Discovery of an undescribed species of Aulacoseira from highland Costa Rica

Abstract

The genus Aulacoseira is cosmopolitan and often abundant in fresh waters. In Costa Rica, freshwater diatom surveys have been restricted to flowing waters, aside from our own explorations. Among sediment samples from some 90 lakes we have encountered an undescribed species which we herein propose to name Aulacoseira umanai Haberyan sp. nov. In this species, the face of larger valves often bears ridges and tubercles (knobs); separation spines are short (<2.3 µm) and longer spines are absent. The ringleiste is thick, solid, and very wide. This, in combination with its short collum, distinguishes A. umanai from many other species of the genus. Aulacoseira umanai is abundant in the surficial sediments of multiple glacial lakes that are over 3450 m in elevation on Cerro Chirripó; it is also abundant in glacial-age deposits in La Chonta bog (2310 m a.s.l.). It seems to have evolved from an ancestor that resembled A. alpigena; the locality of this event is unknown but was likely to have been a high-altitude lake in the Central American isthmus.

Keywords:

• Aulacoseira umanai sp. nov
• new taxa
• diatoms
• taxonomy
• morphology
• tumulus
• freshwater
• Costa Rica

Acknowledgements

We are deeply indebted to the manuscript’s anonymous reviewers, who expanded our literature base, contributed essential information, appropriately challenged our diagnoses, and guided the improvement of this manuscript. We are especially grateful to Mark Edlund for guidance on nomenclature and for commenting on potential rimoportulae. The DIC microscope was graciously made available by Saul Honigberg and Sarah Piccirillo at UMKC. We thank Hedy Kling for her work in recognizing this as an undescribed species in the A. lirata / A. alpigena group. We thank Natasha Erdman, JEOL Product Manager, for advice on imaging uncoated diatoms, and we thank field assistants for their contributions. We are especially grateful to the editors and contributors of the website Diatoms of the United States for their dedication to diatoms.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The SEM and light microscopes were provided by Northwest Missouri State University, and are graciously maintained by Michelle Allen. We are grateful to the The National Geographic Society, The Andrew W. Mellon Foundation, and the University of Tennessee for funding to SPH that supported sample collection.