The Identification of Source and Vector of a Prolific Marine Invader

Abstract

The source and vector of an introduced species inform its ecological and evolutionary history and may guide management that seeks to prevent future introductions. Surprisingly, few studies have successfully used genetic tools to independently inform the specific source and pathway of biological invasions. The ecological history of many introduced species, including their origins and vectors, is often based on suppositions or educated guesses. Here, we used mitochondrial and microsatellite genotyping to trace the invasion of the Asian seaweed Gracilaria vermiculophylla (Rhodophyta) along the three coastlines of the Northern Hemisphere to which it has been introduced: the western coast of North America, eastern coast of the United States and the coasts of Europe and northwest Africa. Analyzing 37 native and 53 introduced sites, we identified the Pacific coastline of northeastern Japan as the ultimate source of the Northern Hemisphere invasion. Coincidentally, most exports of the oyster Crassostrea gigas historically originated from this region and both species often grow in close proximity. Based on genetic signatures, each of the three coastlines likely received thalli directly from Japan, as well as material from another introduced coastline (i.e., a secondary invasion). Our ability to document a source region, which was enabled by a robust sampling of locations and loci that previous studies lacked, reflected strong phylogeographic structure along native coastlines. We suggest Gracilaria vermiculophylla is an important representative example of many species likely exported out of Japan by the oyster trade and its genetic signatures that may be a hallmark of oyster introduction legacies.

Mixed effects of an introduced ecosystem engineer on the foraging behavior and habitat selection of predators

“…A recent ecosystem engineer invasion in the southeastern United States provides an opportunity to investigate the roles these species play in recipient communities, specifically their roles in the foraging patterns of multiple predator species within the same trophic level. Gracilaria vermiculophylla, a red seaweed from the coast of Japan, has invaded many coastal habitats in Europe and North America (Thomsen et al 2009, Kim et al 2010, Krueger-Hadfield et al 2017. Since the early 2000s, the invasive seaweed has considerably altered estuaries of Georgia by creating novel habitat on the previously bare mudflats (Byers et al 2012).…”

“…, Krueger‐Hadfield et al. ). Since the early 2000s, the invasive seaweed has considerably altered estuaries of Georgia by creating novel habitat on the previously bare mudflats (Byers et al.…”

CLONALITY AND POLYPLOIDY CONTRIBUTE TO THE SPREAD OFAVRAINVILLEA LACERATA(BRYOPSIDALES, CHLOROPHYTA) IN HAWAIʻI

“…Further, we sampled over multiple years to quantify the clonal rate at the sites sampled (see discussion in Becheler et al, 2017). These microsatellites will facilitate future studies investigating the invasion history of this alga and could eventually discern the source of the invasion from its native range (see as example Krueger-Hadfield et al, 2017). Not only will quantitative data on the reproductive system aid in the management of this invader, it will test the Otto and Marks (1996) hypothesis of a correlation between the reproductive mode and life cycle, expanding the available population genetic data for macroalgae across marine biomes.…”

“…It is plausible that A. lacerata could have been introduced in a similar manner, and perhaps invaded the mesophotic prior to invading the intertidal in the 1980's. Future work needs to include sampling A. lacerata broadly across the Indo-Pacific and the Hawaiian Archipelago to determine the source populations of A. lacerata in Hawaiʻi (see, as example, Krueger-Hadfield et al, 2017). If the source of the A. lacerata invasion can be determined, comparisons can then be made to understand how the niche of A. lacerata may have shifted in the invasion of the Hawaiian Islands.…”

Non-native hosts of an invasive seaweed holobiont have more stable microbial communities compared to native hosts in response to thermal stress

“…These populations were also visited as part of the global field survey conducted in Bonthond et al (2020) and included Futatsuiwa (Japan; collected on September 14 th 2016), Akkeshi (Japan; September 15 th 2016), Nordstrand (Germany; September 20 th 2016) and Kiel (Germany; September 21 th 2016, see Table S1 for details). Individuals were sampled with gloves and with at least a meter distance in between (Krueger-Hadfield et al, 2017), stored in separate plastic bags and transported to the lab in coolers. Apart from Akkeshi, where single algae were too small to obtain enough tissue for all field and experiment samplings, 12 individuals were collected from each site.…”