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Laboratory Crosses (laboratory + cross)
Selected AbstractsINTERPOPULATION HYBRID BREAKDOWN MAPS TO THE MITOCHONDRIAL GENOMEEVOLUTION, Issue 3 2008Christopher K. Ellison Hybrid breakdown, or outbreeding depression, is the loss of fitness observed in crosses between genetically divergent populations. The role of maternally inherited mitochondrial genomes in hybrid breakdown has not been widely examined. Using laboratory crosses of the marine copepod Tigriopus californicus, we report that the low fitness of F3 hybrids is completely restored in the offspring of maternal backcrosses, where parental mitochondrial and nuclear genomic combinations are reassembled. Paternal backcrosses, which result in mismatched mitochondrial and nuclear genomes, fail to restore hybrid fitness. These results suggest that fitness loss in T. californicus hybrids is completely attributable to nuclear,mitochondrial genomic interactions. Analyses of ATP synthetic capacity in isolated mitochondria from hybrid and backcross animals found that reduced ATP synthesis in hybrids was also largely restored in backcrosses, again with maternal backcrosses outperforming paternal backcrosses. The strong fitness consequences of nuclear,mitochondrial interactions have important, and often overlooked, implications for evolutionary and conservation biology. [source] Fitness differences associated with Pgi SNP genotypes in the Glanville fritillary butterfly (Melitaea cinxia)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2009L. ORSINI Abstract Allozyme variation at the phosphoglucose isomerase (PGI) locus in the Glanville fritillary butterfly (Melitaea cinxia) is associated with variation in flight metabolic rate, dispersal rate, fecundity and local population growth rate. To map allozyme to DNA variation and to survey putative functional variation in genomic DNA, we cloned the coding sequence of Pgi and identified nonsynonymous variable sites that determine the most common allozyme alleles. We show that these single-nucleotide polymorphisms (SNPs) exhibit significant excess of heterozygotes in field-collected population samples as well as in laboratory crosses. This is in contrast to previous results for the same species in which other allozymes and SNPs were in Hardy,Weinberg equilibrium or exhibited an excess of homozygotes. Our results suggest that viability selection favours Pgi heterozygotes. Although this is consistent with direct overdominance at Pgi, we cannot exclude the possibility that heterozygote advantage is caused by the presence of one or more deleterious alleles at linked loci. [source] Differential patterns of hybridization and introgression between the swallowtails Papilio machaon and P. hospiton from Sardinia and Corsica islands (Lepidoptera, Papilionidae)MOLECULAR ECOLOGY, Issue 6 2003R. Cianchi Abstract Proportions of hybridization and introgression between the swallowtails Papilio hospiton, endemic to Sardinia and Corsica, and the holarctic Papilio machaon, were characterized using nine fully diagnostic and two differentiated allozyme loci and a mitochondrial DNA marker. Very low frequencies of F1 hybrids were detected in both Sardinia (0,4%, average 1.4%) and Corsica (0,3%, average 0.5%), as well as of first generation backcrosses (B1). No F2 were observed, in agreement with the hybrid breakdown detected in laboratory crosses. In spite of this minimal current gene exchange, specimens carrying introgressed alleles were found in high proportions in P. machaon but in lower proportions in P. hospiton. Introgression apparently occurred through past hybridization and repeated backcrossing, as evidenced by hybrid index scores and Bayesian assignment tests. Levels of introgression were low (0,1%) at two sex-linked loci and mitochondrial DNA, limited (0.4,2%) at three autosomal loci coding for dimeric enzymes, and high (up to 43%) at four autosomal loci coding for monomeric enzymes. Accordingly, selective filters are acting against foreign alleles, with differential effectiveness depending on the loci involved. The low levels of introgression at sex-linked loci and mitochondrial DNA are in agreement with Haldane's rule and suggest that introgression in P. machaon proceeds mainly through males, owing to a lower fitness of hybrid females. Papilio machaon populations showed higher levels of introgression in Sardinia than in Corsica. The role of reinforcement in the present reproductive isolation between P. machaon and P. hospiton is examined, as well as the evolutionary effects of introgressive hybridization between the two species. [source] Species delimitation in the Acomys cahirinus,dimidiatus complex (Rodentia, Muridae) inferred from chromosomal and morphological analysesBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2007V. VOLOBOUEV Our earlier chromosome banding studies of Acomys cahirinus and Acomys dimidiatus (the latter long considered to be a subspecies of the former) revealed that, despite very close diploid numbers (36 vs. 38), these taxa possess sharply different karyotypes and undoubtedly belong to different species. In this context, the taxonomic status and the relationship between the two chromosomal forms in Sinai (2n = 36) and Israel (2n = 38), chromosomally homozygous across a vast range except for a very narrow hybrid zone, remain poorly documented. Neither of these forms have previously been studied by chromosome banding; thus, the exact nature of chromosomal differences as well as the species to which these forms should be assigned remain unknown. Here, we present the data on comparative G-banding analysis and morphometrics of Acomys from Israel, Sinai, and Saudi Arabia, and a hybrid obtained in laboratory crosses between latter two. The analysis revealed that karyotype of Acomys from Israel is identical to that of Acomys from Saudi Arabia and both are different from that of Acomys from Sinai by one Robertsonian fusion. Therefore, karyotypically, all three are very different from A. cahirinus. It follows from the study that Sinai and probably Arabian peninsula and Minor Asia must be excluded from geographical distribution of A. cahirinus, which is limited from West Sahara to Egypt along Nile river (except Sinai). Furthermore, the synthesis of chromosomal and recent molecular data suggests a phylogeographical scenario explaining the modern distribution of Acomys in the Sinai and Arabian peninsulas and permits the update of the taxonomic status of these populations. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 203,214. [source] | ||||||||||