Genealogical relationships of southern Ontario polyploid unisexual salamanders (genus Ambystoma) inferred from intergenomic exchanges and major rDNA cytotypes
- 115 Downloads
North American unisexual salamanders in the genus Ambystoma are common around the Great Lakes region of North America. They contain an almost identical mitochondrial genome across their distribution that is unlike that of any of the four species whose genomes may be included in their nuclei. Thus, sequence-based phylogenies of unisexual populations are confusing. We used chromosomal intergenomic exchanges and major rDNA cytotypes as combined cytogenetic markers to tentatively construct a genealogy of unisexual Ambystoma in southern Ontario. We employed GISH and sequential/simultaneous GISH/FISH-rDNA to reveal intergenomic exchanges and rDNA cytotypes in unisexual A. laterale – 2 jeffersonianum (LJJ) triploids and their tetraploid derivative A. laterale – 3 jeffersonianum (LJJJ). We identified 10 different patterns of intergenomic exchanges from 18 isolated populations and used them as primary cytogenetic markers. Major rDNA cytotypes served as independent and supplementary markers. Our results suggest that current LJJ and LJJJ populations in southern Ontario are likely derived from a few unisexual individuals. Intergenomic exchanges are common phenomena and widely distributed in the salamanders of the A. laterale – A. jeffersonianum unisexual complex. Integration of GISH and FISH can exhibit multiple unrelated chromosomal markers on the same chromosome spread and demonstrate lineage relationships in unisexual populations. Similar methods may be applied for studying the molecular cytogenetics of other unisexuals to improve our understanding of their genealogical relationships and historical dispersal.
Key wordsAmbystoma cytotypes fluorescence in situ hybridization GISH intergenomic exchanges polyploid rDNA unisexual
Unable to display preview. Download preview PDF.
- Avise JC (2000) Phylogeography: The History and Formation of Species. Cambridge, MA: Harvard University Press.Google Scholar
- Avise JC, Quattro JM, Vrijenhoek RC (1992) Molecular clones within organismal clones. In: MK Hecht, ed. Evolutionary Biology 26. New York: Plenum Press, pp. 225–246.Google Scholar
- Bogart JP (1982) Ploidy and genetic diversity in Ontario salamanders of the Ambystoma jeffersonianum complex revealed through an electrophoretic examination of larvae. Can J Zool 60: 848–855.Google Scholar
- Bogart JP (2003) Genetics and systematics of hybrid species. In Sever DM, ed. Reproductive Biology and Phylogeny of Urodela. Enfield, New Hampshire: Science Publishers, Inc., pp. 109–134.Google Scholar
- Bogart JP, Klemens MW (1997) Hybrids and genetic interactions of mole salamanders (Ambystoma jeffersonianum and A. laterale) (Amphibia: Caudata) in New York and New England. Am Mus Novit 3128: 1–78.Google Scholar
- Conant R, Collins JT (1998) Reptiles and Amphibians: Eastern and Central North America, 3rd edn. New York: Houghton Mifflin.Google Scholar
- Petranka JW (1998) Salamanders of the United States and Canada. Washington DC: Smithsonian Institution Press.Google Scholar
- Sola L, Galetti PM, Monaco PJ, Rasch EM (1997) Cytogenetics of bisexual/unisexual species of Poecilia. VI. Additional nucleolus organizer region chromosomal clones of Poecilia formosa (Amazon molly) from Texas, with a survey of chromosomal clones detected in the Amazon molly. Heredity 78: 612–619.CrossRefGoogle Scholar
- Taylor AS, Bogart JP (1990) Karyotypic analyses of four species of Ambystoma (Amphibia, Caudata) which have been implicated in the production of all-female hybrids. Genome 33: 837–844.Google Scholar