Deep and concordant subdivisions in the self-fertilizing mangrove killifishes (Kryptolebias) revealed by nuclear and mtDNA markers

Andrey Tatarenkov,Bruce J Turner,Waldir M Berbel-Filho,Frans B M Vermeulen,Ryan L Earley,John C Avise,Kristine Marson,D Scott Taylor,Sergio M Q Lima

doi:10.1093/biolinnean/blx103

Abstract

Author(s): Tatarenkov, A; Lima, SMQ; Earley, RL; Berbel-Filho, WM; Vermeulen, FBM; Taylor, DS; Marson, K; Turner, BJ; Avise, JC | Abstract: We use extensive geographical sampling and surveys of nuclear microsatellite and mitochondrial DNA loci to investigate the phylogeographic structure of the only recognized self-fertilizing vertebrates, the mangrove killifishes, currently thought to comprise two cryptic species, Kryptolebias marmoratus and Kryptolebias hermaphroditus. All genetic markers revealed three concordant main clades. The Northern clade includes populations from Florida, northern Cuba, Bahamas, Belize and Honduras and corresponds to K. marmoratus. The Southern clade encompasses populations from Brazil and corresponds to K. hermaphroditus. This species was considered endemic to southeastern Brazil, but molecular data corroborate its occurrence in northeastern Brazil. The Central clade, not previously resolved with genetic data, includes populations from Panama and Antilles. Despite the geographic proximity of the Northern and Central clades, the latter is genetically closer to the Southern clade. The discovery of the Central clade raises some taxonomic issues - it can either be considered a distinct species or united with the Southern clade into a single species with two subspecies. Another possible taxonomic solution is a single selfing species, K. marmoratus, with three subspecies. We show that the Central and Southern clades are highly selfing (97-100%), whereas selfing rates of the Northern clade populations vary geographically (39-99%). Genetic patterns indicate that populations in SE Brazil are recent, contrary to expectations based on the known distributions of related species.

Highlights

The mangrove ecosystem of the western Atlantic is extensive, occupying 3.2 million ha along the coasts of the Americas (Luther & Greenberg, 2009)
Our objectives are to (1) describe population genetic structure of the selfing species of the K. marmoratus complex over its whole geographic distribution and define main genetic lineages; (2) map the geographic distributions of the main genetic lineages; (3) find out whether and how well the main genetic lineages agree with current taxonomy; (4) verify the status of specimens from NE Brazil that were a matter of some controversy; (5) estimate selfing/outcrossing rates of newly sampled populations that have not been studied before; and (6) describe major trends in genetic diversity that could be informative about the origin and evolution of the K. marmoratus species complex
An NJ tree based on the microsatellite data set shows that populations are split into two major lineages; one lineage (Northern clade) includes populations from Florida, Bahamas, Belize and Honduras, while the other lineage encompasses populations from the rest of the Caribbean and Brazil (Fig. 2)

Summary

Introduction

The mangrove ecosystem of the western Atlantic is extensive, occupying 3.2 million ha along the coasts of the Americas (Luther & Greenberg, 2009). Mangroves are a vulnerable ecosystem, declining at a faster rate than inland tropical forests and coral reefs (Giri et al, 2011). Kryptolebias marmoratus and K. hermaphroditus are considered members of K. marmoratus species complex, together with a third species, Kryptolebias ocellatus, better known under its junior synonym Kryptolebias caudomarginatus (Costa, 2011; Avise & Tatarenkov, 2015). Unlike the former two species, K. ocellatus apparently does not reproduce by self-fertilization, even though its populations consist of hermaphrodites and males (Tatarenkov et al, 2009; Costa, Lima & Bartolette, 2010). All other known Kryptolebias species are phylogenetically more distant and are dioecious, implying that hermaphroditism arose in the common ancestor of all three species of the K. marmoratus species complex, with selfing evolving later on in the marmoratus/hermaphroditus common ancestor (Costa et al, 2010)

Objectives

Methods

Results

Conclusion