Biogeography of the Brine Shrimp, Artemia: Distribution of Parthenogenetic and Sexual Populations

Abstract

Sites are listed for Artemia populations where the reproductive mode (sexual or parthenogenetic) is known. In the western hemisphere repro- duction is exclusively sexual, while in the Old World parthenogensis predominates. In addition, all known western hemisphere populations are diploid, while in the parthenogenetic Old World populations higher ploidies are common. The advantages and disadvantages of parthenogenesis and sexuality are dis- cussed with regard to brine shrimp distribution patterns. A higher tolerance for osmotic stress, a higher reproductive rate, and advantageous colonization capa- bilities are postulated as determining factors for the predominance of partheno- genesis in the Old World. In the New World there is no evidence for the evolution of parthenogenetic populations nor any evidence of non-human transport between the Old World and the western hemisphere.