Regional structuring of genetic variation in short-lived rock pool populations of Branchipodopsis wolfi (Crustacea: Anostraca)

Abstract The genetic structure of three metapopulations of the southern African anostracan Branchipodopsis wolfi was compared by analysing allozyme variation at four loci (PGM, GPI, APK, AAT). In total, 17 local populations from three sites (metapopulations) were analysed from rock pools in south-eastern Botswana ranging from 0.2 to 21 m2 in surface area. In three populations we found significant deviations from Hardy-Weinberg (H-W) equilibrium at one or more loci due to heterozygote deficiencies. Genetic variability at one site was significantly lower than at the other sites, which may be linked to a greater incidence of extinction and recolonisation, as the basins at this site are shallower and have shorter hydrocycles. Across all local populations, a significant level of population differentiation was revealed. More than 90% of this variation was explained by differentiation among sites (metapopulations), although this differentiation did not correlate with geographic distance, or with environmental variables. Genetic differentiation among populations within metapopulations was low, but significant at all sites. At only one of the sites was a significantly positive association measured between genetic and geographic distance among local populations. Our data suggest that persistent stochastic events and limited effective long-range dispersal appear to dominate genetic differentiation among populations of B. wolfi inhabiting desert rock pools. The lack of association between geographic distance and genetic or ecological differences between rock pool sites is indicative of historical stochastic events. Low heterozygosity, the significant deviations from H-W equilibrium, and the large inter- but low intra-site differentiation are suggestive of the importance of short-range dispersal. Gene flow between metapopulations of B. wolfi appears to be seriously constrained by distances of 2 km or even less.

[1]  T. Kobayashi,et al.  Gene flow in natural populations of Brassica species , 2002 .

[2]  D. Berg,et al.  Genetic differentiation in North American and European populations of the cladoceran Bythotrephes , 1994 .

[3]  E. Thier.  Allozyme variation among natural populations of Holopedium gibberum (Crustacea; Cladocera) , 1994 .

[4]  Sewall Wright,et al.  Variability within and among natural populations , 1978 .

[5]  A. Bohonak,et al.  Dispersal, Gene Flow, and Population Structure , 1999, The Quarterly Review of Biology.

[6]  E. H. Bryant,et al.  Loss of electrophoretic variation in serially bottlenecked populations , 1990, Heredity.

[7]  H. Wolf,et al.  THE GENETIC STRUCTURE OF LARGE‐LAKE DAPHNIA POPULATIONS , 1986, Evolution; international journal of organic evolution.

[8]  Michael E. Gilpin,et al.  The genetic effective size of a metapopulation , 1991 .

[9]  P. Hebert,et al.  Non‐equilibrium gene frequency divergence: persistent founder effects in natural populations , 1992 .

[10]  P. Hebert.  ENZYME VARIABILITY IN NATURAL POPULATIONS OF DAPHNIA MAGNA I. POPULATION STRUCTURE IN EAST ANGLIA , 1974, Evolution; international journal of organic evolution.

[11]  A. Templeton,et al.  Genetic Revolutions in Relation to Speciation Phenomena: The Founding of New Populations , 1984 .

[12]  L. Brendonck,et al.  The maintenance of egg banks in very short-lived pools - a case study with anostracans (Branchiopoda) , 1998 .

[13]  K. Johannesson,et al.  Strong natural selection causes microscale allozyme variation in a marine snail. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[14]  M. Wade,et al.  EXTINCTION AND RECOLONIZATION: THEIR EFFECTS ON THE GENETIC DIFFERENTIATION OF LOCAL POPULATIONS , 1988, Evolution; international journal of organic evolution.

[15]  M. Kimura,et al.  The neutral theory of molecular evolution. , 1983, Scientific American.

[16]  A. Templeton.  Genetic architectures of speciation. , 1982, Progress in clinical and biological research.

[17]  P. Hebert,et al.  GENETIC CONSEQUENCES OF PASSIVE DISPERSAL IN POND‐DWELLING COPEPODS , 1991, Evolution; international journal of organic evolution.

