Parallel evolution of flower reduction in two alpineSoldanellaspecies (Primulaceae)

Abstract

The European endemic Soldanella has traditionally been divided into two morphologically well-defined sections. Section Tubiflores contains two species growing in high-elevation habitats, whereas most of the 14 species of section Soldanella inhabit montane forests. Section Tubiflores has a reduced floral morphology compared with section Soldanella. A previous phylogenetic study based on internal transcribed spacer (ITS) and AFLP data has revealed that, although the genus Soldanella itself is monophyletic, both sections are paraphyletic. Soldanella alpina (section Soldanella) forms a clade with S. minima and S. pusilla (section Tubiflores), and the grouping of S. alpina with S. pusilla has been hypothesized to be the result of hybridization between S. pusilla and an unidentified species of section Soldanella. We re-examined the phylogenetic relationships among the above species using additional sequence data (plastid DNA) and increasing the sample for ITS and AFLP data. Our new data confirmed that S. alpina is most closely related to S. pusilla. However, our data do not provide any evidence in support of the hypothesis that S. alpina is a hybrid species. In consequence, we consider it likely that the two species of section Tubiflores originated independently. The reduced floral morphology of these two alpine species is probably evidence for increased levels of self-pollination, ensuring reproductive success in a high-altitude habitat.

Karyological patterns in the European endemic genus Soldanella L.: Absolute genome size variation uncorrelated with cytotype chromosome numbers

“…We detected it both in typical snowbell species growing in humid forest biotopes as well as in species occupying higher alpine habitats and characterized by a reduced floral morphology (cf. Pawłowska, 1972; Zhang et al, 2001; Zhang and Kadereit, 2002; Steffen and Kadereit, 2014). In contrast, the dysploid cytotype 2 n = 38 occurs apparently more rare than that the 2 n = 40 cytotype, and it has been confirmed in populations assignable only to five taxa (Table 1; Appendices S1 and S2).…”

“…This hypothesis is also corroborated by the paucity of phylogenetic signal in the ITS region (see Results and cf. Zhang et al, 2001; Steffen and Kadereit, 2014; Bellino et al, 2015; Boucher et al, 2016). Alternative explanations of the AGS stasis in snowbells include existence of particular cytogenetic mechanism, maintaining the AGS conservatism by negative selection against individuals with diversified genomes (cf.…”

“…Members of the section Tubiflores occupy open, sunny habitats in the alpine to subnival belt characterized by arctic‐alpine ecology. Alpine biotopes are, however, inhabited also by two taxa morphologically belonging to the section Soldanella , namely, by S. alpina L. and S. rugosa L. B. Zhang (e.g., Pawłowska, 1972; Zhang and Kadereit, 2002; Steffen and Kadereit, 2014). Recent molecular investigations indicate that the sectional classification based on morphology and ecology is artificial and does not reflect true phylogenetic relationships within the genus (Zhang et al, 2001; Steffen and Kadereit, 2014; Bellino et al, 2015).…”

“…According to the current taxonomic concepts, the genus comprises 24 taxa (18 species and 6 subspecies), inhabiting various biotopes from midaltitudinal mountain forest to snow belt communities in the higher alpine belt of the major European mountain ranges (Pawłowska, 1972; Zhang et al, 2001; Zhang and Kadereit, 2002; Niederle, 2003, 2016; Marhold, 2011; Bellino et al, 2015). Members of this genus are some of the most studied European mountain plants, and a considerable interest has been devoted to their taxonomy, evolution, and biogeography (Pawłowska, 1972; Zhang et al, 2001; Zhang and Kadereit, 2002, 2004; Vargas, 2003; Niederle, 2003, 2016; Marhold, 2011; Steffen and Kadereit, 2014; de Vos et al, 2014; Bellino et al, 2015; Boucher et al, 2016). In spite of this, our knowledge about karyological diversity of snowbells is largely incomplete and fragmentary (see e.g., Kress, 1969, 1984; Zhang and Kadereit, 2002; Anderberg, 2004; Rice et al, 2014).…”

Evolution, ecology and systematics of Soldanella (Primulaceae) in the southern Apennines (Italy)

“…Soldanella with respect to a polyphyletic sect. Tubiflores and the independent evolution of floral reduction in the species of the latter were demonstrated [ 5 , 8 ].…”