Anthropogenic and natural drivers of gene flow in a temperate wild fruit tree: a basis for conservation and breeding programs in apples

Abstract

Gene flow is an essential component of population adaptation and species evolution. Understanding of the natural and anthropogenic factors affecting gene flow is also critical for the development of appropriate management, breeding, and conservation programs. Here, we explored the natural and anthropogenic factors impacting crop-to-wild and within wild gene flow in apples in Europe using an unprecedented dense sampling of 1889 wild apple (Malus sylvestris) from European forests and 339 apple cultivars (Malus domestica). We made use of genetic, environmental, and ecological data (microsatellite markers, apple production across landscapes and records of apple flower visitors, respectively). We provide the first evidence that both human activities, through apple production, and human disturbance, through modifications of apple flower visitor diversity, have had a significant impact on crop-to-wild interspecific introgression rates. Our analysis also revealed the impact of previous natural climate change on historical gene flow in the nonintrogressed wild apple M. sylvestris, by identifying five distinct genetic groups in Europe and a north–south gradient of genetic diversity. These findings identify human activities and climate as key drivers of gene flow in a wild temperate fruit tree and provide a practical basis for conservation, agroforestry, and breeding programs for apples in Europe.

Little White Lies: Pericarp Color Provides Insights into the Origins and Evolution of Southeast Asian Weedy Rice

“…More problematic is the possibility of genetic swamping of the wild progenitor populations ( e.g. , Martínez-Castillo et al 2008; Cornille et al 2015; Fuchs et al 2016), which, in the case of Malaysian O. rufipogon , are increasingly rare and have no in situ conservation status. Introgression from cultivated rice into weedy rice is not uncommon (Xia et al 2011; Ellstrand et al 2013; Jiang et al 2012), and the recent widespread adoption of herbicide-resistant rice production will likely increase hybridization due to selection for introgression of resistance alleles into weed populations (Burgos et al 2014).…”

Genetic variation of naturally growing olive trees in Israel: from abandoned groves to feral and wild?

“…vinifera and V. vinifera subsp. sylvestris ) [3, 4] and apples ( Malus domestica and M. sylvestris ) [5]. In addition to gene flow, dispersal of seeds from cultivated trees into natural surroundings can result in feral populations of natural aspect [6], as shown for several plants introduced to Australia, including Olea europaea [7, 8].…”

“…On this background, knowledge of the status of naturally growing populations of olives is of high importance for developing conservation programs for this valuable germplasm. Conservation efforts should also address the risks of hybridization and introgression from domesticated crops into populations of their wild relatives [32], as recently shown for fruit trees [2, 5]. …”

Pollen-mediated gene flow and fine-scale spatial genetic structure inOlea europaeasubsp.europaeavar.sylvestris

“…Crop-to-wild gene flow has been considered a threat to natural genetic resources and has received particular attention in recent decades. In fruit trees, introgression from cultivars to wild populations has been investigated and shown to be widespread (Cornille et al, 2015, and references therein). For example, crop-to-wild gene flow was shown to be responsible for a decrease in fitness in apple wild populations, leading researchers to consider non-introgressed populations with high levels of genetic diversity as a priority for conservation programmes (Bleeker et al, 2007;Cornille et al, 2015).…”

“…In fruit trees, introgression from cultivars to wild populations has been investigated and shown to be widespread (Cornille et al, 2015, and references therein). For example, crop-to-wild gene flow was shown to be responsible for a decrease in fitness in apple wild populations, leading researchers to consider non-introgressed populations with high levels of genetic diversity as a priority for conservation programmes (Bleeker et al, 2007;Cornille et al, 2015). In olive, recent studies have demonstrated frequent introgression from seed orchards and cultivated stands to wild populations (Besnard et al, 2011(Besnard et al, , 2013Perea and Gutiérrez-Gal an, 2016) showing the importance of assessing gene flow patterns when natural and cultivated stands are in close contact.…”