Superior growth traits of invaded (Caribbean) versus native (Red sea) populations of the seagrass Halophila stipulacea .

The seagrass Halophila stipulacea is native to the Red Sea. It invaded the Mediterranean over the past century and most of the Caribbean over the last two decades. Understanding the main drivers behind the successful invasiveness of H. stipulacea has become crucial. We performed a comprehensive study including field measurements, a mesocosm experiment, and a literature review to identify 'superior growth traits' that can potentially explain the success story of H. stipulacea . We assessed meadow characteristics and plant traits of three invasive H. stipulacea populations growing off the Island of Sint Eustatius (eastern Caribbean). We compared similar parameters between native (Eilat, northern Red Sea) and invasive (Caribbean)  H. stipulacea plants in a common-garden mesocosm. Lastly, we compared our field measurements with published data. The newly arrived H. stipulacea plants from St. Eustatius were characterized by higher percent cover, higher below- and above-ground biomasses, more apical shoots, and faster leaf turnover rates than those measured in both native and older invaded habitats. These results were further confirmed by the mesocosm experiment where the invasive H. stipulacea plants grew faster and developed more apical shoots than the native plants. Results suggest that increased growth vigour is one of the main invasive traits that characterize successful invasive H. stipulacea populations in the Caribbean and potentially in other invaded areas. We encourage long-term monitoring of H. stipulacea in both native and invaded habitats to better understand the future spread of this species and its impacts on communities and their ecosystem functions and services.
Supplementary Information: The online version contains supplementary material available at 10.1007/s10530-023-03045-z.
Competing Interests: Conflict of interestAll authors have no relevant financial or non-financial competing interests to disclose.
(© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)