Observations of the genus Diploneis from Lake Ohrid, Macedonia

Abstract

Lake Ohrid is an important biodiversity hotspot, including diatom diversity and endemism. Numerous, putatively endemic diatom species have been described from the lake, alongside reports of relict taxa otherwise known only as fossils from European Neogene deposits. Diploneis Ehrenberg ex Cleve is considered to be one of the species-rich genera in Lake Ohrid. This study presents a detailed account of Diploneis in Lake Ohrid, providing additional information on some of the infrequently recorded taxa. In addition, sediment core samples from Lake Ohrid were used to provide an historical account of some of the more abundant taxa and to determine the morphological similarity between fossil (core samples) and extant populations. To this end, detailed light and scanning electron microscope observations were carried out to ascertain the identity and describe the morphological variation of Diploneis taxa. As a result, 15 Diploneis taxa from Lake Ohrid are reported with four potentially endemic species described as new: D. parabudayana, D. rotunda, D. pulchra and D. vetusa. Among the remaining taxa, two endemic species (D. heisingeriae Jurilj and D. tavcharii Jurilj) previously described from Lake Ohrid were observed, along with nine widespread species commonly reported throughout Europe and elsewhere.