Diatoms from isolated islands II: Pseudostaurosira diablarum, a new species from a mangrove ecosystem in the Galápagos Islands.

Identifying and describing biodiversity remains fundamental to developing a proper understanding of ecological and biogeographic processes. In this paper, we describe Pseudostaurosira diablarum Seddon & Witkowski sp. nov., a new diatom (Bacillariophyceae) species discovered from Las Diablas wetlands, a brackish water coastal lagoon on the Galápagos Islands. The taxon was observed in both the surface (i.e., extant) and core (i.e., sub-fossil) material from the lagoon, found on shaded mangrove substrata with salinities between 5.2 and 8 g L-1. These observations were confirmed by estimating the salinity tolerances of core samples from the palaeoecological record using a diatom salinity transfer function. We provide light and electron microscope images of P. diablarum sp. nov. Under the light microscope, the best diagnostic features are its lanceolate-elliptical shape, and the striae which are composed of a single row of areolae and do not occur all the way to the apices. Under the scanning/transmission electron microscope, the most distinctive features are the delicate closing plates which are less articulated and branched than in many of the other members of this genus, in addition to the simple, stunted spines which interrupt the striae on the valve margin. The taxon described here constitutes further evidence that the Diablas wetlands are an important site for diatom research, with the potential to provide insights into the processes resulting in the dispersal and evolution of its diatom species. © 2014 © 2014 The International Society for Diatom Research.