Barnacle Invasions: Introduced, Cryptogenic, and Range Expanding Cirripedia of North and South America

Abstract

Barnacles are some of the most conspicuous and well-known ship fouling organisms in the world and thus many species no doubt owe parts of their modern distribution to human-mediated translocations over the past several centuries. Reviewed here, as a window into global patterns, are the introduced, cryptogenic, and range expanding barnacles of the Atlantic and Pacific coasts of North and South America. Five species of thoracic barnacles have invaded the Pacific coasts of the Americas: Amphibalanus improvisus, A. eburneus, and A. subalbidus, all from the Atlantic, and A. amphitrite and A. reticulatus from the Indo-West Pacific. Seven species have invaded the Atlantic coasts of the Americas; six of these are from the Pacific: A. amphitrite and A. reticulatus (shared as invaders with the Pacific coast) , and Balanus trigonus, B. glandula, Striatobalanus amaryllis, and Megabalanus coccopoma. The Western North Atlantic A. subalbidus has invaded the Western South Atlantic. Striking are the few barnacle invasions that have occurred on the Pacific coast of South America and these species (A. improvisus, A. amphitrite and A. reticulatus) are reported only from northernmost locations (Ecuador, Colombia, and Peru) . For the first 100 years (1853–1955) two species, A. amphitrite and A. improvisus, constituted the majority of invasion events in the Americas, the sole exception being the arrival of the Pacific Balanus trigonus in the 1860s and 1870s in the Atlantic. After 1955, the first records of invasions of A. reticulatus, A. eburneus, B. glandula, M. coccopoma, and S. amaryllis appear, an increased diversity of introductions in close concert with general observations of increasing invasions globally of marine organisms after World War II. Known since the 1970s in Brazil, M. coccopoma appears to be responding to warming northern latitudes and has expanded to North Carolina as of 2005. The native Western Atlantic barnacle Chthamalus fragilis arrived in New England in the 1890s, a range expansion perhaps facilitated by an earlier coastal warming period concomitant with the decline in abundance of its colder-water competitor Semibalanus balanoides, although the latter also appears to have expanded south on the North American Atlantic coast in the twentieth century due to increased habitat availability. Chthamalus is predicted to move north, and Semibalanus is predicted to return to its historical range, both due to continued warming. In turn, the native Eastern North Pacific barnacle Tetraclita rubescens is expanding north due to coastal warming as well. Future invasion scenarios include increased introductions facilitated through a newly expanded Panama Canal, the potential arrival of Austrominius modestus on the North American Atlantic coast (despite its failure to do so throughout the last half of the twentieth century) , and the arrival on the warmer North and Central American Pacific coasts of Chthamalus proteus.