Two new Achnanthidium (Bacillariophyceae) species from a recent alpine lake in the National Park of Ecrins (South of France)

Auteurs

Vassal V., Heudre D., Wetzel C.E., Tudesque L.

Référence

Nova Hedwigia, vol. 117, n° 1-4, pp. 143-163, 2023

Description

Few scientific articles deal with benthic diatoms of high mountain lakes. At the same time, they represent a primary biological compartment in diversity and abundance in these hyperoligotrophic environments forcing organisms to extreme living conditions. Also, Pavé lake, located at 2840 m in the National Park of Ecrins (South of France), appeared to us as an exciting subject to study the first lifeforms in a recent alpine lake. Our samples revealed several remarkable species according to their scarcity in the literature [Nitzschia alpina Hustedt, Encyonema brevicapitatum Krammer and Cymbella parva (W.Smith) Kirchner] and other species still undetermined (Nitzschia sp. aff. frustulum, Nitzschia cf. fonticola). The great species diversity of Achnanthidium Kützing led us to disentangle the Achnanthidium minutissimum species complex collected in our samples. The present paper aims at clarifying the Achnanthidium community recorded in the Lake Pavé. In a first step, the main outcome is the recognition of two species that could not be identified with currently available literature. After comparison with similar taxa and a thorough morphological analysis based on detailed LM and SEM observations, they are described as Achnanthidium pavense sp. nov. and Achnanthidium ecrinense sp. nov. In a second step, through our paper we wish to clarify the identity of Achnanthidim minutissimum sensu stricto based on already published illustrations of type material of taxa and the morphological criteria observed in the Pavé Lake population. Additionally we illustrate three other Achnanthidium species also found in the lake, A. lineare W.Smith, A. sublineare Van de Vijver, Jarlman & Ector and A. hoffmannii Van de Vijver, Ector, Mertens & Jarlman, and, finally, the ecology and bio-indication meanings of these species belonging to the Achnanthidium minutissimum complex are given. According to the ecological preferences of the associated flora in the type sample, the two new species should be considered as biological indicators of environmental conditions specific to Alpine stage.

Lien

doi:10.1127/nova_hedwigia/2023/0852