The genetic architecture of divergence between threespine stickleback species

Abstract

The genetic and molecular basis of morphological evolution is poorly understood, particularly in vertebrates. Genetic studies of the differences between naturally occurring vertebrate species have been limited by the expense and difficulty of raising large numbers of animals and the absence of molecular linkage maps for all but a handful of laboratory and domesticated animals. We have developed a genome-wide linkage map for the threespine stickleback (Gasterosteus aculeatus), an extensively studied teleost fish that has undergone rapid divergence and speciation since the melting of glaciers 15,000 years ago 1 The benthic species feeds on invertebrates near shore and has a great reduction in the amount of body armor, increased body depth, and a decreased number of gill rakers for filtering ingested food. The limnetic species more closely resembles an ancestral marine fish, with more extensive body armor, a longer and more streamlined body, and an increased number of gill rakers. Despite reproductive isolation between the two species in the wild 3-6 , it is possible to establish productive matings between the two species under laboratory conditions 2 . The resulting F1 hybrids are viable and fertile, making it possible to carry out a formal genetic analysis of the number and location of loci responsible for the adaptive morphological differences between these naturally occurring vertebrate species.To develop resources for genome-wide linkage mapping in Gasterosteus aculeatus, we used large-scale library screening and sequencing to identify a collection of genomic and cDNA clones containing microsatellite repeat sequences. Initially, we sequenced of 192 kb of random genomic clones and showed that CA dinucleotides were the most common form of microsatellite in sticklebacks, occurring approximately once every 14 kb. We subsequently screened genomic and cDNA libraries with a (GT) 15 probe, sequenced 3560 clones, and identified 1176 new microsatellite loci. Primers flanking 410 new and 18 previously identified microsatellites 7-9 were designed and used to type a genetic cross between the benthic and limnetic species from Priest Lake, British Columbia (Figure 1). For this cross, an individual Priest benthic female was mated with a single Priest limnetic male, and a single F1 male (B 1 L 1 ) was crossed to a second Priest benthic female (B 2 B 3 ) to generate 103 progeny. Of the 281 markers that amplified robust bands from the F1 and benthic parent, 227 (81%) were polymorphic, and therefore informative, in one or both parents. Higher rates of polymorphism were seen in the F1 male than the benthic female parent (71% vs. 57% of 281 markers), consistent with a greater level of genetic diversity between the distinct populations of benthic and limnetic fish than within the benthic population.The segregation patterns of the 227 informative markers were scored on 92 progeny from the cross, and the 20,884 resulting genotypes were analyzed for linkage using JoinMap software 10 . The markers were ordered into 26 linkage groups co...

Population genomics of parallel phenotypic evolution in stickleback across stream–lake ecological transitions

“…Nonetheless, several studies have been carried out in stickleback, which link markers to morphological traits that differ between the stream-lake sticklebacks. For example, in a cross between benthic and limnetic sticklebacks, Peichel et al [41] mapped the location of QTLs influencing length of the pelvic spines (marker: Chr8 17.7 Mb) and first dorsal spine (marker: Chr1 18.9 Mb; Chr2 20.2 Mb). Although stream -lake fish in the current study differ in dorsal and pelvic spine lengths, none of the outlier regions we identified map near the previously described QTLs.…”

Highly conserved Z and molecularly diverged W chromosomes in the fish genus Triportheus (Characiformes, Triportheidae)

“…Rapid degeneration of recently formed Y chromosomes has been demonstrated in Drosophila (Bachtrog et al, 2008) and sticklebacks (Peichel et al, 2001). However, there are few empirical data for W chromosomes.…”

Physiological and genetic basis for variation in migratory behavior in the three-spined stickleback, Gasterosteus aculeatus

“…3 Schema of thyroid hormone signaling pathways in anadromous and resident forms of three-spined sticklebacks genome size, and generation time are smaller than those of salmonids. QTL mapping of several morphological and behavioral traits has been successfully performed for G. aculeatus (Peichel et al 2001;Colosimo et al 2004Colosimo et al , 2005Cresko et al 2004;Shapiro et al 2004;Albert et al 2008;Kitano et al 2009;Greenwood et al 2011). …”