Morphological, genetic and host-plant diversification in pollen-beetles of the Brassicogethes coracinus group (Coleoptera: Nitidulidae: Meligethinae)

The 17 known members of the mostly Western Palaearctic Brassicogethes coracinus species group (highly specialized pollen beetles associated with flowers of Brassicaceae) were re-analyzed, with the aim to reconstruct their phylogenetic relationships and the pattern of evolution of their larval/host-plant associations. Evidence from mtDNA data (COI marker), combined with an estimation of divergence times, placed the main differentiation of the clade around 5 My with most species likely differentiated in the last 1–2 My. Combined evidence from mtDNA, morphology and ancestral state parsimony reconstruction of larval/host-plant associations, suggested that Brassicaceae of the tribe Brassiceae likely represented the ancestral host plants for the group, with a subsequent series of independent host shifts during the evolution and radiation of the clade (in association first with Cardamineae, and later with Arabideae, Sisymbrieae, Erysimeae, Hesperideae and Anchonieae). Molecular and ecological evidence also suggests the need to formally separate European populations of the widespread Brassicogethes subaeneus (Sturm, 1845) into two distinct and widely sympatric cryptic taxa, one of them described herein as new (Brassicogethes cardaminicola sp. nov.). The neotype of the true B. subaeneus is also herein designated.