Drivers of Invasion Success in Rugulopteryx okamurae: insights from Physiology, Genetics, and Herbivory

Abstract

Rugulopteryx okamurae, an invasive macroalga from the northwestern Pacific, is rapidly

expanding across southern European coastlines, raising serious ecological and socioeconomic

disruption. Since its first detection in Spanish waters in 2015, the species has spread widely,

displacing native communities and generating substantial economic costs due to its impacts on

fisheries and coastal infrastructure. The present study focuses on understanding the

mechanisms driving its establishment and spread along the Catalan coast, a region where the

species has been recently detected. Specifically, the study integrates physiological, ecological,

and genetic approaches to assess both abiotic and biotic factors influencing invasion dynamics.

This study explores the potential of the native sea urchin Paracentrotus lividus as a biocontrol

agent and evaluates the influence of temperature and nutrient availability on the growth of R.

okamurae as abiotic factors that can control the growth, along with the genetic origin of the

populations recently detected in Catalonia. Genetic analyses indicated a shared origin with

southern Spanish populations, suggesting similar introduction. In parallel, herbivory

experiments across sites with different invasion durations revealed a temporal shift in sea urchin

feeding preferences, with increasing avoidance of the invasive alga over time. Thermal tolerance

assays showed significant growth at intermediate temperatures (16–24 °C), no growth at

temperatures between 10-14ºC and sharp declines under thermal stress (>26 °C), while nutrient

availability had a minimal effect on short-term growth. These findings highlight temperature as

a key abiotic driver of invasion success, the limited long-term effectiveness of native herbivory,

and the need for early detection and integrated management strategies.

Overall, this multidisciplinary study highlights the critical role of temperature in shaping the

invasion potential of R. okamurae, the limitations of biotic resistance over time, and the

importance of integrating ecological and molecular tools in managing biological invasions. Early

detection, long-term monitoring, and adaptive management strategies will be essential to

mitigate the future impacts of this invasive species under accelerating climate change

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