# Plant Volatile Organic Compounds Evolution: Transcriptional Regulation, Epigenetics and Polylploidy
## 4 Evolution of VOCs: The Role of Polylploidy and Transgenerational Memory
Such changes in floral traits could impact pollinator attraction and lead to differentiation in the pollinator spectrum [154, 132], causing the isolation of diploids and polyploids and facilitating polyploid establishment. Although gene duplication and later neofunctionalization [155, 156] can promote such scent changes, rapid scent shifts could be presumably attributed to epigenetic remodeling following WGD [39, 136]. Therefore, the role of the epigenetic change associated with polyploidy on scent biosynthesis and emission (and its evolutionary contribution) deserves further investigation. In this respect, the carnation complex of _Dianthus broteri_ is an appropriate study system to investigate the interplay between epigenetics and polyploidy on the evolutionary change of floralvolatiles. This Iberian endemic complex represents the most extensive polyploid series of the _Dianthus_ genus, with diploid (2n = 30), tetraploid (2n = 60), hexaploid (2n = 90) and dodecaploid (2n = 180) individuals [157]. Molecular and genome size studies have demonstrated that it is an autopolyploid complex [158], in which the different cytotypes form independent and monophyletic lineages and show disjunct geographic distributions with monocytotypic populations and different ecological niches within an aridity gradient, with the higher cytotypes (6\(\times\) and 12\(\times\)) being those that inhabit more restricted and extreme habitats [159, 160]. It is also remarkable that, in this complex, polyploidy leads to an increased degree of DNA methylation [161] and of epigenetic variability, which may be crucial to phenotypic divergence (i.e., changes in VOCs), adaptation and shifts in biotic interactions [162, 37, 163]. Previous studies [164, 16] have shown phenotypic differences in floral traits (floral size, distance to access the nectar and scent) between _D. broteri_ cytotypes that may promote changes in pollinator patterns. The highest ploidy level (12\(\times\), _D. inoxianus_) involves a highly specialized pollination by a single pollinator, _Hyles livornica._ The floral scent of this cytotype is dominated by sesquiterpenoids and fatty acid derivatives (2-ketones), which shown a circadian emission [16]. The 2-ketones elicit responses in the antennae of the single pollinator, but also have a repellent/insecticide activity [165]. They show an explosive increase in production, triggered by experimental damage to _D. inoxianus_ flowers, which indicates that 2-ketones may be acting like a floral filter of the alleged pollinator spectrum, leading to pollinator specialization [16]. Supporting this \"filtering hypothesis\", these ketones appear in low quantities at diploid and tetraploid levels, which show a wider pollinator spectrum [166]. In addition, dominant aromatic compound changes (e.g., the disappearance of \(\beta\)-ocimene in 4\(\times\) and 12\(\times\) and the dominance of \(\beta\)-caryophyllene in 2\(\times\) and 4\(\times\)) suggest that shifts in the expression of scent-related genes may be promoting greater specialization in higher polyploids. We suggest a combination of epigenomics, biochemical and pollination biology methods to investigate whether epigenetics is involved in polyploid evolution by means of floral VOCs and pollinator shifts.