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Abstract—The diverse and spectacular Hibisceae tribe comprises over 750 species. No studies, however, have broadly sampled across the dozens of genera in the tribe, leading to uncertainty in the relationships among genera. The non-monophyly of the genusHibiscusis infamous and challenging, whereas the monophyly of most other genera in the tribe has yet to be assessed, including the large genusPavonia.Here we significantly increase taxon sampling in the most complete phylogenetic study of the tribe to date. We assess monophyly of most currently recognized genera in the tribe and include three and thirteen newly sampled sections ofHibiscusandPavonia,respectively. We also include five rarely sampled genera and 137 species previously unsampled. Our phylogenetic trees demonstrate thatHibiscus, as traditionally defined, encompasses at least 20 additional genera. The status ofPavoniaemerges as comparable in complexity toHibiscus. We offer clarity in the phylogenetic placement of several taxa of uncertain affinity (e.g.Helicteropsis,Hibiscadelphus, Jumelleanthus,andWercklea). We also identify two new clades and elevate them to the generic rank with the recognition of two new monospecific genera: 1)BlanchardiaM.M.Hanes & R.L.Barrett is a surprising Caribbean lineage that is sister to the entire tribe, and 2)AstrohibiscusMcLay & R.L.Barrett represents former members ofHibiscus caesiuss.l.CraveniaMcLay & R.L.Barrett is also described as a new genus for theHibiscus panduriformisclade, which is allied toAbelmoschus. Finally, we introduce a new classification for the tribe and clarify the boundaries ofHibiscusandPavonia. 

Abstract Background Mosses in high-latitude ecosystems harbor diverse bacterial taxa, including N 2 -fixers which are key contributors to nitrogen dynamics in these systems. Yet the relative importance of moss host species, and environmental factors, in structuring these microbial communities and their N 2 -fixing potential remains unclear. We studied 26 boreal and tundra moss species across 24 sites in Alaska, USA, from 61 to 69° N. We used cultivation-independent approaches to characterize the variation in moss-associated bacterial communities as a function of host species identity and site characteristics. We also measured N 2 -fixation rates via 15 N 2 isotopic enrichment and identified potential N 2 -fixing bacteria using available literature and genomic information. Results Host species identity and host evolutionary history were both highly predictive of moss microbiome composition, highlighting strong phylogenetic coherence in these microbial communities. Although less important, light availability and temperature also influenced composition of the moss microbiome. Finally, we identified putative N 2 -fixing bacteria specific to some moss hosts, including potential N 2 -fixing bacteria outside well-studied cyanobacterial clades. Conclusions The strong effect of host identity on moss-associated bacterial communities demonstrates mosses’ utility for understanding plant-microbe interactions in non-leguminous systems. Our work also highlights the likely importance of novel bacterial taxa to N 2 -fixation in high-latitude ecosystems. 

Moss-associated N2 fixation provides a substantial but heterogeneous input of new N to nutrient-limited ecosystems at high latitudes. In spite of the broad diversity of mosses found in boreal and Arctic ecosystems, the extent to which host moss identity drives variation in N2 fixation rates remains largely undetermined. We used 15N2 incubations to quantify the fixation rates associated with 34 moss species from 24 sites ranging from 60° to 68° N in Alaska, USA. Remarkably, all sampled moss genera fixed N2, including well-studied feather and peat mosses and genera such as Tomentypnum, Dicranum, and Polytrichum. The total moss-associated N2 fixation rates ranged from almost zero to 3.2 mg N m−2 d−1, with an average of 0.8 mg N m−2 d−1, based on abundance-weighted averages of all mosses summed for each site. Random forest models indicated that moss taxonomic family was a better predictor of rate variation across Alaska than any of the measured environmental factors, including site, pH, tree density, and mean annual precipitation and temperature. Consistent with this finding, mixed models showed that trends in N2 fixation rates among moss genera were consistent across biomes. We also found “hotspots” of high fixation rates in one-fourth of sampled sites. Our results demonstrated the importance of moss identity in influencing N2 fixation rates. This in turn indicates the potential utility of moss identity when making ecosystem N input predictions and exploring other sources of process rate variation.