title: Isolation by distance and stochastic migration in a fragmented population ofProsopis alba.
abstract: OBJECTIVE
  Gene flow through dispersal of seeds and pollen is a fundamental determinant of spatial genetic structure (SGS) in natural populations of trees at different spatial scales. Within continuous populations, restrictions to gene flow should be manifested in a process of local genetic differentiation, known as isolation by distance. The present work examines the SGS of aProsopis albapopulation in a patchy region where urban, forest, and agricultural areas coexist. The analysis discussed here expands our knowledge about the processes affecting the distribution of the genetic variability in populations of disturbed landscapes.
  
  
  METHODS
  Three sites with different landscape and demographic characteristics were analyzed. Seven highly variable microsatellite markers were used to survey the relevance of both isolation by distance and stochastic migration in the SGS of the population.
  
  
  RESULTS
  The analyses showed that (1) the genetic similarity declined with increasing geographic distance, (2) the population may be conceived as a single genetically continuous unit showing spatial differentiation as consequence of isolation by distance, rather than a structured population following the island model, and (3) there is evidence supporting a past immigration event into one of the study sites, which promoted a local pattern of genetic structure.
  
  
  CONCLUSIONS
  These results indicate that in spite of the population fragmentation produced by land-use changes,P. albamaintains the genetic cohesion and a continuous genetic structure in the analyzed area.
authors.affiliation: Universidad de Buenos Aires, Consejo Nacional de lnvestigaciones Científicas y Técnicas, Instituto de Ecología, Genética y Evolución (IEGEBA), Facultad de Ciencias Exactas y Naturales, Departamento Ecología, Genética y Evolución, Genética de Especies Leñosas (GEEL), 1428, Buenos Aires, Argentina learoser@gmail.com.
authors.forename: Leandro G
authors.initials: LG
authors.lastname: Roser
authors.affiliation: Universidad de Buenos Aires, Consejo Nacional de lnvestigaciones Científicas y Técnicas, Instituto de Ecología, Genética y Evolución (IEGEBA), Facultad de Ciencias Exactas y Naturales, Departamento Ecología, Genética y Evolución, Genética de Especies Leñosas (GEEL), 1428, Buenos Aires, Argentina.
authors.forename: Laura I
authors.initials: LI
authors.lastname: Ferreyra
authors.affiliation: Estación Experimental Fernández, Universidad Católica de Santiago del Estero, 4200, Santiago del Estero, Argentina.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Ewens
authors.affiliation: Universidad de Buenos Aires, Consejo Nacional de lnvestigaciones Científicas y Técnicas, Instituto de Ecología, Genética y Evolución (IEGEBA), Facultad de Ciencias Exactas y Naturales. Departamento Ecología, Genética y Evolución, Genética de Poblaciones Aplicada (GPA), 1428, Buenos Aires, Argentina.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Vilardi
authors.affiliation: Universidad de Buenos Aires, Consejo Nacional de lnvestigaciones Científicas y Técnicas, Instituto de Ecología, Genética y Evolución (IEGEBA), Facultad de Ciencias Exactas y Naturales, Departamento Ecología, Genética y Evolución, Genética de Especies Leñosas (GEEL), 1428, Buenos Aires, Argentina.
authors.forename: Beatriz O
authors.initials: BO
authors.lastname: Saidman
mesh_terms: D001118:Argentina; D017753:Ecosystem; D051456:Gene Flow; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D018895:Microsatellite Repeats; D011058:Pollen / Q000235:genetics; D011157:Population Dynamics; D029862:Prosopis / Q000235:genetics* / Q000254:growth & development; D060047:Reproductive Isolation; D058614:Seed Dispersal / Q000235:genetics; D017422:Sequence Analysis, DNA; D013269:Stochastic Processes
keywords: Fabaceae; Prosopis alba; isolation by distance; kinship; landscape genetics; microsatellites; spatial genetic structure; stochastic migration