Morphological and genetic divergence between Agave inaequidens, A. cupreata and the domesticated A. hookeri. Analysis of their evolutionary relationships

PLoS One. 2017 Nov 8;12(11):e0187260. doi: 10.1371/journal.pone.0187260. eCollection 2017.

Abstract

Agave inaequidens and A. cupreata are wild species with some populations under incipient management, while A. hookeri is exclusively cultivated, used for producing the fermented beverage pulque. These species are closely related and sympatric members of the Crenatae group, but taxonomists have previously hypothesized that A. inaequidens is the most probable ancestor of A. hookeri. Our study aims at evaluating patterns of morphological and genetic divergence among populations of the three species, in order to analyze their ecological and possible evolutionary relationships. We studied 24 agave populations, 16 of them of Agave inaequidens, four of A. cupreata and four of A. hookeri. Population morphometric and genetics studies were performed using 39 morphological characters and 10 nuclear microsatellites, respectively. We estimated levels of morphological and genetic diversity and dissimilarity, as well as genetic structure and gene flow among populations and species. The three species were clearly differentiated by general plant size, lateral teeth, terminal spines, flowers and fruit size. The largest plants were those of A. hookeri followed by A. inaequidens and the smallest were A. cupreata. Multivariate analyses indicated greater morphological similarity between A. hookeri and cultivated A. inaequidens, while A. cupreata consistently appeared as a separate group. We identified similar levels of morphological diversity index (MDI) in the three species, but higher genetic diversity in A. inaequidens (MDI = 0.401-0.435; HE = 0.704-0.733), than in A. cupreata (MDI = 0.455-0.523; HE = 0.480-0.510) and the predominantly vegetative propagated crop A. hookeri (MDI = 0.335-0.688; HE = 0.450-0.567), a pattern consistent with our expectations. The morphological and genetic similarities between cultivated A. inaequidens and A. hookeri support the hypothetical evolutionary relationships among these species, but studies with cpDNA and SNPs, and including other member of the Crenatae group are necessary to further resolve these relationships.

MeSH terms

  • Agave / anatomy & histology*
  • Agave / genetics*
  • Bayes Theorem
  • Biological Evolution*
  • Cluster Analysis
  • Discriminant Analysis
  • Domestication*
  • Genetic Variation*
  • Mexico
  • Phenotype
  • Phylogeny
  • Reproduction

Grants and funding

This work was supported by (1) Grant name: Domesticación y manejo in situ de recursos genéticos forestales en Mesoamérica, Funding Institution: Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT), Dirección General de Asuntos del Personal Académico (DGAPA), Universidad Nacional Autónoma de México (UNAM), Mexico, Project number IN209214, Funded field and laboratory work, AC; (2) Project name: Domesticación y manejo in situ de recursos genéticos en el Nuevo Mundo: Mesoamérica, Los Andes y Amazonia, Consejo Nacional de Ciencia y Tecnología, Mexico (CONACYT), Mexico, Project number CB-2013-01-221800, Funded field and laboratory work, AC; (3) Project name: Domesticación y manejo in situ de recursos genéticos en el Nuevo Mundo: Mesoamérica, la región andina, amazónica y del nordeste de Brasil Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT), Dirección General de Asuntos del Personal Aacadémico (DGAPA), Universidad Nacional Autónoma de México (UNAM), Mexico, Project number IN206217, Funded field and laboratory work, AC.