From the river to the ocean: mitochondrial DNA analyses provide evidence of spectacled caimans (Caiman crocodilus Linnaeus 1758) mainland–insular dispersal

Abstract

There are few studies that have investigated the evolutionary history of large vertebrates on islands off the Caribbean coast of South America. Here we use the spectacled caiman (Caiman crocodilus) to investigate among- and within-population patterns of genetic diversity to understand connectivity between island and mainland populations. The spectacled caiman is naturally distributed across Central and South America including the islands of Trinidad and Tobago, which are considered to have the only natural insular populations of the species. Because of this apparent isolation, we sought to determine whether caimans on Trinidad and Tobago comprise a unique lineage and have reduced genetic diversity compared to mainland caimans. We test these hypotheses by using mitochondrial DNA variation to assess the phylogenetic and phylogeographical relationships of the C. crocodilus populations inhabiting these islands within the evolutionary context of the entire spectacled caiman complex. Phylogenetic analyses placed the Trinidad and Tobago samples together with samples from Colombia, Venezuela and Brazil into one well-supported clade, which corresponds to the defined Orinoco/upper Negro lineage. Interestingly, the majority of sequences from Trinidad and Tobago are similar or identical to haplotypes reported from Venezuela and Colombia, supporting the idea of a dispersal process from the Orinoco River to these islands. We discuss the implications of our findings for systematics and the conservation of the species and how these dispersal movements could shape the current phylogeographical structure depicted for C. crocodilus.

Biogeography of Greater Antillean freshwater fishes, with a review of competing hypotheses

“…Freshwater connections are often limited on narrow peninsulas or isthmuses. For instance, Caribbean rivers of Costa Rica and Panam a are steep and short (Sosa Gonzalez et al, 2016), discharging onto a narrow continental shelf, and suggesting little potential for interconnection during sea-level falls (Bagley, Hickerson, Johnson, 2018). Accordingly, secondary freshwater fishes dominate the Central American fish fauna (Matamoros et al, 2015) because the narrow Isthmus of Panam a restricted dispersal by primary freshwater fishes (Smith & Bermingham, 2005).…”

“…Non-cyprinodontiform families from North America are diminished in the WGM and MT bioregions because deserts and mountains limit southward immigrations (Miller et al, 2005;Rico et al, 2022). Non-cyprinodontiform families from South America are diminished in the CB and MT bioregions due to barrier effects of the Isthmus of Panam a and former Central American Seaway (Matamoros et al, 2015;Bagley et al, 2018). Increased prevalence of cyprinodontiforms in the WGM, MT, and CB bioregions illustrates their superior dispersal ability.…”

“…Large rafts occur episodically and their dispersal may require strong winds or currents (Thiel & Haye, 2006). Although rare, favourable conditions appear sometimes to align along potential dispersal routes (Measey et al ., 2007; Balaguera‐Reina et al ., 2021). Relevant examples in the Caribbean include freshwater turtles, snakes, and crocodilians (Charles, 2013; Brown et al ., 2021).…”

Biogeography of Greater Antillean freshwater fishes, with a review of competing hypotheses

“…Large rafts occur episodically and their dispersal may require strong winds or currents (Thiel & Haye, 2006). Although rare, favourable conditions appear to sometimes align along potential dispersal routes (Measey et al, 2007; Balaguera-Reina et al, 2021). Relevant examples in the Caribbean include freshwater turtles, snakes, and crocodilians (Charles, 2013; Brown et al, 2021).…”