Insight Into Genomic Changes Accompanying Divergence: Genetic Linkage Maps and Synteny ofLucania goodeiandL. parvaReveal a Robertsonian Fusion

Abstract

Linkage maps are important tools in evolutionary genetics and in studies of speciation. We performed a karyotyping study and constructed high-density linkage maps for two closely related killifish species, Lucania parva and L. goodei, that differ in salinity tolerance and still hybridize in their contact zone in Florida. Using SNPs from orthologous EST contigs, we compared synteny between the two species to determine how genomic architecture has shifted with divergence. Karyotyping revealed that L. goodei possesses 24 acrocentric chromosomes (1N) whereas L. parva possesses 23 chromosomes (1N), one of which is a large metacentric chromosome. Likewise, high-density single-nucleotide polymorphism−based linkage maps indicated 24 linkage groups for L. goodei and 23 linkage groups for L. parva. Synteny mapping revealed two linkage groups in L. goodei that were highly syntenic with the largest linkage group in L. parva. Together, this evidence points to the largest linkage group in L. parva being the result of a chromosomal fusion. We further compared synteny between Lucania with the genome of a more distant teleost relative medaka (Oryzias latipes) and found good conservation of synteny at the chromosomal level. Each Lucania LG had a single best match with each medaka chromosome. These results provide the groundwork for future studies on the genetic architecture of reproductive isolation and salinity tolerance in Lucania and other Fundulidae.

Hybridization and introgression in two ecologically dissimilarFundulushybrid zones

“…Berdan et al. () demonstrated that Robertsonian fusion has played a key role in divergence and reproductive isolation between hybridizing species in another genus of fundulids ( Lucania ). Members of the F. notatus species complex similarly exhibit substantial, and potentially significant karyotypic variation.…”

Genomic landscape of reproductive isolation inLucaniakillifish: The role of sex chromosomes and salinity

“…homogametic (Uyeno & Miller 1971;Berdan et al, 2014). Therefore, we evaluated the 297 possibility of a male determining locus as well as a female determining locus.…”

“…In both the L. parva map and the hybrid map, linkage group 1 represents a fusion of two linkage 348 groups (1A and 1B) from L. goodei. All maps had 22 additional linkage groups and are 349 numbered based on synteny (see Berdan et al, 2014) Bayesian Credible Interval 0.5-3 cM; Figure 1A). Using these same data and the L. parva map, 357…”

“…There were also significant interactions between 376 linkage groups 13 and 16, linkage groups 21 and 22, and linkage groups 23 and 2. The 377 interaction between linkage group 21 and 22 is interesting because it involves markers that 378 mapped to linkage group 21 in one species and linkage group 22 in the other (a putative 379 translocation: Berdan et al 2014). All of these interactions among loci involved an over-380…”

“…For each sample, the supernatant was removed leaving 220 behind the protein pellet. Six hundred µl of isopropanol was added and the sample was kept at -Li et al, 2008) following methods used for constructing L.parva and L. goodei 242 maps as described inBerdan et al (2014).…”