Diversity and Distributions

Abstract

Aim: Mutualistic interactions between plants and animals are fundamental for the maintenance of natural communities and the ecosystem services they provide. However, particularly in human-dominated island ecosystems, introduced species may alter mutualistic interactions. Based on an extensive dataset of plant–frugivore interactions, we mapped and analysed a meta-network across the Caribbean archipelago. Specifically, we searched for subcommunity structure (modularity) and identified the types of species facilitating the integration of introduced species in the Caribbean meta-network.

Location: Caribbean archipelago (Lucayan archipelago, Greater Antilles, Lesser Antilles).

Methods: We reviewed published scientific literature, unpublished theses and other nonpeer-reviewed sources to compile an extensive dataset of plant–frugivore interactions. We visualized spatial patterns and conducted a modularity analysis of the cross-island meta-network We also examined which species were most likely to interact
with introduced species: (1) endemic, nonendemic native or introduced species, and (2) generalized or specialized species.

Results: We reported 3060 records of interactions between 486 plant and 178 frugivore species. The Caribbean meta-network was organized in 13 modules, driven by a combination of functional or taxonomic (modules dominated by certain groups of frugivores) and biogeographical (island-specific modules) mechanisms. Few introduced species or interaction pairs were shared across islands, suggesting little homogenization of the plant–frugivore meta-network at the regional scale. However, we found evidence of “invader complexes,” as introduced frugivores were more likely to interact with introduced plants than expected at random. Moreover, we found generalist
species more likely to interact with introduced species than were specialized species.

Main conclusions: These results demonstrate that generalist species and “invader complexes” may facilitate the incorporation of introduced species into plant–frugivore communities. Despite the influx of introduced species, the meta-network was structured into modules related to biogeographical and functional or taxonomic affinities. These findings reveal how introduced species become an integral part of mutualistic systems on tropical islands.

Abstract

Aim: To evaluate how the spatial distribution of a heavily exploited marine gastropod (i.e. Queen conch) varies in response to a number of known biotic and abiotic variables within and between study areas that vary in environmental conditions.

Location: Three study areas in the north-eastern Caribbean, Anguilla, Saba Bank and St. Eustatius.

Methods: A novel towed video system and complemented belt transects to estimate adult queen conch densities throughout its depth range. Bayesian hierarchical spatial models (integrated nested Laplace approximations) modelled distribution patterns of adult conch.

Results: Our study revealed patchy distribution patterns of adult conch caused by spatial dependency. This dependency is most likely related to aggregating behaviour during spawning events. Environmental variables, such as algal cover, distance to the open ocean and depth, showed important nonlinear effects on conch abundance, although these differed among study areas. Intermediate and deep areas (ca. 17–45 m) contain most of the reproductive output of conch in the study areas and are highly important for the reproductive capacity.

Main conclusions: The general patchy distribution pattern and the lack of strong generic relationships between biotic and abiotic factors and adult conch abundance and distribution are likely to be at least partly due to spatial dependency and locationspecific factors, which affect different phases of the conch's life history. The depth distribution of conch also indicates that surveying areas at depths beyond the practical limitation of divers is of great importance to obtain more reliable population estimates.

Abstract

Aim

A detailed understanding of spatial genetic structure (SGS) and the factors driving contemporary patterns of gene flow and genetic diversity are fundamental for developing conservation and management plans for marine fisheries. We performed a detailed study of SGS and genetic diversity throughout the overharvested queen conch (Lobatus gigas) fishery. Caribbean countries were presented as major populations to examine transboundary patterns of population differentiation.

Location

Nineteen locations in the greater Caribbean from Anguilla, the Bahamas, Belize, Caribbean Netherlands, Honduras, Jamaica, Mexico, Turks and Caicos, and the USA.

Methods

We genotyped 643 individuals with nine microsatellites. Population genetic and multivariate analyses characterized SGS. We tested the alternate hypotheses: (1) SGS is randomly distributed in space or (2) pairwise genetic structure among sites is correlated with oceanic distance (IBOD).

Results

Our study found that L. gigas does not form a single panmictic population in the greater Caribbean. Significant levels of genetic differentiation were identified between Caribbean countries (FCT = 0.011; p = .0001), within Caribbean countries (FSC = 0.003; p = .001), and among sites irrespective of geographic location (FST = 0.013; p = .0001). Gene flow across the greater Caribbean was constrained by oceanic distance (p = .0009; Mantel r = .40), which acted to isolate local populations.

Main conclusions

Gene flow over the spatial scale of the entire Caribbean basin is constrained by oceanic distance, which may impede the natural recovery of overfished L. gigas populations. Our results suggest a careful blend of local and international management will be required to ensure long-term sustainability for the species.

Invasion science is the study of the causes and consequences of the introduction of organisms to the areas outside their native ranges. It concerns all aspects relating to the transport, establishment and spread of organisms in a new target region, their interactions with resident organisms, and the costs and benefits of invasion with reference to human value systems. ‘Invasion science’ is a more appropriate name for the broad domain than ‘invasion ecology’ or ‘invasion biology’ because of the importance of engaging with many disciplines other than biology and ecology in understanding and managing invasions...