Najas flexilis (Hydrocharitaceae) in Alaska : a reassessment

Abstract

Fifteen Najas flexilis collections were made in Alaska during the summer of 2012, with 13 of the stations representing either new or formerly undocumented localities for this imperiled Alaskan species. These field collections characterize the Alaskan habitats of N. flexilis as shallow water sites (<1.5 m) with sand-dominated substrates (71% of sites) and have documented an additional 28 species associates (a 300% increase). However, the additional collections have not extended the elevational, latitudinal, or longitudinal extent of N. flexilis from the limits indicated by previous Alaskan collections. Najas flexilis remains rare in Alaska as evidenced by a low specimen recovery rate (10%) from potentially suitable sites, and a total of only 12 geographically distinct localities known across the entire state. The new collections have furnished valuable study material for morphological and genetic analyses, which have confirmed the identity of Alaskan populations as N. flexilis, rather than N. canadensis, a recently identified, cryptic, allotetraploid derivative. A synthesis of information indicates that N. flexilis is indigenous to Alaska, where it originated via past (versus recent) migrations from other North American rather than Old World populations.