Habitat fragmentation is a major factor that threatens survival and reproduction of plant species, leading populations to become more isolated and reduced in size (Lienert, 2004). The destruction of natural sites in which tree species belong may often produce a disequilibrium in ecological interactions with pollinators (Mendes et al., 2022) and seed dispersers (Giombini et al., 2009). Studies that have addressed the current genetic diversity of allogamous tropical tree species through molecular markers frequently found high or moderate levels of genetic variation in natural populations (Collevatti et al., 2014, Souza et al., 2017, Muniz et al., 2022). But also becoming more common are studies documenting significant reduction in genetic diversity and changes in the genetic structure of populations when comparing conserved forests with sites that underwent habitat loss (Muniz et al., 2022) and fragmentation (Vranckx et al., 2012, González et al., 2020). A decay in genetic variation has also been described when analyzing succeeding generations, that is adult e juvenile trees (Waqar et al., 2021). Conservation geneticists claim that it is a matter of urgency that humankind should embrace strategies for the long term conservation of species and that an integrated view of knowledge and practices for conservation is timely (Pizzuto et al., 2021).
The reproduction of several tree species occurs through sexual means and it is often to find that trees have allogamous or mixed systems of mating. In the latter, both selfing and outcrossing occur in populations, with variable patterns of the relative contribution of selfing and outcrossing among species (Olson et al., 2016). Scarcely documented for woody tree species though, is the ability to reproduce by both sexual and assexual means and its genetic consequences. Populations of Betula humilis from Poland showed significant clonality levels after 522 samples were screened with microsatellite markers and 86 genets were found, 76% of them sharing the same genotype with their nearest neighbor (Bona et al., 2019). Populations of the neotropical tree Pentaclethra macroloba were sampled in distinct elevational gradients in Costa Rica and also showed a degree of clonal propagation as revealed by microsatellites. However, clonal individuals were found in inundated swamp areas only, and those produced higher genetic structure in comparison to the other populations (Gaddis et al., 2014). An older study with populations of Quercus chrysolepsis attested clonal propagation through isozyme loci, where clustered trees belonged to single clones (Montalvo et al., 1997).
In the aforementioned studies, although clonality was present, population genetic statistics suggested that sexual reproduction was predominant. This was not the case of populations of the endangered tree Elaeocarpus williamsianus, that showed single clones in most populations, and two genets at maximum in the most protected areas in Australia, after analyses with microsatellites and RAPD markers (Rossetto et al., 2004). The same study discussed that the genetic differences among individuals was much lower than expected and low seed viability was also observed in the populations. The authors recognized a disturbance in the balance between sexual and vegetative reproduction in this species due to habitat fragmentation. Morris et al. (2004) reached a similar conclusion with Fagus grandifolia populations analyzed with ISSR markers, as the frequency of clonal reproduction indicated to be higher in more severely disturbed sites.
Eremanthus erythropappus (DC.) Mac-Leishn is an Asteraceae member that reaches a shrub or a tree to 10m in height and 10cm in diameter. E. erythropappus flowering and fruiting occur from June to November in a natural distribution area located in the southeastern regions of the Central Plateau in Brazil in altitudes varying from 700 to 2400m. The species is common in colonies in the middle of secondary forests of the Atlantic Forest and in Cerrado (Brazilian savanna), being found in the states of Espírito Santo, Rio de Janeiro, Minas Gerais and São Paulo. Populars commonly refer to it as “candeia” or “pau de candeia” (candlestick) (MacLeish, 1987).
E. erythropappus has important economic applications due to the production of an essential oil containing α-bisabolol that is extracted for production of cosmetics and pharmaceuticals (de Oliveira et al., 2009). Essential oils of the species also showed acaricidal effect (Marchesini et al., 2021). E. erythropappus is also recommended for forest restoration, especially in degraded sites, as it is adapted to poor fertility and rocky outcrops (da Silva et al., 2007).
However, the intense habitat fragmentation and indiscriminate exploitation have led to reduction in population size throughout the species original habitat range (de Pádua et al., 2021). Such interference may result in allele losses, reduction of genetic diversity and changes in genetic structure over time. Prior study with adults and juvenile individuals from managed and unmanaged stands of E. erythropappus revealed high genetic diversity in both areas, however, managed stands showed changes in genetic structure possibly due to management (Rocha et al., 2021). In another study, cpDNA-RFLP markers indicated a genetic structure between populations from the northern range of distribution and populations from the center-south (Rocha et al., 2020a). Using climate-based ecological modeling, a severe reduction in the range of distribution of E. erythropappus is predicted from their study.
Management of E. erythropappus populations may also increase the propagation of the species by vegetative means, with the production of sprouts mainly from the roots (Fonseca et al., 2021). Therefore, this work was developed under the hypothesis that forest management increases clonal propagation in comparison to non-managed stands. We used population genetics approaches to investigate whether managed and unmanaged areas differ in clonality and how the genetic diversity and structure might potentially be altered.