Palynotaxonomy of Centauropsis (Compositae, Vernonieae) an endemic genus from Madagascar

Abstract

Centauropsis is a genus of eight species in the family Compositae, all of which are endemic to Madagascar. There is almost no information about the pollen of this genus, with only one species having its pollen described to date, which hinders systematic studies involving this genus and closely related taxa. In this study, we comprehensively characterise the pollen of Centauropsis, with details on morphology and ultrasculpture for six of the eight species of the genus. The pollen of Centauropsis is here characterised as 3-colporate, with sublophate ornamentation and nanoreticulate sexine. The species differ from each other mostly in length of the axis, morphology of the colporus endoaperture, and spine shape and size. The correlation between palynological characters and their variation within and between species was explored using principal component analyses (PCA) and cluster analyses (unweighted pair group method with arithmetic mean [UPGMA] and Euclidean distance). Full palynological descriptions, measurements and scanning electron microscopy (SEM) and light microscopy (LM) images are provided for all examined species.