Use of hierarchical designs to detect scales of heterogeneity in the invasive species <em>Sargassum muticum</em>

Abstract

suMMarY: invasion of alien species poses serious threats to many ecosystems. despite the potential of Sargassum muticum to spread and invade new areas, no attention has been given to the study of variability of structural or morphological features across different spatial scales. We employed a hierarchical sampling design to examine patterns of spatial variability of fertility and morphological variables of S. muticum over different spatial scales (quadrats, sites, locations, rias) ranging from metres to tens of kilometres. We repeated the sampling in March, april and July to test for the consistency of patterns through time. there was no variability between rias (tens of kilometres apart), but substantial differences occurred at the other scales examined. Fertility and percent cover varied between locations (1.5-3 km apart), whereas morphological variables varied between sites (tens of metres apart) and quadrats (metres apart). Furthermore, patterns of variation were not consistent over time. the study demonstrated the importance of a multi-scale sampling programme for monitoring seaweed invasion.Keywords: spatial scale, morphology, fertility, distribution, invasion success, Galician coast, Sargassum muticum. resuMen: Uso de diseños jerárquicos en la detección de escalas de heterogeneidad en la especie invasora SargaSSum muticum. -las especies invasoras representan una seria amenaza para muchos ecosistemas. a pesar del potencial de Sargassum muticum para extenderse e invadir nuevas áreas, no se ha dedicado ninguna atención al estudio de la variabilidad de las características estructurales o morfológicas a diferentes escalas espaciales. Hemos usado un diseño de muestreo jerárquico para examinar patrones de variabilidad espacial de las variables fenológicas y morfológicas de S. muticum a diferentes escalas espaciales (cuadrantes, sitios, localidades, rías) que van desde unos pocos metros a decenas de kilómetros. repetimos el muestreo en marzo, abril y julio para comprobar la consistencia de los patrones a lo largo del tiempo. no hubo variabilidad entre rías (decenas de kilómetros de separación), pero se encontraron diferencias sustanciales a otras escalas. la fertilidad y el porcentaje de cobertura variaron entre localidades (1.5-3 km) y tiempo, mientras que las variables morfológicas variaron entre sitios (decenas de metros) y cuadrantes (metros). asimismo, los patrones de variabilidad no fueron consistentes en el tiempo. el estudio demostró la importancia de los programas de muestreo utilizando múltiples escalas espaciales para el seguimiento de algas invasoras.Palabras clave: escala espacial, morfología, fertilidad, distribución, éxito de invasión, costa de Galicia, Sargassum muticum.

Variability of epifaunal assemblages associated with native and invasive macroalgae

“…These results, in combination with other studies carried out along the Galician coast that have demonstrated differential effects of this species on native assemblages (e.g. Olabarria et al 2009;Rossi et al 2010), highlight the importance of future research into the spread and impact of introduced algae. Because of their worldwide distribution and differential effects in different coastal habitats, introduced algae are potentially important agents of global ecological change.…”

“…The rapid spread of S. muticum on the Galician coast might have important effects on the composition and structure of native assemblages on rocky shores and sandy beaches (via stranded seaweed). For example, although the impact of S. muticum on macroalgal assemblages of rocky shores was limited, the total number of native species and some morpho-functional groups, such as filamentous and foliose algae, were negatively affected by its presence (Olabarria et al 2009). On sandy beaches, this invasive species might alter the food web, as previous results show that it modified temporal food supply when the native brown seaweeds were absent (Rossi et al 2010).…”

Study of Sargassum muticum impact on the surrounding algae in the Moroccan Atlantic coast

“…On the Iberian Peninsula coast, the presence of S. muticum was rst reported from Asturias in the 1980s and subsequently it was observed on the Galician coast in 1986 [15]. Since then, a strong interest has been arisen to understand the biotic and abiotic interactions that mediate the establishment and spread of S. muticum and its interaction with native marine communities [16,17,18,19]. This species is a remarkably successful invader [10].…”