New fossil genus and new extant species of diatoms (Stephanodiscaceae, Bacillariophyceae) from Pleistocene sediments in the Neotropics (Guatemala, Central America): adaptation to a changing environment?

Christine Paillès,Sandrine Conrod,Alain Tonetto,Jean-Charles Mazur,Florence Sylvestre

doi:10.5852/ejt.2020.726.1169

Abstract

Several taxa of Stephanodiscaceae were found in the upper section of Pleistocene sediments from Lake Petén-Itzá (Guatemala). A new fossil genus Cyclocostis Paillès gen. nov. and new extant species Discostella gabinii Paillès & Sylvestre sp. nov. are described. Cyclocostis gen. nov. is characterized by a strongly tangentially undulated valve surface, coarse unequal striation reaching a central punctum in the valve center, an absence of central lamina and domed criba, widely open alveoli with one median recessed costa bearing marginal fultoportulae and a single rimoportula all within a ring. A single valve face fultoportula is present on the raised part of the valve opposite the rimoportula. Differences relative to similar genera and the delimitation of a new genus are discussed. Discostella gabinii sp. nov. is distinguished by circular and flat valves, a small central area bearing 5 to > 30 scattered large areolae giving a colliculate appearance, medium-sized alveoli, marginal fultoportulae on every 4–5th costa, a single rimoportula and internally smooth valve center. Differences to similar taxa in the genus Discostella are discussed. The succession of the species of Cyclotella, Discostella and Cyclocostis gen. nov. in our record could represent eco-phenotypic responses to particular environmental stress / change.

Highlights

Publications describing freshwater diatoms from Central America are scarce
If few paleolimnological studies based on diatoms have been conducted in Costa Rica (e.g., Chávez & Haberyan 1996; Haberyan & Horn 1999, 2005), Nicaragua (e.g., Slate et al 2013) and Panama (e.g., Temoltzin-Loranca et al 2018), even fewer have been conducted in the Yucatan Peninsula, and these are generally limited to the Holocene (Whitmore et al 1996; Rosenmeier et al 2004)
The upper part of the sedimentary sequence between 60–16 ka is characterized by an alternation of the species of Cyclotella and Discostella (Fig. 1): Cyclotella meneghiniana Kütz., C. petenensis, Discostella stelligera (Cleve & Grunow) Houk & Klee, C. caspia Grunow, C. cassandrae, a new species of Discostella, and what appears to be a new genus of Stephanodiscaceae

Summary

Introduction

If few paleolimnological studies based on diatoms have been conducted in Costa Rica (e.g., Chávez & Haberyan 1996; Haberyan & Horn 1999, 2005), Nicaragua (e.g., Slate et al 2013) and Panama (e.g., Temoltzin-Loranca et al 2018), even fewer have been conducted in the Yucatan Peninsula, and these are generally limited to the Holocene (Whitmore et al 1996; Rosenmeier et al 2004). Longer diatom records originated from the Mexico Basin (Bradbury 2000; Ortega et al 2010). The record of Cohuo et al (2018) is based on the same sedimentary sequence as the present study. A few taxonomic studies have been recently published on diatom species from, e.g., Panama (Lange-Bertalot & Metzeltin 2009) or El Salvador (Wetzel & Ector 2014; Krahn et al 2018), with one dealing with centric diatom species of Cyclotella (Kütz.) Bréb. from Guatemala (Paillès et al 2018)

Methods

Results

Conclusion