Species richness patterns, hotspots and phytogeographic affinities of thalloid liverworts (Marchantiophyta) and hornworts (Anthocerotophyta) of Sri Lanka

Abstract

Sri Lanka is a tropical island and lies in the Indian Ocean, near the southwestern tip of India sharing the same continental shelf. The island has a highly varied climate and topography, spanning from coastal region and lowlands with a tropical climate to central highlands with a cool temperate climate. Sri Lanka harbours a rich diversity of bryophytes. The aim of this study was to trace the species richness patterns and phytogeographic affinites of Sri Lankan thalloid liverworts and hornworts. The analysis is based on comprehensive field excursions carried out throughout the island covering all possible geographic localities. Distribution patterns were deduced for each taxon reported and phytogeographic affinities were traced on the basis of its present worldwide distribution. Their distribution patterns were compared with the floristic regions recognized for flowering plants of Sri Lanka. A variation in the species diversity and pattern of aggregation of species in different climatic and topographic zones was observed. Central Highlands in the wet and intermediate zones, represented the center of diversity of almost all reported taxa. Thalloid liverworts and hornworts are distributed in all floristic regions recognized for angiosperms, except in the coastal, marine and dry zone floristic regions. Zones of highest taxonomic diversity or “hotspots”, have been inferred for taxa encountered in the island. Seventy five percent of all thalloid liverworts and hornworts reported from Sri Lanka are shared with the Western Ghats of India and 90% of taxa are shared with mainland India.