Small genomes dominate in plants growing on serpentine soils in West Balkans, an exhaustive study of 8 habitats covering 308 taxa

Abstract

Habitats on ultramafic substrate present a hostile environment for plant development. We aimed to determine whether any particular range of genome size is favoured in such habitats. Genome sizes of natural serpentinophyte populations were estimated using propidium iodide cytometry and compared with published data by phylogeny paired t-tests with plants from other substrata. The panel included 308 taxa belonging to 213 genera, with new values for 28 genera and 93 species. Using Leitch’s criteria, 56 % taxa belong to the group very small genomes (1C ≤ 1.4 pg), 22 % to small (1.4–3.5 pg), 19 % to intermediary (3.5–14 pg), 3 % to large (14–35 pg) and 0.31 % to very large (1C ≥ 35 pg). The majority of species were either indifferent for substrate (56 %) or facultative serpentinophytes (33 %). Most obligate serpentinophytes possessed very small genomes, and none exceeded 5 pg (1C). On average, plants growing on serpentine exhibited lower Cx-values than the same taxa growing on other soil types. About 4 % of species were annuals and 88 % perennials. Hemicryptophytes were dominant. Presence of at least two ploidy levels was recorded for 10 species. Water stress, high temperatures and presence of heavy metals in serpentine habitats impose a high selective pressure and favour perennial species with very small genomes.