Pablo Octavio-Aguilar

Extinction Risk of Zamia inermis (Zamiaceae): A Genetic Approach for the Conservation of Its Single Natural Population

Zamia inermis, a narrowly endemic cycad, has been classified under the International Union for Conservation of Nature Red List as critically endangered on the basis of a 75% population decline over past 50 yr. There is only one known population occupying an area of less than 10 km2, with 654 individuals with extremely low seed production and recruitment. This study compares the genetic diversity of the only known in situ population of Z. inermis and one ex situ population established 5 yr ago by a local community running a rural backyard nursery. We aimed to assess the current conservation status and to propose a more efficient management strategy. Our results by using a total of 10 simple sequence repeat loci showed a low observed heterozygosity (0.151 ± 0.075) in comparison to other New World cycads. Significant differences were found between ex situ population and wild populations (differentiation index FST1, 156 = 0.734, P < 0.001), with lower variation within (27%) than among (73%) populations. Zamia inermis presented the lowest genetic diversity to be reported for Mexican cycads. The ex situ population had a lower variation than wild population and thus does not fully represent the genetic diversity of the species. This suggests that there was a poor representation of genetic diversity among the seed collected to establish the ex situ population. Alternative conservation strategies are suggested.

Fine-Scale Genetic Structure of Zamia furfuracea: Variation with Life-Cycle Stages

Fine-scale spatial genetic structure (SGS) analysis has proved to be a useful tool to establish the distribution of genetic variability between individuals and how these patterns are affected by microenvironmental conditions, associations with pollinators and dispersers, and sex ratio. In this study, the correlation between the fine-scale SGS of a population of Zamia furfuracea L. fil. and its dependence on the patterns of spatial aggregation between categories of life cycle and the proportion of males and females was determined by using intersimple sequence repeat markers. Results showed an aggregation pattern dependent on reproductive adults of up to 10 m; however, dependence on sex was restricted to only 3 m, suggesting limited pollen and seed dispersal. Gene neighborhoods did not exceed 10 m, with three well-defined families within the population. The small size of the neighborhoods, high mortality rate of seedlings, and loss of genetic variability in the juvenile category suggest that this population is severely affected. Our results contribute to the understanding of genetic and spatial dynamics in natural populations of cycads. Such information should be considered for the implementation of ex situ population-management programs.