Spatio-temporal history of the disjunct family Tecophilaeaceae: a tale involving the colonization of three Mediterranean-type ecosystems

Evolutionary diversity of the endemic genera of the vascular flora of Chile and its implications for conservation

As a direct consequence of global change, both natural and human-induced, a high percentage of biodiversity is now under threat worldwide. This has urged conservation planners to formulate and/or improve existing strategies to preserve species and their ecosystems. In this context, the present study focuses on two strategies using phylogeny-based measures of biodiversity to account for the processes that led to the biodiversity patterns observed today. It will contribute additional information that can aid decision-making regarding the assignment of threat status for some species, thus strengthening measures currently in use and facilitate the allocation of often scarce conservation resources. The Evolutionarily Distinct (ED) index prioritises species that are on long branches of the tree of life with few descendants, and the Evolutionarily Distinct and Globally Endangered (EDGE) index integrates evolutionary history with IUCN Red List threat status of species. It has been used mostly in animal groups, but since the threats faced by many plants have not been evaluated, it has been more difficult to compile for plants worldwide. Here, we apply the EDGE metric to species of the endemic genera of Chile. However, more than 50% of the endemic flora of the country are still lacking official threat status. We thus used an alternative measure (Relative Evolutionary Distinctness-RED), based on a range-weighted phylogenetic tree, which uses geographic ranges to adjust branch lengths, and calculate ED. The RED index was shown to be a suitable measure, yielding similar results compared to EDGE, at least for this group of species. Given the urgency to halt biodiversity loss and the time it would take to evaluate all species, we propose that this index is used to set conservation priorities until we can calculate EDGE for these unique endemic species. This would allow guiding decision-making until we can gather more data to assess and assign conservation status to new species.

Biogeographic history and environmental niche evolution in the palearctic genus Helianthemum (Cistaceae)

The biogeographic history and the degree of environmental niche conservatism provide essential clues to decipher the underlying macroevolutionary processes of species diversification and to understand contemporary patterns of biodiversity. The genus Helianthemum constitutes an excellent case study to investigate the impact of the geo-climatic changes and the environmental niche shifts on the origins of plant species diversity in the Mediterranean hotspot. It is a palearctic species-rich lineage with c. 140 species and subspecies mostly belonging to three distinct evolutionary radiations, almost confined to the Mediterranean region and occurring across varied environmental conditions. In this work, we studied the ample and rapid diversification of the genus Helianthemum across its whole distribution range by performing phylogenetic reconstructions of ancestral ranges and environmental niche evolution. We observed a striking synchrony of biogeographic movements with niche shifts between the three major clades of the genus Helianthemum, likely related to the geo-climatic events occurred in the Mediterranean Basin since the Upper Miocene. In particular, Late Miocene and Early Pliocene were dominated by episodes of range expansions, the Late Pliocene by range contraction and vicariance events, and Pleistocene by most intense environmental niche shifts and in-situ diversification. Our study also provides evidence for four main environmental niches in Helianthemum (i.e., Mediterranean, subdesert, humid-montane and subtropical-insular) and a tendency toward environmental niche conservatism within different subclades, with few niche shifts mostly occurring from Mediterranean ancestors. The relative longer time spent in Mediterranean areas by the ancestors of Helianthemum suggests that the larger species diversity observed in the Mediterranean (i.e. Northern Africa and Southern Europe) may have been generated by a time-for-speciation effect reinforced by environmental niche conservatism. Overall, our work highlights the role of the Mediterranean Basin as a 'cradle of diversity' and an 'evolutionary hub', facilitating the environmental transitions and determining the building up of a global plant biodiversity hotspot.

Phylogeny and biogeography of Maianthemum (Asparagaceae: Nolinoideae) revisited with emphasis on its divergence pattern in SW China

Maianthemum is a genus with more than 35 species from the tribe Polygonateae (Asparagaceae), widely distributed between North to Central Americas and eastern Asia with high diversity in the eastern Himalayas to the Hengduan Mountains of SW China. Although most species from SW China form a well-supported clade, phylogenetic relationships within this clade remain unclear. With a broad level of taxon sampling and an extensive character sampling from eight DNA regions, this study intends to revisit the phylogeny and biogeography of the genus to better understand the divergence patterns of species from SW China. Phylogenetic results suggested the monophyly of Maianthemum with recognition of nine strongly supported clades, but backbone relationships among these clades remained largely uncertain. For the SW China clade, individuals from the same species are grouped into different lineages. Our results revealed that the fast radiation of the SW China clade was occurred in the eastern Himalayas, followed by subsequent radiation in the Hengduan Mountains in the Pliocene. Intercontinental disjunctions of Maianthemum in the Northern Hemisphere appear to have occurred multiple times during the late Miocene to the Pliocene, likely resulted by a combination of both vicariance and long-distance dispersal events.

