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The islands of Southeast Asia comprise one of the most geologically and biogeographically complex areas in the world and are a centre of exceptional floristic diversity, harbouring 45,000 species of flowering plants. Cyrtandra, with over 800 species of herbs and shrubs, is the largest genus in the family Gesneriaceae and is one of the most emblematic and species-rich genera of the Malesian rainforest understorey. The high number of species and tendency to narrow endemism make Cyrtandra an ideal genus for examining biogeographic patterns. We sampled 128 Cyrtandra taxa from key localities across Southeast Asia to evaluate the geo-temporal patterns and evolutionary dynamics of this clade. One nuclear and four chloroplast regions were used for phylogenetic reconstruction, molecular dating, and ancestral range estimation. Results from the dating analysis suggest that the great diversity of Cyrtandra seen in the Malesian region results from a recent radiation, with most speciation taking place in the last five million years. Borneo was recovered as the most likely ancestral range of the genus, with the current distribution of species resulting from a west to east migration across Malesia that corresponds with island emergence and mountain building. Lastly, our investigation into the biogeographic history of the genus indicates high levels of floristic exchange between the islands on the Sunda shelf and the important role of the Philippines as a stepping stone to Wallacea and New Guinea. These patterns underlie much of the plant diversity in the region and form an emerging paradigm in Southeast Asian plant biogeography.

The Miocene convergence of the Sunda shelf, Sahul shelf and Wallacea facilitated the exchange of previously isolated floras across the Sunda–Sahul Convergence Zone (SSCZ). The SSCZ is a hotspot of biogeographical research; however, phytogeographical patterns across the region remain poorly understood. We conducted multivariate analysis on a comprehensive species checklist of SSCZ vascular plants to quantify the extent of exchange, characterize phytogeographical patterns and investigate their abiotic drivers. We found that Lydekker's and Wallace's Lines are not reflected in floristic composition at any taxonomic level, with 46% of genera distributed across these biogeographical lines. In contrast, environment is significantly correlated with floristic composition, with annual rainfall and seasonality being the strongest correlates. Mainland Asia, Borneo, the Philippines, New Guinea and Australia were major routes of exchange throughout the Cenozoic, possibly because these areas have been persistent landmasses throughout the entire period of convergence. We conclude that Sunda–Sahul floristic exchange has substantially influenced the assembly of the regional flora and that modern phytogeographical patterns have been influenced more by environmental variables and available landmass (i.e. establishment conditions) than by putative barriers to movement such as Wallace's and Lydekker's Lines (i.e. vagility). [ABSTRACT FROM AUTHOR]

The collision between India and Eurasia in the mid‐Palaeogene facilitated terrestrial floristic exchange. However, due to the complexity of this geological event and scarcity of fossil record, the plant migration patterns between the two plates are still highly debated. In this study, we focus on the Oligocene floristic exchange between India and Pan‐Indochina mainly based on a carpological study of Annonaceae, an emblematic family unique in its pantropical distribution and frugivore‐based dispersal strategy. A new seed species, Anonaspermum orientalis sp. nov., is described from the upper Oligocene Yongning Formation of Guangxi, southern China. The species represents the earliest known occurrence of this family in Pan‐Indochina. The specimens are characterized by ovate–elliptic seed shape, thicker seed testa, two‐lobed organization, lamelliform rumination and an obvious cone‐like plug. The palaeobiogeographical reconstruction of Annonaceae indicates that the most parsimonious dispersal scenario for the annonaceous taxon from the late Oligocene of China is the Out‐of‐India route, in parallel with other plant genera inferred to have migrated between India and Pan‐Indochina during that period. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To evaluate how biogeographical and ecological processes influenced species distributions and community assembly in a continental rain forest flora with mixed biogeographical origins. Location: Continental Australia. Methods: We identified 795 species with Sahul ancestry (Australian rain forest flora of Gondwanan origin) and 604 species with Sunda ancestry (rain forest plant lineages of Indo‐Malaysian origin) from a total of 1,872 free‐standing Australian woody rain forest taxa. We then compared the distribution of Sunda to Sahul species in relation to variation in species richness and phylogenetic endemism at continental scale, and local species distributions in available plot data from the Tropics (Cape York and the Australian Wet Tropics in northern Queensland) and subtropics (Nightcap‐Border Ranges, Washpool and Dorrigo, in northern New South Wales). We compared the dispersal and persistence characteristics, and key functional traits (leaf size, fruit size, wood density and maximum height at maturity) of the Sunda and Sahul components of the continental rain forest flora. The influence of climate (temperature) and local environmental (altitude) factors in driving fine‐scale distributional patterns was evaluated. Results: Sunda rain forest species richness decreased with increasing latitude but maintained high levels of endemism, including in the south. Sunda species traits suggest more efficient dispersal and faster growth than Sahul lineages. Resprouting (persistence) was less evident in species with Sunda than Sahul ancestry. We show that Sunda lineage distributions were influenced by interacting environmental and climatic factors, as well as historical contingencies. Main conclusions: Efficient dispersal and relatively fast growth likely facilitated the establishment and spread of Sunda lineages in Australia. However, the Sunda invasion was resisted in stable, saturated communities of Sahul lineages, and in the temperate south where climate acted as a strong filter. The results highlight the importance of integrating historical biogeography and contemporary ecological processes to study continental‐scale rain forest distribution and assembly. [ABSTRACT FROM AUTHOR]