Gypsum soil restriction drives genetic differentiation in Fouquieria shrevei (Fouquieriaceae).
OBJECTIVE
Although species adapted to grow in unusual soils contribute importantly to regional diversity, the microevolutionary processes responsible for that diversity remain to be understood. We aimed to answer this question by analyzing which processes are responsible for the genetic differentiation in Fouquieria shrevei (Fouquieriaceae), a species confined to gypsum soils of northern Mexico.


METHODS
We analyzed sequence variation in three chloroplast intergenic spacers from five populations.


RESULTS
Total genetic diversity was high (Hd = 0.743). Genetic differentiation was high (FST = 0.651), as most haplotypes were unique to individual populations, and three populations had only one haplotype. Haplotypes were more similar in nearby populations, resulting in a phylogeographic structure (i.e., GST = 0.850 was significantly lower than NST = 0.930) and a significant Mantel test (P = 0.04). Tajima's D (-0.019, not significant) indicates that effective population size has remained constant.


CONCLUSIONS
We conclude that genetic drift has been intense and gene flow low in differentiating populations that follow an island-like pattern of gypsum deposits of the deserts of North America. The interaction between these forces could promote speciation events that in turn would increase regional diversity and may explain the high number of narrow endemics associated with soil restrictions.
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apartado Postal 70-275, Circuito exterior s/n junto al Jardín Botánico, Coyoacán, México, D.F. 04510 México.
Jonas A
JA
Aguirre-Liguori
Enrique
E
Scheinvar
Luis E
LE
Eguiarte
D002133:Calcium Sulfate / Q000032:analysis; D018742:DNA, Chloroplast / Q000235:genetics; D021901:DNA, Intergenic / Q000235:genetics; D017753:Ecosystem; D019143:Evolution, Molecular; D014644:Genetic Variation; D006239:Haplotypes; D019684:Magnoliopsida / Q000235:genetics / Q000502:physiology*; D008800:Mexico; D008969:Molecular Sequence Data; D010802:Phylogeny; D058974:Phylogeography; D016133:Polymerase Chain Reaction; D058614:Seed Dispersal; D017422:Sequence Analysis, DNA; D012987:Soil
D018742:DNA, Chloroplast; D021901:DNA, Intergenic; D012987:Soil; D002133:Calcium Sulfate
Chihuahuan Desert; Fouquieria shrevei; Fouquieriaceae; allopatric divergence; ecological adaptation; genetic differentiation; gypsophile species; narrow endemics; phylogeography