Plant dispersal across the tropical Atlantic by wind and sea currents

This review brings together evidence on the monophyly and ages of angiosperm lineages ranging across the tropical Atlantic with data on the direction, strength, and speed of sea currents and wind jets across that ocean. Mainly for pragmatic reasons (data availability), the focus is on genera, which introduces a rank-based constraint into the analysis. However, trans-Atlantic disjunctions at the genus level seemed more likely to be attributable to long-distance dispersal than those involving families or species; family-level disjunctions often may date back to the breakup of Africa and South America, and species-level disjunctions often may be anthropogenic. At least 110 genera (listed in this article) contain species on both sides of the tropical Atlantic. Molecular phylogenies and age estimates from molecular clocks are available for 11 disjunct genera, tribes, and species. Inferred directions and modes of dispersal can be related parsimoniously to water currents between Africa and South America and to exceptional westerly winds blowing from northeastern Brazil to northwest Africa. Based on diaspore morphology and inferred dispersal biology in the 110 genera, trans-Atlantic dispersal by water (in both directions) appears more common than dispersal by wind or on birds. Wind dispersal appears to have occurred in the direction from South America to West Africa but rarely in the opposite direction

Historical biogeography and ecological niche modelling of the Asimina-Disepalum clade (Annonaceae): role of ecological differentiation in Neotropical-Asian disjunctions and diversification in Asia

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The biogeographic origin of a radiation of trees in Madagascar: implications for the assembly of a tropical forest biome

Abstract Background Madagascar’s rain forests are characterized by extreme and uneven patterns of species richness and endemicity, the biogeographic and evolutionary origins of which are poorly understood. Methods Here we use a time-calibrated phylogeny of a dominant group of trees in Madagascar’s eastern rain forests, Canarium, and related Burseraceae (Canarieae), to test biogeographic hypotheses regarding the origin and radiation of the flora of this unique biome. Results Our findings strongly support the monophyly of Malagasy Canarium, suggesting that this clade represents a previously undocumented in situ radiation. Contrary to expectations of dispersal from Africa during the Oligocene, concurrent with the formation of Madagascar’s rain forest biome, our analyses support a late Miocene origin for Malagasy Canarium, probably by long distance dispersal from Southeast Asia. Discussion Our study illustrates the importance of considering long distance dispersal as a viable explanation for clades with pantropical distributions diversifying subsequent to the Oligocene, and it highlights the formation of the Indo-Australian Archipelago and associated fast-moving equatorial surface currents, suggesting an under-appreciated evolutionary link among tropical centers of endemism. Conclusions We postulate that the relatively recent establishment and radiation of Canarium in Madagascar may have been facilitated by the highly stochastic climates associated with these forest ecosystems. </jats:sec

<i>Aporosa</i> Blume from the paleoequatorial rainforest of Bikaner, India: Its evolution and diversification in deep time

The Gondwanan origin, northward migration and subsequent collision with Asia means that the Indian subcontinent is of particular interest regarding the origin and dispersal of numerous plants and animal species. With this in mind, we describe a fossil leaf of Aporosa Blume (Phyllanthaceae) from the Paleogene of the Indian subcontinent and discuss its evolution and diversification with respect to the moving Indian plate and its connection with Southeast Asia since the early Cenozoic. At present, Aporosa Blume is confined to Southeast Asia with a few species in India and New Guinea. It is represented by six endemic species growing in the evergreen forests of India and Sri Lanka, including Aporosa acuminata Thwaites, which is morphologically close to the here described fossil from Bikaner, Rajasthan, India. From the age of the fossil and the distribution of its modern comparable form, it is assumed that Aporosa originated on the Indian subcontinent and then was distributed to Southeast Asia, supporting the ‘Out of India’ hypothesis. Diversification of the genus might have taken place either in the Paleogene or Neogene. Our fossil leaf material also indicates the existence of palaeoequatorial (< 10° N) tropical rain forests in western India during the Paleogene in contrast to dry and desertic climate occurring today

Historical biogeography of Melastomataceae

Melastomataceae and Memecylaceae are pantropically distributed sister groups for which an ndhF gene phylogeny for 91 species in 59 genera is here linked with Eurasian and North American fossils in a molecular clock approach to biogeographical reconstruction. Nine species from the eight next-closest families are used to root phylogenetic trees obtained under maximum likelihood criteria. Melastomataceae comprise ∼3000 species in the neotropics, ∼1000 in tropical Asia, 240 in Africa, and 225 in Madagascar in 150-166 genera, and the taxa sampled come from throughout this geographic range. Based on fossils, ranges of closest relatives, tree topology, and calibrated molecular divergences, Melastomataceae initially diversified in Paloecene/Eocene times in tropical forest north of the Tethys. Their earliest (Eocene) fossils are from northeastern North America, and during the Oligocene and Miocene melastomes occurred in North America as well as throughout Eurasia. They also entered South America, with earliest (Oligocene) South American fossils representing Merianieae. One clade (Melastomeae) reached Africa from the neotropics 14-12 million years ago and from there spread to Madagascar, India, and Indochina. Basalmost Melastomataceae (Kibessieae, Astronieae) are species-poor lineages restricted to Southeast Asia. However, a more derived Asian clade (Sonerileae/Dissochaeteae) repeatedly reached Madagascar and Africa during the Miocene and Pliocene. Contradicting earlier hypotheses, the current distribution of Melastomataceae is thus best explained by Neogene long-distance dispersal, not Gondwana fragmentation

