Isolation and differentiation of Rivulus hartii across Trinidad and neighboring islands

Abstract

Diversification of freshwater fishes on islands is considered unlikely because the traits that enable successful colonization-specifically, broad salinity tolerances and the potential for oceanic dispersal-may also constrain post-colonization genetic differentiation. Some secondary freshwater fish, however, exhibit pronounced genetic differentiation and geographic structure on islands, whereas others do not. It is unclear what conditions give rise to contrasting patterns of differentiation because few comparative reconstructions of population history have been carried out for insular freshwater fishes. In this study, we examined the phylogeography of Hart's killifish (Rivulus hartii) across Trinidad, with reference to neighboring islands and northern South America, to test hypotheses of colonization and differentiation derived from comparable work on co-occurring guppies (Poecilia reticulata). Geographic patterns of mitochondrial DNA haplotype variation and microsatellite genotype variation provide evidence of genetic differentiation of R. hartii among islands and across Trinidad. Our findings are largely consistent with patterns of geographically structured ancestry and admixture found in Trinidadian guppies, which suggests that both species share a history of colonization and differentiation and that post-colonization diversification may be more common among members of insular freshwater fish assemblages than has been previously thought.

Annotated list and key to the stream fishes of Trinidad & Tobago

“…Though an accurate review of the fish fauna of Tobago is hampered by the fact that there have been few reported surveys on the island (limited to Ramnarine et al 1994 andPhillip 1998), recent phylogenetic evidence from Anablepsoides hartii (Walter et al 2011) has shown that the zoogeography of Tobago may be more complex than previously expected.…”

“…Although we here refer to all Rivulus (=Anablepsoides) from Trinidad as A. hartii, recent genetic work (Walter et al 2011) indicates that differentiation has occurred, some of which warrants taxonomic recognition.…”

“…Later in the same year, Schories et al (2009) declared the guppies of the northern Oropuche River to be a new species, Poecilia (Acanthophacelus) obscura (= Poecilia reticulata), based on new molecular evidence. Willing et al (2010) and Walter et al (2011) provided a different interpretation to the phylogeography of P. reticulata and A. hartii, believing that their data were consistent with multiple invasions of Trinidad by these species, and limited genetic exchange between drainages on the island, which lead to post-colonisation divergence. Bertaco & Malabarba (2010) provided a re-description of Hemibrycon taeniurus from T&T.…”

Environmental and Organismal Predictors of Intraspecific Variation in the Stoichiometry of a Neotropical Freshwater Fish

“…For example, a recent study reveals the presence of different genetic lineages of R. hartii in Trinidad [45]. The geographic boundaries of these lineages are poorly understood, but some appear to be defined by stream or watershed boundaries [45].…”

“…For example, a recent study reveals the presence of different genetic lineages of R. hartii in Trinidad [45]. The geographic boundaries of these lineages are poorly understood, but some appear to be defined by stream or watershed boundaries [45]. A phylogenetic signature in organismal stoichiometry has been observed even within closely related insect taxa [46], and it is possible that combining phylogenetic and stoichiometric analyses can explain the remaining portion of spatial variability in the stoichiometry of R. hartii .…”