Marine Stickleback Research Paper

ic skeleton, which is composed of bilateral pelvic spines, trochlear joints, and a concealed girdle that covers part of the fish’s ventral and lateral anatomy. While marine stickleback retained this defensive structure to protect against soft-mouthed predators, freshwater species have experienced both partial and complete loss of the pelvic skeleton, possibly in response to the predators found in their environment. Since fossil evidence supports recent evolution, researchers crossed a marine female stickleback with a substantial pelvic skeleton and a benthic freshwater male from Paxton Lake who possessed a deficient pelvic structure. A single pair of hybrid parents with complete pelvic structures from the F1generation were then bred, resulting
in a F2generation containing 375 adults. The F2progeny were all killed in order to map the evolution of their pelvic structures, and then separated into genotypes based on existing microsatellite markers. The traits being examined were qualitative- unaffected pelvic structure versus any reduction, loss, or dissymmetry- and researchers noted the mendelian 3:1 ratio of normal to altered pelvic skeleton structure. Using qualitative trait linkage (QTL) they found a high correlation between a region on chromosome seven and variance in the pelvic structure size, length, and height. The majority of the variance were mapped to specific chromosomal regions, with a small unassigned percentage deemed to be the responsibility of minor loci that remained undetected due to the nature of the study. The researchers then delved deeper, but isolating the bacterial artificial chromosome clones