Type analysis of the South American diatom Achnanthes haynaldii (Bacillariophyta) and description of Planothidium amphibium sp. nov., from aerial and aquatic environments in Oregon (USA)

Abstract

Background and aims – Planothidium haynaldii (Schaarschm.) Lange-Bert. (≡Achnanthes haynaldii Schaarschm.) is a widely reported species from temperate and cold zones of southern and northern hemispheres despite being originally described from a high altitude stratovolcano (Antisana, 4100 m a.s.l.) in Ecuador (tropical climatic zone). Although widely cited in the literature, studies concerning the original material were never carried out. The main objective of this paper is to clarify the identity of Planothidium haynaldii and two related species from North-western USA and Antarctic environments. Methods – The original type slide of Achnanthes haynaldii Schaarschm. was observed. Additionally, selected samples containing populations currently identified either as Planothidium haynaldii or Achnanthes lanceolata var. capitata O.Müll. collected in Oregon (USA) and James Ross Island (Antarctica) were observed. The samples were analyzed using light (LM) and scanning electron microscopy (SEM). Key results – A new species, commonly improperly identified as Planothidium haynaldii, is described as Planothidium amphibium C.E.Wetzel, Ector & L.Pfister sp. nov. from aerial and aquatic habitats of Oregon (USA). This species is widely distributed in the northern hemisphere according to illustrated literature records. Achnanthes lanceolata var. capitata is erected to species level and transferred to the genus Planothidium. Planothidium capitatum (O.Müll.) Van de Vijver, Kopalová, C.E.Wetzel & Ector comb. & stat. nov. seems to be an important component of the communities in the Antarctic region where large populations were found on James Ross Island and Livingston Island living in the epilithon and epipelon of large lakes. Finally, Planothidium haynaldii seems to be rarer than initially expected and its occurrence is confirmed only in the Andes mountain range in South America (recent freshwater sample from Ecuador and as fossil in Chile).