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Non‐vascular plant distribution patterns were examined in three microhabitats along an altitudinal gradient on a recent lava flow of the Piton de la Fournaise volcano (La Réunion, Mascarene archipelago). The uniform nature of the lava flow provides an excellent system to study the relationship between altitude and species diversity and distribution, and at the same time avoiding confusing multiple effects of substrate and vegetation heterogeneity. Non‐vascular plants were surveyed with quadrats within an altitudinal range from 250 m to 850 m a.s.l. Fine‐scale variations in bryophyte communities between three ecological microhabitats (the ground and on the rachises of two fern species) were investigated. Three specific questions were addressed: (1) What is the species diversity of bryophyte communities on a 19‐year‐old lava flow? (2) How does altitude influence the diversity and distribution of bryophytes on a lava flow? (3) Does microhabitat variation control bryophyte diversity? In our study, bryophyte diversity increased with altitude. Unexpectedly, species richness was very high; 70 species of bryophytes were recorded including nine new records for the island. Diversity was also controlled by ecological microhabitats. Bryophyte species were structured into six categories according to altitude and microhabitat preferences. Results suggested that the high diversity of these cryptic organisms on this lava flow is fostered in part by their host substrate and their adaptative strategies on new substrates. On a broader scale, it was concluded that lava flows as primary mineral environments are important to conserve, as they support a high diversity of pioneer organisms that constitute the early stages of the development of La Réunion's remnant lowland rainforest.

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Abstract.A checklist of the bryoflora of the Taita Hills (Kenya) containing 168 taxa in 40 families is presented. Whilst previously only 22 mosses and 39 liverworts were recorded for the area, this study extended our knowledge to 85 and 83 respectively. Twenty taxa are newly recorded for Kenya.

: 124 species of bryophytes, belonging to 46 families are reported for the Aberdare Mountains, of which 58 species are new for the Aberdares and 6 records are new for Kenya, indicated by * and ** respectively. The wetter, more humid southern and south-eastern parts of the range contain the greatest diversity of species, particularly in the montane forests while the drier northern part is poor in species.The Aberdare (or Nyandarua) Range of mountains of Kenya lies to the east of the Gregory Rift Valley and is about 80km north of Nairobi and 17km from Nyeri town. It is an elongated massif, running approximately north-south, parallel to the direction to the Rift Valley, about 50 km to the west of Mt. Kenya. The steep western side of the range forms the eastern wall of the Rift, and the massifs of Mt.Kenya and the Aberdares together form the Central Highlands. The upper slopes of the range form an important water catchment area, the slopes are steep and densely forested while the foothills has been cleared of forest and used for cultivation. Two dams, the Sasumua and Ruiru, provide Nairobi with water. The massif extends over a wide area .