Abstract
Morphological plasticity can enable algae to adapt to environmental change and increase their invasibility when introduced into new habitats. Nevertheless, there is still a lack of knowledge on how such plasticity can affect the invasion process of an invasive species. In this context, the high plasticity in the genus Caulerpa is well documented. However, after an extremely hot summer, a previously unreported filamentous morphology of Caulerpa cylindracea was detected; indeed, this morphology could only be confirmed taxonomically after in-depth morphological characterization and molecular analysis with the genetic marker tufA. We describe an ex situ culture experiment which showed that stressful conditions, such as high temperatures, can trigger this morphological change. Almost all of the thalli maintained at a constant extreme temperature of 29°C died, but after being returned to optimum temperature conditions, the filamentous morphology began to develop from the surviving microscopic tissue. In contrast, thalli at a control temperature of 21°C maintained the regular morphology throughout the experiment. When C. cylindracea develops this filamentous morphology, it may act as a cryptic invader because it is difficult to detect in the field. Furthermore, the filaments likely improve C. cylindracea’s invasive capabilities with regard to resistance, persistence and dispersion and may have an important role in the re-colonization process, after a population disappears following a period of stressful conditions. Possibly, C. cylindracea’s ability to respond plastically to stressful conditions might explain its remarkable success as an invasive species.
Highlights
Biological invasions refer to the process by which different organisms, commonly known as invasive species, can arrive and establish in a new habitat, where they disrupt the normal functioning of the system
Cryptic Morphology of Caulerpa cylindracea ecosystems, where biological invasions are on the rise due to the increases in their main vectors of introduction, such as shipping traffic, the aquarium trade, or the opening and widening of new corridors (Katsanevakis et al, 2013; Seebens et al, 2013; Galil et al, 2017); and in the future, the establishment of non-native species is expected to continue increasing due to climate change (Stachowicz et al, 2002; Lejeusne et al, 2010)
Our culture experiments showed that extreme environmental conditions, in this case high temperatures maintained for long periods of time (i.e., 14 days at 29◦C), affected the survival of Caulerpa cylindracea and triggered the development of a new Accession Herbarium Site number code
Summary
Biological invasions refer to the process by which different organisms, commonly known as invasive species, can arrive and establish in a new habitat, where they disrupt the normal functioning of the system. Plants and algae can adapt by modifying, among other things, photosynthetic traits (Molina-Montenegro et al, 2012; Zanolla et al, 2015), leaf-area and shoot allocation (Arenas et al, 2002; Liu and Su, 2016) and growth form (Van Kleunen and Fisher, 2001; Monro and Poore, 2009) allowing them to respond to changes in light, temperature or herbivory pressure (Lewis et al, 1987; Monro and Poore, 2005; Nicotra et al, 2010) In this sense, understanding how this phenotypic plasticity affects the success of an invasive species is crucial to our understanding of its invasion process (Schaffelke et al, 2006; Theoharides and Dukes, 2007) and might have important implications for the successful management of the species (Hobbs, 2000; Simberloff et al, 2005)
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