High-latitude Tertiary Migrations of an Exclusively Tropical Clade: Evidence from Malpighiaceae

Explanations of tropical intercontinental disjunctions involving South America and Africa typically invoke vicariance of western Gondwanan biotas or long-distance dispersal. However, many plant groups originated and diversified well after the last direct connection between Africa and South America (ca. 105 million years before the present [mybp]), and it is unlikely that long-distance dispersal accounts for the distribution of all of these. A less commonly invoked explanation, the boreotropics hypothesis, indicates that some tropical disjunctions arose during the Tertiary via high-latitude land connections when northern forests supported tropical vegetation. Malpighiaceae are widely distributed across Africa and South America and have been explained as ancient "Gondwanian aborigines" (i.e., vicariants of western Gondwanan biotas) or more recent "American colonists" (i.e., long-distance dispersalists from South America into the Old World). Fossil and phylogenetic evidence from clock-independent estimates of molecular divergence times indicate that Malpighiaceae originated in South America during the latest Cretaceous (ca. 68 mybp), in isolation from Africa, and that six amphi-Atlantic disjunctions within the family occurred during three major episodes: late Paleocene (ca. 60 mybp), latest Eocene-earliest Oligocene (ca. 34-31 mybp), and early Miocene (ca. 21-17 mybp). These age estimates reject a Gondwanan origin for Malpighiaceae, and strict dispersal scenarios ignore paleoclimate, paleoland configurations, and fossil evidence that indicates that the family once inhabited northern latitudes. Instead, these data suggest that Paleocene-Oligocene amphi-Atlantic disjunct groups in Malpighiaceae moved into North America from South America via the Caribbean Basin, crossed the North Atlantic into Eurasia, and subsequently reached the Old World Tropics during warm intervals when land configurations would have facilitated this migration. Whether Miocene migrations of evergreen thermophilic Malpighiaceae proceeded via northern latitudes or long-distance dispersal is less clear.Organismic and Evolutionary Biolog

Evolution and Biogeography of the Slipper Orchids: Eocene Vicariance of the Conduplicate Genera in the Old and New World Tropics

Intercontinental disjunctions between tropical regions, which harbor two-thirds of the flowering plants, have drawn great interest from biologists and biogeographers. Most previous studies on these distribution patterns focused on woody plants, and paid little attention to herbs. The Orchidaceae is one of the largest families of angiosperms, with a herbaceous habit and a high species diversity in the Tropics. Here we investigate the evolutionary and biogeographical history of the slipper orchids, which represents a monophyletic subfamily (Cypripedioideae) of the orchid family and comprises five genera that are disjunctly distributed in tropical to temperate regions. A relatively well-resolved and highly supported phylogeny of slipper orchids was reconstructed based on sequence analyses of six maternally inherited chloroplast and two low-copy nuclear genes (LFY and ACO). We found that the genus Cypripedium with a wide distribution in the northern temperate and subtropical zones diverged first, followed by Selenipedium endemic to South America, and finally conduplicate-leaved genera in the Tropics. Mexipedium and Phragmipedium from the neotropics are most closely related, and form a clade sister to Paphiopedilum from tropical Asia. According to molecular clock estimates, the genus Selenipedium originated in Palaeocene, while the most recent common ancestor of conduplicate-leaved slipper orchids could be dated back to the Eocene. Ancestral area reconstruction indicates that vicariance is responsible for the disjunct distribution of conduplicate slipper orchids in palaeotropical and neotropical regions. Our study sheds some light on mechanisms underlying generic and species diversification in the orchid family and tropical disjunctions of herbaceous plant groups. In addition, we suggest that the biogeographical study should sample both regional endemics and their widespread relatives

Dispersal of thermophilic beetles across the intercontinental Arctic forest belt during the early Eocene

Abstract Massive biotic change occurred during the Eocene as the climate shifted from warm and equable to seasonal and latitudinally stratified. Mild winter temperatures across Arctic intercontinental land bridges permitted dispersal of frost-intolerant groups until the Eocene-Oligocene boundary, while trans-Arctic dispersal in thermophilic groups may have been limited to the early Eocene, especially during short-lived hyperthermals. Some of these lineages are now disjunct between continents of the northern hemisphere. Although Eocene climate change may have been one of the most important drivers of these ancient patterns in modern animal and plant distributions, its particular events are rarely implicated or correlated with group-specific climatic requirements. Here we explored the climatic and geological drivers of a particularly striking Neotropical-Oriental disjunct distribution in the rove beetle Bolitogyrus, a suspected Eocene relict. We integrated evidence from Eocene fossils, distributional and climate data, paleoclimate, paleogeography, and phylogenetic divergence dating to show that intercontinental dispersal of Bolitogyrus ceased in the early Eocene, consistent with the termination of conditions required by thermophilic lineages. These results provide new insight into the poorly known and short-lived Arctic forest community of the Early Eocene and its surviving lineages