Chara zeylanica J.G.Klein ex Willd. (Charophyceae, Charales, Characeae): First European Record from the Island of Sardinia, Italy

The first record of a species belonging to the genus Chara L. subgenus Chara R.D.Wood section Grovesia R.D.Wood subsect. Willdenowia R.D.Wood from Europe is presented here, thus challenging the interpretation of its distribution pattern as an intertropical group of charophytes. The morphological characters of the specimens, as well as the results of a phylogenetic analysis, clearly identified them as Chara zeylanica J.G.Klein ex Willd. Although the subsection Willdenowia has yet to receive a thorough taxonomic treatment, a discussion of its relationship to other taxa of this subsection is provided despite the lack of a commonly agreed upon taxonomic concept. The ecological conditions of the Sardinian site of C. zeylanica are presented. Moreover, the status of and threats to this taxon, and hypotheses regarding potential pathways through which it reached Europe, are discussed.

Preface

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.

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

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.