Historical Biogeography and Speciation in the Creole Wrasses (Labridae, Clepticus)
Total Page：16
File Type：pdf, Size：1020Kb
Mar Biol DOI 10.1007/s00227-008-1118-5 ORIGINAL PAPER Historical biogeography and speciation in the Creole wrasses (Labridae, Clepticus) Ricardo Beldade · J. B. Heiser · D. R. Robertson · J. L. Gasparini · S. R. Floeter · G. Bernardi Received: 10 April 2008 / Accepted: 16 December 2008 © The Author(s) 2008. This article is published with open access at Springerlink.com Abstract We tested whether vicariance or dispersal was (» 0.60 to 0.12 mya; 0.3% sequence divergence) of the the likely source of speciation in the genus Clepticus by Brazilian and African sister morpho-species. Both these evaluating the evolutionary timing of the eVect of the phylogenetic events occurred well after the formation of mid-Atlantic barrier, which separates C. brasiliensis and the two barriers that currently separate those three allopat- C. africanus, and the Amazon barrier, which separates ric populations. The planktonic larval duration of these C. parrae and C brasiliensis. Genetic data from three mito- species (35–49 days) and coastal pelagic habits may have chondrial genes and one nuclear gene were used. Mitochon- facilitated dispersal by this genus across those dispersal drial genes separated Clepticus into three well supported barriers after they formed. clades corresponding to the three recognized allopatric morpho-species. All analyses provided consistent support for an initial separation (»9.68 to 1.86 mya; 4.84% Introduction sequence divergence) of the Caribbean and South Atlantic lineages, followed by a much more recent divergence Allopatric speciation is thought to result from two possible mechanisms: dispersal into separate regions, or the forma- tion of a barrier that isolates populations as a vicariant event. In both cases, gene Xow is eliminated and genetic Communicated by M.I. Taylor. diVerences accumulate over time, leading ultimately to spe- R. Beldade (&) · G. Bernardi ciation (Brown and Lomolino 1998; Coyne and Orr 2004). Department of Ecology and Evolutionary Biology, In the marine environment, many organisms, including University of California, Santa Cruz, CA 95060, USA nearly all bony reef Wshes, have life histories that include a e-mail: [email protected] pelagic larval stage (Leis and McCormick 2002). During J. B. Heiser this phase, larvae are subjected to transport by ocean cur- Department of Ecology and Evolutionary Biology, rents and are, thus, potentially widely dispersed. However, Stimson Hall, Cornell University, Ithaca, NY 14853, USA many barriers that eliminate or restrict gene Xow have been identiWed in the marine environment. In the Atlantic ocean, D. R. Robertson Smithsonian Tropical Research Institute, those include two major breaks in adult habitat: the broad Panama, Unit 0948, APO AA 34002, USA zone of Amazon–Orinoco discharge, and the deep expanse of ocean that forms the mid-Atlantic barrier (Briggs 1974; J. L. Gasparini Floeter and Gasparini 2000; Rocha 2003; Floeter et al. Departamento de Ecologia e Recursos Naturais, Universidade Federal do Espírito Santo, 2008) (Fig. 1). Within this setting, both vicariance and dis- Vitória, ES 29060-900, Brazil persal have been described as driving population structure in marine organisms (e.g. Bernardi et al. 2003). S. R. Floeter The Amazon discharge is thought to have begun acting Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, as a biogeographic barrier to marine shore organisms, Florianopolis, SC 88010-970, Brazil approximately 11 mya (Hoorn et al. 1995; Rocha 2003). 123 Mar Biol Fig. 1 Map of the collection sites with a schematic illustration of the Noronha, Vitória and Cabo Frio; outgroups are indicated by circles. biogeographic barriers. The Amazon barrier and mid-Atlantic barrier Semicossyphus pulcher: Santa Rosalillita (SR, Mexico), and Bodianus are indicated by thick straight lines. The origin of samples is indicated diplotaenia Bahia de Los Angeles (BL, Mexico) by stars. Clepticus: Bahamas, Panama, São Tome, Fernando de However, accumulating evidence shows that it often acts as islands, and São Tomé indicate that Clepticus species are a permeable barrier (see Floeter et al. 2008, for a sum- usually found between the surface to 40 m depth on sea- mary). The mid-Atlantic barrier began to develop with the ward reef slopes and shallow patch reefs, and that their start of the split of Africa and South America that began typical habitat is clear and often relatively turbulent water. approximately 84 mya (Briggs 1974; Pittman et al. 1993), Clepticus are plankton feeding species (Lieske and Myers and has likely been an eVective barrier to the dispersal of 1994; personal observation of the authors). They spawn in shore organisms for a considerable time since that event. the pelagic environment, forming breeding aggregations in That barrier is considered to be currently far more eVective open water (Robertson and HoVman 1977; Allsop and West than the Amazon, although it too has been breached by a 2003). After hatching, larvae of C. parrae spend between number of species (Floeter et al. 2008). 