No abstract

The current infrafamilial taxonomy of the Iridaceae recognizes four subfamilies; Isophysidoideae (1: 1); Nivenioideae (6: ca. 92), Iridoideae (29: 890), and Crocoideae (29: 1032). Phylogenetic analyses of sequences of five plastid DNA regions, rbcL, rps4, trnL–F, matK, and rps16, confirm most aspects of this classification and the evolutionary patterns that they imply, importantly the sisiter relationship of Isophysidoideae to the remainder of the family and the monophyly of Iridoideae. Subfamily Nivenioideae is, however, paraphyletic; Crocoideae is consistently found nested within it, sister to the core Nivenioideae, the woody Klattia, Nivenia, and Witsenia. This clade is sister to Aristea, which in turn is sister to the Madagascan Geosiris, and then to the Australasian Patersonia. We treat Aristea, Geosiris, and Patersonia as separate subfamilies, Aristeoideae and the new Geosiridaceae and Patersonioideae, rendering Nivenioideae and Crocoideae monophyletic. The alternative, uniting a widely circumscribed Nivenioideae and Crocoideae, seems undesirable because Nivenioideae have none of the numerous synapomorphies of Crocoideae, and that subfamily includes more than half the total species of Iridaceae. Main synapomorphies of Crocoideae are: pollen operculate; exine perforate; ovule campylotropous; root xylem vessels with simple perforations; rootstock a corm; inflorescence usually a spike; plants deciduous. Four more derived features of Crocoideae are shared only with core Nivenioideae: flowers long-lived; perianth tube well developed; flowers sessile; and septal nectaries present. The genera of the latter subfamily are evergreen shrubs, have monocot-type secondary growth, tangentially flattened seeds, and the inflorescence unit is a binate rhipidium. The latter feature unites core Nivenioideae with Aristea, Geosiris, and Patersonia, which have fugaceous flowers and, with few exceptions, a blue perianth. Molecular-based phylogenetic trees using sequences from five plastid DNA regions now show discrete generic clusters within Crocoideae and Iridoideae, the foundation for the tribal classification. The five tribe classification of Iridoideae, initially based on morphological characters and subsequently supported by a four plastid DNA region sequence analysis, continues to receive support using additional DNA sequences. Application of molecular clock techniques to our phylogeny indicates that the Iridaceae differentiated in the late Cretaceous and diverged from the next most closely related family, Doryanthaceae circa 82 mya, thus during the Campanian. The Tasmanian Isophysis is the only extant member of the clade sister to the remainder of the Iridaceae, from which it may have diverged 66 mya, in the Maastrichtian. The generic phylogeny shows the proximal clades of the family are all Australasian, which corroborates past hypotheses that the Iridaceae originated in Antarctica-Australasia, although its subsequent radiation occurred elsewhere, notably in southern Africa and temperate and highland South America at the end of the Eocene or later.

ABSTRACT. Onagraceae are a family of 17 genera in seven tribes, with the majority of species in tribes Onagreae and Epilobieae. Despite the species-richness of these two tribes, to date no phylogenetic study has been done with suf cient taxon sampling to examine relationships between and within these tribes. In this study, we used DNA sequence data from one nuclear region (ITS) and two chloroplast regions (trnL-trnF and rps16) to infer phylogenetic relationships among 93 taxa across the family, with concentrated sampling in the large tribe Onagreae. Results strongly suggest that tribe Gongylocarpeae is sister to tribes Epilobieae 1 Onagreae, both of which are monophyletic. Within Onagreae, Camissonia seems to be broadly paraphyletic, and Oenothera is also paraphyletic. In Oenothera there appear to be two lineages, one of which has Gaura 1 Stenosiphon nested within it. At the base of the Onagraceae phylogeny, we have clari ed previous confusion regarding con icting placements of Hauya and Lopezia based on nuclear versus chloroplast data. Results of these analyses are supported by morphology and suggest the need for new taxonomic delimitations, which are forthcoming.

