title: Zamia (Cycadales: Zamiaceae) on Puerto Rico: asymmetric genetic differentiation and the hypothesis of multiple introductions.
abstract: OBJECTIVE
  This study of Zamia in Puerto Rico is the most intensive population genetics investigation of a cycad to date in terms of number of markers, and one of few microsatellite DNA studies of plants from the highly critical Caribbean biodiversity hotspot. Three distinctive Zamia taxa occur on the island: Z. erosa on the north coast, and Z. portoricensis and Z. pumila, both in the south. Their relationships are largely unknown. We tested three hypotheses about their genetic diversity, including the possibility of multiple introductions.
  
  
  METHODS
  We used 31 microsatellite loci across 10 populations and analyzed the data with AMOVA, Bayesian clustering, and ABC coalescent modeling.
  
  
  RESULTS
  Puerto Rican zamias exhibit an amalgam of patterns of genetic differentiation that have been reported for cycads. Overall, the taxa are slightly inbred, with high infra-populational variation and little evidence of recent bottlenecks. Zamia erosa exhibits a more than threefold greater degree of population differentiation than the other two taxa. Admixture is evident only between Z. portoricensis and Z. pumila. Zamia portoricensis is inferred to be the youngest taxon on the island, on the basis of estimates of coalescence time and effective population size. A selective sweep may be underway in a small population of Z. erosa in a saline environment.
  
  
  CONCLUSIONS
  Zamia erosa may represent an independent introduction into Puerto Rico; Z. portoricensis and Z. pumila fit a scenario of allopatric speciation. This will be explored further in the context of genetic analysis across the entire Caribbean region.
authors.affiliation: USDA-ARS-SHRS, National Germplasm Respository, Miami, Florida 33158, USA. alan.meerow@ars.usda.gov
authors.forename: Alan W
authors.initials: AW
authors.lastname: Meerow
authors.forename: Javier
authors.initials: J
authors.lastname: Francisco-Ortega
authors.forename: Michael
authors.initials: M
authors.lastname: Calonje
authors.forename: M Patrick
authors.initials: MP
authors.lastname: Griffith
authors.forename: Tomás
authors.initials: T
authors.lastname: Ayala-Silva
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Stevenson
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nakamura
mesh_terms: D000483:Alleles; D000704:Analysis of Variance; D001499:Bayes Theorem; D016000:Cluster Analysis; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D005787:Gene Frequency; D014644:Genetic Variation; D005843:Geography; D018895:Microsatellite Repeats / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011156:Population Density; D011157:Population Dynamics; D011647:Puerto Rico; D017422:Sequence Analysis, DNA; D032481:Zamiaceae / Q000145:classification / Q000235:genetics*
chemical_list: D018744:DNA, Plant