New Hannaea Patrick (Fragilariaceae, Bacillariophyta) species from Asia, with comments on the biogeography of the genus

Light and scanning electron microscope observations are provided on four new Hannaea Patrick species from Asia. The areas in Asia the new taxa are described from include Tibet, Mongolia and the Pamir mountainous region in western Asia. Both subgroups of the genus are represented, including H. tibetiana Q. Liu, Glushchenko, Kulikovskiy & Kociolek, sp. nov. and H. pamirensis Glushchenko, Kulikovskiy, Q. Liu & Kociolek, sp. nov., from the group that includes the generitype and has striae composed of single rows of areolae and one rimoportula per valve. Hannaea dorofeyukae Kulikovskiy, Glushchenko, Q. Liu & Kociolek, sp. nov. and H. mongolica Glushchenko, Kulikovskiy, Q. Liu & Kociolek, sp. nov. have striae composed of two rows of areolae and two rimoportulae; one at each end of the valve.  The group with two rimoportulae per valve and biseriate striae is known only from Lakes Baikal, Khövsgöl and the surrounding areas in Asia. New combinations are proposed for four other species. These taxa are also known from Asia. Two of them are known from Japan, one is from China and one is from Lake Baikal in Russia. It appears that Asia is an important center of diversity for Hannaea.