Marsupella emarginata, Bakalin & Fedosov, 2019

Bakalin, Vadim A., Fedosov, Vladimir E., Fedorova, Alina V. & Nguyen, Van Sinh, 2019, Integrative taxonomic revision of Marsupella (Gymnomitriaceae, Hepaticae) reveals neglected diversity in Pacific Asia, Cryptogamie, Bryologie 20 (7), pp. 59-85 : 71-72

OF MARSUPELLA EMARGINATA

The most complex question is infraspecific structure of Marsupella emarginata for which Váňa et al. (2010) list four infraspecific taxa: subsp. emarginata and subsp. tubulosa (Steph.) N.Kitag. , including three varieties: var. apertifolia (Steph.) N.Kitag. , var. patens N.Kitag. and var. tubulosa (Steph.) N.Kitag. The cited paper ( Váňa et al. 2010) marks certain advance in recognition of some infraspecific taxa at the species level. Marsupella aquatica before was uniformly treated as the variety within M. emarginata (noticeable exclusions are the treatments by Schljakov (1981) and Grolle (1976), where it is the species; major works published at the end of 19th and the beginning of 20th century also recognized it as the taxon of species rank, cf. Schuster 1974).

Another complex taxon that after description was rarely treated as an independent species is Marsupella tubulosa . The only examples in the second half of the 20th century known to the authors are in Schlajkov (1981) and Grolle (1976) although the latter only references to Schljakov’s (1973) record from North Ural and cannot be regarded as independent finding. These listed papers as well as Schuster (1974) have introduced the usage of this name (regardless as variety or as the species) outside of Sea of Japan Basin which we suggest was a mistake. Originally Marsupella tubulosa is viewed from Japan. The study of dry material (also by Kitagawa 1963) could hardly reveal the stable distinction characters. The mentioned main differentiation characters (cf. Schljakov 1981; Schuster 1974) as the leaves asymmetry, more acute leaf sinus, and even ( Schuster 1974, for subsp. tubulosa var. latior R.M.Schust. ) supposed absence of red pigmentation (although type in G is red colored). Later, as it was shown in Japanese literature, Marsupella tubulosa in its narrow sense (e.g. var. tubulosa ) is characterized by distinctly biconcentric oil bodies ( Iwatsuki 2001) ( Fig. 5 R-T), a feature remained neglected outside of Japan. Our study of fresh material from East Asia has revealed this is the species of Japanese-Korean distribution, stretching the area to the Kurils and Kamchatka and, probably, as evident rarity, occurs in Sikhote-Alin. In any way, this taxon could hardly expand beyond Pacific Eastern Asia especially to the areas with a continental climate. Taking into account the genetic differences, this taxon needs to be recognized as a separate species. It is also worth to mention that the status of two varieties distinguished within “ M. emarginata subsp. tubulosa ”, by Kitagawa (1963) as var. apertifolia and var. patens require further discussion that is provided below.

Kitagawa (1963) treated the latter two taxa ( var. apertifolia (Steph.) N.Kitag. and var. patens N.Kitag. ) as varieties within Marsupella emarginata ssp. tubulosa (Steph.) N.Kitag. based on supposedly intergrading character of differentiation features. To some degree, we may agree with him, because such features as the presence of red coloration and other features may not be easily observed in some depauperate plants or populations from shady habitats. On the other hand, the genetic analysis displayed robust distances between all these three taxa that even some “small” difference should help to recognize the taxa morphologically.

Indeed M. apertifolia possesses somewhat similar characters that differentiates it from M. tubulosa as do M. aquatica when compared with M. emarginata . These differences are in larger size, not so deeply lobed leaves, less recurved leaf margin, thick-walled cell walls in the midleaf and sometimes shortly bistratose leaf base (although not noted in the literature for M. apertifolia , but observed in our and type material). Kitagawa suggested both M. aquatica and M. aptertifolia as independent derivates from M. emarginata ssp. emarginata and M. emarginata subsp. tubulosa correspondingly. However, the results of comparison of genetic structure show the opposite situation. These taxa ( M. aquatica and M. apertifolia ) are more closely related to one another than to any M. emarginata or M. tubulosa . The former pair of taxa is better to regard as the result of more recent divergence probably due to geographic gap in distribution: both taxa show distinct amphi-oceanic tendencies in distribution, where M. aquatica is generally a sub-Atlantic taxon, whereas M. apertifolia is an oro-boreo-temperate West Pacific taxon. The morphological differences between these two taxa we were able to find are the absence of red pigmentation in M. apertifolia , whereas this coloration is common in M. aquatica , and distinctly (at least sometimes) striolate leaf cuticle in M. apertifolia (noted by Schuster (1996) as the peculiar feature of Apomarsupella within Gymnomitriaceae !), vs constantly smooth cuticle in M. aquatica . According to the obtained topology, the closest relative of M. apertifolia in fact is M. aquatica , not M. tubulosa ; these species form highly supported clade and are similar morphologically. Thus, M. apertifolia cannot be considered an infraspecific taxon of M. tubulosa and should be either regarded as a separate species, or synonymized with M. aquatica . However, the distance between two clades in a genetic sense ( Fig. 1) and the robust difference in distribution and somewhat morphology (absence of red or purple pigmentation in M. apertifolia ) suggest a re-establishment of this taxon as a distinct species under the name Marsupella apertifolia Steph. (Bulletin de l’herbier Boissier, sér. 2, 1 [2]: 162 [23], 1901; holotype: Japan, Miyo Kosan, U., 1897, Faurie 75, G9469/00065015!).

Principally another situation is with “ Marsupella emarginata subsp. tubulosa var. patens ” that is characterized strongly by unequally bilobed leaves that even “look like to Diplophyllum ” ( Kitagawa 1963: 90). Further Kitagawa (1963) noted the resemblance of var. patens with Marsupella pseudofunckii , from which, however, the species differ in larger size, rounded leaf lobes and not so prominently complicate leaves. Indeed, the genetic results have shown the strong relationship of this taxon with another group of other strictly East Asian taxa with unequal lobes and folded leaves: M. alata , M. yakushimensis , M. koreana Bakalin & Fedosov , sp. nov., and M. pseudofunckii . In our opinion, there are no reasons to merge this taxon with M. tubulosa and it should be regarded as the taxon of species rank. It easily differs from the other bulk of listed taxa in strongly unequal leaf lobes (by this feature joined with M. pseudofunckii , M. koreana Bakalin & Fedosov , sp. nov.), greenish to brown pigmentation without the red color (joined with M. alata , M. pseudofunckii ), not keeled leaves (joined with M. pseudofunckii and M. koreana Bakalin & Fedosov , sp. nov.) and rounded leaf lobes. Therefore a new combination is needed: