Abstract
Recent phylogenetic works have begun to address long-standing questions regarding the systematics of Campanula (Campanulaceae). Yet, aspects of the evolutionary history, particularly in northwestern North America, remain unresolved. Thus, our primary goal in this study was to infer the phylogenetic positions of northwestern Campanula species within the greater Campanuloideae tree. We combined new sequence data from 5 markers (atpB, rbcL, matK, and trnL-F regions of the chloroplast and the nuclear ITS) representing 12 species of Campanula with previously published datasets for worldwide campanuloids, allowing us to include approximately 75% of North American Campanuleae in a phylogenetic analysis of the Campanuloideae. Because all but one of North American Campanula species are nested within a single campanuloid subclade (the Rapunculus clade), we conducted a separate set of analyses focused specifically on this group. Our findings show that i) the campanuloids have colonized North America at least 6 times, 4 of which led to radiations, ii) all but one North American campanuloid are nested within the Rapunculus clade, iii) in northwestern North America, a C. piperi – C. lasiocarpa ancestor gave rise to a monophyletic Cordilleran clade that is sister to a clade containing C. rotundifolia, iv) within the Cordilleran clade, C. parryi var. parryi and C. parryi var. idahoensis exhibit a deep, species-level genetic divergence, and v) C. rotundifolia is genetically diverse across its range and polyphyletic. Potential causes of diversification and endemism in northwestern North America are discussed.
Highlights
The Campanulaceae, or Bellflowers, is a nearly cosmopolitan family known worldwide for its attractive bluish, bell-shaped flowers
Our analyses provide new insights into the biogeographic and evolutionary history of Campanula in North America
The Campanuloideae tree (Fig. 1) generated from three concatenated cpDNA markers exhibits a high degree of structure, revealing the diversity of North American Campanula and their evolutionary relationships
Summary
The Campanulaceae, or Bellflowers, is a nearly cosmopolitan family known worldwide for its attractive bluish, bell-shaped flowers. Though it has received considerable attention by taxonomists, the classification and phylogenetic relationships within the family remain highly controversial. The 84 genera of Campanulaceae are divided among five subfamilies, the largest and most widespread being Campanuloideae Burnett and Lobelioideae Burnett, with 1045 and 1192 species, respectively [2]. Within the Campanuloideae, taxonomists variously assign species to one of 35 to 55 genera across three tribes – the Campanuleae, the Wahlenbergiaeae, and the Platycodoneae [3,4]. [2,3,5] of the tribe Campanuleae [6] Most species (ca. 420) are currently included within the poorly resolved, polyphyletic genus Campanula L. [2,3,5] of the tribe Campanuleae [6]
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