Bruno Mies

New or Interesting Lichens from the Limousin Region (Western Massif Central, France)

Abstract: Mies, B. A. 2015. New or interesting lichens from the Limousin region (Western Massif Central, France). — Herzogia 28: 473–483. The mountainous landscape of Limousin region (Massif Central, France), swept by an Atlantic climate and high precipitation, bears a rich lichen flora with 43 lichens worthy of mention. Platismatia norvegica and Micarea farinosa are new species for the lichen biota of France and continental Europe, and Arthothelium spectabile, Naetrocymbe fraxinii and Usnea longissima are new to central and western France. These are also new records for the three Departments, Creuse (no. 23), Haute-Vienne (no. 87) and Corrèze (no. 19), as well as Arthonia vinosa, Arthopyrenia persoonii, Bacidina phacodes, Bunodophoron melanocarpum, Calicium glaucellum, Callome multipartita, Flavocetraria cucullata, Graphis inustuloides, Lecanora cadubriae, Melanohalea elegantula, Mycomicrothelia confusa, Psilolechia clavulifera and Zwackhia viridis. Confirmation of pre-1959 records for one of the three Departments or for an additional locality in a neighbouring one are Alyxoria culmigena, A. varia, Arthonia didyma, Buellia schaereri, Caloplaca cerina, Catillaria nigroclavata, Cetrelia olivetorum, Chaenotheca chrysocephala, Ch. furfuracea, Chaenothecopsis pusilla, Collema nigrescens, Dendrographa decolorans, Lecania cyrtella, Lecidella elaeochroma f. flavicans, Melanohalea laciniatula, Nephroma laevigatum, Parmelina carporrhizans, Peltigera membranacea, Ramalina calicaris, R. fastigiata, Sticta fuliginosa, S. sylvatica, Thelopsis rubella and Usnea subfloridana.

Topography, Climate and Soils

The Socotra Archipelago is located in the north-western part of the Indian Ocean, close to the Horn of Africa. Socotra itself (ca. 3,600 km2) can be divided into three main topographical regions: (1) the granitic Hagghier mountains; (2) limestone plateaus, which occur between 300 and 700 m and occupy by far the largest part of the island; and (3) coastal plains. The arid tropical climate of Socotra is characterised by pronounced seasonal, altitudinal, spatial and inter-annual variability, with the seasonally reversing monsoons exerting a major influence on weather patterns. The overall arid macroclimate is also greatly modified by the diverse topography of the island and the extent of cloud cover. Rainfall is the chief form of available water at the lower elevations, either directly or indirectly through surface and subsurface redistribution. However, at higher altitudes, where forest is developed, fog and mist provide an important input of moisture, substantially augmenting the amount of plant-available water. Due to the arid nature of the climate, soils are poorly developed over much of the island. Pedogenesis involving chemical processes and the synthesis of organic matter is mainly restricted to the upper mesic montane zone where there is dense vegetation cover and the climate is more humid.

Ecology and Adaptive Strategies

Most of the Socotra Archipelago is occupied by desert or semi-desert vegetation types, and deserts impose severe restrictions on plant growth. Few detailed studies have been carried out on adaptive features of Socotran plants to their environment, and the information that is forthcoming mainly relates to plants of the desert plains in both the north and south of the island. In this chapter, some key adaptations to arid desert environments are discussed, followed by a brief overview of the adaptations to saline and high montane ecosystems. The Raunkiaer life-form classification system is of limited use for predominantly desert ecosystems, because it is rather restricted in its structure–function relationships relevant to desert life. The five main types are briefly discussed, followed by a more detailed overview of the major growth-forms. Other classification systems place greater emphasis on the role of physiological adaptations, and “plant functional types”, which reduce the complexity of species diversity in biological systems to a limited number of key types, can facilitate a better understanding of important ecosystem processes. Several of the more common functional classification systems are outlined, and their application to the flora of Socotra is indicated. Short accounts of topics such as pollination ecology, including the potential significance of bird-pollination, seed dispersal and germination are given.

Flora and Biogeography

In the first part of this chapter, the history of botanical exploration is explored. The most important floristic work to appear in recent times is the Ethnoflora of the Soqotra Archipelago, outlining 828 species of vascular plants that have been recorded from the area. A striking feature is the high proportion (37%) of endemics. Palaeoendemics appear to be rather poorly represented, and recent molecular phylogenetic studies are beginning to emphasise the role of neoendemism in shaping the flora. The vascular flora has its closest affinities to the adjacent regions of the Horn of Africa and southern Arabia, but distinct links exist to other geographical areas much further afield. Recent evidence also suggests that long-distance dispersal of ancestral species has contributed substantially to the development of the present-day flora, as demonstrated by various examples. It can be assumed that with the arrival of the first settlers on the islands, many native plant communities have been subject to pronounced changes in species composition, and examples of the two major groups that have benefited from human impact, “invaders” and “colonisers”, are given. Twenty-six species of fern are known from the archipelago, with only one endemic. Fairly detailed overviews now exist of the bryophyte and lichen flora. The biogeography of these two groups is of considerable interest, as they are quite ancient in geological terms and occur in comparable habitats throughout the world.