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

Abstract

The distribution of genetic diversity and structure for three populations of Dioon edule Lindley (Zamiaceae) at Monte Oscuro (MO), El Farallón (EF) and Rancho del Niño (RN) in Veracruz, Mexico was studied using 20 allozyme loci, considering four life history classes: seeds, seedlings, juveniles and adults. The MO population is genetically less diverse than the EF and RN populations. Total and local inbreeding differ significantly between life history classes. An increment of inbreeding among all classes was observed, and genetic differentiation among populations was higher in seeds and seedlings than in juveniles and adults. In terms of percentage of polymorphic loci, the MO seeds showed least (80%), followed by RN (95%) and EF had the highest values (100%), probably because of a reduction in effective population size and habitat fragmentation processes. In this context, the mean effective population size was 23.2 ± 11.3 for all populations. We conclude that seed cohorts in EF and RN represent a reservoir of genetic diversity within these two populations. Also, preservation of adult plants is an essential aspect to consider in management and conservation efforts for populations of Dioon edule in natural conditions.

Genetic consequences of subtropical rainforest fragmentation onMacadamia tetraphylla(Proteaceae)

“…These differences were observed despite the surrounding fragments having only been separated from the continuous patch for 10-30 years. Such a pattern has also been recorded for other tree species (FARWIG, 2008;ORTEGO et al, 2010), as well as a cycad (OCTAVIO-AGUILAR, 2009). Yet post-fragmentation cohorts do not always display higher levels of differentiation than their pre-fragmentation counterparts: a number of studies have found low levels of differentiation for both cohorts (LATOUCHE-HALLÉ, 2003;SCHWARCZ et al, 2010), sometimes still with significantly higher values for juveniles than adults (RIBEIRO et al, 2005;FIGUEROA-ESQUIVEL, 2010).…”

Effects of shade on germination traits of the endangered cycad Dioon edule (Zamiaceae)

“…Various studies have revealed that some cy- (Frett, 1987;López-Ovando and Treviño-Garza, 2008;Lázaro-Zermeño et al, 2012;Lopez-Gallego, 2013). The ability of seeds to germinate under both shade conditions indicates that D. edule seeds can germinate under the oak canopy or near the mother plant, forming a transient seed bank (seeds live in or on the soil for up to one year) (Walck et al, 2005;Octavio-Aguilar et al, 2009). High germination balances the limited seed production and its high mortality, and elevated seedling mortality may have more impact on population structure (Yáñez-Espinosa et al, 2014).…”

Genetic diversity in Atlantic Forest trees: fragmentation effects on Astronium graveolens (Anacardiaceae) and Metrodorea nigra (Rutaceae), species with distinct seed dispersal strategies

“…(Zamiaceae), although the mean f was 0.27, when looking only at adults this coefficient was always > 0.30 and in at least one of the studied populations it reached values of 0.472 for juveniles and 0.475 for adults. Also the F ‐values tend to increase with life cycle class, never being > 0.165 in seed samples (Octavio‐Aguilar, González‐Astorga & Vovides, 2009). The authors suggested that this may be attributable to an extensive mortality event and subsequent founder effects.…”