Newly described Gomphonema and Gomphosphenia from Rocky Mountain Front Range streams, Colorado, USA, with additional discussion of rarely reported taxa

Abstract

A new species of Gomphonema, G. capsulare, and a new species of Gomphosphenia, G. praegnans, are described from samples collected from two streams in the Front Range of the Colorado Rocky Mountains. Gomphonema capsulare is small with linear valve margins and its stigma lies very close to the centre of the valve. Gomphosphenia praegnans is very small with widely lanceolate-clavate valves readily distinguishing it from other described Gomphosphenia species. In addition to the two new species, two other species in the same genera were also identified from these samples, Gomphonema exilissimum (Grunow) Lange-Bertalot & E. Reichardt in Lange-Bertalot & Metzeltin and Gomphosphenia americana Kociolek & E.W. Thomas in Kociolek et al. This paper provides the first images and morphological description of a population of G. exilissimum from North America. Gomphonema exilissimum is morphologically similar to G. parvulum (Kützing) Kützing but has a different ecological niche. Documentation of G. americana in this paper expands the currently known range of this species. In addition, this paper documents the presence of internal hymenate occlusions in the areolae in both G. americana and G. praegnans, a feature previously unknown in this genus.