The evolution and biogeographic history of epiphytic thalloid liverworts

Temperature dependence of liverwort diversification reveals a cool origin and hot hotspots

The evolutionary history underlying gradients in species richness is still subject to discussions and understanding the past niche evolution might be crucial in estimating the potential of taxa to adapt to changing environmental conditions. In this study we intend to contribute to elucidation of the evolutionary history of liverwort species richness distributions along elevational gradients at a global scale. For this purpose, we linked a comprehensive data set of genus occurrences on mountains worldwide with a time-calibrated phylogeny of liverworts and estimated mean diversification rates (DivElev) and mean ages (AgeElev) of the respective genera per elevational band. In addition, we reconstructed the ancestral temperature preferences of the genera. We found that diversification rates increase linearly with temperature, and hence decrease with elevation. This pattern is mainly driven by epiphytic genera. In contrast, overall genus age is highest at intermediate elevations where liverwort species richness peaks and decreases towards both ends of the elevational and thermal gradient. Our results further indicate that the ancestral lineages from which the extant liverwort genera descended had a preference for cool and humid habitats. We conclude that the extant liverwort species diversity accumulated over long time under these climatic conditions, which are today prevailing at mid-elevations of the world's mountains. Subsequently, liverworts expanded their ranges from these temperate areas towards warm (with high diversification rates) and cold regions (with low diversification rates), located in contemporaneous (tropical) lowlands and high mountains, respectively. The conserved preference for temperate climates shared by the majority of liverwort lineages gives reason to the assumption that they will not be able to cope with the conditions induced by rapid climate warming, whereas the current low-elevation radiation may be less affected by climate change.

Gains and losses of the epiphytic lifestyle in epidendroid orchids: review and new analyses of succulence traits

BACKGROUND AND AIMS

Epiphytism has evolved repeatedly in plants and has resulted in a considerable number of species with original characteristics. Because water supply is generally erratic compared to that in soils, succulent forms in particular are widespread in epiphytic species. However, succulent organs also exist in terrestrial plants, and the question of the concomitant evolution of epiphytism and succulence has received little attention, not even in the epidendroid orchids, which account for 67.6 % of vascular epiphytes.

METHODS

We built a new time-calibrated phylogenetic tree of Epidendroideae with 203 genera treated in genus Orchidacearum, from which we reconstructed the evolution of epiphytism as well as traits related to water scarcity (stem and leaf succulence and the number of velamen layers), while testing for the correlated evolution between the two. Furthermore, we estimated the ancestral geographical ranges to evaluate the palaeoclimatic context in which epiphytism evolved.

KEY RESULTS

Epiphytism evolved at least three times: 39.0 million years ago (Mya) in the common ancestor of the Malaxideae and Cymbidieae that probably ranged from the Neotropics to Southeast Asia and Australia, 11.5 Mya in the Arethuseae in Southeast Asia and Australia, and 7.1 Mya in the neotropical Sobralieae, and it was notably lost in the Malaxidiinae, Collabieae, Calypsoeae, Bletiinae and Eulophiinae. Stem succulence is inferred to have evolved once, in a terrestrial ancestor at least 4.1 Mya before the emergence of epiphytic lineages. If lost, stem succulence was almost systematically replaced by leaf succulence in epiphytic lineages.

CONCLUSIONS

Epiphytism may have evolved in seasonally dry forests during the Eocene climatic cooling, among stem-succulent terrestrial orchids. Our results suggest that the emergence of stem succulence in early epidendroids was a key innovation in the evolution of epiphytism, facilitating the colonization of epiphytic environments that later led to the greatest diversification of epiphytic orchids.

A complete genus-level phylogeny reveals the Cretaceous biogeographic diversification of the poppy family

Angiosperms, a trigger for the Cretaceous Terrestrial Revolution (KTR), underwent a rapid expansion and occupied all the environments during the Mid-Upper Cretaceous. Yet, Cretaceous biogeographic patterns and processes underlying the distribution of angiosperm diversity in the Northern Hemisphere are still poorly known. Here, we elucidated the biogeographic diversification of the angiosperm family Papaveraceae, an ancient Northern Hemisphere clade characterized by poor dispersal ability and high level of regional endemism. Based on both plastome and multi-locus datasets, we reconstructed a robust time-calibrated phylogeny that includes all currently recognized 45 genera of this family. Within the time-calibrated phylogenetic framework, we conducted 72 biogeographic analyses by testing the sensitivity of uncertainties of area delimitation, maxarea constraints, and the parameters of the model, i.e., j (describing jump-dispersal events) and w (modifying dispersal multiplier matrices), to ancestral range estimations. We also inferred ancestral habitat and ecological niches. Phylogenetic analyses strongly support Papaveraceae as monophyletic. Pteridophylloideae is strongly supported as sister to Hypecoideae-Fumarioideae. Our results indicate that the j parameter and number of predefined areas strongly affect ancestral range estimates, generating questionable ancestral ranges, whereas maxarea constraint and w parameter have no effect and improve model fit. After accounting for these uncertainties, our results indicate that Papaveraceae differentiated in Asian wet forests during the Lower Cretaceous and subsequently occupied the Asian and western North American arid and open areas. Three dispersals from Asia to western North America via the Bering land bridge occurred in the Mid-Upper Cretaceous, largely in agreement with the KTR. Habitat shift and ecological niche divergence resulted in the subsequent disjunctions between Asia and western North America. These findings suggest that the interplay of range expansion and niche divergence-driven vicariance might have shaped Cretaceous biogeographic patterns of angiosperms with Papaveraceae-like ecological requirements and dispersal abilities in the Northern Hemisphere, hence contributing to the knowledge on the geographic expansion of angiosperms during the KTR.

Liverwort oil bodies: diversity, biochemistry, and molecular cell biology of the earliest secretory structure of land plants

Liverworts are known for their large chemical diversity. Much of this diversity is synthesized and enclosed within oil bodies (OBs), a synapomorphy of the lineage. OBs contain the enzymes to biosynthesize and store large quantities of sesquiterpenoids and other compounds while limiting their cytotoxicity. Recent important biochemical and molecular discoveries related to OB formation, diversity, and biochemistry allow comparison with other secretory structures of land plants from an evo-devo perspective. This review addresses and discusses the most recent advances in OB origin, development, and function towards understanding the importance of these organelles in liverwort physiology and adaptation to changing environments. Our mapping of OB types and chemical compounds to the current liverwort phylogeny suggests that OBs were present in the most recent common ancestor of liverworts, supporting that OBs evolved as the first secretory structures in land plants. Yet, we require better sampling to define the macroevolutionary pattern governing the ancestral type of OB. We conclude that current efforts to find molecular mechanisms responsible for the morphological and chemical diversity of secretory structures will help understand the evolution of each major group of land plants, and open new avenues in biochemical research on bioactive compounds in bryophytes and vascular plants.