Abstract
Allele frequency variation is described at nine polymorphic enzyme loci in 21 samples from populations of the introduced Giant Toad, Bufo marinus, in the region of Townsville in north Queensland, Australia. Some of these populations appear to have been established through the introgression of other populations that previously had been isolated. Comparisons of allele frequencies at three polymorphic loci between the introgressed populations and the original populations are used to obtain admixture estimates. These are used to estimate a rate of gene flow among the populations of approximately 2 km/year. This is consistent with an estimate based on the rate at which Bufo marinus has colonised new areas in Australia when discontinuities in the pattern of this colonisation are taken into account.The estimate of gene flow is combined with published data on population density to estimate neighbourhood size. The estimate obtained is substantially greater than the effective population size estimate determined previously from data on allele frequency variances in other populations. This discrepancy is most likely due to inaccuracies in the population density estimates, to underestimates of the extent of offspring number variance and perhaps to occasional departures from sex ratio parity. It has important implications for the study of the genetic structure of populations which are discussed.
Similar content being viewed by others
Article PDF
References
Baker, A E M. 1981. Gene flow in house mice: introduction of a new allele into free living populations. Evolution, 35, 243–258.
Cavalli-Sforza, L L, and Bodmer, W F. 1971. The Genetics of Human Populations Freeman, San Francisco.
Coyne, J A, Boussy, I A, Prout, T, Bryant, S H, Jones, J S, and Moore, J A. 1982. Long-distance migration of Drosophila. Amer Natur, 119, 589–595.
Crawford, M H, Gonzalez, N L, Schanfield, M S, Dykes, D D, Skradski, K, and Polesky, H F. 1981. The black Caribs (Garifuna) of Livingston, Guatemala: Genetic markers and admixture estimates. Hum Biol, 53, 87–103.
Daly, J C. 1981. Effects of social organization and environmental diversity on determining the genetic structure of a population of the wild rabbit, Oryctolagus cuniculus. Evolution, 35, 689–706.
Eanes, W F, and Koehn, R K. 1978. An analysis of genetic structure in the monarch butterfly, Danaus plexippus. Evolution, 32, 784–797.
Easteal, S. 1981. The history of introductions of Bufo marinus (Amphibia: Anura); a natural experiment in evolution. Biol J Linn Soc, 16, 93–113.
Easteal, S. 1982. The genetics of introduced populations of the giant toad, Bufo marinus; a natural experiment in evolution. Ph.D. Thesis, Griffith University.
Easteal, S. 1985a. The ecological genetics of introduced populations of the giant toad, Bufo marinus. II. Effective population size. Genetics, 110, 107–122.
Easteal, S. 1985b. The ecological genetics of introduced populations of the giant toad Bufo marinus. III. Geographical patterns of variation. Evolution, 39, 1065–1075.
Easteal, S, and Floyd, R B. 1985. The ecological genetics of introduced populations of the giant toad, Bufo marinus. Dispersal and neighbourhood size. Biol J Linn Soc (in press).
Easteal, S, Van Beurden, E K, Floyd, R B, and Sabath, M D. 1985. Continuing spread of Bufo marinus in Australia: Range expansion between 1974 and 1980. J Herpetol, 19, 185–188.
Ehrlich, P R, and Raven, P H. 1969. Differentiation of populations. Science, 165, 1228–1232.
Endler, J A. 1977. Geographic Variation, Speciation and Clines Princeton University Press, Princeton.
Floyd, R B, Boughton, W C, Easteal, S, Sabath, M D, and Van Beurden, E K. 1981. Distribution records of the marine toad (Bufo marinus). Part 1, Australia (2nd edition). AES Working Paper 3/81. School of Australian Environmental Studies, Griffith University.
Franco, M H L P, Weimer, T A, and Salzano, F M. 1981. Blood polymorphisms and racial admixture in two Brazilian populations. Amer J Phys Anthrop 58, 127–132.
Gill, D E. 1978. Effective population size and interdemic migration rates in a metapopulation of the red-spotted newt, Notophthalamus vividescens (Rafinesque). Evolution, 32, 839–849.
Handel, S N. 1983. Contrasting gene flow patterns and genetic subdivision in adjacent populations of Cucumis sativus (Cucurbitaceae). Evolution, 37, 760–771.
Jones, J S, Bryant, S H, Lewontin, R C, Moore, J A, and Prout, T. 1981. Gene flow and geographical distribu-tion of a molecular polymorphism in Drosophila pseudoobscura. Genetics, 98, 157–178.
Larson, A, Wake, D B, and Yanev, K P. 1984. Measuring gene flow among populations having high levels of genetic fragmentation. Genetics, 106, 293–308.
Mayr, E. 1963. Animal Species and Evolution. Harvard Univ. Press, Cambridge, Mass.
McCauley, D E. 1983. Gene flow distances in natural populations of Tetraopes tetraophthalamus. Evolution, 37, 1239–1246.
Mungomery, R W. 1937. The present situation regarding the giant American toad in Queensland. Cane Grower's QuartBull, 5, 12.
Nei, M. 1978. Estimation of average heterozygosity and genetic distance from a small number of individuals. Genetics, 89, 583–590.
Patton, J L, and Feder, J H. 1981. Microspatial genetic heterogeneity in pocket gophers: Non random breeding and drift. Evolution, 35, 912–920.
Sabath, M D, Boughton, W C, and Easteal, S. 1981. Expansion of the range of the introduced toad Bufo marinus in Australia from 1935 to 1974. Copeia, 1981, 676–680.
Schaal, B A. 1980. Measurement of gene flow in Lupinus texensis. Nature, 284, 450–451.
Singleton, G E, and Hay, D A. 1983. The effect of social organization on reproductive success and gene flow in colonies of wild house mice, Mus musculus. Behav Ecol Sociobiol, 11, 49–56.
Slatkin, M. 1981. Estimating levels of gene flow in natural populations. Genetics, 99, 323–321.
Sneath, P H A, and Sokal, R R. 1973. Numerical Taxonomy. Freeman, San Francisco.
Stanley, S M. 1979. Microevolution: Pattern and Process Freeman, San Francisco.
Ward, R H, and Neel, J V. 1976. The genetic structure of a tribal population, the Yanomama indians. XIV. Clines and their interpretation. Genetics, 82, 103–121.
Workman, P L. 1973. Genetic analysis of hybrid populations. In Methods and Theories of Anthropological Genetics, ed. M. H. Crawford and P. L. Workman, pp 117–150. University of New Mexico Press, Albuquerque.
Workman, P L, and Niswander, J D. 1969. Population studies on southwestern Indian tribes. II. Local genetic differentiation in the Papago. Amer J Hum Gent, 22, 24–49.
Wright, S. 1943. Isolation by distance. Genetics, 16, 97–159.
Zera, A J. 1981. Genetic structure of two species of waterstriders (Gerridae: Hemiptera) with differing degrees of winglessness. Evolution, 35, 218–226.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Easteal, S. The ecological genetics of introduced populations of the Giant Toad, Bufo marinus. IV. Gene flow estimated from admixture in Australian populations. Heredity 56, 145–156 (1986). https://doi.org/10.1038/hdy.1986.25
Received:
Issue date:
DOI: https://doi.org/10.1038/hdy.1986.25
