Population Genetics of <i>Agave peacockii</i>: A Hybrid Microendemic Complex

Agave species can readily hybridize, leading to polyploidy and genetic differentiation. To identify the parent plants of such crosses, it is necessary to use various genetic tools to understand the variations among the species that grow in the same habitat. The maguey cacaya (A. peacockii) is an agave found only in the Tehuacán Valley, Puebla, with occasional presence in Hidalgo and Tlaxcala Mexican states. Its limited distribution may be due to its hybrid origin, resulting from a cross between A. marmorata and A. kerchovei. This study aimed to evaluate six populations of the maguey cacaya and their parent plants to determine their genetic relationship and sources of variation. There was high genetic diversity in the sampled populations (He=0.38±0.03), with a strong genetic structure (FST=0.33, P<0.001). All populations are in Hardy-Weinberg equilibrium ( χ2=11.4±6.9, df=18.2,12.3, P>0.1 in all cases) and show no signs of bottlenecks, but they exhibit high outbreeding (FIS=−0.22±0.07). The highest levels of variation occur in the central region of the species’ distribution. However, the analysis suggests that A. marmorata is not a parental source of A. peacockii and shows that crossing between different agave species is rare. The population’s genetic equilibrium and strong outbreeding suggest increased genetic variability due to hybridization. Agave kerchovei appears to share its genetic information among most populations, except in one locality close to the distribution center where other parent plants may be involved.