[18]  P. Hebert,et al.  PROVINCIALISM IN PLANKTON: ENDEMISM AND ALLOPATRIC SPECIATION IN AUSTRALIAN DAPHNIA , 1994, Evolution; international journal of organic evolution.

[19]  M. Wheeler.  Studies in Genetics VII , 1971 .

[20]  R. Nichols,et al.  The genetic consequences of long distance dispersal during colonization , 1994, Heredity.

[21]  F. Abreu-Grobois,et al.  Genetic differentiation and speciation in the brine shrimp Artemia. , 1982, Progress in clinical and biological research.

[22]  B. Riddoch.  The adaptive significance of electrophoretic mobility in phosphoglucose isomerase (PGI) , 1993 .

[23]  L. Meester.  Local genetic differentiation and adaptation in freshwater zooplankton populations: Patterns and processes , 1996 .

[24]  B. Taylor,et al.  Chance events, habitat age, and the genetic structure of pond populations , 1994 .

[25]  S. Harrison,et al.  Genetic and evolutionary consequences of metapopulation structure. , 1996, Trends in ecology & evolution.

[26]  M. Nei,et al.  Estimation of average heterozygosity and genetic distance from a small number of individuals. , 1978, Genetics.

[27]  L. Brendonck,et al.  Wind‐borne short‐range egg dispersal in anostracans (Crustacea: Branchiopoda) , 1999 .

[28]  F. Rousset,et al.  AN EXACT TEST FOR POPULATION DIFFERENTIATION , 1995, Evolution; international journal of organic evolution.

[29]  M. Nei,et al.  F‐statistics and analysis of gene diversity in subdivided populations , 1977, Annals of human genetics.

[30]  S. Giessler.  Gene flow in the Daphnia longispina hybrid complex (Crustacea, Cladocera) inhabiting large lakes , 1997, Heredity.

[31]  N. Hairston,et al.  Evolutionary and ecological aspects of crustacean diapause , 1998 .

[32]  G. E. Hutchinson,et al.  A treatise on limnology. , 1957 .

[33]  G. E. Hutchinson,et al.  A Treatise on Limnology Vol. II: Introduction to Lake Biology and the Limnoplankton , 1967 .

[34]  Genetic population structure of the fairy shrimp Branchinecta coloradensis (Anostraca) in the Rocky Mountains of Colorado , 1998 .

[35]  M. Gilpin,et al.  Metapopulation Biology: Ecology, Genetics, and Evolution , 1997 .

[36]  P. Hebert.  Ecological differences between genotypes in a natural population of Daphnia magna , 1974, Heredity.

[37]  G. Carvalho,et al.  Microgeographic genetic differentiation in the intertidal isopod Jaera albifrons Leach. II. Temporal variation in allele frequencies , 1995 .

[38]  M. Lynch.  The consequences of fluctuating selection for isozyme polymorphisms in Daphnia. , 1987, Genetics.

[39]  E. Thompson,et al.  Performing the exact test of Hardy-Weinberg proportion for multiple alleles. , 1992, Biometrics.

[40]  N. Mantel.  The detection of disease clustering and a generalized regression approach. , 1967, Cancer research.

[41]  P. Leberg.  EFFECTS OF POPULATION BOTTLENECKS ON GENETIC DIVERSITY AS MEASURED BY ALLOZYME ELECTROPHORESIS , 1992, Evolution; international journal of organic evolution.

[42]  François Rousset,et al.  GENEPOP (version 1.2): population genetic software for exact tests and ecumenicism , 1995 .

[43]  Enzyme variability in natural populations of Daphnia magna , 1976, Genetics.

[44]  W. Rice.  ANALYZING TABLES OF STATISTICAL TESTS , 1989, Evolution; international journal of organic evolution.

[45]  Geographic patterns of genetic differentiation among sexual populations of Daphnia pulex , 1991 .