Research Square

Superior biological traits of invaded (Caribbean) versus native (Red Sea) populations of the seagrass Halophila stipulacea

Abstract

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 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, Red Sea) and invasive H. stipulacea plants in a common-garden mesocosm. Lastly, we also 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 mesocosm experiments 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.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
St. Eustatius

Rapid declines in lionfish catches in the Saba Bank lobster and snapper trap fisheries, Dutch Caribbean

Abstract

Since its introduction in the Western Atlantic more than 30 years ago, the lionsh (Pterois volitans/miles complex) has spread throughout the Gulf of Mexico and the Caribbean having massive and unprecedented ecological impacts. This invasion is among the most studied marine sh invasions but very little is still really known about the population dynamics of the species and the factors ultimately governing its abundance. We here document a large population crash for the lionsh following its rapid increase in abundance on the Saba Bank following its appearance in 2010. In doing so we document the third case of apparent local population boom-bust event for the Greater Caribbean, and the rst for the Eastern Caribbean. We also document gradual increases in the mean size of lionsh of the Saba Bank that coincided with the increase and subsequent decline in lionsh abundance. Contrary to the previously documented epizootic disease outbreak associated with the population crash observed in the Gulf of Mexico we were unable to nd any signs of the occurrence of epizootic disease. We suggest that the population crash on the Saba Bank might have been due to non-local causes, such as reduced reproductive output in distant larval source populations. Boom-bust dynamics are often witnessed in biological invasions and have critical implications for both understanding and managing invasive species. While the underlying cause for the boom-bust event we document remains unknown, our work helps improve our understanding of this most serious biological invasion.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Saba bank

An integrative approach to assess non-native iguana presence on Saba and Montserrat: are we losing all native Iguana populations in the Lesser Antilles?

Abstract

Invasive alien species are among the main drivers of the ongoing sixth mass extinction wave, especially affecting island populations. Although the Caribbean is well-known for its high species richness and endemism, also for reptiles, equally important is the regional contribution of non-native species to island biodiversity. The Lesser Antilles encompass high genetic diversity in Iguana, though most native populations either have gone extinct or are declining following competitive hybridization with invasive non-native iguanas. Here we assessed non-native presence in two poorly-studied native melanistic Iguana iguana populations using available genetic tools, and explored utilizing size-dependent body measurements to discriminate between native and non-native iguanas. Genetic samples from Saba and Montserrat were genotyped across 17 microsatellite loci with STRUCTURE and multivariate analyses indicating non-native iguanas presence only on Saba. This was corroborated by mtDNA and nDNA sequences, highlighting a non-native origin in Central America and the ABC islands. We identied preliminary evidence suggestive of hybridization. Morphological variation among size-dependent characteristics showed that non-native iguanas have signicantly larger subtympanic plates than native iguanas. Non-native individuals also differed in scalation and coloration patterns. Overall, our ndings demonstrate the need for continuous monitoring for non-native iguanas within remaining native Iguana populations in the Lesser Antilles, with those not directly threatened by non-native iguanas restricted to only 8.7% of the historic range. Although genetic data allows for identication of non-native or hybrid iguana presence, this eld-to-lab workow is time consuming. Rapid in-situ identication of non-native individuals is crucial for conservation management, and besides scale and coloration patterns, we have highlighted the utility of size-dependent variables for rapid diagnosis. We urge regional partners to build morphometric databases for native Iguana populations that will help to quickly detect future incursions of non-native iguanas and allow the rapid implementation of effective countermeasures during the early phase of invasion.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Saba