Diversity and Genetic Structure of Dioon holmgrenii (Cycadales: Zamiaceae) in the Mexican Pacific Coast Biogeographic Province: Implications for Conservation

Abstract

Dioon holmgrenii De Luca, Sabato et Vázq.Torres is an endangered species; it is endemic and its distribution is restricted to the biogeographic province of the Mexican Pacific Coast. The aim of this work was to determine the diversity and genetic structure of nine populations. The genetic diversity parameters and Wright’s F statistics were determined with six microsatellite loci. The genetic structure was determined by using the Structure software and by a discriminant analysis. The genetic diversity of the populations was high. The proportion of polymorphic loci was 0.89, the observed heterogeneity was higher (Ho = 0.62 to 0.98) than expected (He = 0.48 to 0.78), and the fixation index was negative (IF = −0.091 to −0.601). Heterozygous deficiency (FIT = 0.071) was found at the species level and heterozygotes excess (FIS = −0.287) at the population level. The genetic differentiation between populations was high (FST = 0.287), with the number of migrants less than one. Three groups of populations were differentiated, and the variation within populations, between populations, and between groups was: 65.5, 26.3, and 8.2%, respectively. Multiple factors explain the high genetic diversity, while the genetic structure is due to geographic barriers. Community reserves are urgent in at least one most diverse population of each group.

Evolutionary and ecological trends in the Neotropical cycad genus Dioon (Zamiaceae): An example of success of evolutionary stasis

“…Other possible explanations are that historical environmental discontinuities have kept the species in isolation, or that they rely on distinct brood-site pollinator mutualists with a limited distribution range such that interbreeding was not possible due to that Patterns of ND were identified between D. holmgrenii and D. califanoi. This is not surprising because they occur at distinct biomes; D. califanoi occurs at semidry and oak forests at high elevations (around 2000 m asl) in northern Oaxaca (Figure 1), whereas D. holmgrenii occurs at seasonally dry forests, in montane areas around 1000 m asl in southern Oaxaca (Velasco-García et al, 2021). ND was also detected between in the sister pair of D. angustifolium and D. edule-South.…”

“…Patterns of ND were identified between D. holmgrenii and D. califanoi . This is not surprising because they occur at distinct biomes; D. califanoi occurs at semidry and oak forests at high elevations (around 2000 m asl) in northern Oaxaca (Figure 1), whereas D. holmgrenii occurs at seasonally dry forests, in montane areas around 1000 m asl in southern Oaxaca (Velasco‐García et al, 2021). ND was also detected between in the sister pair of D. angustifolium and D. edule ‐South.…”

Population Genomics Study and Implications for the Conservation of Zabelia tyaihyonii Based on Genotyping-By-Sequencing

“…The genetic diversity of plant species is related to their distribution range, population size, life cycle, mating system and gene flow [ 38 , 40 ]. Of these factors, a narrow distribution range and small population size tend to reduce genetic diversity [ 37 , 38 ] as a consequence of genetic drift and inbreeding [ 14 , 37 , 38 , 41 , 42 , 43 ]. Additionally, in species that reproduce both sexually and vegetatively, such as Z. tyaihyonii , the intensity of vegetative reproduction has a significant effect on the genetic diversity of a population.…”

Conservation genomics of Dioon holmgrenii (Zamiaceae) reveals a history of range expansion, fragmentation, and isolation of populations

“…Characterizing the genetic diversity of a species and detecting how that diversity is spatially structured requires sufficient genetic data across the species' range. To date, no study has included the full range of D. holmgrenii when assessing genetic diversity and most studies in Dioon species have relied on allozyme data or microsatellites (González-Astorga et al 2003, 2005González-Astorga et al 2008a, b;Cabrera-Toledo et al 2008, 2010González-Astorga et al 2008a, b;Velasco-García et al 2021). However, several groups have utilized single nucleotide polymorphism (SNP) data in Dioon and other cycad species (Clugston et al 2019(Clugston et al , 2022Gutiérrez-Ortega et al 2020).…”