Societal Impact Statement Crop wild relatives (CWR) are plant taxa closely related to crops and are a source of high genetic diversity that can help adapt crops to the impacts of global change, particularly to meet increasing consumer demand in the face of the climate crisis. CWR provide vital ecosystem services and are increasingly important for food and nutrition security and sustainable and resilient agriculture. They therefore are of major biological, social, cultural and economic importance. Assessing the extinction risk of CWR is essential to prioritise in situ and ex situ conservation strategies in Mesoamerica to guarantee the long‐term survival and availability of these resources for present and future generations worldwide. Summary Ensuring food security is one of the world's most critical issues as agricultural systems are already being impacted by global change. Crop wild relatives (CWR)—wild plants related to crops—possess genetic variability that can help adapt agriculture to a changing environment and sustainably increase crop yields to meet the food security challenge. Here we report the results of an extinction risk assessment of 224 wild relatives of some of the world's most important crops (i.e. chilli pepper, maize, common bean, avocado, cotton, potato, squash, vanilla and husk tomato) in Mesoamerica—an area of global significance as a centre of crop origin, domestication and of high CWR diversity. We show that 35% of the selected CWR taxa are threatened with extinction according to The International Union for Conservation of Nature (IUCN) Red List demonstrates that these valuable genetic resources are under high anthropogenic threat. The dominant threat processes are land use change for agriculture and farming, invasive and other problematic species (e.g. pests, genetically modified organisms) and use of biological resources, including overcollection and logging. The most significant drivers of extinction relate to smallholder agriculture—given its high incidence and ongoing shifts from traditional agriculture to modern practices (e.g. use of herbicides)—smallholder ranching and housing and urban development and introduced genetic material. There is an urgent need to increase knowledge and research around different aspects of CWR. Policies that support in situ and ex situ conservation of CWR and promote sustainable agriculture are pivotal to secure these resources for the benefit of current and future generations.

No abstract

Mexico is a megadiverse country. Presently, 22 126 species of angiosperms have been registered within its territory and 11 001 are considered to be endemic. However, their geographical distributions are far from homogeneous. In addition, Mexico is the center of diversification of several groups. Our analysis focused on such groups. The aims were to identify areas of species richness and endemism. A data matrix with 766 species and 25 579 geographical records was analyzed. It included Calochortus (Liliaceae); Bletia (Orchidaceae); Tigridieae (Iridaceae); Amaryllidaceae; Poliantheae, Echeandia (Asparagaceae); Crassulaceae; Hylocereus (Cactaceae); Solanum, Lycianthes and Physalinae (Solanaceae); Salvia section Membranaceae (Lamiaceae); and Cosmos and Dahlia (Asteraceae). Using Geographic Information Systems, we determined richness and distribution based on: (i) Mexican political divisions, (ii) biogeographical regions and provinces, (iii) a grid of 0.5 × 0.5° cells, and (iv) elevation. The areas of endemism were estimated using the endemicity analysis. The highest number of taxa and endemic plants were concentrated within the Transmexican Volcanic Belt in the Mexican Transition Zone. This mountain range has been recognized as a province on the basis of geologic, tectonic, geomorphologic, physiographic and biogeographic criteria. It is a 1000 km long volcanic arc that extends east to west through Central Mexico and is variably from 80 to 230 km wide, between 17°30′ to 20°25′N and 96°20′ to 105°20′W. Our results represent a local deviation from the global richness latitudinal gradient of angiosperm species.

The phylogenetic relationships among 23 species of the tribe Tigridieae (lridaceae) were inferred using morphological data and nucleotide sequences from nuclear ITS and three intergenic spacers of the cpDNA: psbA-trnH, trnT-trnL, and trnL-trnE Although all data sets supported a monophyletic Mexican-Guatemalan Tigridiinae including two taxa usually placed in Cipurinae (Cardiostigma longispatha and Nemastylis convoluta), neither morphology, cpDNA, nor ITS resolved phylogenetic relationships within this lineage. A graphical tree of trees analysis showed the cladograms derived from morphology to be the most topologically distinct within the set of all trees examined and to be the set with most divergent trees. Finally, cladistic analysis of the combined data sets supported the recurrent dispersal of Cipurinae from South to North America and a South American origin of the Mexican-Guatemalan subtribe Tigridiinae.

Here, we review progress and prospects to explicitly test for long distance dispersal biogeographic events. Long distance dispersal represents a “jump” across some kind of barrier, such as a topographic feature or a zone of unsuitable climate and may include repeated jumps, or stepping‐stone dispersals. Long distance dispersals were considered integral for explaining the organization of biodiversity at large and small scales by early biogeographers, such as Darwin and Wallace. Darwin, Wallace, and others envisioned that long distance dispersals were predictable events because the vectors for dispersal, such as animals, winds, and currents, behaved in non‐random ways. However, these early biogeographers found that dispersal was hard to observe, and, later, with the advent of the theory of Continental Drift, vicariance became regarded as a better scientific explanation for the arrangement of biodiversity, because it represented a falsifiable hypothesis. Thus, long distance dispersal was reduced to a nuisance parameter in biogeography; a random possibility that could never fully be ruled out in a scenario in which evidence supported vicariance. Today, there is strong interest to more fully integrate long distance dispersal into understanding the assembly and organization of biodiversity on earth. In this review, we discuss progress and prospects for explicitly testing long distance dispersal hypotheses including through uses of molecular, morphological, paleontological, and informatics methods. We focus on hypothesis testing of long distance dispersals involved in the assembly of the flora of North America, which is a robust preliminary study system on account of its extant and extinct biodiversity being well‐catalogued.