bermudense sp. nov. (Pyrenulaceae), a new saxicolous from Bermuda

Franz BERGER, Scott LaGRECA & André APTROOT

Abstract: Lithothelium bermudense F.Berger, LaGreca & Aptroot is described as a new saxicolous lichen from Bermuda, mainly characterized by its endolithic thallus and its red- brown, 3-distoseptate spores with diamond-shaped lumina. Key words: Pyrenulaceae

Introduction

The Lithothelium Müll. Arg. (Pyrenulaceae) comprises at least 28 species of pyrenocarpous in the Pyrenulaceae (Aptroot 2006, 2007). It is characterized by distoseptate ascospores with rounded lumina, unbranched paraphyses (reported to be anastomosing in one species) and cylindrical asci that have a conspicuous ocular chamber. The ocular chamber is often rounded, but in some species (or specimens) it is decidedly invaginated (sagittiform)—however, it cannot be ruled out that this invagination is simply a more mature stage of development, as it seems to be more common in asci with mature spores, just prior to ascospore release. Most species occur in the tropics, and only few are widely distributed or locally abundant. As the name already suggests, they can be growing on rock, which is furthermore unknown in the family.

As part of an ongoing revision of Bermudian lichens by the first two authors, a lichen was collected in 2007 that was recognized by the third author as a new species of Lithothelium. Bermuda is a group of over 130 islands (the ”Bermuda Archipelago“), situated at roughly 32° 20´N and 64° 45´W. The islands—basically fossilized dunes (Vacher & Rowe 1997)—are roughly 900,000 years old, and are among the more isolated islands in the world, situated 960 km offshore from the nearest landmass, North Carolina, USA. Unlike North Carolina, however, Bermuda supports a subtropical biota due to the effects of the powerful, nearby Gulf Stream.

The new Lithothelium species was collected in the Walsingham Jungle region (Hamilton Parish), one of Bermuda’s last remaining primary-growth forests. The area has escaped the strong developmental pressures that have altered so much of the archipelago by virtue of its rough, terrain of hard limestone, caused by the partially collapsed ceilings of caves below. As this jungle is also in the lee of the prevailing westerly winds, it is quite protected, which contributes to its reputation as the most undisturbed, pristine forest on Bermuda. Walsingham is home to the most diverse and important cryptogam communities (Britton 1918, Rendle 1936), including some endemic species of ferns and lichens. Indeed, the new species, described below, is endemic to Bermuda, and grows in close association with other characteristic Bermudian lichens, as listed below.

Methods

This paper is based on specimens collected in 2007 by the first two authors, deposited in BM, ABL and the private herbarium of the first author (designated here as hb Berger). The specimen were examined with an Olympus SZX7 stereomicroscope and an Olympus BX50 compound microscope with interference contract, connected to a Nikon Coolpix digital camera. Microscope sections were cut by hand and mounted in water. Spores were also studied with 10 % KOH added.

The Species

Lithothelium bermudense F. Berger, LaGreca & Aptroot sp. nov.

Lithothelium calcicolum thallo endolithico, peritheciis semiimmersis, 0.4-0.6 mm diametro, ascosporis fuscis, 3-distoseptatis, non ornamentatis, 20-25 × 7-8 µm. Typus: Bermuda, Hamilton Parish, Walsingham Jungle, Tom Moore Trail, 32°20,7´N–64°42,75´W, alt. 3 m, on hard limestone, 02 November 2007, F. Berger 22300 & S. LaGreca (BM – holotypus, barcode no. BM000921379; hb Berger, ABL – isotypes). (Figs …)

Thallus endolithic, appearing as a pink to pale brownish spot, up to 2 cm diam., prothallus absent; algae Trentepohlia, cells c. 4-8 µm diam. Ascomata solitary, closed, conical, semi-immersed, nacked, leaving black pits, smooth, black, 0.4-0.6 mm diam,.Walls brittle like charcoal; excipulum and involucrellum fully integrated, the latter throughout carbonized, combined wall c. 150- 200 µm thick above and at the sides, c. 100 µm thick below the asci, KOH - .. Ostiole apical, inconspicuous, hymenium not inspersed with oil globules, gel IKI-negative. Paraphyses unbranched, slender, c. 1-1.5 µm wide. Asci cylindrical, with a rounded ocular chamber (at least when the ascospores are mature), wall to 5 µm thick, containing 8 ascospores. Ascospores fusiform with protruding tips, reddish-brown, darkening in KOH, initially with 1 euseptum, later with 2 additional, incomplete eusepta and always with 3 distosepta, endospore c. 2 µm thick, outer lumina directly against exospore, inner lumina diamond-shaped, 20-25 × 7-8 µm, till to maturity with an open tubulus between the outer and inner lumina (fig. #), perispore absent, spore wall not ornamented, spores getting dark brown and shrinking when overmature Pycnidia not observed.

