Genetic imprints of Brosimum alicastrum (Moraceae) in Mexico

PREMISE: Mechanisms generating the geographical distributions of genetic
diversity are a central matter in evolutionary biology. The amount of
genetic diversity and its distribution are controlled by several factors,
including dispersal abilities, physical barriers and environmental and
climatic changes. We investigated the patterns of genetic diversity and
differentiation among populations of the widespread species Brosimum
alicastrum in Mexico. METHODS: Using nuclear DNA microsatellite data, we
determined the current state of genetic diversity and its distribution to
determine if the genetic structure was consistent with geographical
settings of Mexico and to infer the role of past events in the genetic
diversity patterns. RESULTS: Our results suggested that Mexican B.
alicastrum is well differentiated into three main lineages. Patterns of
the genetic structure at a finer scale did not entirely correspond with
the present-day geographic barriers to gene flow. CONCLUSIONS: We propose
that differentiation patterns might reflect: 1) an ancient differentiation
that occurred in Central America and South America; 2) the effects of past
climatic changes, and 3) the action of some physical barriers to gene
flow. This study provides insights into the possible mechanisms underlying
the geographic genetic variation of B. alicastrum along a moisture
gradient in tropical lowland forests.