Bruce Turner

Bruce Turner
Virginia Polytechnic Institute and State University | VT · Department of Biological Sciences

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125
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Publications

Publications (125)
Preprint
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Small populations with limited geographic distributions are predicted to be threatened by inbreeding and lack of genetic diversity, both of which may negatively impact fitness and exacerbate population decline. One of the most extreme natural examples is the Devils Hole pupfish (Cyprinodon diabolis), an iconic and critically endangered species with...
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Significance Most biodiversity evolved in rapid bursts of new species, adaptations, and ecological niches. However, this process of adaptive radiation is poorly understood. We used large-scale genomic sequencing across the entire Caribbean range of pupfishes to understand why radiation in this group is restricted to a single Bahamian island. We fou...
Preprint
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To investigate the origins and stages of vertebrate adaptive radiation, we reconstructed the spatial and temporal histories of genetic variants underlying major phenotypic axes of diversification from the genomes of 202 Caribbean pupfishes. Ancient standing variation from disparate spatial sources was reassembled into new combinations which are und...
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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 ma...
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Our recent estimation of the divergence time and isolation of Death Valley pupfishes, including the iconic Devil’s Hole pupfish (DHP), rewrote widespread assumptions about this group. These species were previously assumed to be relic populations isolated over millions of years; our genomic analyses indicated recent colonization of Devil’s Hole with...
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One of the most endangered vertebrates, the Devils Hole pupfish Cyprinodon diabolis, survives in a nearly impossible environment: a narrow subterranean fissure in the hottest desert on earth, Death Valley. This species became a conservation icon after a landmark 1976 US Supreme Court case affirming federal groundwater rights to its unique habitat....
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We used 32 polymorphic microsatellite loci to investigate how a mixed-mating system affects population genetic structure in Central American populations (N = 243 individuals) of the killifish Kryptolebias marmoratus (mangrove rivulus), 1 of 2 of the world's only known self-fertilizing vertebrates. Results were also compared with previous microsatel...
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The extent to which genome sizes and other nucleotypic factors influence the phyletic diversification of lineages has long been discussed but remains largely unresolved. In the present work, we present evidence that the genomes of at least 16 species of the neotropical rivulid killifish genus Austrolebias are unusually large, with an average DNA co...
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The annual killifish (Cyprinodontidae) species Pterolebias hoignei and Pterolebias zonatus from the Orinoco basin, Venezuela, have been regarded as conspecific ecomorphs, but P. hoignei has a diploid number of 46, whereas P. zonatus has a diploid number of 42. Metacentric chromosome counts also differ between these two species. Pterolebias hoignei...
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The coastal South American species Cyprinodon dearborni contains two lineages distinct at both mitochondrial and nuclear loci. One appears to be a long-term South American endemic, whereas the other is a more recent colonizer related to the widespread Cyprinodon variegatus.
Article
Three pupfish (Cyprinodon) morphotypes (two endemic) occur in some of the young (6000 ypb) saline lakes on the Bahamian island of San Salvador. The ‘normal’ morph, a detritivore/omnivore, is not different in its general features from Cyprinodon variegatus from other Bahamian islands. ‘Bulldog’ is a scale-eater/piscivore that preys upon normal pupfi...
Article
Reports of new habitats for a major group of organisms are rare. Fishes display diverse adaptations for temporary (amphibious) existence on land, but to our knowledge, none have ever been reported regularly living inside emergent logs. Here, we show that the mangrove killifish, Kryptolebias marmoratus, a species previously known to emerse (leave th...
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We employ a battery of 33 polymorphic microsatellite loci to describe geographical population structure of the mangrove killifish (Kryptolebias marmoratus), the only vertebrate species known to have a mixed-mating system of selfing and outcrossing. Significant population genetic structure was detected at spatial scales ranging from tens to hundreds...
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Question: Does the persistently high frequency of males in the Twin Cays population of Kryptolebias (formerly Rivulus) mamoratus (Pisces: Rivulidae), a self-fertilizing, androdioecious species, result from ecophenotypic effects or genetic divergence from other populations? Hypothesis: Because males are easily produced in the laboratory by temperatu...
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Mixed-mating systems, in which hermaphrodites can either self-fertilize or outcross, are common in many species of plants and invertebrates and have been informative models for studying the selective forces that can maintain both inbreeding and outbreeding in populations. Here, we document a remarkable instance of evolutionary convergence to an ana...
