Shorebirds and the Dispersal of Bipolar Plant Species to South America

Abstract

Among the most distantly separated plant species are those that are found on the polar regions of the northern and southern hemispheres, the so-called bipolar species. Two routes of introduction have been proposed—long-distance dispersal (LDD) and mountain hopping (MH). Shorebirds have been implicated in the distribution of the bipolar species by several authors, but the most likely participants and the most probable routes of introduction have been little investigated. The Global Biodiversity Information Facility database was accessed to determine the geographic range of those angiosperm species that have been reported to have bipolar distributions. A bipolar plant species was considered most likely to have been dispersed by LDD if it has a distinct disjunct distribution between North and South America, and through MH if it is found in intermediate latitudes. The Atlas of Bird Migrations and the Cornell Birds of the World database were searched to discover which birds make long-distance migrations from Arctic North America to the tip of South America, and their mode of travel. Twenty-three plant species have been identified as bipolar. LDD appears to have been more important than MH in their dispersal, as seventeen (75%) have disjunct distributions and six (25%) are found in intermediate latitudes. The most likely players in the LDD dispersal of the bipolar plant species are the Eskimo Curlew, Hudsonian Godwit, Red Knot, Ruddy Turnstone and Whimbrel. Of these five long flyers, the Hudsonian Godwit may have delivered the most seeds as its breeding and migration ranges overlap with the most bipolar species, 12 in all.