Unexpectedly high genetic diversity and divergence among populations of the apomictic Neotropical tree Miconia albicans

Abstract

Since tropical trees often have long generation times and relatively small reproductive populations, breeding systems and genetic variation are important for population viability and have consequences for conservation. Miconia albicans is an obligate, diplosporous, apomictic species widespread in the Brazilian Cerrado, the savanna areas in central Brazil and elsewhere in the Neotropics. The genetic variability would be, theoretically, low within these male-sterile and possibly clonal populations, although some variation would be expected due to recombination during restitutional meiosis. We used ISSR markers to assess genetic diversity of M. albicans and to compare with other tropical trees, including invasive species of Melastomataceae. A total of 120 individuals from six populations were analysed using ten ISSR primers, which produced 153 fully reproducible fragments. The populations of M. albicans presented mean Shannon's information index (I) of 0.244 and expected heterozygosity (H ) of 0.168. Only two pairs of apparently clonal trees were identified, and genetic diversity was relatively high. A hierarchical amova for all ISSR datasets showed that 74% of the variance was found among populations, while only 26% of the variance was found within populations of this species. Multivariate and Bayesian analyses indicated marked separation between the studied populations. The genetic diversity generated by restitutional meiosis, polyploidy and possibly other genome changes may explain the morpho-physiological plasticity and the ability of these plants to differentiate and occupy such a wide territory and different environmental conditions. Producing enormous amounts of bird-dispersed fruits, M. albicans possess weedy potential that may rival other Melastomataceae alien invaders.

Fine-scale analysis reveals a potential influence of forest management on the spatial genetic structure of Eremanthus erythropappus

“…Long-lived and outcrossing species show most of the genetic variability within populations (Nybom 2004). In fact, several studies have found a tendency for high genetic variation within populations of tropical outbreeding tree species (Duarte et al 2015;Brito et al 2016;Dias et al 2017). AMOVA results showed that most of the genetic variance is retained within populations (96%).…”

Towards a unified terminology for angiosperm reproductive systems

“…However, the different apomictic mechanisms (apospory, diplospory or adventitious embryony) are in association with different levels of sexual reproduction and diverse selective pressures that interfere with the production of viable pollen grains. This leads to higher degrees of genetic diversity within populations (Whitton et al 2008;Tucker & Koltunow 2009;Dias et al 2017).…”

“…Obligate apomictic species present lower pollen viability compared to facultative ones, once the former do not require such resource for reproduction. However, some levels of genetic variability may still exist among obligate apomictics through different pathways, such as somatic recombination, chromosomal gain or loss, mutations and the occurrence of restitutional meiosis (Richards 1996;Dias et al 2017). Apomixis is rarely obligate in angiosperms, since most of apomictic species produce descendants through sexual and asexual forms (Hojsgaard & Hörandl 2015).…”

Secondary origin, hybridization and sexual reproduction in a diploid–tetraploid contact zone of the facultatively apomictic orchid Zygopetalum mackayi

“…The AMOVA of Z. mackayi populations revealed that more than half of the total genetic variation (55.3%) is present within the populations, as expected for non‐apomictic populations. In contrast, Dias et al (2018) found 74% of genetic variation distributed among populations of the obligate apomictic Miconia albicans . Also, the analyses of genetic diversity and estimation of the number of multilocus genotypes within all populations of Z. mackayi indicated similar and high levels of genetic diversity among them.…”