Effects of natural and artificial selection on survival of columnar cacti seedlings: the role of adaptation to xeric and mesic environments

Abstract

Escontria chiotilla, Polaskia chichipe, and Stenocereus pruinosus are species of Mexican columnar cacti that are economically important because of their edible fruits. These species are managed by gathering fruits from the wild, silvicultural management in agroforestry systems, and cultivation in home gardens. Previous studies reported that artificial selection favored individuals that produced larger fruits, which indirectly led to the production of larger seeds and seedlings, with possible effects on survival. We hypothesized that seedlings from managed populations would be larger but more susceptible to xeric conditions than those from wild populations. We evaluated the effects of artificial and natural selection on seedling survival of the three species in wild and managed populations, which were managed with low and high intensity, respectively. We tested seedling performance in gradients of shade (0, 40, and 80%) and humidity (low and high). A GLM of seedling survival showed significant differences among species, shade, and humidity treatments, with each species having environmental requirements associated with their particular adaptations. High humidity decreased seedling survival of all species, and high solar radiation decreased survival of S. pruinosus and P. chichipe. The effect of management type was significant only in S. pruinosus. Significant differences in the initial growth of seedlings among species were detected with ANOVA. In optimal conditions, the hypocotyl and the cotyledons decreased in size and the epicotyl grew, whereas under stress, these structures remained unchanged. The optimum conditions of shade and humidity varied among species and management types. The seedlings of S. pruinosus were the largest and the most susceptible, but in all species, seedlings from managed populations were more susceptible to environmental conditions. Thus, artificial selection influenced the susceptibility of these cacti to xeric environments.

Wild Edible Fruits: A Systematic Review of an Under-Researched Multifunctional NTFP (Non-Timber Forest Product)

“…Ravikanth et al (2009) [96] speculate that harvesting may reduce the genetic diversity in some populations of NTFP species, and Horn et al (2012) [97] highlight that lowered genetic stock from harvesting could exacerbate external threats such as those mentioned above. Studies in this review found that management and harvest of WEF species do not constrain genetic flow [98][99][100], but can render propagules (seeds) more vulnerable in harsh environmental conditions such as low humidity and high solar radiation [101,102].…”

Genetic effects of anthropogenic habitat fragmentation on remnant animal and plant populations: a meta‐analysis

“…We excluded data for tree offspring because they may not represent genetic diversity as found among mature trees in the field. This is because offspring are usually grown from seeds under benign greenhouse conditions and are exposed to reduced pressures of natural selection (Guillen et al 2015). Similarly, natural thinning through intraspecific competition did not yet take place in studies based on saplings.…”

Climate change shapes the future evolution of plant metabolism

“…For example, a recent study compared seedling growth of three related cactus species under differential light and humidity conditions and found significantly different growth performance across them. 113 Similarly, various ecotypes of the biomass crop Arundo donax, commonly known as the giant reed, exhibit different productivities under drought stress. 114 Stemming from these initial findings, it may be possible to identify stress-tolerance-related candidate genes and pathways by correlating differential gene expression with variable phenotypic performances under specific stress conditions across a diversity panel.…”

“…To elucidate unknown adaptive mechanisms underpinning plant environmental tolerance, particularly in nonmodel plants, we may consider comparing closely related species or ecotypes of the same species that have adapted to different environments (Figure 2C). For example, a recent study compared seedling growth of three related cactus species under differential light and humidity conditions and found significantly different growth performance across them 113 . Similarly, various ecotypes of the biomass crop Arundo donax , commonly known as the giant reed, exhibit different productivities under drought stress 114 .…”