Taxonomy of Klebsormidium (Klebsormidiales, Charophyceae) in New Zealand streams and the significance of low-pH habitats

Abstract

A new species, Klebsormidium acidophilum, is proposed to accommodate a newly described organism isolated from strongly acidic (pH < 3.0) mine-contaminated streams on the west coast of the South Island, New Zealand. This organism differs from Klebsormidium dissectum, isolated from pH-neutral habitats, according to filament diameter and morphological response to pH manipulation in culture. Transmission electron microscopy showed that these species and Klebsormidium elegans (also from pH-neutral habitats) all contained typical Klebsormidium ultrastructure of (I) a pyrenoid traversed by multiple, approximately parallel, thylakoid membranes and (2) a peroxisome closely appressed between the nucleus and chloroplast. These features were essential to confirm the generic identification because attempts to initiate zoosporogenesis failed. Klebsormidium acidophilum grows best in culture at pH ≤3.4, and morphologies observed at higher pH were never seen in field material. Klebsormidium dissectum grows best at pH 4.8-6.2, and morphologies seen in field material were seen in cultures from pH 3.4-8.3. These observations and the topology of a phylogenetic tree of rbcL sequences indicate that K. acidophilum derived recently from local populations of pH-neutral K. dissectum. Local speciation of acidophilic Klebsormidium is likely to be a global phenomenon.