35 and 49 days in the pelagic environment before settling Fishes of the genus Clepticus (family Labridae) include (Victor 1986). only three morpho-species, which span the Orinoco– The analyses by Floeter et al. (2008) of the relationships Amazon barrier and the mid-Atlantic divide: the Caribbean of pan-Atlantic Wsh species indicate that the level of con- C. parrae (Creole wrasse), the southwestern Atlantic nectivity is much greater across the Amazon barrier than C. brasiliensis (Brazilian Creole wrasse) and the tropical across the mid-Atlantic barrier. Based on this pattern, we eastern Atlantic C. africanus (African Creole wrasse). The expected the Caribbean and Brazilian species to be more geographic ranges of these three species do not overlap. In closely related than either of these is to the eastern Atlantic the western Atlantic, the Creole wrasse (C. parrae) occurs species. In contrast, morphological data suggest that the from the Carolinas throughout the Greater Caribbean to eastern Atlantic and Brazilian species are closer together Trinidad (Randall 1996; Floeter et al. 2008), whereas the than either of these is to their Caribbean counterpart (Heiser Brazilian Creole wrasse (C. brasiliensis) is found oV main- et al. 2000). Given the historical formation of the above- land Brazil (south of the Amazon) and the oceanic islands mentioned barriers, the ecological characteristics of Clepti- of St. Paul’s Rocks, Fernando de Noronha, Atol das Rocas cus and the morphological similarities of the species, the and Trindade. In the Eastern Atlantic, the African Creole phylogenetic relationship within this group should provide wrasse (C. africanus) has only been collected in São Tomé insights into their evolutionary history and speciation pat- and Príncipe, Gulf of Guinea (Heiser et al. 2000). Our terns, as well as evaluate the eVectiveness of the Amazon observations in the Caribbean, Brazilian coast and oceanic and mid-Atlantic barriers. 123 Mar Biol We tested whether vicariance or dispersal promoted SwoVord 2002) and MrBayes (version 2.1, Huelsenbeck speciation in Clepticus by examining the timing of and Ronquist 2001). Nucleotide sequence evolution models phylogenetic events relative to the ages of the Amazon and were evaluated using likelihood ratio tests implemented by mid-Atlantic barriers. If vicariance drove speciation within Modeltest v.3.6 (Posada and Crandall 1998). Most parsimo- this genus, then we would expect the timing of divergence nious trees were obtained using a branch and bound search. between species to match the formation of the barriers. Neighbour-joining reconstructions were based on substitu- Whereas if dispersal is the evolutionary mechanism driving tion models obtained with Modeltest (HKY + I + G for speciation in Clepticus, then the phylogenetic events would mitochondrial genes and HYQ + G for S7). Statistical con- not correspond to the timing of the formation of those Wdence in nodes was evaluated using 2,000 non-parametric barriers. bootstrap replicates (Felsenstein 1985). MrBayes default settings for the Bayesian analysis were adopted including the GTR model (unequal base frequencies and six substitu- Materials and methods tion rates). Stationarity of tree likelihood, sampled every 100 cycles, was consistently achieved after 2,100 genera- Samples of Clepticus were collected from the Caribbean, tions and all sampled trees preceding stationarity were São Tomé (Gulf of Guinea) and Brazil. The closely related discarded. Topological diVerences were tested using a Semycossyphus and Bodianus species (Westneat and Alfaro Shimodaira–Hasegawa test (Shimodaira and Hasegawa 2005) were used as outgroups (Fig. 1). Immediately after 1999) implemented by PAUP. collection, Wn clips were placed in 95% ethanol and stored The time of divergence between species can be estimated at ambient temperature in the Weld, and then at 4°C in the using genetic divergence, or an estimate of coalescence time lab. Total genomic DNA was prepared from 20 mg of Wn (Edwards and Beerli 2000). In both cases, mutations are tissue by proteinase K digestion in lysis buVer (10 mM assumed to proceed randomly and uniformly (molecular Tris, 400 mM NaCl, 2 mM EDTA, 1% SDS) overnight at clock). Molecular clock enforcements were tested using a 55°C. This was followed by puriWcation using phenol/chlo- Shimodaira and Hasegawa test (Shimodaira and Hasegawa roform extractions and alcohol precipitation (Sambrook 1999) implemented by PAUP. Genetic divergence was esti- et