Ecology: This species grows together with Ionaspis tropica, Stromatella bermudana and small liverworts on low, sheltered, limestone outcrops in primary, coastal rainforest. Other associated species include Strigula bermudana, Gyalecta farlowii, Verrucaria cf. halizoa, Toninia sp., Opegrapha sp., Cryptothecia striata, Lempholemma lingulata, Collema thamnodes, Leptogium austroamericanum and Paulia sp. Notes: The new species superficially resembles some endolithic Verrucaria sp., but is easily distinguished by the red-brown, 3-distoseptate spores. According to Aptroot (2006), it would key out as Lithothelium australe from Chatham Island near New Zealand, but the latter species differs by possessing rounded ascospore lumina. The new species is probably more closely related to some other Lithothelium species with brown ascospores with diamond-shaped lumina, e.g. L. austropacificum from Lord Howe Island near Australia, which is lacking any eusepta and is dwelling on basalt with a conspicuous thallus (McCarthy 1996).. Ontogeny of the spores: Young spores have three distosepta; at maturity one euseptum at the medium of the spore is always present, but does never touch the external wall at all (fig. 2.); the tubulus between the external and the inner lumen is still present at this time. Overmature spores are loosing the tubulus and 2 more discrete eusepta between the lumina are developed. The colour darkens with ongoing maturity.

Additional specimen: Bermuda, Hamilton Parish, Walsingham Jungle, Tom Moore Trail, 32°20,61´N-64°42,8´W, alt. 8 m, on hard limestone, 5 November 2007, F. Berger 22452 & S. LaGreca.

Discussion The species of Lithothelium differ mainly in ascospore size and pigmentation (from hyaline to red brown), relative sizes and forms of the lumina, substrate (on bark or on calcareous rock; with immersed or superficial thallus), and ostiole position (apical to lateral). The ascomata can be solitary or clustered in groups, with or without a common ostiole. Species with brown ascospores resemble some species in the genus Ach., but these have a different ascospore pigmentation (not red brown) and lumina that are angular (not rounded) when the ascospores are mature. Because ascospores of mature Lithothelium resemble immature ascospores of some Pyrenula species, the genus Lithothelium gives the impression to comprise neotaenic (or original) developmental forms of Pyrenula Aptroot (2006). The genus was revised by Aptroot (2006), who provided descriptions and a key to all known species. Three more species were added by Aptroot (2007). Most species are uncommon and relatively inconspicuous. Some have inconspicuous, immersed, whitish thalli and are mistaken for non-lichenized fungi in the field, and so are usually left uncollected by lichenologists. In other words, they are undercollected, except in North America and tropical Asia, where some species are locally abundant. Because of the scattered collections of so many species, and the fact that most species are still known only from one country or even one specimen, it is impossible to estimate the level of endemism in various geographic regions, or the centre(s) of diversity of the whole genus. As limestone outcrops are relatively scarce in the tropics, species are often thought to have a very restricted distribution. Sometimes, however, a second record of a species previously thought to be endemic is found on another continent altogether.

This work was supported by a grant to FB and SLG from the Bermuda Zoological Society. Christine Watlington is warmly thanked for generously providing accomodation for SLG, and for assisting with all aspects of our fieldwork. Jack Ward graciously provided access to, and fieldwork assistance in, Walsingham Jungle. This is contribution number 143 of the Bermuda Biodiversity Project (BBP), Bermuda Aquarium, Natural History Museum and Zoo.

REFERENCES

Aptroot, A. (2006) Three new species of Lithothelium (Pyrenulaceae) from China and Thailand, with a revised world key and annotated list of species. Lichenologist 38: 541-548. Aptroot, A. (2007) New species, combinations, lectotypifications and synonyms on Australian Pyrenulaceae. Australasian Lichenology 60: 34-41. Britton, N.L. (1918) The Flora of Bermuda. New York: Scribner’s. 585 pp. Rendle, A.B. (1936) Notes on the flora of the Bermudas. Journal of Botany 74: 42-50. McCArthy, P.M. (1996) Lithothelium austropazificum sp. Nov, (Pyrenulaceae) from Lord Howe Island, Australia.28: 290–293, , Vacher, H. L., & Rowe, M. P. (1997) Geology and hydrology of Bermuda. Developments in Sedimentology 54: 35-90. Australasian Lichenology 60: 34-41

F. Berger: A–4794, Kopfing 130, Austria; email: [email protected] S. LaGreca: the Natural History Museum, Cromwell Road, London, SW7 5BD U.K. A. Aptroot: ABL Herbarium, G.v.d.Veenstr. 107, NL-3762 XK Soest, The Netherlands