10. Biogeography of River Algae

Biogeography, or the study of the distribution of organisms in time and space, has a rich history. New molecular tools are providing another line of evidence in understanding distributions: in some instances confirming previous morphological data, while in other cases providing new insights. There have been few studies devoted to the biogeography of river algae, but much information can be gleaned from floristic surveys and systematic research. Water, wind, animals, and humans have played an important role as dispersal agents and may affect river algal biogeography. There is convincing evidence that some species of river algae are specialists and others generalists. There have been various invasions of freshwater rivers by marine algae and some of these events have raised awareness of and studies on possible transport mechanisms of microorganisms. Many recent studies of river algae have shown similar results to other microorganisms that many species are not ubiquitous, but are more geographically restricted than was previously reported. This certainly seems to be the case for freshwater Rhodophyta for which new molecular data are being amassed. Lastly, there is a need for easily accessed repositories of biogeographic data to better understand these organisms and their global distributions.