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The mangrove killifish (Kryptolebias marmoratus) is the only vertebrate known to be capable of self-fertilization. Its gonad is typically an ovotestis that simultaneously produces eggs and sperm, and fertilization is internal. Although most populations of this species consist primarily or exclusively of hermaphroditic individuals, gonochoristic mal...
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The killifish Rivulus marmoratus is the only known selfing hermaphroditic vertebrate, and males of the species are usually exceedingly rare or non-existent in nature. Collections on several Belize cays in 1988 and 1989 yielded 13.5–24% males. Factors responsible for this unusually high proportion of males are currently not understood. Likewise, the...
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Repetitive sequences are predominant components of eukaryotic genomes, including those of fishes, but they represent largely unchartered territory for the student of fish evolution and population differentiation. Three examples of the use of repetitive sequences are presented. In one, a Hind 111 monomeric unit of an adjacent repeat (satellite) sequ...
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The cyprinodont fish Ri~w1tc.r nlari9?or.ntus is strongly ai%!iated with the red mangrove Rhizophoru mungle and distributed tl~roughout the tropical western Atlantic including the Belize Cays. Vie have studied this animal for 16 years on the cays during six investigations since 1988. We summarize our findings in the field and explore the significan...
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The pupfishes of Death Valley (genus: Cyprinodon) are a classic example of rapid (post-Pleistocene) allopatric divergence with several populations exhibiting striking morphological, physiological, and behavioural differences. However, genetic changes accompanying or causing this divergence have been poorly resolved and/or difficult to detect. In or...
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Conventional Giemsa and silver staining techniques were used to analyze the chromosome complement of the “pupfish” Cyprinodon dearborni, using specimens from Margarita Island, Venezuela. This species is of potential interest because of its unique geographic distribution: All other pupfish species are Nearctic or Antellian, and no other Nearctic kil...
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Karyotypes of three species of toadfish (Amphichthys cryptocentrus, Batrachoides manglae and Thalassophryne maculosa), reported here for the first time revealed diploid complements of 46 chromosomes. Karyo-evolutionary trend of these species is discussed. Based on differences in arm number, we suggest that T. maculosa possesses the most evolved kar...
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Rivulus marmoratus is a self-fertilizing hermaphroditic fish found in the tropical Atlantic as populations of homozygous clones, with the exception of a single site in Belize where male fish are abundant and heterozygosity is the norm. The presence of male fish apparently leads to outcrossing and heterozygosity, but males have been found in limited...
Article
Rivulus marmoratus is the only known vertebrate with obligate, synchronous hermaphroditic fertilization. Males can be experimentally induced in the laboratory and are rare or absent in most populations, but at the isolated Twin Cays, Belize, locality, males are relatively abundant. At this locality, evidence of outcrossing has been documented in th...
Article
Rivulus marmoratus is the only known vertebrate with obligate, synchronous hermaphroditic fertilization. Males can be experimentally induced in the laboratory and are rare or absent in most populations, but at the isolated Twin Cays, Belize, locality, males are relatively abundant. At this locality, evidence of outcrossing has been documented in th...
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A population survey of the Death Valley pupfishes (Cyprinodontidae: Cyprinodon sp.) for insertional variation associated with ''Swimmer 1'' (SW1), a retrotransposon family, was conducted with Southern blot hybridization. Numerous polymorphic insertion sites were detected, providing compelling evidence that SW1 has been retrotrans-positionally activ...
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The aplocheiloid killifish Rivulus marmoratus is the only known self-fertilizing hermaphroditic vertebrate. Most natural populations consist almost entirely of hermaphrodites and comprise arrays of homozygous clones. However, in almost all populations thus far studied, clonal variation, as detected with molecular techniques, is very high. A karyolo...
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A large fraction, sometimes the largest fraction, of a eukaryotic genome consists of repeated DNA sequences. Copy numbers range from several thousand to millions per diploid genome. All classes of repetitive DNA sequences examined to date exhibit apparently general, but little studied, patterns of "concerted evolution." Historically, concerted evol...
