Observations of the genus Muelleria (Bacillariophyceae) from the Republic of North Macedonia

Abstract

Background and aims – An increased interest in the diatom flora from subaerial habitats in the Republic of North Macedonia has revealed the presence of a large number of interesting and often unknown, species. During a recent biodiversity survey, seven Muelleria species were recorded, several of which could not be identified based on the available literature.
 Methods – Using both Light Microscopy and Scanning Electron Microscopy techniques, the morphology of several Muelleria species has been analysed. The morphology of all taxa is described, illustrated and compared with other possible similar Muelleria taxa, known worldwide.
 Key results – Four already documented Muelleria species, M. gibbula, M. islandica, M. terrestris and M. undulata (= Navicula gibbula f. undulata) were identified, while two distinct species are described as new. These new species belong to the M. gibbula complex, and can be differentiated by valve size, stria density, shape of the proximal raphe ends and the shape of external areola foramina. The identity of one taxon remains uncertain due to a low number of observed specimens in the samples. As their ultrastructure is almost entirely unknown, they are briefly discussed.
 Conclusions – The diversity of Muelleria in Europe and the North Hemisphere is most likely underestimated and some of the previous records of M. gibbula belong to other species. Observations of diatoms from “extreme” habitats such as intermittent ponds, wet mosses and soils can reveal the existence of interesting and new species.

Espèces de diatomées saumâtres observées à la source bitumineuse du Puy de la Poix : un îlot de curiosité

“…Hantzschia amphioxys (Ehrenberg) Grunow in Cleve & Grunow that lives in prolongedly dry and only temporarily wetted (aerial) biotopes, such as soils and rock crevices, underlined that the level of water was low at this site (Lange-Bertalot et al 2017). Muelleria terrestris was observed in soils (Petersen 1915;Spaulding et al 1999;Foets et al 2021), and on wet mosses in an intermittent spring of a village in Macedonia (Levkov et al 2019). Muelleria terrestris was also present in a petrifying Cratoneurion spring in Belgium (Denys & Oosterlynck 2015).…”

Study of terrestrial diatoms in corticolous assemblages from deciduous trees in Central Europe with descriptions of two new Luticola D.G.Mann taxa

“…Diatom terminology and identification were based on Round et al (1990) , Krammer and Lange-Bertalot (1986 , 1988 , 1991a , b ), Krammer (2000) , Lange-Bertalot (1993) , Lange-Bertalot et al (2003 , 2011 , 2017 ), Levkov et al (2013 , 2017 , 2019 ) and Houk et al (2017) .…”