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Karyotypes of Eight Species of Toads (Genus Bufo) in North America

Charles J. Cole, Charles H. Lowe and John W. Wright
Copeia
Vol. 1968, No. 1 (Mar. 15, 1968), pp. 96-100
DOI: 10.2307/1441555
Stable URL: http://www.jstor.org/stable/1441555
Page Count: 5
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Karyotypes of Eight Species of Toads (Genus Bufo) in North America
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Abstract

Analysis of chromosomes from representatives of most species groups of Bufo occurring in North America reveals striking similarities in the karyotypes of B. alvarius, B. cognatus, B. microscaphus, B. punctatus, B. retiformis, B. valliceps, and B. woodhousii. Each of these species has a diploid number of 22 chromosomes (metacentric and submetacentric), of which 12 are relatively large and 10 are distinctly smaller. The largest pair of chromosomes (metacentric) has a distinct secondary constriction near the centromere. The karyotype of B. marinus sharply differs from that of the other species examined. It has a diploid number of 22 chromosomes (metacentric and submetacentric), of which 12 are relatively large, eight are relatively small, and two are intermediate in size. The intermediate-sized pair of chromosomes (submetacentric) has a distinct secondary constriction in the short arm near the centromere. The karyotype of B. marinus is strikingly similar to that of the South American B. arenarum. These data support the hypothesis that B. arenarum and B. marinus were derived from an ancient Bufo stock in South America that was isolated from the stock giving rise to the majority of the North American species; presumably B. marinus dispersed northward after such isolation.

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