Article
We used a survey of hypervariable, variable number of tandem repeat (VNTR) loci to detect nuclear genetic differentiation within and among populations of striped bass Morone saxatilis in the lower Chesapeake Bay. This species has been refractory to population genetic analysis because it is depauperate in genetic variability. Previously described mo...
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Full-text available
A large fraction, sometimes the largest fraction, of a eukaryotic genome consists of repeated DNA sequences. Copy numbers range from several thousand to millions per diploid genome. All classes of repetitive DNA sequences examined to date exhibit apparently general, but little studied, patterns of "concerted evolution." Historically, concerted evol...
Article
Previous investigations of natural populations of the hermaphroditic, self-fertilizing fish species Rivulus marmoratus demonstrated a surprising amount of interclonal differentiation among highly polymorphic "DNA fingerprint" loci. The genetic differentiation observed among clones was thought to be the effect of extreme population mixing because of...
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The killifish Rivulus marmoratus, mangrove rivulus, represents the one of the two potentially truly “mangrove dependent” fish species in western Atlantic mangrove ecosystems. The distribution of this species closely parallels the range of red mangroves. These plants and fish exhibit parallel ecological and physiological tolerances to the wide range...
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The Neotropical killifish Rivulus marmoratus is widely distributed, but locally rare, throughout much of coastal south and central Florida. Habitat alteration has affected the species throughout the state, especially on the east coast (Indian River Lagoon) where the destruction of mangroves and impounding of high marsh for mosquito control has alte...
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Several workers have suggested that multilocus multilocus variable number of tandem repeat (VNTR) based ‘DNA fingerprints’ are not useful in detecting differentiation among outbred populations. They suggest that the extremely high mutation rates and complexity associated with multilocus VNTR fragments make detection of interpopulation differences a...
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The canonical monomers (approximately 170 bp) of an abundant (1.9 x 10(6) copies per diploid genome) satellite DNA sequence family in the genome of Cyprinodon variegatus, a "pupfish" that ranges along the Atlantic coast from Cape Cod to central Mexico, are divergent in base sequence in 10 of 12 samples collected from natural populations. The diverg...
Article
The fish species Cyprinidon artifrons, Floridichthys carpio, and Gambusia yucatana inhabit shallow mangrove ponds off the coast of Belize. Portions of these ponds experience a diurnal temperature change from 26 °C at night to 40 °C and above during midday. Repeated field observations indicate Cyprinidon prefer the warmer (and much larger) portions...
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Recombination is unknown in natural populations of Rivulus marmoratus, a selfing hermaphrodite, and genetic variation is likely due to mutation alone. DNA fingerprinting with an array of microsatellite [e.g., (CT)9] and minisatellite (e.g., the 33.15 core sequence) probes reveals very high clonal diversity within samples of seven Floridian populati...
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The measurement of clonal heterogeneity is central to understanding the evolutionary and population genetics of the roughly 50 species of vertebrates that lack effective genetic recombination. Simple-sequence DNA fingerprinting with oligonucleotide probes (CAC)5 and (GACA)4 is a sensitive and efficient means of detecting this heterogeneity in natur...
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This report provides a synopsis of fil.'1d studil'S of RiI'll/liS man1l0ralllS from two population surveys of mangro\'C islands adjacent to the Belize barrier fl'Cf and observations made over fifteen years at several sites in South Florida. Florida populations consist ne.uly exclusively of hermaphrodites (> 99%), while the Belize populations contai...
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An allozyme survey of thirty-four loci from seventeen populations of the goodeid fish Goodea atripinnis was conducted to examine the extent of differentiation between continuous and isolated populations. Differentiation, based upon the Rogers genetic distance, among a group of populations isolated since the Pleistocene was no greater than that obse...
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Isozyme electrophoresis was used to assess biochemical genetic variation in spawning striped bass Morone saxatilis captured from two tributaries of Kerr Reservoir, Virginia-North Carolina in 1979 and 1980. Only 3 of 56 scorable loci were polymorphic. Average heterozygosity was estimated at 1.6%, similar to measurements made on anadromous Atlantic c...
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An electrophoretic survey of enzyme polymorphisms was conducted on samples of Goodea atripinnis and Chapalichthys encaustus from Lake Chapala, Mexico, to determine the extent of intralacustrine differentiation in these two species. Statistical analyses revealed significant overall genic heterogeneity within the lake for both species. The level of h...