Philippine Journal of Science
142:(3) 211-213, Special Issue
ISSN 0031 - 7683
The Selaginella Flora, A Good Indicator of the Philippine Pleistocene Island Groups
Benito C. Tan
Department of Biological Sciences, National University of Singapore and
The Jepson and University Herbaria, University of California at Berkeley,
Berkeley, CA, USA
ABSTRACT
The present day distribution patterns of some species of Philippine Selaginella were observed to coincide with the alleged large island groups formed in the Philippines during the Pleistocene Ice age period. The dioecious reproductive biology of the plant group which produces large sized megaspore to house the female plant and separate small sized microspore to house the male plant has probably restricted the plant species from attaining long distance dispersal, and hence, resulted in having the locally generated species to spread slowly via only adjacent land connection over the geologic time period.
INTRODUCTION
The taxonomy of the Philippine Selaginella has been studied by Alston (1935) and Tan and Jermy (1981). It consists today of a total of 50 species, which includes 46 indigenous and 26 or 56% are local endemics) and four introduced species (see Table 1). The high endemism of the genus is brought partly by its unique reproductive biology of having dioecious gametophytes and partly by the isolation of the population resulting from the geographical formation of the island groups in the Philippines in historical past. . . . read more
