The genus Grimmia Hedw. has been considered taxonomically difficult because of its great morphological variability, and its treatments by different specialists have led to incongruent results. One of the debates in the genus is the species status of Grimmia limprichtii Kern, an Asian-European disjunct moss species that has been considered identical to Grimmia anodon Bruch & Schimp. or Grimmia tergestina Tomm ex Bruch & Schimp. It has also been regarded as the muticous-leaved male plants of G. tergestina. Based on a detailed analysis of the type and many non-type specimens combining the molecular and morphological data, the reinstatement of species rank for G. limprichtii is proposed. The diagnostic characteristics of G. limprichtii and its distinction from some closely related species, with which it may be confused, are discussed. Grimmia obtusifolia C. Gao & T. Cao is considered a synonym of G. limprichtii based on molecular and morphological data.

Asia-Europe disjunction, Grimmia obtusifolia, phylogenetic taxonomy

The genus Grimmia is one of the largest genera of the moss family Grimmiaceae (Feng et al. 2013). Its species are found on all continents, and most of them prefer dry and temperate or cold environments, and all of them are saxicolous with a marked preference for acidic bedrock (Hastings and Greven 2007). Its taxonomy is reputedly difficult because of great morphological variability in most of its species and the difficulty of properly assessing some crucial characteristics (Feng et al. 2014). Therefore, its treatment by different specialists has led to incongruent results (Muñoz 1999; Ignatova and Muñoz 2004). One example is the number of species accepted in the genus, ranging from 51, according to Maier (2010), who synonymized many names of morphologically diverging taxa, to 71, as reported by Muñoz and Pando (2000), to 95, following Hastings and Greven (2007). Some of the controversial species have recently been resolved based on molecular and morphological data (Hugonnot et al. 2018; Kou et al. 2019; Feng et al. 2021).

Grimmia limprichtii Kern was described in 1897. However, since it was discovered, this species has been considered identical to Grimmia anodon Bruch & Schimp. (Loeske 1930) and this treatment was accepted by following authors (such as Wijk et al. 1962; Muñoz and Pando 2000). In recent years, it was synonymized with Grimmia tergestina Tomm. ex Bruch & Schimp. by emphasizing the cell pattern, structural characteristics of the costa, and characteristics of the perigonial leaves, as well as the occasional presence of both muticous and hair-pointed leaves in the same plant of the latter species (Maier 2002). Soon afterwards, G. limprichtii was regarded as the muticous-leaved male plant of G. tergestina, as its male plants were associated with sporulating G. tergestina in Tibet (Greven 2009).

Grimmia obtusifolia C. Gao & T. Cao was first described in Tibet, China, and later, it was discovered in many other provinces, such as Qinghai, Xinjiang, Sichuan, Tibet of China, and three locations in Mongolia (Tsegmed and Ignatova 2007; Jia and He 2013). In addition, this species may appear in Pakistan (Gruber and Peer 2010). Although G. obtusifolia was accepted by some authors (Redfearn et al. 1996; Tan and Jia 1997; Muñoz and Pando 2000; Liu et al. 2011; Jia and He 2013), soon after it was described, G. obtusifolia was synonymized by other authors with G. limprichtii (Greven and Sotiaux 1995) and G. tergestina (Maier 2002, 2010; Greven 2009). Maier (2010) synonymized G. obtusifolia with G. limprichtii due to similarities in leaf shape, laminal basal cells, and costal architecture, while Greven (2009) believed that G. obtusifolia and G. limprichtii were muticous-leaved male plants of G. tergestina. Plants with muticous leaf apices are not rare in G. tergestina and G. anodon, and the similar leaf shape, areolation of the leaf base, and costal architecture explain the synonymization with G. tergestina, and the nearly unistratose upper laminal cells may explain that with G. anodon (Maier 2002, 2010). Grimmia limprichtii and G. obtusifolia have a similar habit, concave leaves, cucullate and rounded-obtuse leaf apex, architecture of the costa, and areolation of the leaf base. The only difference between the two species is that G. obtusifolia has nearly bistratose upper laminal cells, while G. limprichtii has unistratose cells with bistratose ridges (Maier 2002; Greven 2014).

