Today, about 30 years aft er the beginning of the "molecular revolution" of systematics, we have relatively good knowledge of angiosperm evolution and interrelationships among major groups ( APG III, 2009 ). Th ere are, however, still unanswered phylogenetic questions and unresolved nodes. Furthermore, contemporary knowledge of plant phylogeny typically derives from plastid data, which have been widely used for resolving evolutionary relationships. Early phylogenetic studies based on analysis of the rubisco gene rbcL ( Olmstead et al., 1992 ;Chase et al., 1993 ;Bremer et al., 1995 ) inspired, and the availability of universal primers (e.g., Zurawski and Clegg, 1987 ;Taberlet et al., 1991 ) enhanced molecular laboratory work, resulting in numerous phylogenetic studies on land plants during the subsequent decades. Typically, these studies were single-gene or multigene studies, i.e., they were based on one to several gene regions. Following recent developments, new sequencing techniques permit time-and cost-effi cient production of much more data, e.g., entire genomes, but it is nevertheless still not fully clear to what extent phylogenomics can signifi cantly increase our understanding of land plant phylogeny.While it was early recognized that data from the nuclear and mitochondrial genomes are desirable, such data have been much less used for the purpose of resolving evolutionary relationships in plants than have plastid data. Using nuclear genes may pose biological challenges associated with, for example, allelic variation and paralogy, as well as methodological problems with availability of general primers and requirements of fresh plant material (see e.g., Zimmer and Wen, 2012 ). The exception is nuclear ribosomal DNA, which is present in many copies that are assumed to be
PREMISE OF THE STUDY:Reconstruction of plant phylogeny has heavily relied on single-gene or multigene plastid data. New sequencing methods have led to an increasing number of studies based on data from the entire plastid, but the mitochondrion has rarely been used to infer plant phylogeny because of an assumed information poverty and demonstrated lateral transfer of mitochondrial gene regions between distantly related species.
METHODS:We explored phylogenetic information from the plant mitochondrion using 57 representatives of the species-rich coff ee family as study system and assessed consistency with previous results based (mostly) on plastid data.
KEY RESULTS:We showed that the mitochondrial genome can provide structured and statistically signifi cant information on plant phylogeny. While most of our results are consistent with those based on plastid data, some surprising and statistically signifi cant confl icts emerge, and our study demonstrates with striking clarity that the phylogeny of Rubiaceae is far from resolved.CONCLUSIONS: It appears unlikely that confl icts between results retrieved from the diff erent genomic compartments would be restricted to Rubiaceae. Rather, they are probably a general phenomenon and an important facto...