The fruticose genera in the Ramalinaceae (Ascomycota, Lecanoromycetes): their diversity and evolutionary history

We present phylogenetic analyses of the fruticose Ramalinaceae based on extensive collections from many parts of the world, with a special focus on the Vizcaíno deserts in north-western Mexico and the coastal desert in Namibia. We generate a four-locus DNA sequence dataset for accessions of Ramalina and two additional loci for Niebla and Vermilacinia. Four genera are strongly supported: the subcosmopolitan Ramalina, the new genus Namibialina endemic to SW Africa, and a duo formed by Niebla and Vermilacinia, endemic to the New World except the sorediate V. zebrina that disjunctly occurs in Namibia. The latter three genera are restricted to coastal desert and chaparral where vegetation depends on moisture from ocean fog. Ramalina is subcosmopolitan and much more diverse in its ecology. We show that Ramalina and its sister genus Namibialina diverged from each other at c. 48 Myrs, whereas Vermilacinia and Niebla split at c. 30 Myrs. The phylogeny of the fruticose genera remains unresolved to their ancestral crustose genera. Species delimitation within Namibialina and Ramalina is rather straightforward. The phylogeny and taxonomy of Vermilacinia are fully resolved, except for the two youngest clades of corticolous taxa, and support current taxonomy, including four new taxa described here. Secondary metabolite variation in Niebla generally coincides with major clades which are comprised of species complexes with still unresolved phylogenetic relationships. A micro-endemism pattern of allopatric species is strongly suspected for both genera, except for the corticolous taxa within Vermilacinia. Both Niebla and saxicolous Vermilacinia have chemotypes unique to species clades that are largely endemic to the Vizcaíno deserts. The following new taxa are described: Namibialina gen. nov. with N. melanothrix (comb. nov.) as type species, a single new species of Ramalina (R. krogiae) and four new species of Vermilacinia (V. breviloba, V. lacunosa, V. pustulata and V. reticulata). The new combination V. granulans is introduced. Two epithets are re-introduced for European Ramalina species: R. crispans (= R. peruviana auct. eur.) and R. rosacea (= R. bourgeana auct. p.p). A lectotype is designated for Vermilacinia procera. A key to saxicolous species of Vermilacinia is presented.

The Biogeographic South-North Divide of Polygonatum (Asparagaceae Tribe Polygonateae) within Eastern Asia and Its Recent Dispersals in the Northern Hemisphere

Eastern Asia (EA) is a key region for the diversification of flowering plants in the Northern Hemisphere, but few studies have focused on the biogeographic history within EA in the context of the other northern continents. Polygonatum is an important medicinal genus widely distributed in the Northern Hemisphere with its highest species richness in EA, and it represents an excellent model for studying the evolution of biogeographic patterns in this region. Divergence time estimation was used to examine the biogeographic history of Polygonatum based on nuclear ITS and four plastid sequences (rbcL, matK, psbA-trnH and trnC-petN) from 30 Polygonatum species and 35 outgroup taxa. The ancestral area of Polygonatum and subsequent dispersal routes were inferred using Bayes-Lagrange. Polygonatum was estimated to have originated in southern EA during the middle Miocene (14.34-13.57 Ma) with subsequent south-to-north expansion in the late Miocene. Multiple intercontinental dispersal events were inferred between EA and Europe or North America, and all of them have occurred recently in the late Miocene to Pliocene. The separation of Polygonatum into the south and north lineages and their subsequent diversifications in the late Miocene supports the existence of a biogeographic divide between the northern and southern parts of EA that also coincides with the retreat and redevelopment of the arid zone in EA in the Neogene. Our results demonstrate the complexity of biogeographic history of Polygonatum in the Northern Hemisphere including early vicariance followed by frequent and recent dispersals in the Neogene.

Fossil evidence for open, Proteaceae-dominated heathlands and fire in the Late Cretaceous of Australia

PREMISE OF THE STUDY

The origin of biomes is of great interest globally. Molecular phylogenetic and pollen evidence suggest that several plant lineages that now characterize open, burnt habitats of the sclerophyll biome, became established during the Late Cretaceous of Australia. However, whether this biome itself dates to that time is problematic, fundamentally because of the near-absence of relevant, appropriately aged, terrestrial plant macro- or mesofossils.

METHODS

We recovered, identified, and interpreted the ecological significance of fossil pollen, foliar and other remains from a section of core drilled in central Australia, which we dated as Late Campanian-Maastrichtian.

KEY RESULTS

The sediments contain plant fossils that indicate nutrient-limited, open, sclerophyllous vegetation and abundant charcoal as evidence of fire. Most interestingly, >30 pollen taxa and at least 12 foliage taxa are attributable to the important Gondwanan family Proteaceae, including several minute, amphistomatic, and sclerophyllous foliage forms consistent with subfamily Proteoideae. Microfossils, including an abundance of Sphagnales and other wetland taxa, provided strong evidence of a fenland setting. The local vegetation also included diverse Ericaceae and Liliales, as well as a range of ferns and gymnosperms.

CONCLUSIONS

The fossils provide strong evidence in support of hypotheses of great antiquity for fire and open vegetation in Australia, point to extraordinary persistence of Proteaceae that are now emblematic of the Mediterranean-type climate southwestern Australian biodiversity hotspot and raise the profile of open habitats as centers of ancient lineages.

Origins of Plant Diversity in the California Floristic Province

Recent biogeographic and evolutionary studies have led to improved understanding of the origins of exceptionally high plant diversity in the California Floristic Province (CA-FP). Spatial analyses of Californian plant diversity and endemism reinforce the importance of geographically isolated areas of high topographic and edaphic complexity as floristic hot spots, in which the relative influence of factors promoting evolutionary divergence and buffering of lineages against extinction has gained increased attention. Molecular phylogenetic studies spanning the flora indicate that immediate sources of CA-FP lineages bearing endemic species diversity have been mostly within North America—especially within the west and southwest—even for groups of north temperate affinity, and that most diversification of extant lineages in the CA-FP has occurred since the mid-Miocene, with the transition toward summer-drying. Process-focused studies continue to implicate environmental heterogeneity at local or broad geographic scales in evolutionary divergence within the CA-FP, often associated with reproductive or life-history shifts or sometimes hybridization.