Ecogeography of teosinte

Abstract

Adaptation of crops to climate change has motivated an increasing interest in the potential value of novel traits from wild species; maize wild relatives, the teosintes, harbor traits that may be useful to maize breeding. To study the ecogeographic distribution of teosinte we constructed a robust database of 2363 teosinte occurrences from published sources for the period 1842-2016. A geographical information system integrating 216 environmental variables was created for Mexico and Central America and was used to characterize the environment of each teosinte occurrence site. The natural geographic distribution of teosinte extends from the Western Sierra Madre of the State of Chihuahua, Mexico to the Pacific coast of Nicaragua and Costa Rica, including practically the entire western part of Mesoamerica. The Mexican annuals Zea mays ssp. parviglumis and Zea mays ssp. mexicana show a wide distribution in Mexico, while Zea diploperennis, Zea luxurians, Zea perennis, Zea mays ssp. huehuetenangensis, Zea vespertilio and Zea nicaraguensis had more restricted and distinct ranges, representing less than 20% of the total occurrences. Only 11.2% of teosinte populations are found in Protected Natural Areas in Mexico and Central America. Ecogeographical analysis showed that teosinte can cope with extreme levels of precipitation and temperatures during growing season. Modelling teosinte geographic distribution demonstrated congruence between actual and potential distributions; however, some areas with no occurrences appear to be within the range of adaptation of teosintes. Field surveys should be prioritized to such regions to accelerate the discovery of unknown populations. Potential areas for teosintes Zea mays ssp. mexicana races Chalco, Nobogame, and Durango, Zea mays ssp. huehuetenangensis, Zea luxurians, Zea diploperennis and Zea nicaraguensis are geographically separated; however, partial overlapping occurs between Zea mays ssp. parviglumis and Zea perennis, between Zea mays ssp. parviglumis and Zea diploperennis, and between Zea mays ssp. mexicana race Chalco and Zea mays ssp. mexicana race Central Plateau. Assessing priority of collecting for conservation showed that permanent monitoring programs and in-situ conservation projects with participation of local farmer communities are critically needed; Zea mays ssp. mexicana (races Durango and Nobogame), Zea luxurians, Zea diploperennis, Zea perennis and Zea vespertilio should be considered as the highest priority taxa.

Fig 1. Occurrence records for teosinte species compiled from field observations and collection specimens.

Fig 2. Natural distribution and dispersion areas of teosinte in the world.

Fig 3. Principal component analysis of collecting sites of teosinte using ecogeographic data (Zea mays ssp. parviglumis designated with a blue square; Zea mays ssp. mexicana race Chalco designated with a red circle, race Durango designated with an orange circle, race Central Plateau designated with a lawngreen triangle, race Nobogame designated with a pink circle; Zea mays ssp. huehuetenangensis designated with a cyan square; Zea perennis designated with a purple star; Zea diploperennis designated with a magenta star; Zea luxurians designated with a darkgreen diamond; Zea nicaraguensis designated with a gray diamond; Zea luxurians from San Felipe Usila, Oaxaca designated with a brown diamond; Zea vespertilio designated with a yellow diamond).

Fig 4. Actual and potential distribution of teosinte.

Fig 5. Potential distribution of teosinte taxa.

Fig 6. Actual and potential distribution of teosinte and geographical location of PNAs.