Population genetics of the spotted seahorse (Hippocampus kuda) in Thai waters : implications for conservation

A population genetics approach was used to investigate the genetic diversity of the spotted seahorse (Hippocampus kuda) in Thai waters; specifically, the degree of genetic differentiation and species evolution was inferred from sequence analysis of 353 bp of the mitochondrial (mt)DNA control region. The data were then used to identify discrete populations in Thai waters for effective conservation and management. Spotted seahorses were collected from 4 regions on the east and west coasts of the Gulf of Thailand and a geographically separated region in the Andaman Sea. Of the 101 mtDNA sequences analyzed, 7 haplotypes were identified, 5 of which were shared among individuals from the east and west coasts of the Gulf of Thailand. The remaining haplotypes were restricted to individuals from the Andaman Sea. Nucleotide and haplotype diversities were similar within the Gulf of Thailand samples, whereas diversity was lower in the Andaman Sea sample. Genetic differentiation appeared between pairs of samples from the Gulf of Thailand and Andaman Sea (FST, p &lt; 0.0001). A large genetic variance appeared among the 2 population groups (94.46%, &Phi;CT = 0.94464, p &lt; 0.01). A Neighbor-joining tree indicated that individuals from the Gulf of Thailand and Andaman Sea formed 2 phylogenetically distinct groups, which were segregated into different population-based clades. While results reported here indicate that populations from the Gulf of Thailand and Andaman Sea should be treated as separate conservation units, a larger sample size from the Andaman Sea is required to confirm this genetic partitioning and low level of diversity observed in the present study.<br /

A half-century of studies on a chromosomal hybrid zone of the house mouse

The first natural chromosomal variation in the house mouse was described nearly 50 years ago in Val Poschiavo on the Swiss side of the Swiss–Italian border in the Central Eastern Alps. Studies have extended into neighboring Valtellina, and the house mice of the Poschiavo-Valtellina area have been subject to detailed analysis, reviewed here. The maximum extent of this area is 70 km, yet it has 4 metacentric races and the standard 40-chromosome telocentric race distributed in a patchwork fashion. The metacentric races are characterized by highly reduced diploid numbers (2n = 22–26) resulting from Robertsonian fusions, perhaps modified by whole-arm reciprocal translocations. The races hybridize and the whole Poschiavo-Valtellina area can be considered a “hybrid zone.” The studies of this area have provided insights into origin of races within hybrid zones, gene flow within hybrid zones and the possibility of speciation in hybrid zones. This provides a case study of how chromosomal rearrangements may impact the genetic structure of populations and their diversification.Fil: Giménez, Mabel Dionisia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina. University of York; Reino UnidoFil: Förster, Daniel W.. Leibniz-institute For Zoo And Wildlife Research; Alemania. University of York; Reino UnidoFil: Jones, Eleanor P.. University of York; Reino Unido. Fera Science; Reino UnidoFil: Jóhannesdóttir, Fríđa. University of York; Reino Unido. Cornell University; Estados UnidosFil: Gabriel, Sofia I.. Universidade de Lisboa; Portugal. University of York; Reino UnidoFil: Panithanarak, Thadsin. Burapha University; Tailandia. University of York; Reino UnidoFil: Scascitelli, Moira. University of York; Reino UnidoFil: Merico, Valeria. Universita Di Pavia; ItaliaFil: Garagna, Silvia. Universita Di Pavia; ItaliaFil: Searle, Jeremy B.. University of York; Reino Unido. Cornell University; Estados UnidosFil: Hauffe, Heidi C.. Instituto Agrario San Michele All'adige Fondazione Edmund Mach. Centro Ricerca E Innovazione; Italia. University of York; Reino Unid

Molecular studies of races, raciation, speciation and species identification

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Data from: Empirical demonstration of hybrid chromosomal races in house mice

Western house mice (Mus musculus domesticus) and common shrews (Sorex araneus) are important models for study of chromosomal speciation. Both had ancestral karyotypes consisting of telocentric chromosomes, and each is subdivided into numerous chromosomal races many of which have resulted from fixation of new mutations (Robertsonian fusions and whole-arm reciprocal translocations). However, some chromosomal races in both species may alternatively have originated through hybridization, with particular homozygous recombinant products reaching fixation. Here, we demonstrate the process of generation of hybrid chromosomal races for the first time in either species using molecular markers. Analysis of centromeric microsatellite markers show that the Mid Valtellina (IMVA) and Upper Valtellina (IUVA) chromosomal races of the house mouse are recombinant products of hybridization of the Lower Valtellina (ILVA) and Poschiavo (CHPO) chromosomal races, supporting earlier theoretical analysis. IMVA and IUVA occupy a small area of the Italian Alps where ILVA makes contact with CHPO. IUVA and CHPO have previously been shown to be reproductively isolated in one village, emphasizing that hybrid chromosomal races in small mammals, as in plants, have the potential to be part of the speciation process

