﻿New and poorly known "araphid" diatom species (Bacillariophyta) from regions near Lake Titicaca, South America and a discussion on the continued use of morphological characters in "araphid" diatom taxonomy.

Eduardo A Morales,Luc Ector,Carlos E Wetzel

doi:10.3897/phytokeys.187.73338

Abstract

Based on two Andean Altiplano samples and on light and scanning electron microscopy analyses, we present six new species of “araphid” diatoms in the genus Pseudostaurosira, P.aedessp. nov., P.frankenaesp. nov., P.heteropolarissp. nov., P.oblongasp. nov., P.occultasp. nov., and P.pulchrasp. nov. Additional data are provided for four other known taxa, Nanofrustulumcataractarum, N.rarissimum, P.sajamaensis and P.vulpina, the latter species corresponding to a stat. nov. based on a variety of P.laucensis. Each taxon is described morphologically and compared with closely related published taxa, using characters such as axial area, virgae, vimines, areolar shape, volae, internal striae depositions, spines, flaps and apical pore fields, which are not usually used for species distinction within the genus. It is our intention that the detailed morphological descriptions of each taxon and the elaborate comparative tables we provide serve as a basis for correction of neo and paleo-databases for the Altiplano to produce a better account of autecological data and ecological change in the region. Some arguments for our continued use of a morphologically based approach are given in the context of rapid environmental degradation in the Andes and the difficulties in applying molecular approaches in countries such as Bolivia.

Highlights

In the last two decades, many new “araphid” taxa have been described, clarifying the morphological concepts of existing genera or better delimiting the boundaries of widely reported species (e.g. Lange-Bertalot and Ulrich 2014; Wetzel and Ector 2015; Wengrat et al 2016; Almeida et al 2017; García et al 2017; Van de Vijver et al 2020a)
The more noticeable blisters on the mantle for Bolivian specimens could be due to the state of preservation of the material and the possible higher availability of silica in the environment
The lack of apical pore fields, stipules and flaps are typical in this taxon, but the most noticeable characteristic at the time of its identification under LM is the round shape of its valves and areolation pattern of the valve face and mantle, which resemble the smallest members of Aulacoseira Thwaites

Summary

Introduction

In the last two decades, many new “araphid” taxa have been described, clarifying the morphological concepts of existing genera or better delimiting the boundaries of widely reported species (e.g. Lange-Bertalot and Ulrich 2014; Wetzel and Ector 2015; Wengrat et al 2016; Almeida et al 2017; García et al 2017; Van de Vijver et al 2020a). The study of type material helped in the latter endeavor, which coupled with illustrated reports and newly found populations, gave a clearer view of diagnostic characters and added other features that had not been used before for recognition of purportedly well-known species (e.g. Edlund et al 2006; Cejudo-Figueiras et al 2011; Wetzel et al 2013a, b; Talgatti et al 2014; Delgado et al 2015; Van de Vijver et al 2020a, b) Such is the case, for example, with Pseudostaurosira brevistriata (Grunow) D.M. Williams & Round (Morales et al 2015, 2019b) and Staurosirella pinnata (Ehrenberg) D.M. Williams & Round (Morales et al 2013a, 2019a). The literature for both is extensive, revealing a history of taxonomic drift, lumping and imprecise reports of their autecology (Morales et al 2013a, 2014c, 2019b)

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