Propagule pressure and functional diversity: interactive effects on a macroalgal invasion process

Abstract

Invasive species are considered an increasing global threat to marine ecosystems. Understanding which factors can accelerate or reduce invasion success is one of the main goals of invasion ecology. The present study investigated the interactive effects of propagule pressure and native functional diversity on the invasion success of the invasive alga Sargassum muticum (Yendo) Fensholt over a 1 yr invasion process (i.e. settlement, recruitment and colonisation). The invasibility of macroalgal assemblages with different functional diversity was assessed under high and low propagule pressure. Synthetic assemblages resembling natural marine macroalgal assemblages were built and used as model systems. Recruitment discs were used to record early settlement in the assemblages. Recruitment and colonisation success were monitored in the field 2 and 10 mo after exposure to propagule rain in the laboratory. The availability of resources (space and photosynthetically active radiation [PAR]) was also monitored for each assemblage and used as predictive variables in the analyses. The effects of propagule pressure and functional diversity varied among the invasion stages. Space availability did not play a significant role in the recruitment success of the invader. However, PAR was a key resource in its invasion success. Overall, the invasion success of S. muticum was influenced differently by different traits of the recipient assemblages. Hence, invasion success may be better explained by the interaction of environmental factors that co-vary with species diversity and identity at different invasion stages. KEY WORDS: Invasion success · Propagule pressure · Resources · Functional diversity · Sargassum muticum · Macroalgae Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 471: [51][52][53][54][55][56][57][58][59][60] 2012 ultimate goal of any NIS. Understanding which factors influence invasion success through the different stages, and to what extent, is extremely important in invasion ecology (Kolar & Lodge 2001, White & Shurin 2007. Overall, 3 factors are usually cited as determining the fate of invasions: the biology of the introduced species (species invasiveness), the number and frequency of introductions (propagule pressure [PP]) and the susceptibility of the native community to invasion (community invasibility) (Lons dale 1999). Nonetheless, invasion studies are usually focused on only one of these factors (Lonsdale 1999).It is widely accepted that highly diverse communities are more resistant to invasions because of a more complete utilisation of resources, the socalled biotic resistance theory (see Elton 1958, Levine 2000, Fridley et al. 2007 for a review of diversity-invasibility relationships). For benthic algal communities as sessile photosynthetic organisms, space and light are important limiting resources (Sousa 1979). For example, lack of space and low light availability have been shown to negatively affect the invasion success of the brown macroalga Sargass...

Resident-Invader Phylogenetic Relatedness, Not Resident Phylogenetic Diversity, Controls Community Invasibility

“…Functional similarity based on three single phylogenetically conserved traits also influenced invader abundance. Note that a number of studies have demonstrated the role of resident-invader functional similarity (e.g., Fargione et al 2003;Ordonez et al 2010;Eisenhauer et al 2013) or functional diversity of resident communities (e.g., Dukes 2001;Britton-Simmons 2006;Moseman et al 2009;Vaz-Pinto et al 2012;Byun et al 2013) for predicting invader success. In those studies that focused on functional diversity, the effects of functional diversity and similarity were presumably confounded with each other; it remains to be seen whether findings similar to ours would be obtained if these studies also take resident-invader functional similarity into account.…”

Invasive Seaweeds in the Iberian Peninsula: A Contribution for Food Supply

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Growth and competition in a warmer ocean: a field experiment with a non-native and two native habitat-building seaweeds

“…However, Saccharina and Fucus maintain a perennial canopy which could reduce recruitment of Sargassum (Sánchez & Fernández 2006) or survival of recruits through shading (Britton-Simmons 2006, Vaz-Pinto et al 2012. These effects are also likely to be important in determining the success of Sargassum (Vaz-Pinto et al 2014).…”