Evolutionary and food supply implications of ongoing maize domestication by Mexicancampesinos

Abstract

Maize evolution under domestication is a process that continues today. Case studies suggest that Mexican smallholder family farmers, known as , contribute importantly to this, but their significance has not been explicitly quantified and analysed as a whole. Here, we examine the evolutionary and food security implications of the scale and scope under which produce maize. We gathered official municipal-level data on maize production under rainfed conditions and identified agriculture as occurring in municipalities with average yields of less than or equal to 3 t ha Environmental conditions vary widely in those municipalities and are associated with a great diversity of maize races, representing 85.3% of native maize samples collected in the country. We estimate that in those municipalities, around 1.38 × 10 genetically different individual plants are subjected to evolution under domestication each season. This implies that 5.24 × 10 mother plants contribute to the next generation with their standing genetic diversity and rare alleles. Such a large breeding population size also increases the total number of adaptive mutations that may appear and be selected for. We also estimate that agriculture could potentially feed around 54.7 million people in Mexico. These analyses provide insights about the contributions of smallholder agriculture around the world.

The temporal dynamics of background selection in non-equilibrium populations

“…(Eyre-Walker et al 1998; Tenaillon et al 2004; Wright et al 2005;Beissinger et al 2016; Wang et al 2017;Bellon et al 2018), there is little agreement on the magnitude and timing of these effects, and estimates of the modern maize population vary by several orders of magnitude. And while the estimated demography of African populations is relatively stable compared to that of non-Africans (Torres et al 2018), the demography of teosinte is not well understood but is likely to include substantial nonequilibrium dynamics(Wang et al 2017).…”

Resistance and Tolerance to Root Herbivory in Maize were Mediated by Domestication, Spread, and Breeding

“…Similarly, its spread from present-day Mexico exposed maize to new environments, and confronted it to novel suites of herbivores, which adopted the novel crop as a host because of its abundance and advantages, e.g., weakened defenses, superior nutritional value, refuge from natural enemies. With domestication and spread, the distribution and abundance of maize increased beyond those of Balsas teosinte, its wild ancestor, and with those increases maize broadened its genetic diversity as it was challenged by novel abiotic and biotic stresses (Hufford et al, 2012a;Hufford et al, 2012b;Bellon et al, 2018). Breeding in the last 100 years narrowed maize's genetic diversity to increase its productivity in the context of resource-rich environments (including fertilizers, irrigation, and pesticides) in which tolerance-and resistance-based defenses were favored or neglected through systematic breeding, mainly for yield.…”

The global economic costs of substituting dietary protein from fish with meat, grains and legumes, and dairy

“…Several studies conclude that small‐scale polyculture is more productive than large‐scale monoculture in terms of total output, enabling provision of a more complete set of nutrients per unit of land (Altieri, ; Ebel, Cárdenas, Miranda, & González, ; Pittelkow et al., ; Tscharntke et al., ; Zhang, Postma, York, & Lynch, ). Higher genetic diversity in small‐scale polyculture also contributes to resilient food production in a context of rapid environmental change (Altieri, ; Altieri et al., ; Bellon et al., ; Jacobsen et al., ), and its role is considered as increasingly important for global food security (Altieri, Funes‐Monzote, & Petersen, , ; Erisman et al., ; Tscharntke et al., ).…”