Data from: Do positive interactions between marine invaders increase likelihood of invasion into natural and artificial habitats?

Positive species interactions such as facilitation are important for
enabling species to persist, especially in stressful conditions, and the
nature and strength of facilitation varies along physical and biological
gradients. Expansion of coastal infrastructure is creating hotspots of
invasive species which can spillover into natural habitats, but the role
of positive species interactions associated with biological invasions
remains understudied. Theory suggests that stronger biotic pressure in
natural habitats inhibits invasion success. In space-limited marine
systems, sessile organisms can overcome this limiting resource by settling
as an epibiont on a substrate organism - basibiont. Using a series of
spatially extensive surveys, we explored the role of invasive and native
basibionts in providing habitat for other invasive and native epibionts,
and tested whether environmental context (i.e. if the receiving habitat
was natural or artificial), altered ecological outcomes. Overall,
provision of space by basibionts was more important for invasive epibionts
than for native epibionts but was dependent on the environmental context.
Invasive basibionts facilitated invasive epibionts in natural habitats,
and appeared to be more important for native epibionts in artificial
habitats respectively. Native basibionts facilitated invasive, but not
native epibionts in both natural and artificial habitats. These results
advance our understanding of facilitation and highlight the idiosyncratic
nature of biofouling and epibiosis, and the potentially important
influence of environmental context. The degree to which native
habitat-forming species vs. invasive habitat-forming species either do or
do not facilitate other native or non-native species is a rich area for
investigation. Experimental work is required to disentangle the processes
underpinning these patterns.