Population ecology of the invasive kelp Undaria pinnatifida in California: environmental and biological controls on demography

Abstract

We combined field monitoring and laboratory experiments to examine the population ecology of both the microscopic and macroscopic stages of a new invasion of Undaria pinnatifida in California. Over the course of 1 yr, we observed 2 distinct recruitment pulses of individuals in the Santa Barbara harbor; the appearance of these pulses was strongly correlated with a 4°C drop in ocean temperature approximately 2 mo prior to recruitment. Cultures of zoospores and successive microscopic stages revealed thermal tolerances consistent with field recruitment data; individuals grown at 13°C had significantly higher survivorship than individuals grown at higher temperatures (harbor temperatures annually ranged from 12 to 21°C). The 2 cohorts also differed greatly in individual size, growth rate, and survival to maturity. Grazing by herbivores, predominately the native kelp crab Pugettia producta, effectively prevented nearly all individuals in the second cohort from reaching reproductive maturity. Grazer control was effective despite far higher rates of recruitment during the second recruitment pulse. Our results highlight the potential for extreme variability in U. pinnatifida demography mediated by local oceanographic and biotic factors. Understanding controls on U. pinnatifida demography helps to explain variation in the spread and impact of this invader worldwide, and allows better prediction of when and where U. pinnatifida may continue its invasion along the west coast of North America.

Interspecific and interhabitat variation in hsp70 gene expression in native and invasive kelp populations

“…To date, the majority of studies on invasive species have been conducted within their introduced ranges, and ecologists often know little about the ecology of such species in their native ranges (Hierro et al 2005). A few studies have shown that invasive species behave differently in their new range (Perez et al 1988, Hay & Villouta 1993, Thornber et al 2004, but whether that is due to a plastic response to a new environment, genetically controlled shifts in traits, founder effects, or various other factors remains uncertain.…”

Origin ofFucus serratus(Heterokontophyta; Fucaceae) populations in Iceland and the Faroes: a microsatellite-based assessment

“…tomentosoides and Caulerpa taxifolia (reviewed in Walker & Kendrick, 1998;Siguan, 2003;see also, Jousson et al, 1998;Trowbridge & Todd, 1999a, b;Meusnier et al, 2002;Thornber et al, 2004;Provan et al, 2005;Voisin et al, 2005). Two examples of older introductions (>100 years ago) are Fucus evanescens and F. serratus, both of which are major components of rocky intertidal communities on North Atlantic shores.…”

Differential shuffling of native genetic diversity across introduced regions in a brown alga: Aquaculture vs. maritime traffic effects

“…pinnatifida (Laminariales, Alariaceae), otherwise known as the edible seaweed wakame, is an Asian species native to Japanese, Korean, and Chinese waters, where it is extensively cultivated. The first observation of this species outside its native Asian range was recent (1971, (31); slow longdistance spread in European marinas, concomitant with the presence of wakame farms in Brittany, France (32); and heavy proliferation and naturalization in both harbors and natural subtidal zones in Australasia (28,33,34) and Argentina (35). The rapid spread of the species within regions of introduction is thought to be linked to its biological characteristics (i.e., annual life history, high growth rates, and high fecundity), typical of pioneer species (36).…”

“…Despite increased public awareness and, in some cases, legislative measures, until now the few empirical studies of U. pinnatifida have concentrated on spread and local ecological dynamics (26,31,33). However, phylogeographic analyses lend insight into the mechanisms of introduction, colonization, and spread of invaders (23).…”