Re-examination of Cyclotella lacunarum Hustedt (Bacillariophyta) from lakes in the Pamir Mountains, western China, and description of two similar Lindavia taxa collected from Tajikistan and Nepal

Abstract

Originally described from a sample collected in the Pamir Mountains at the end of the nineteenth century, Cyclotella lacunarum Hustedt is a centric diatom species that is not-well defined and seldom reported in the scientific literature. Our investigations revealed that the type locality of this taxon, now referred to as Lindavia lacunarum (Hustedt) Nakov et al., is actually in western China and not in Tajikistan, as wrongly assumed previously. Light microscope (LM) and scanning electron microscope (SEM) observations of the type material and of modern material collected at the type locality allowed us to emend the description of this species. Its most remarkable character is that it possesses central fultoportulae with only two satellite pores instead of three as generally reported for similar species of Lindavia. Lindavia lacunarum was then compared to two similar populations of Lindavia collected from high elevation lakes in Tajikistan and Nepal. These two populations were originally identified as Cyclotella/Lindavia lacunarum and represent the only reported occurrences of this taxon outside its type locality. The population from Tajikistan differs from L. lacunarum by having cells of smaller size, with an almost flat valve face and has been described as a new variety Lindavia lacunarum var. karakulensis var. nov. The Nepalese population is more clearly differentiated from L. lacunarum by having a different type of colliculate pattern in the central area and significantly lower density of central fultoportulae and is therefore described as a new species, Lindavia nepalensis sp. nov.

Acknowledgements

We thank Václav Houk from the Institute of Botany at the Czech Academy of Sciences for his encouragement at the very beginning of this project and deeply regret that he could not contribute to this study due to illness. We are grateful to Bank Beszteri and Sarah Olischläger from the Hustedt Diatom Collection, Bremerhaven, Germany, for the loan of the type material of Cyclotella lacunarum, to Edgley Cesar from the Natural History Museum in London for processing the syntypes and to the engineer Yan Xin at IGG-CAS for her assistance with the SEM. We thank Thomas Hübener and Aleksandra Cvetkoska for their constructive comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed at https://doi.org/10.1080/0269249X.2020.1745896

ORCID

Patrick Rioual http://orcid.org/0000-0001-9491-9197

Yumei Peng http://orcid.org/0000-0001-5054-4442

Zhangdong Jin http://orcid.org/0000-0002-1457-0552

Andrea Lami http://orcid.org/0000-0003-3627-0363

Aldo Marchetto http://orcid.org/0000-0002-1033-4114

Steffen Mischke http://orcid.org/0000-0003-3821-8497

Fei Zhang http://orcid.org/0000-0002-9038-7047

Xiaoping Yang http://orcid.org/0000-0001-8702-1813

Additional information

Funding

Patrick Rioual is currently supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (grant number XDB26000000). Fieldwork in the Pamir Mountains was funded by the National Science Foundation of China (grant number 41430532) and the Chinese Academy of Sciences (grant number: kzcx2-yw-119).