Ascidians and their microbial symbionts

Abstract

I obtained my PhD in Zoology in 2005 studying the biology and ecology of Mediterranean ascidians at both the University of Barcelona (UB; Spain) and the University of Perpignan (France). In 2006, I obtained a Fulbright postdoctoral fellowship to continue my studies at the University of North Carolina Wilmington (UNCW; USA). I returned to Spain in 2010 and joined the faculty at UB. While there, my husband Dr. Patrick Erwin (microbiologist) and I created the iMESA Lab, which stands for “integrated Molecular Ecology of Sponges and Ascidians.” A few years later, we returned to UNCW and continued the iMESA Lab work (Figure 1). Most recently, research at the iMESA Lab has focused on biological invasions (Figure 2).

Ascidians are ideally suited for the study of introduction processes because they rely on anthropogenic transport for their long-distance dispersal. There are many successfully introduced ascidians worldwide (e.g., López-Legentil* et al. 2015, Villalobos* et al. 2017, Streit* et al. 2021, Nydam* et al. 2022). Some of their success has been ascribed to rapid growth and high reproductive outputs (Pineda* et al. 2013); however, ascidians also have hidden microbial allies. Historically, most studies of microbial symbionts in ascidians focused on cyanobacteria, until pioneering work at the iMESA Lab provided the most comprehensive characterization of the ascidian microbiome (Erwin et al. 2014). This study revealed exceptional microbial biodiversity inhabiting the ascidian tunic and a high degree of host-specificity (Erwin et al. 2014).

Furthermore, microbial symbionts may play a major role in facilitating the establishment of their hosts in a new habitat (Evans et al. 2017, 2018, Goddard-Dwyer* et al. 2021). For example, we showed that microbiomes in a native ascidian differed across natural (reef) and artificial (harbor) habitats, while a non-native ascidian hosted stable microbial symbiont communities that may allow them to thrive in a wider range of habitats (Evans et al. 2018). Across larger distances (inter-continental), spatial variation manifested in compositional and structural changes to the microbiome (beta-diversity) rather than changes in symbiont richness and evenness (alpha-diversity; Goddard-Dwyer* et al. 2021, López-Legentil* et al. 2023). Moreover, the comparative influence of host and location on microbiome similarity differed between colonial and solitary ascidians, with colonial ascidians hosting less diverse microbiomes but with greater distinctions from the seawater bacterioplankton than their solitary counterparts (López-Legentil* et al. 2023). Further research will focus on achieving a greater understanding of the ascidian microbiome and its contributions to host invasiveness potential and evolution.