How do microbiota associated with an invasive seaweed vary across scales?

Abstract

Communities are shaped by scale dependent processes. To study the diversity and variation of microbial communities across scales, the invasive and widespread seaweed Agarophyton vermiculophyllum presents a unique opportunity. We characterized pro‐ and eukaryotic communities associated with this holobiont across its known distribution range, which stretches over the northern hemisphere. Our data reveal that community composition and diversity in the holobiont vary at local but also larger geographic scales. While processes acting at the local scale (i.e., within population) are the main structuring drivers of associated microbial communities, changes in community composition also depend on processes acting at larger geographic scales. Interestingly, the largest analysed scale (i.e., native and non‐native ranges) explained variation in the prevalence of predicted functional groups, which could suggest a functional shift in microbiota occurred over the course of the invasion process. While high variability in microbiota at the local scale supports A. vermiculophyllum to be a generalist host, we also identified a number of core taxa. These geographically independent holobiont members imply that cointroduction of specific microbiota may have additionally promoted the invasion process.

The role of host promiscuity in the invasion process of a seaweed holobiont

“…Algae were sampled from August 27 th to September 21 st (2017) from seven populations also collected for Bonthond et al [ 28 ], including three native populations; Akkeshi (Japan), Soukanzan (Japan), Rongcheng (China); and four non-native populations; Pleudihen-sur-Rance (France), Nordstrand (Germany), Cape Charles Beach (Viriginia) and Tomales Bay (California, Fig. 1 , Table S1 ).…”

“…Subsequently, both groups received new ASW with 2 mL PES weekly and individuals treated with antibiotics received also 2 mL inoculum. The inoculum was prepared from individuals of all 7 populations, following the procedure to remove epibiota as described in Bonthond et al [ 28 ]. Briefly, apical fragments of 1 g were separated from the thallus and transferred to 50 mL tubes containing 15 ± 1 glass beads (3 mm) and 15 mL ASW and vortexed for 6 min to separate epibiota from the algal tissue.…”

“…Before weighing the individual on aluminum foil, it was dipped twice on a separate aluminum foil sheet, to reduce attached water in a systematic way. Endo- and epiphytic microbiota were sampled in the field (t field , [ 28 ]), at the start of the experiment (t 0 ), after one week (t 1 ), two weeks (t 2 ), four weeks (t 4 ) and six weeks (t 6, Fig. 1 ).…”

“…Several studies have demonstrated that the interaction between this host and associated microbiota differs between native and non-native populations [ 25 – 27 ]. Moreover, the microbial communities associated with A. vermiculophyllum vary in composition and function, across the scale of its known distribution, both locally and between the native and non-native range [ 28 ]. Together these studies suggest a shift in the interaction between host and microbiota may have occurred during the invasion process.…”

Using RAD‐seq to develop sex‐linked markers in a haplodiplontic alga

“…2017b, Bonthond et al. 2020). In addition, recent studies have demonstrated the necessity of understanding the evolutionary ecology of haplodiplontic life cycles in the context of biological invasions (Lees et al.…”