Background:

Human management of plant populations can modify the amounts and distribution of their genetic diversity.

Questions:

What is the phylogeographic structure of Crescentia alata and how is it related to past climatic changes? What are the genetic diversity levels of homegarden populations and how are they associated to human management?

Studied species:

Crescentia alata Kunth (Bignoniaceae).

Study site and dates:

Mexico and Central America 2009-2011.

Methods:

We analyzed 243 trees from 10 homegarden and 25 wild populations. Chloroplast haplotypes were identified through six microsatellite loci. Haplotype relationships were reconstructed with a median-joining network. Genetic diversity and structuring were evaluated with R ST and G ST indexes and AMOVA. Geographical barriers among populations were identified with Monmonier’s algorithm. The hypothesis of historical demographic growth was evaluated through the paired differences distribution and the species potential distribution was projected onto the past during the Middle Holocene, Last Glacial Maximum and Last Inter Glacial periods.

Results:

A latitudinal pattern of phylogeographic structure was identified with geographical barriers in the northern Pacific Ocean and the Tehuantepec Isthmus. We detected a significant demographic growth, likely associated to glacial environmental conditions. Most homegarden trees were found to be tolerated and share chloroplast haplotypes with sympatric wild populations.

Conclusions:

Human management has not modified the natural phylogeographic structure of C. alata and homegarden populations represent a genetic reservoir where introgression processes are favored by seed mediated propagation.

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