A new species of Amphorotia (Bacillariophyta) from a freshwater section of the Pearl River with comments on associated species and biogeography of the genus

Abstract

Based on a review of material previously studied, and new water samples, species of the genus <i>Amphorotia</i> were investigated with respect to their morphology and geographical distribution, especially in subtropical Asian coastal areas. Six <i>Amphorotia</i> species from China are investigated. They all possess amphoroid frustule symmetry, presence of spines and, when detected, a single plastid. These features as well as other details of the frustules were documented with light and scanning electron microscopy. Five of the taxa, <i>A. reimerii</i>,<i> A. mokonensis</i>,<i> A. baicalensis</i>,<i> A. zhujiangensis</i>, and <i>A. curvata</i> are newly recorded as fossil specimens in the Jianghan Plain. Further comments on the taxonomy and morphological variation of several known species are given. One taxon, <i>A. liangyanlingii</i> sp. nov. was discovered from freshwater samples in the Pearl River. This new species is most similar to<i> A. zhujiangensis</i> Wu, Williams et Flower when observed in LM, but can be distinguished by ultrastructural details when viewed with the scanning electron microscope (SEM). Taxonomical studies of species in the genus <i>Amphorotia</i> are considered together with their biogeography and ecology.