Morphometric comparison of the neotype of Asterionella formosa Hassall (Heterokontophyta,Bacillariophyceae) with Asterionella edlundii sp. nov. from Lake Hovsgol, Mongolia

Abstract

We conducted a morphometric study to compare Asterionella specimens from Lake Hovsgol, Mongolia with the neotype specimens of A. formosa Hassall from the Glienicker See, Berlin, Germany. Specimens were digitized and measured for valve length, mid-valve width, head pole width, and foot pole width, and length to mid-valve ratio was calculated. Plots of morphometric measures revelaed that specimens from Lake Hovsgol are not in the same size class as those from the Glienicker See. Size change series for each population revealed different rates of size diminution. For Lake Hovsgol specimens valve length change to mid-valve wideth change had a vlaue of 0.217. For the neotype specimens of A. formosa, valve length change with respect to mid-valve width change was 0.41. A related rate, as a proxy for the relation between size diminution betwenn each lake's population had a value of -1.25 which indicates that each population vegetatively reproduces at a different rate. Cluster analysis using all morphometric measure resulted in Lake Hovsgol specimens aggregating in a group separate from the neotype A. formosa. With evidend of endemism being more prevalent in diatoms tha what was once thougt, genetic evidence of possible species differences among Asterionella in other lakes, and different environmental conditions between the two locales of Asterionella in this study, we propose that the Asterionella specimens from Lake Hovsgol are different from the neotypes of A. formosa and should be treated as A. edlundii Stoermer & Pappas sp. nov.