a thin layer of thallus; ascospores 5(-7)-septate, 20-32 × 4-5 μm ·································································································· Porina corruscans
19a Perithecia not overgrown by the thallus; ascospores 5- or more septate ····································· 20
20. Ascospores 5-septate, 15-30 × 5-7 μm ····················································· Porina subnitidula
20a. Ascospores 7- or more septate ······················································································ 21
21. Ascospores 7-septate, 20-34 μm long ··························································· Porina cupreola
21a. Ascospores 7-9-septate, 41-63 μm long (20-35 μm long vide McCarthy 2001) ···· Porina karnatakensis
22. Perithecia 0.14-0.25 mm in diam.; sometimes greyish tomentose, ascospores 5-septate, 20-32 × 3.5-6 μm ······································································································· Porina nitidula
22a. Perithecia 0.16-0.31 mm in diam.; ascospores mostly 7-septate, 22-42 × 3.5-7 μm ····· Porina atrocoerulea
23. Thallus saxicolous; perithecia hemispherical to subglobose, black, 0.23-0.48 mm in diam.;
involucrellum uniformly black lacking algal cells; ascospores (3-)5-7(-9)-septate, 22-49 × 3.5-6.5 μm ·········································································································· Porina guentheri23a. Thallus corticolous ··································································································· 24
24. Ascospores transversely septate ····················································································· 25
24a Ascospores muriform ································································································· 28
25. Ascospores elongate fusiform to subacicular, 10-14-septate, 25-52 × 5-8 μm; perithecia hemispherical to subglobose, 0.1-0.3 mm in diam. ························································· Porina meridionalis
25a. Ascospores fusiform ································································································· 26
26. Ascospores (7-)9-11(-13)-septate ····························································· Porinainternigrans
26a. Ascospores consistently 7-septate ·················································································· 27
27. Ascospores 4-9 μm wide, perispore indistinct ················································ Porina tetracerae
27a. Ascospores 6-13 μm wide, perispore distinct ··············································· Porina mastoidea
28. Ascospores narrowly to broadly fusiform, 50-76 × 12-20 μm ······················· Porina nuculastrum
28a. Ascospores broadly ellipsoidal, 40-70 × 15-25 μm ····································· Porina eminentior
