Extant Gyrogonite Populations of Chara zeylanica and Chara haitensis: Implications for Taxonomy and Palaeoecology

Abstract

Chara zeylanica (Klein ex Willdenow) R.D.Wood is known to develop populations which display either four- or eight-scutate antheridia. Despite only minor differences in the vegetative features, plants with these two types of male gametangia proved to be reproductively isolated and C. haitensis Turpin was validated as the correct name for the octoscutate plants (Proctor et al. 1971). Here we provide data for the calcified female reproductive organs (gyrogonites) of both species in order to determine whether they can be distinguished or not. Ten populations from both field collections and culture material were studied. The morphological characteristics of the gyrogonites were determined on the basis of measurements of 100 specimens for each population. The gyrogonites of four- and eight-scutate plants proved to be significantly different and thus enhanced separation at species level. Ecology, biogeography and the possible phylogenetic relationships of the taxa are discussed. Unlike C. zeylanica, which displays worldwide distribution within the tropical belt, the modern distribution of C. haitensis seems hitherto restricted to the American continent. Within this area, C. zeylanica grows preferentially in permanent lakes whereas C. haitensis is only found in temporary water bodies. Given these different ecological requirements, the fossil record of both taxa, determined from their specific gyrogonite morphology, can provide information about the nature of ancient lake-ecosystems particularly useful for Quaternary studies in the Americas.