A new freshwater gomphonemoid diatom genus from India, with the description of a new species from the Eastern Ghats

Abstract

ABSTRACT We present light and SEM observations of a new astigmate gomphonemoid diatom from the Eastern Ghats of India. This species, and a closely allied one from the Western Ghats that has a stigma, are similar to other members of the Gomphonemataceae in terms of symmetry and certain valve features. They differ, however, in having groups of differentiated pore fields at both apices. At the headpole, the area bearing the groups of pores is flattened and positioned on the valve mantle, and is not easily seen in light microscopy. For these species we propose the genus Indiconema gen. nov. within the Gomphonemataceae. We evaluate the phylogenetic position of this group and relationships within the family based on valve and girdle band features, which suggest that the new genus is sister to Afrocymbella, a genus apparently endemic to Africa. We compare this basal phylogenetic position with other groups of organisms also found in the Western and Eastern Ghats of India, as well as to fossil taxa in the Gomphonemataceae. The sister taxon relationship with a genus known only from Africa supports a close relationship of the floras of the two regions.