Abstract
Ports and farms are well‐known primary introduction hot spots for marine non‐indigenous species (NIS). The extent to which these anthropogenic habitats are sustainable sources of propagules and influence the evolution of NIS in natural habitats was examined in the edible seaweed Undaria pinnatifida, native to Asia and introduced to Europe in the 1970s. Following its deliberate introduction 40 years ago along the French coast of the English Channel, this kelp is now found in three contrasting habitat types: farms, marinas and natural rocky reefs. In the light of the continuous spread of this NIS, it is imperative to better understand the processes behind its sustainable establishment in the wild. In addition, developing effective management plans to curtail the spread of U. pinnatifida requires determining how the three types of populations interact with one another. In addition to an analysis using microsatellite markers, we developed, for the first time in a kelp, a ddRAD‐sequencing technique to genotype 738 individuals sampled in 11 rocky reefs, 12 marinas, and two farms located along ca. 1,000 km of coastline. As expected, the RAD‐seq panel showed more power than the microsatellite panel for identifying fine‐grained patterns. However, both panels demonstrated habitat‐specific properties of the study populations. In particular, farms displayed very low genetic diversity and no inbreeding conversely to populations in marinas and natural rocky reefs. In addition, strong, but chaotic regional genetic structure, was revealed, consistent with human‐mediated dispersal (e.g., leisure boating). We also uncovered a tight relationship between populations in rocky reefs and those in nearby marinas, but not with nearby farms, suggesting spillover from marinas into the wild. At last, a temporal survey spanning 20 generations showed that wild populations are now self‐sustaining, albeit there was no evidence for local adaptation to any of the three habitats. These findings highlight that limiting the spread of U. pinnatifida requires efficient management policies that also target marinas.
Highlights
Nonindigenous species (NIS) exert a plethora of effects on native flora and fauna, not the least of which is the breakdown of biogeographical boundaries and biotic homogenization (Capinha, Essl, Seebens, Moser, & Pereira, 2015), trends unlikely to slow down in the near future (Seebens et al, 2017)
Our study focused on the postintroduction colonization dynamics of one marine NIS, the invasive kelp U. pinnatifida, with the specific aim to understand the relationships between populations established in the primary sites of introduction and the nearby natural reefs to which the species had spread, and determine whether some location adaptation had occurred
This study provided evidence for our hypothesis of the persistent effect of human-mediated transport, such as boating activities, on connectivity of U. pinnatifida at a regional scale
Summary
Nonindigenous species (NIS) exert a plethora of effects on native flora and fauna, not the least of which is the breakdown of biogeographical boundaries and biotic homogenization (Capinha, Essl, Seebens, Moser, & Pereira, 2015), trends unlikely to slow down in the near future (Seebens et al, 2017). Considering the short life cycle, the likely limited dispersal distance by spores and gametes, and the high population density of U. pinnatifida in marinas and farms, we hypothesized that: (a) human- mediated dispersal, through leisure boating, plays a prominent role in connectivity patterns at a regional scale (the lack of relationship between the genetic and geographic distances would support this hypothesis); (b) the sustainable establishment of wild populations depends on immigrants from anthropogenic habitats (marinas or farms), the alternative hypothesis being that wild populations are self-sustaining; and (c) considering the long time elapsed since the introduction (80 generations in the study range), signs of local adaptation, either contrasting northern and southern populations (Brittany is a transition zone between two biogeographical provinces) or habitats, should be observed, except if counterbalanced by high inter-habitat or inter-province gene flow These questions can be efficiently addressed using population genomics approaches (Viard et al, 2016), in species that show relatively low polymorphism such as U. pinnatifida (Daguin, Voisin, Engel, & Viard, 2005; Grulois et al, 2011). We used DNA obtained in 2005 and 2009, 20 and 12 generations earlier respectively, to investigate temporal changes in genetic composition in each of these three habitat types in a single bay
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
