Radula jonesii is a species of liverwort in the family Radulaceae.[2] It is known from a few locations on Madeira and one location on Tenerife. The populations are small and vulnerable.[1]
| Radula jonesii | |
|---|---|
Scientific classification 
| |
| Kingdom: | Plantae |
| Division: | Marchantiophyta |
| Class: | Jungermanniopsida |
| Order: | Porellales |
| Family: | Radulaceae |
| Genus: | Radula |
| Species: | R. jonesii
|
| Binomial name | |
| Radula jonesii Bouman, Dirkse & Yamada
| |
This liverwort forms dark green to olive-green mats on rocks or on trees such as Laurus novocanariensis and Ocotea foetens. It is part of the old growth laurel forest ecosystem on the islands. On Madeira this ecosystem is protected.[3]
Taxonomy
editRadula jonesii was formally described in 1988 in the Journal of Bryology by Adrianus Cornelis Bouman, Gerardus Martinus Dirkse and Kohsaku Yamada. The specific epithet jonesii honors Eustace Wilkinson Jones, who made significant contributions to the study of African liverworts. The holotype specimen (RIN 003367) was collected from the Anaga Mountains of Tenerife at an elevation of 750 meters and is preserved at the Utrecht University Herbarium (U), with an isotype stored at the Hattori Botanical Laboratory (NICH) in Japan.[4]
When first discovered between 1984 and 1987, the species was initially mistaken for Radula holtii. However, detailed examination revealed it to be distinct from any known European, African, North American, or South American species of Radula.[4]
Radula jonesii belongs to a clade of species closely related to the R. complanata/R. lindenbergiana complex, which is widely distributed in the northern hemisphere. This relationship has been confirmed through molecular analysis of plastid DNA sequences. It is one of two endemic Radula species in Macaronesia, along with R. wichurae.[5]
Description
editRadula jonesii is a medium-sized liverwort that forms loose, slightly procumbent (lying along the ground) mats. The plants appear dark to olive-green in color, with main stems measuring 10–15 mm in length. These stems branch irregularly in a pinnate pattern, similar to the arrangement of a feather. The species possesses several unique characteristics in its cellular structure, most notably in its stem anatomy where the outer (epidermal) cells closely resemble the inner (medullary) cells, both featuring thick walls and triangular thickenings called trigones. The leaf-like structures, known as lobes, are narrowly ovate (egg-shaped) to ovate in shape, with distinctive curved bases that never extend across the stem. Within these lobes, the cells display uniformly thin walls without trigones, a feature that helps distinguish this species from its relatives.[4]
The reproductive structure, called a perianth, is cylindrical with an irregularly lobed opening at its tip. R. jonesii is paroecious, meaning male and female reproductive organs are found on the same branch but in different locations. When reproducing, the species produces green spores measuring 18–22 μm in diameter. Researchers have not observed any methods of vegetative reproduction (reproduction without spores) in this species, suggesting it relies entirely on spore production for propagation.[4]
Habitat and distribution
editThis liverwort is known only from its type locality in the Anaga Mountains of Tenerife, specifically on the northwest slope of El Pijaral (Pico de Limante). It grows at elevations between 700–800 meters above sea level in laurel forest environments. The species can be found on wet, shaded rocks, though these areas may experience dry conditions during summer months.[4]
Associated species
editRadula jonesii is commonly found growing alongside other bryophytes (mosses and liverworts) including Lejeunea eckloniana, Radula wichurae, Radula lindenbergiana, Radula carringtonii, Harpalejeunea ovata, Drepanolejeunea hamatifolia, Marsupella emarginata, Trichostomum brachydontium, and Hypnum cupressiforme.[4]
Conservation
editThe species is classified as endangered on the IUCN Red List, reflecting its extremely limited distribution and potential vulnerability to habitat changes.[5]
References
edit- ^ a b Sim-Sim, M.; Hodgetts, N.; Martins, A. (2019). "Radula jonesii". IUCN Red List of Threatened Species. 2019: e.T39211A87715659. doi:10.2305/IUCN.UK.2019-2.RLTS.T39211A87715659.en. Retrieved 16 November 2021.
- ^ "Radula jonesii Bouman, Dirkse & K. Yamada". Catalogue of Life. Species 2000: Leiden, the Netherlands. Retrieved 25 October 2024.
- ^ Radula jonesii. Archived 2015-09-23 at the Wayback Machine Swedish University of Agricultural Sciences.
- ^ a b c d e f Bouman, A.C.; Dirkse, G.M.; Yamada, K. (1988). "Radula jonesii spec. nov. (Hepaticae), a new species from Tenerife". Journal of Bryology. 15 (1): 161–164. doi:10.1179/jbr.1988.15.1.161.
- ^ a b Stech, Michael; Sim-Sim, Manuela; Esquível, M. Glória; luís, Leena; Fontinha, Susana; Lobo, Carlos; Garcia, César; Martins, Soraia; Vieira, Cristiana; Barroso, José; Pedro, Luis G.; Figueiredo, A. Cristina S. (2010). "Molecular, phytochemical and morphological characterization of the liverwort genus Radula in Portugal (mainland, Madeira, Azores)". Systematics and Biodiversity. 8 (2): 257–268. doi:10.1080/14772001003723579.