Data from: Empirical demonstration of hybrid chromosomal races in house mice

Western house mice (Mus musculus domesticus) and common shrews (Sorex araneus) are important models for study of chromosomal speciation. Both had ancestral karyotypes consisting of telocentric chromosomes, and each is subdivided into numerous chromosomal races many of which have resulted from fixation of new mutations (Robertsonian fusions and whole-arm reciprocal translocations). However, some chromosomal races in both species may alternatively have originated through hybridization, with particular homozygous recombinant products reaching fixation. Here, we demonstrate the process of generation of hybrid chromosomal races for the first time in either species using molecular markers. Analysis of centromeric microsatellite markers show that the Mid Valtellina (IMVA) and Upper Valtellina (IUVA) chromosomal races of the house mouse are recombinant products of hybridization of the Lower Valtellina (ILVA) and Poschiavo (CHPO) chromosomal races, supporting earlier theoretical analysis. IMVA and IUVA occupy a small area of the Italian Alps where ILVA makes contact with CHPO. IUVA and CHPO have previously been shown to be reproductively isolated in one village, emphasizing that hybrid chromosomal races in small mammals, as in plants, have the potential to be part of the speciation process

Empirical demonstration of hybrid chromosomal races in house mice

Western house mice (Mus musculus domesticus) and common shrews (Sorex araneus) are important models for study of chromosomal speciation. Both had ancestral karyotypes consisting of telocentric chromosomes, and each is subdivided into numerous chromosomal races many of which have resulted from fixation of new mutations (Robertsonian fusions and whole-arm reciprocal translocations). However, some chromosomal races in both species may alternatively have originated through hybridization, with particular homozygous recombinant products reaching fixation. Here, we demonstrate the process of generation of hybrid chromosomal races for the first time in either species using molecular markers. Analysis of centromeric microsatellite markers show that the Mid Valtellina (IMVA) and Upper Valtellina (IUVA) chromosomal races of the house mouse are recombinant products of hybridization of the Lower Valtellina (ILVA) and Poschiavo (CHPO) chromosomal races, supporting earlier theoretical analysis. IMVA and IUVA occupy a small area of the Italian Alps where ILVA makes contact with CHPO. IUVA and CHPO have previously been shown to be reproductively isolated in one village, emphasizing that hybrid chromosomal races in small mammals, as in plants, have the potential to be part of the speciation process.Fil: Giménez, Mabel Dionisia. University of York; Reino Unido. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Panithanarak, Thadsin. University of York; Reino Unido. Burapha University. Institute of Marine Science; TailandiaFil: Hauffe, Heidi C.. Instituto Agrario San Michele All'adige Fondazione Edmund Mach. Centro Ricerca E Innovazione; Italia. University of York; Reino UnidoFil: Searle, Jeremy B.. University of York; Reino Unido. Cornell University; Estados Unido

Microsatellite genotypes

Spreadsheet of all microsatellite genotypes used in the stud

Data from: Understanding the basis of diminished gene flow between hybridizing chromosome races of the house mouse

Speciation may be promoted in hybrid zones if there is an interruption to gene flow between the hybridizing forms. For hybridizing chromosome races of the house mouse in Valtellina (Italy) distinguished by whole-arm chromosomal rearrangements, previous studies have shown that there is greater interruption to gene flow at the centromeres of chromosomes that differ between the races than at distal regions of the same chromosome or at the centromeres of other chromosomes. Here, by increasing the number of markers along race-specific chromosomes, we reveal a decay in between-race genetic differentiation from the centromere to the distal telomere. For the first time, we use simulation models to investigate the possible role of recombination suppression and hybrid breakdown in generating this pattern. We also consider epistasis and selective sweeps as explanations for isolated chromosomal regions away from the centromere showing differentiation between the races. Hybrid breakdown alone is the simplest explanation for the decay in genetic differentiation with distance from the centromere. Robertsonian fusions/whole-arm reciprocal translocations are common chromosomal rearrangements characterizing both closely related species and races within species, and this fine-scale empirical analysis suggests that the unfitness associated with these rearrangements in the heterozygous state may contribute to the speciation process

Understanding the basis of diminished gene flow between hybridizing chromosome races of the house mouse

Speciation may be promoted in hybrid zones if there is an interruption to gene flow between the hybridizing forms. For hybridizing chromosome races of the house mouse in Valtellina (Italy) distinguished by whole-arm chromosomal rearrangements, previous studies have shown that there is greater interruption to gene flow at the centromeres of chromosomes that differ between the races than at distal regions of the same chromosome or at the centromeres of other chromosomes. Here, by increasing the number of markers along race-specific chromosomes, we reveal a decay in between-race genetic differentiation from the centromere to the distal telomere. For the first time, we use simulation models to investigate the possible role of recombination suppression and hybrid unfitness in generating this pattern. We also consider epistasis and selective sweeps as explanations for isolated chromosomal regions away from the centromere showing differentiation between the races. Hybrid unfitness alone is the simplest explanation for the decay in genetic differentiation with distance from the centromere. Robertsonian fusions/whole-arm reciprocal translocations are common chromosomal rearrangements characterizing both closely related species and races within species and this fine-scale empirical analysis suggests that the unfitness associated with these rearrangements in the heterozygous state may contribute to the speciation process