On the Phytogeography of Mosses in Taiwan

Abstract

Moss flora of Taiwan is characterized by high species density and low level of endemism. Except for the widespread species (49.4%), moss flora of Taiwan shares the highest identity (30.3%) with Japan and China. Nevertheless, taxa that are also distributed in Indochina, Himalayas and tropical Asia add the complexity of the moss flora of this island. Although long-distance dispersal of spores in mosses is possible, the floristic composition is rather related between neighboring areas. High floristic similarity, which appears proportional inversely to geographical distance, between Taiwan and South China reveals physical constraint on spore dispersal in average taxa.High diversity in Andreaea, a taxon growing at alpine tundra, of Taiwan may be ascribed to two different origins of its composing taxa: namely one from mainland China, including A. wangiana, and the other from tropical Asia, including A. mutabilis. The Himaland origin hypothesis is not only supported by the distribution pattern of A. wangiana but also by another alpine genus, Pseudopleuropus.Species of Fissidens, a worldwide genus distributed in low and middle elevations of this island, of east Asian countries are compared. Among the 64 total species, with 23 species being widespread 26.6% taxa are restricted to the As2 region. Eleven species also distributed in As3 region or the Himalayas constitute the elements of south or southwest China. Four species frequently found in tropical Asia are located either in Hainan Island or the Henchun Peninsula of Taiwan. Aongstroemia orientalis, a representative of bamboo grassland at middle or high elevations, is discretely distributed in Taiwan and southwest China. The ecology of this species is correlated with the recurrent fire at grassland. Its evolutionary history in Taiwan might have co-evolved with the invasion of yushania and miscanthus, dominant grasses of this vegetation type, during the last withdraw of glacier.Horikawaea is another low land genus for demonstrating the high affinity between Taiwan and south China.Three species are distributed in Taiwan, south China, Vietnam, and Philippines with an overlapping at Hainan Island. Horikawaea nitida, distributed in Taiwan and south China, and H. dubia, distributed in west of the former species, represent the northern limit of distribution of the family Phyllogoniaceae they belong.Floristic composition of mosses appears complicated with multiple origins on Taiwan. Except for the widespread species, large proportion of the composing taxa are restricted to East Asia. Taxa with distribution in Himalaya-SW China-Taiwan may reveal the geographical and geological history.