Phylogenetic relationships of the monotypic genera Halacsya and Paramoltkia and the origins of serpentine adaptation in circum‐mediterranean Lithospermeae (Boraginaceae): insights from ITS and matK DNA sequences

Abstract

AbstractHalacsya and Paramoltkia are monotypic and partially sympatric genera in the Balkans, with no clear relationships among extant Lithospermeae due to striking morphological autapomorphies and scarcity of phylogenetic analyses in this group. The two species H. sendtneri and P. doerfleri show a strict selectivity for serpentine soils, posing the question whether this edaphic specialization reflects a common ancestry or a parallel process of adaptive evolution in unrelated lineages. DNA sequences from the nuclear ITS and chloroplast matK regions were generated from multiple accessions of Halacsya and Paramoltkia, and from representatives of 16 other genera of Mediterranean Lithospermeae. SEM analyses of pollen morphology were also conducted to test relationships indicated by molecular phylogenies. Parsimony analyses retrieved a clade of morphologically well differentiated monotypic Lithospermeae including Halacsya and Paramoltkia. ITS provided a better resolution of relationships and showed the two genera to be sistergroups close to Mairetis and Moltkiopsis, and no affinity to Moltkia as supposed by past authors. Pollen characters corroborated the phylogenetic link between the two Balkan genera. Five further monophyletic clades were recognised: Onosma‐Echium, Moltkia, Lithospermum s.l., Arnebia‐Macrotomia, and Alkanna‐Podonosma. Mapping the edaphic preferences of Lithospermeae onto molecular cladograms showed that serpentinophytism as an obligate condition originated separately in the clade of monotypic genera and in that of Onosma‐Echium. In Halacsya and Paramoltkia it represents an early ecological synapomorphy which probably originated in situ from non‐serpentine ancestors related to Moltkiopsis and Mairetis.