Dicranodontium Schwabei (Bryophyta, Dicranaceae) Revisited: Some Taxonomic and Nomenclatural Considerations
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Polish Botanical Journal 62(2): 175–182, 2017 e-ISSN 2084-4352 DOI: 10.1515/pbj-2017-0018 ISSN 1641-8190 DICRANODONTIUM SCHWABEI (BRYOPHYTA, DICRANACEAE) REVISITED: SOME TAXONOMIC AND NOMENCLATURAL CONSIDERATIONS Halina Bednarek-Ochyra, Vítězslav Plášek & Ryszard Ochyra1 Abstract. Dicranodontium schwabei Thér. & Herzog, a poorly known species from Western Patagonia in Chile, is briefly as- sessed taxonomically. Some morphological and anatomical details of the species are illustrated and the problems associated with the typification of its name are discussed. The conspecificity of this species and Chorisodontium aciphyllum (Hook.f. & Wilson) Broth. is confirmed and the geographical distribution and ecology of the latter species is briefly reviewed. Key words: Chile, Chorisodontium, Holodontium, Musci, nomenclature, Patagonia, South America, taxonomy Halina Bednarek-Ochyra & Ryszard Ochyra, Department of Bryology, W. Szafer Institute of Botany, Polish Academy of Sciences, ul. Lubicz 46, 31-512 Kraków, Poland; e-mail: [email protected] Vítězslav Plášek, Department of Biology and Ecology, University of Ostrava, Chittussiho 10, CZ-710 00 Ostrava, Czech Republic; e-mail: [email protected] Introduction Dicranodontium schwabei Herzog & Thér. was de- currently considered as Campylopus asperifolius scribed by Herzog (1939) from a single specimen Mitt. (Frahm 1981a, 1987). collected by the Schwabes in Western Patagonia. For over a half century D. schwabei remained This author consulted the French bryologist an entirely neglected species. Frahm (1991, 1997) I. Thériot about the status of the original mate- was the first to provide a comment on its taxo- rial and he stated that this was a new species of nomic status. Having examined the putative type Dicranodontium Bruch & Schimp., close to the material, he excluded it from the genus Dicrano- Javanese D. nitidum Dozy & Molk. [= D. unci- dontium and assigned it to the genus Chorisodon- natum (Harv.) A. Jaeger]. The Chilean species is tium (Mitt.) Broth., but without indication of its a robust and very handsome moss which is distinct affinities and giving any reasons for this taxonomic in the anatomy of the costa, the strongly porose conclusion. Although this generic placement is lower leaf cells, and distinctly mammillose and correct in the light of the subsequent assessments rough costa on the abaxial side. These diagnostic of the original collection of D. schwabei, it is ques- characters are clearly illustrated in the protologue. tionable whether it was based on an examination The discovery of this species was remarkable be- of the true type specimen. cause it was then the second record of the pre- dominantly Holarctic genus Dicranodontium in Taxonomy and nomenclature South America (Greene 1986). The first one was D. asperifolium (Mitt.) Broth. which was origi- Dicranodontium schwabei was described on the nally described by Mitten (1869) from Ecuador basis of the single specimen collected in Western and Tatanara in ‘Andes Chilenses’ which is at pre- Patagonia by G. H. Schwabe and E. Schwabe in sent situated in Peru (Frahm 1991). This species is the Cerro Tesoro near the village of Puyuhuapi in the province of Aysén (XI Région, Chile) 1 Corresponding author (Fig. 1), whereas Frahm (1991, 1997) cited the Received: 19 Sept.2017. Publication date(s): online fast track, n/a; in print and online issues, 15 Dec. 2017 176 POLISH BOTANICAL JOURNAL 62(2). 2017 Fig. 1. The label of the lectotype of Chorisodontium aciphyllum (Hook.f. & Wilson) Broth. (JE). specimen collected by Grosse in Istmo de Ofqui only, from Istmo de Ofqui collected by Grosse No. in Provincia de Aisén as type. It was designated 40 which is determined as Dicranodontium sp. holotype but in the Haussknecht Herbarium in Unfortunately, it does not bear any annotation of Jena (JE) no material of D. schwabei from this J.-P. Frahm. It was examined during the present locality is available. However, this herbarium does research and it correctly represents Holodontium hold a small specimen, consisting of a few shoots strictum (Hook.f. & Wilson) Ochyra, an austral H. BEDNAREK-OCHYRA ET AL.: RECONSIDERATION OF DICRANODONTIUM SCHWABEI 177 amphiatlantic subantarctic species of the mono- Chorisodontium aciphyllum (Hook.f. & Wilson) typic genus Holodontium (Mitt.) Broth. (Ochyra Broth. 