Comparative genome mapping between Chinook salmon (Oncorhynchus tshawytscha) and rainbow trout (O. mykiss) based on homologous microsatellite loci.

Comparative genome mapping can rapidly facilitate the transfer of DNA sequence information from a well-characterized species to one that is less described. Chromosome arm numbers are conserved between members of the teleost family Salmonidae, order Salmoniformes, permitting rapid alignment of large syntenic blocks of DNA between members of the group. However, extensive Robertsonian rearrangements after an ancestral whole-genome duplication event has resulted in different chromosome numbers across Salmonid taxa. In anticipation of the rapid application of genomic data across members of the Pacific salmon genus Oncorhynchus, we mapped the genome of Chinook salmon (O. tshawytscha) by using 361 microsatellite loci and compared linkage groups to those already derived for a well-characterized species rainbow trout (O. mykiss). The Chinook salmon female map length was 1526 cM, the male map 733 cM, and the consensus map between the two sexes was 2206 cM. The average female to male recombination ratio was 5.43 (range 1-42.8 across all pairwise marker comparisons). We detected 34 linkage groups that corresponded with all chromosome arms mapped with homologous loci in rainbow trout and inferred that 16 represented metacentric chromosomes and 18 represented acrocentric chromosomes. Up to 13 chromosomes were conserved between the two species, suggesting that their structure precedes the divergence between Chinook salmon and rainbow trout. However, marker order differed in one of these linkage groups. The remaining linkage group structures reflected independent Robertsonian chromosomal arrangements, possibly after divergence. The putative linkage group homologies presented here are expected to facilitate future DNA sequencing efforts in Chinook salmon.

Genetic population structure and mobility of two nectar-feeding bats from Venezuelan deserts: inferences from mitochondrial DNA.

Glossophaga longirostris and Leptonycteris curasoae are nectar-feeding bats associated with arid zones in northern South America. Despite their close phylogenetic relationship, sympatric condition and niche similarities, morphological and ecological evidence suggest that these species differ in dispersal capabilities. Using mitochondrial DNA, we tested the hypothesis that these species exhibit different levels of population structure that are congruent with their particular movement capabilities. We sequenced a section of the control region of mtDNA for 41 G. longirostris and 42 L. curasoae from 11 zones in Venezuela. Population subdivision in G. longirostris (FST = 0.725) was considerably higher than in L. curasoae (FST = 0.167). L. curasoae individuals shared haplotypes at greater distances (812 km) than G. longirostris (592 km). Our results offer preliminary evidence for one of two possible scenarios, either greater mobility in L. curasoae or a higher degree of female philopatry in G. longirostris.