Effect of clones, year of harvest and geographical origin of fruits on quality and chemical composition of Argan oil

Argan oil is precious oil with food and cosmetic uses. In recent years, this oil has been subject to an increasing national and international demand. The present work aims at studying the effect of clones and age, year of harvest and geographical origin on Argan oil quality and chemical composition. The results indicate that age does not affect Argan oil quality and fatty acids content. However, clones had a significant effect on fatty acids and tocopherol levels. Saturated and unsaturated fatty acids were highly influenced by the year of harvest and geographical origin, presumably due to climatic conditions. Unsaturated fatty acids varied from 78.28% to 81.77%. Depending on clones, total tocopherols varied from 687.40 mg/kg to 1068 mg/kg. This study is useful for the choice of clones with the aim of developing Argan trees orchards destined to oil production.

Do island plant populations really have lower genetic variation than mainland populations? Effects of selection and distribution range on genetic diversity estimates

Ecological and evolutionary studies largely assume that island populations display low levels of neutral genetic variation. However, this notion has only been formally tested in a few cases involving plant taxa, and the confounding effect of selection on genetic diversity (GD) estimates based on putatively neutral markers has typically been overlooked. Here, we generated nuclear microsatellite and plastid DNA sequence data in Periploca laevigata, a plant taxon with an island-mainland distribution area, to (i) investigate whether selection affects GD estimates of populations across contrasting habitats; and (ii) test the long-standing idea that island populations have lower GD than their mainland counterparts. Plastid data showed that colonization of the Canary Islands promoted strong lineage divergence within P. laevigata, which was accompanied by selective sweeps at several nuclear microsatellite loci. Inclusion of loci affected by strong divergent selection produced a significant downward bias in the GD estimates of the mainland lineage, but such underestimates were substantial (>14%) only when more than one loci under selection were included in the computations. When loci affected by selection were removed, we did not find evidence that insular Periploca populations have less GD than their mainland counterparts. The analysis of data obtained from a comprehensive literature survey reinforced this result, as overall comparisons of GD estimates between island and mainland populations were not significant across plant taxa (N = 66), with the only exception of island endemics with narrow distributions. This study suggests that identification and removal of markers potentially affected by selection should be routinely implemented in estimates of GD, particularly if different lineages are compared. Furthermore, it provides compelling evidence that the expectation of low GD cannot be generalized to island plant populations.