1993a). In its overall aspect Holodontium is similar Chorisodontium is a small Southern Hemisphere to dicranalean genera and its very broad costa, genus, having the main centre of its diversity in South occupying one third or more of the leaf lamina, America, with only one species, Ch. aciphyllum, with a central row of enlarged guide cells which having a wide panholantarctic range (Ochyra et al. separate two stereid bands, long-subulate leaves 2008). The genus is poorly defined and in fact it is and large alar cells, suggests its close affinity to diagnosed only by its bistratose laminal cells at the Campylopus Brid. and Chorisodontium. How- leaf shoulders and in the leaf subula which gradu- ever, numerous lengthwise cuticular ridges which ally fuse with the costa. This gives the impression densely cover the adaxial and abaxial surfaces of that the costa is distinctly flaring outwards at the the leaf lamina and give them a papillose appear- junction of the leaf base and the subula. Externally, ance in transverse section, strongly falcato-secund Chorisodontium is similar to the genus Campylopus leaves, often forming penicillate tufts at the tips with which it shares the shape and anatomy of the of shoots, clearly exclude any relationship of the costa, the leaf areolation and the distinct alar cells. specimen from Istmo de Ofqui with Chorisodon- The only difference between the two genera is the tium. Accordingly, the typification of Dicrano- absence of stomata in Campylopus (always present dontium schwabei by Frahm (1991, 1997) has to in Chorisodontium). be superseded. According to Art. 9.19 of the ICN Chorisodontium consists of eight species, al- (McNeill et al. 2012), the specimen indicated by though in total it included about 30 species and va- this author as the holotype is in serious conflict rieties (Wijk et al. 1959, 1969; Frahm 1981b). They with the protologue, because it has not been used are divided into two distinct groups which are iso- by Herzog (1939) for description of Ch. schwabei, lated geographically. The southern cool-temperate and its morphological and anatomical traits do not group includes five species that occur primarily in fit the description and illustrations of this species. southern South America and occasionally extend A decade later, the original collection of Di- to the Subantarctic region, Antarctica and New cranodontium schwabei was examined by Müller Zealand (Roivainen & Bartram 1937; Hyvönen (2002), who concluded that ‘it presents excellent, 1991). They are characterised by a very broad well developed (plants 5 to 8 cm high, leaves costa, shorter leaves with entire or nearly so leaf ca 1.5 cm long) material of Ch.[orisodontium] margins, less distinct alar cells, a deciduous annulus aciphyllum’. Because no discussion on the taxo- and small unicellular spores, 18–30 µm wide, and nomically important characters of this species is they are often peat-forming plants. The neotropical provided, the type material is briefly assessed and group comprises three species which occur at high illustrated (Fig. 2). Also, no annotation label of this elevations in the páramo vegetation in the Central author is available in the specimen of D. schwabei and Northern Andes (Frahm 1989; Ochyra 2003). in JE. Müller (2002) indicated the specimen exam- This group is distinct in having larger leaves which ined in the Herzog Herbarium in JE as holotype, are markedly serrate at the apex, a much narrower although lectotypification would be necessary since costa, large alar cells that are often thick-walled then there existed no fewer than two replicates of and coloured, a persistent annulus and large, often the type specimen in the Thériot Herbarium in PC multicellular spores, 20–80 µm in diameter, germi- and in the Haussknecht Herbarium in JE, but none nating precociously in the capsules. of them was indicated as type. Nevertheless, Mül- The plants of the type material of Dicranodon- ler’s (2002) use of holotype can be considered an tium schwabei are large, to 13 cm long, and their error to be corrected for lectotype under Art. 9.9 of rigid, straight leaves, to 15 mm long, immediately the ICN (McNeill et al. 2012). The taxonomic con- attract attention. They are crowded, erect and ap- clusion presented by Müller (2002) is correct, and pressed and, from an oblong-ovate, concave and Dicranodontium schwabei is truly conspecific with somewhat clasping base with distinct hyaline to 178 POLISH BOTANICAL JOURNAL 62(2). 2017 brownish alar cells, gradually taper into a long, seta- phenotypes of Ch. aciphyllum have been recognised ceous, tubulose and involute subula that is straight or by different authors as separate taxa (Bell 1973, somewhat flexuose distally and up to twice as long 1977; Hyvönen 1991; Ochyra 1993b, 1994, 1996, as the leaf base. The leaves are entire throughout, 1999). The adaxial stereid band is strong, 4–5-stra- except for the extreme apex which is sharply or tose, such as seen in the type material from Hermite bluntly serrate. The costa is very broad, 300–400 μm Island near Cape Horn (Hooker & Wilson 1844). wide in mid-lamina, and occupies about half the In this context the taxonomic status of Chori- leaf base and the entire subula. It is mostly not sodontium dicranellatum needs re-assessment sharply defined, pale and concolorous with the and it is likely that this species may represent laminal cells, and imperceptibly merges with the a somewhat depauperate habitat modification of bistratose lamina at the shoulders and in the subula. Ch. aciphyllum, as suggested by Hyvönen (1991), In transverse section it is strongly flattened in the who accepted it only provisionally as a species in basal part and lunate in the subula, and it is in- its own right.