A Multigene Phylogeny of Native American Hawkweeds (Hieracium Subgen. Chionoracium, Cichorieae, Asteraceae): Origin, Speciation Patterns, and Migration Routes

Abstract

Native American hawkweeds are mainly mountainous species that are distributed all over the New World. They are severely understudied with respect to their origin, colonization of the vast distribution area, and species relationships. Here, we attempt to reconstruct the evolutionary history of the group by applying seven molecular markers (plastid, nuclear ribosomal and low-copy genes). Phylogenetic analyses revealed that Chionoracium is a subgenus of the mainly Eurasian genus Hieracium, which originated from eastern European hawkweeds about 1.58–2.24 million years ago. Plastid DNA suggested a single origin of all Chionoracium species. They colonized the New World via Beringia and formed several distinct lineages in North America. Via one Central American lineage, the group colonized South America and radiated into more than a hundred species within about 0.8 million years, long after the closure of the Isthmus of Panama and the most recent uplift of the Andes. Despite some incongruences shown by different markers, most of them revealed the same crown groups of closely related taxa, which were, however, largely in conflict with traditional sectional classifications. We provide a basic framework for further elucidation of speciation patterns. A thorough taxonomic revision of Hieracium subgen. Chionoracium is recommended.

Sperm‐dependent asexual species and their role in ecology and evolution

“…Recent data offer controversial support for this hypothesis since most known tetraploids derived from extant triploids are rather sterile or have a fitness disadvantage (reviewed in Choleva & Janko, 2013). Nevertheless, there exists empirical evidence that established obligatory asexuals may revert to sex, as found, for example, in Oribatid mites (Domes et al, 2007) and some plant taxa, like Hieracium pilosella (Fehrer et al, 2005). In fish, Squalius (Cunha et al, 2008), the asexuals relying on sperm apparently reverted to normal meiosis after gaining balanced genome composition following sperm incorporation.…”