Throughout our continuing investigation of xerophilic mosses, which are particularly prevalent in Tibet, many Grimmia specimens were collected. Some of them belong to either G. obtusifolia or G. limprichtii. Detailed observations revealed that these samples bear archegonia, which is contradictory compared to the point of view that G. obtusifolia and G. limprichtii are muticous-leaved male plants of G. tergestina. This discovery prompted us to conduct further morphological and molecular studies to confirm their systematic position.

Grimmia limprichtii is a remarkable species characterized by small and slender plants, muticous, concave to somewhat keeled and oblong-ovate leaves, somewhat cucullate and rounded-obtuse leaf apex, plane leaf margins, and a costa ending below the apex. In addition, its sexual condition is dioicous. Although the androecia of G. limprichtii were discovered in Europe and Asia (Greven and Sotiaux 1995), its archegonia were usually found in our collections from Inner Mongolia (Feng 2014) and Tibet (Fig. 4), but androecia were not found. Our findings showed that the presumption that G. limprichtii is the muticous-leaved male plant of G. tergestina (Greven 2009) is unreliable. The generation of a single generative organ in a specific area may explain why the sporophytes are not generated. The characteristic bistratose, partially bistratose or unistratose with bistratose ridges in the upper part of laminal cells is an intraspecific variation influenced by ecological factors, based on our molecular and morphological results.

Figure 4. 

Grimmia limprichtii archegonia. Photos: Chao Feng (Zi Wang 20180808022).

Morphologically, G. limprichtii is most similar to G. tergestina, a widely distributed species (Muñoz 1999; Ignatova and Muñoz 2004). Both species share similar leaf shapes, plane leaf margins, and indistinct costa. Additionally, some specimens of the latter species are found in leaves both with and without hair-points (Maier 2002). However, G. limprichtii can be readily distinguished from G. tergestina by its small and slender plants, costa ending below the apex, and costal guide cells in laminal parts that are distinct from laminal cells. While G. tergestina has rather stiff plants, costa percurrent and guide cells of the laminal part of the costa are hardly distinct or even indistinct from lamina cells, due to their similarity.

Grimmia crassiuscula H.C.Greven & C.Feng, a species that was recently described from the Helan mountains, China (Greven and Feng 2014), resembles G. limprichtii in the oblong-ovate and muticous leaves, cucullate leaf apex, plane leaf margins, and costa ending below the apex. Nevertheless, G. crassiuscula differs from G. limprichtii in having plants in loose and succulent mats, absence of a central strand of the stem, and costa without stereids.

Grimmia limprichtii was previously synonymized with Grimmia anodon Bruch & Schimp., a widely distributed species (Muñoz 1999; Hastings and Greven 2007). Although hair-point presence and length and the number of cell layers in leaf cross sections are variable in the latter species (Muñoz 1999), G. anodon can be separated readily from G. limprichtii by its keeled and broadly oblong-lanceolate leaves, elongate-rectangular laminal basal cells, and autoicous sexuality. G. limprichtii, by contrast, has concave and oblong-ovate leaves, quadrate to rectangular laminal basal cells, and dioicous sexuality.

We are very grateful to Dr Jesús Muñoz, Real Jardín Botánico, for his valuable advice while the authors were studying the genus Grimmia and for sending important literature to us. We really appreciate Genevieve E. Tocci of Harvard University Herbaria (FH) for providing many fine photos of the type of G. limprichtii and correcting the draft. We thank Dr Wei Li and the curator of IFP for the loan of the type and non-type specimens of G. obtusifolia to us, and to the curator of FH and Dr Marc Appelhans of GOET for the loan of the type of G. limprichtii. We are very grateful to Dr Matt von Konrat of Field Museum and an anonymous reviewer for instructive advice, comments, and corrections to draft of this paper. This work was supported by the Natural Science Foundation of China (grant no. 32060051, 42001045, 31660051), Shenzhen Key Laboratory of Southern Subtropical Plant Diversity (grant no. 99203030), the Natural Science Foundation of Inner Mongolia (grant no. 2022MS03066), and the Innovative team of China’s Ministry of Education-Research on the sustainable use of grassland resources (IRT_17R59).