Order coccolithales (haptophyta): classification and phylogenetic relationships of extant families using phenetic and cladistic methods / Orden cocolithales (haptophyta): relaciones filogeneticas y clasificación de las familias vivientes mediante metodos feneticos y cladisticos

ABSTRACT

Cladistic and/or phenetic methods have not been used frequently in taxonomy and systematic of microalgae to develop more natural classifications. In this paper, these methods are applied for the first time to analyze eleven extant genera of Coccolithales. Also, the derived trees are compared with those ones suggested by fossil evidence and traditional systematic. Coccoliths morphological data of the following genera are used calcidiscus kamptner, cocolithus schwarz, crenalithus roth, cyclolithela loeblich & tappan, emiliania hay & mohler, gephyrocaspa kamptner, hayaster bukry, helicosphaera kamptner, oolithotus reinhardt, tergestiella kamptner, and umbilicosphaera lohmann. Cladistic analysis suggests the existence of six evolutionary lineages, the most important of them are those formed by calcidiscus-cyclolithela-umbilicosphaera, and tergestiella-oolithotus. These lineages, and those suggested by fossil evidence and traditional systematic, are very similar. Helicosphaera could represent a very different lineage, an it may integrate another family. Homoplasies and reversions seem to be more frequent in Haptophyta than in other groups of microalgae. These results may explain partly the surprising diversification observed on this group of microalgae. These results may explain partly the surprising diversification observed on this group after the frequent massive extinctions showed by geological record.