Population genetics of Dioon edule Lindl. (Zamiaceae, Cycadales): biogeographical and evolutionary implications

Abstract

Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule and the geographical variety D. edule var. angustifolium (Miq.) Miq. Dioon edule has a north to south distribution in eastern Mexico. In this study, we analysed 14 allozymic loci in eight populations of D. edule from its total distribution range by sampling all known populations. Patterns of diversity and genetic variability, within and among populations, were obtained. The mean number of alleles per locus ( A ) was 1.44 and the percentage of polymorphic loci was relatively high ( P = 54.78). The mean observed ( H O ) and expected heterozygosity ( H E ) were 0.27 and 0.24, respectively. F ‐statistics revealed an excess of heterozygous genotypes, locally and globally ( F = −0.17 and f = −0.27, respectively). The genetic variation explained by differences among populations was only 7.5%. We also detected a negative relationship between genetic diversity and latitude. On average, the gene flow between population pairs was relatively high ( Nm = 2.98); furthermore, gene flow between population pairs was significantly correlated with geographical distances ( r = −0.38, P = 0.025). Therefore, patterns of genetic diversity in D. edule appear to be associated with the post‐Pleistocene spread of the species, from its southerly (origin) to its northerly range (derived populations, including its central distribution). The biogeographical and evolutionary aspects of the results of this study are discussed. We recognize Dioon angustifolium Miq. for the northernmost disjunct populations. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 457–467

Phylogenetic Relationships of the Neotropical Genus <I>Dioon</I> (Cycadales, Zamiaceae) Based on Nuclear and Chloroplast DNA Sequence Data

“…PCR amplification with lower temperatures (52-56°C) did not recover any additional alleles for these loci. The observed heterozygosity confirms previous allozyme studies and is congruent with Dioon's mating system (González-Astorga et al, 2003;Cabrera-Toledo et al, 2010). The number of alleles for the transferred loci ranged from one to seven, and H o and H e ranged from 0.33 to 0.89 and 0.24 to 0.71, respectively ( Note: N = number of individuals.…”

“…They can live up to 2000 yr and have slow growth rates with long reproductive cycles (Vovides, 1990). Despite legal protection in the Norma Oficial Mexicana of the Secretaría de Medio Ambiente y Recursos Naturales (Nom-059 SEMARNAT-2010) Allozyme variation in D. edule has shown that there is unusually high genetic diversity in this genus (González-Astorga et al, 2003;Cabrera-Toledo et al, 2010, 2012, but these markers are limited in their scale of analysis and in their use for conservation, as they lack individual-level resolution and are dominant markers. Independent laboratories (J. C. Bede, A. Cibrián-Jaramillo, D. Cabrera-Toledo, and L. Yañez-Espinosa, personal communication) have been unable to replicate microsatellites previously developed for D. edule (Moynihan et al, 2007).…”

Genetic diversity through life history of Dioon edule Lindley (Zamiaceae, Cycadales)

“…Hamrick & Godt (1996), Epperson & Tian-Quan (1997) and Duminil et al (2007) suggested that the main life history traits that modify the genetic structure of a population are: life form, area of geographical distribution, breeding systems and seed and pollen dispersal. Other research emphasised effects of natural selection and genetic drift between age classes, although little work has been done on long-lived plants (Linhart et al 1981;Eguiarte et al 1992;Conte et al 2003;González-Astorga et al 2003;González-Astorga & Castillo-Campos 2004).…”

Reevaluación del riesgo de extinción de cinco especies del género Polianthes l. (Agavaceae)

“…Los análisis de la variación y estructura hereditaria, flujo de genes y efectos de botella, indican que poblaciones endémicas pequeñas, genéticamente poco diversas, son especialmente vulnerables a la extinción como consecuencia del cambio de uso del suelo, destrucción del hábitat y remoción de individuos (González-Astorga et al, 2005). Los estudios que permitan conocer la estructura alélica de las poblaciones son altamente recomendados, ya que con ellos se puede predecir si éstas podrán adaptarse a los cambios ambientales (González-Astorga et al, 2003). Los monitoreos de carácter demográfico en áreas con diferentes tipos de perturbación son particularmente importantes para asegurar el éxito del manejo de las especies a largo plazo (Octavio-Aguilar et al, 2008).…”