Abstract
Dalmatian sage (Salvia officinalis L., Lamiaceae) is a well-known aromatic and medicinal Mediterranean plant that is native in coastal regions of the western Balkan and southern Apennine Peninsulas and is commonly cultivated worldwide. It is widely used in the food, pharmaceutical and cosmetic industries. Knowledge of its genetic diversity and spatiotemporal patterns is important for plant breeding programmes and conservation. We used eight microsatellite markers to investigate evolutionary history of indigenous populations as well as genetic diversity and structure within and among indigenous and cultivated/naturalised populations distributed across the Balkan Peninsula. The results showed a clear separation between the indigenous and cultivated/naturalised groups, with the cultivated material originating from one restricted geographical area. Most of the genetic diversity in both groups was attributable to differences among individuals within populations, although spatial genetic analysis of indigenous populations indicated the existence of isolation by distance. Geographical structuring of indigenous populations was found using clustering analysis, with three sub-clusters of indigenous populations. The highest level of gene diversity and the greatest number of private alleles were found in the central part of the eastern Adriatic coast, while decreases in gene diversity and number of private alleles were evident towards the northwestern Adriatic coast and southern and eastern regions of the Balkan Peninsula. The results of Ecological Niche Modelling during Last Glacial Maximum and Approximate Bayesian Computation suggested two plausible evolutionary trajectories: 1) the species survived in the glacial refugium in southern Adriatic coastal region with subsequent colonization events towards northern, eastern and southern Balkan Peninsula; 2) species survived in several refugia exhibiting concurrent divergence into three genetic groups. The insight into genetic diversity and structure also provide the baseline data for conservation of S. officinalis genetic resources valuable for future breeding programmes.
Highlights
For thousands of years, people have gathered plant and animal resources for their needs, resulting in changes to genetic structure of populations over the course of cultivation and domestication
The analysis of 30 populations of S. officinalis using eight microsatellite markers revealed a high degree of genetic diversity in 23 indigenous populations and significantly lower genetic diversity in seven cultivated/naturalised populations; the two groups on the Balkan Peninsula could clearly be separated according to their origin
Cultivated/naturalised populations had significantly lower values of both observed and expected heterozygosity (Table 1). These findings are typical for domesticated species as the cultivation of wild plants always produces genetic bottlenecks, and results in loss of genetic diversity because of founder effects and unconscious or conscious artificial selection [106]
Summary
People have gathered plant and animal resources for their needs, resulting in changes to genetic structure of populations over the course of cultivation and domestication. This process is manifested in crop species used for food [1], but is less evident in medicinal and aromatic plants (MAP), which are still harvested primarily from wild populations [2, 3]. The cultivation of plants in proximity to their natural environment can induce introgressive hybridization between domesticated forms and their wild relatives, thereby impacting the initial loss of genetic diversity [1, 12]. Similarities in habitat and climate conditions can foster the naturalization of cultivated plants, expanding their influence on natural populations and surrounding biodiversity [13,14,15,16]
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