Marine fish diversity in Tropical America associated with both past and present environmental conditions

Abstract

Aim Tropical America, including the Tropical Eastern Pacific and the Caribbean Sea, presents a high level of marine biodiversity, but its fish fauna has been poorly documented. In early studies marine species distributions were interpreted based on tectonic activity during the late Cenozoic, while more recent studies have highlighted a link with the present‐day environment. Here, we described the assemblage richness and composition of fishes in Tropical America and related these properties to both the past evolution of marine environmental conditions and current environmental gradients. Location Tropical America. Taxon Demersal and benthic fishes. Methods We mapped the distribution of 2,216 demersal and benthic fish species of Tropical America using existing occurrence data. We computed three assemblage indicators: species richness, composition and nestedness, which we explained by environmental gradients. We linked compositional distance to environmental differences using distance‐based redundancy analysis, species richness and nestedness using a generalized linear model. We ran simulations of a mechanistic model in which three processes determine the spatial dynamics of biodiversity: speciation, dispersal and extinction. This model yielded estimates for species assemblage properties following palaeogeographic changes in the region that shaped the current coastal habitat configuration. Results Fish species richness in Tropical America peaks around the Florida Peninsula, Bahamas and Greater Antilles. Fish composition varies along a depth gradient, between the Tropical Eastern Pacific and the Caribbean Sea, and forms distinct domains within the Caribbean region. The nestedness component of β‐diversity is lower in shallower assemblages, especially those along the outer section of the Greater Caribbean. Species richness and nestedness are partly explained by current environmental conditions, but model simulations illustrate how this may be further explained by the tectonic history of the region. Main conclusions Species richness peaks in the Greater Caribbean, coinciding with generally favourable current environmental conditions for demersal and benthic fishes. The high species richness and the low nestedness of fish assemblages in the Cuba region are compatible with the results of palaeo‐environmental changes that have occurred in that area. Effects of the plate tectonic history might still be present in the organization of fish fauna in this region.

Benchmarking bioinformatic tools for fast and accurate eDNA metabarcoding species identification

“…Performance indices for the empirical data set are lower than the ones on the simulated data due to a high number of false negatives (some due to the too stringent similarity threshold) and some false positives. It is likely that with an eDNA sampling limited to one day, all of the species present on site were not detected and that divers did not detect elusive or hidden species (Aglieri et al, 2020; Polanco et al, 2020). In order to reduce the number of false negatives and false positives, it would be necessary to extend the eDNA sampling of each site to several seasons and to consider similarity thresholds adapted for the taxonomic assignment.…”

Mapping tree species for restoration potential resilient to climate change

“…Moreover, we found that species have generally higher median area coverage in some regions compared with others (median area covered by the distribution of one species, Indomalayan=984 km2, Afrotropic=4’436 km2, Palearctic=4’805 km2, Neotropics=6’145 km2, Australasia=11’363 km2, Nearctic=16’455 km2), suggesting that tree species could have larger environmental niche width in some regions compared with others. Unlike previous large scale modelling efforts (Thuiller et al 2011), our approach combined both species distribution modelling and the geographic range limits, which can for instance represent dispersal limitations (Merow, Wilson, and Jetz 2017; Polanco et al 2020). Complementing previous local use of species distribution models to inform forest management (Booth 2018), our modelling synthesis provides a general approach to inform the suitability of potentially dominant and frequent species at local sites and provides structuring species for reforestation in the context of global restoration projects.…”

“…Hence, maximizing the success of active ecosystem restoration and management initiatives across the globe requires fundamental information about which mixtures of species are best suited to surviving in those specific regions (Crouzeilles et al 2020). By combining species distribution modelling (Guisan and Zimmermann 2000) with spatial polygons to constrain the suitable area to the native range (Polanco et al 2020), we provide suitability for many tree species, beyond regions where species range maps are already available and broadly used by forester to manage forest resources (Caudullo, Welk, and San-Miguel-Ayanz 2017).…”

“…Unlike previous modelling approaches (Rondinini et al 2011), our pipeline considers both spatial boundaries and ecological suitability and can serve the mapping of organisms beyond tree species (Polanco et al 2020). Typically, while global species range maps are available for well-known taxonomic groups such as vertebrates (BirdLife International & NatureServe 2015) and from the IUCN (2015) Red list for amphibians and terrestrial mammals), there exist still no high resolution mapping for tree species (Serra-Diaz et al 2018).…”

Global patterns and drivers of beta diversity facets of reef fish faunas

“…Despite the importance of historical and contemporary factors in shaping current beta diversity patterns, it is important to highlight the high percentage of unexplained inertia, which suggests that observed dissimilarities in taxonomic, phylogenetic and trait reef fish composition could also be explained by other processes, such as dispersal limitation. Indeed, it is worth noting that we did not explicitly consider the influence of dispersal processes associated to plate tectonics, which were found to be major drivers of tropical reef fish diversity worldwide (Leprieur, Descombes, et al, 2016; Polanco et al, 2020). Indeed, the isolation from the biodiversity centres that we used as a proxy for the influence of plate tectonics does not integrate the impact of soft and hard barriers to dispersal as well as stepping stones processes.…”