Genetic and ecological approaches to guide conservation of teosinte (Zea mays ssp. parviglumis), the wild progenitor of maize

The teosinte taxon, Zea mays ssp. parviglumis , is the most closely related wild relative to maize and houses a significant amount of genetic diversity that could be important for maize improvement. Populations of parviglumis are found throughout southwest Mexico where recent changes in land use such as conversion to ranching and industrial agriculture threaten their persistence. Five populations of parviglumis in the rapidly changing rural landscape of central Jalisco were investigated in order to assess evidence for recent population bottlenecks and associated impacts of land use. Smaller, more fragmented, relic populations in regions with pervasive cattle grazing were shown to have less genetic diversity and stronger evidence of recent bottlenecks than larger, more continuous populations. Genetic diversity was strongly structured between populations with divergence occurring in populations separated by merely a few kilometers. The striking amount of regional genetic structure can be explained by the prevalence of pollen flow over short distances revealed through indirect paternity analysis in a separate investigation described here. This analysis of pollen flow also revealed trends related to land use and underscored the importance of considering cryptic population structure when estimating mating system parameters. Finally, a common garden comparison of thousands of plants from the five populations provided convincing evidence of inbreeding depression in smaller, more fragmented populations. These data, when considered together, underscore the need for concerted conservation effort toward parviglumis. Protection of these populations can be achieved through extension efforts with local land managers and by establishing parviglumis as a reference species for ecological and evolutionary studies based on the molecular tools available from maize.