Reconstructing the history of Campanulaceae with a Bayesian approach to molecular dating and dispersal–vicariance analyses

Abstract

a b s t r a c tWe reconstruct here the spatial and temporal evolution of the Campanula alliance in order to better understand its evolutionary history. To increase phylogenetic resolution among major groups (Wahlenbergieae-Campanuleae), new sequences from the rbcL region were added to the trnL-F dataset obtained in a previous study. These phylogenies were used to infer ancestral areas and divergence times in Campanula and related genera using a Bayesian approach to molecular dating and dispersal-vicariance analyses that takes into account phylogenetic uncertainty. The new phylogenetic analysis confirms Platycodoneae as the sister group of Wahlenbergieae-Campanuleae, the two last ones inter-graded into a well-supported clade. Biogeographic and dating analyses suggest that Western Asia and the Eastern Mediterranean have played a major role as centers of migration and diversification within the Campanula alliance, probably in relation to the intense orogenic activity that took place in this region during the Late Neogene, and that could have promoted isolation and allopatric speciation within lineages. Diversification rates within several Campanula lineages would have increased at the end of the Miocene, coinciding with the Messinian Stage. Strong selective pressures from climate changes and the expansion of mountainous regions during this period are suggested to explain the adaptation to drought, cold or disturbed environments observed in many Campanula species. Several independent long-distance dispersal events to North America are inferred within the Rapunculus clade, which seem to be related to high ploidy levels.

Phylogenetic assessment and biogeographic analyses of tribe Peracarpeae (Campanulaceae)

“…3) Adenophora, Hanabusaya and Campanula have been placed in the tribe Campanuleae (Hong et al 1983;Kolakovskii 1987;Hong 1995;Takhtajan 1997). Campanula has been shown to be polyphyletic (Eddie et al 2003;Haberle et al 2009;Roquet et al 2009). Nevertheless, Campanula and its close allies, including Adenophora, Hanabusaya and Zeugandra P.H.…”

“…These fossil seeds have been ascribed to Campanula paleopyramidalis Lanc-Srod., as they closely resemble those of C. pyramidalis L., an Italian-Balkan extant species in the Rapunculus clade (the c-2 clade in Haberle et al 2009), although some of the seed characteristics appear in other species of this clade (Haberle et al 2009). With the difficulty in placing the fossils with confidence in the large polyphyletic genus Campanula (Haberle et al 2009;Roquet et al 2009), Roquet et al (2009) adopted a conservative approach and used these fossils as a minimum age constraint for the whole campanuloids. Cellinese et al (2009) and Frajman and Schneeweiss (2009) used the same fossil record to date the stem age of C. pyramidalis and its sister species C. carpatica Jacq.…”

“…Taxa of campanuloids in North America were hypothesized to have migrated from Eurasia (Haberle et al 2009;Roquet et al 2009). Our biogeographic analyses using LAGRANGE suggest the ancestral area of the Rapunculus clade (the c-2 clade in Haberle et al 2009) and the c-2a clade (Fig.…”

“…He also proposed that Homocodon may be most closely related to Adenophora Fisch., which has the chromosome number x = 17. Recent molecular analyses (Eddie et al 2003;Cosner et al 2004;Haberle et al 2009;Roquet et al 2009) have supported two major clades in Campanulaceae: the platycodonoids sister to a clade that includes the walenbergioids and campanuloids. The smaller platycodonoid clade includes taxa with colporate/colpate pollen grains, and the clade includes Codonopsis Wall., Platycodon A.DC., and several other eastern Asian genera.…”

“…The trans-Beringia distributions have been explained by the Beringia serving as a glacial refugium, or the Bering land bridge as a dispersal highway, or relicts that were more widely distributed in the past or recent long-distance dispersals (see review by Ickert-Bond et al 2009). The circumpolar Campanula rotundifolia was supposed to have dispersed from Eurasia to the Arctic North America (Roquet et al 2009). Nevertheless, our focus in the present study is to evaluate the disjunction between eastern Asia and western North America, and we will not discuss the cases of transBeringian and circumpolar distributions here.…”