Dorstenia gigas
| Dorstenia | |
|---|---|
 |
|
| Dorstenia gigas | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Rosids |
| Order: | Rosales |
| Family: | Moraceae |
| Tribe: | Dorstenieae |
| Genus: |
Dorstenia L. |
Dorstenia is a predominately Old and New World plant genus within the family Moraceae, but there is one Dorstenia species that is located in Indonesia and South Asia. There are 105 species within this genus that are fairly equally distributed between the Afrotropics and Neotropics, second only in number to the Ficus genera in Moraceae, but Dorstenia is unique when compared to other members of the Moraceae because of their extremely diverse growth habits and life forms. The majority of the Moraceae is woody perennials, while Dorstenia is dominated by herbaceous, succulent, or suffrutescent perennials, and only 10% exhibit the typical woody habit of the Moraceae. Dorstenia also have a striking reproductive structure composed of clusters of bisexual flowers on disc-shaped receptacles that are often adorned with variable size and shape bracts. Like most members of the Moraceae, Dorstenia have drupe fruits like peaches (peaches are not a member of the Moraceae), but another special feature of Dorstenia drupes is that they explode to release the seed. The seeds are usually small with a minuscule endosperm. The Dorstenia genus is also well known by indigenous people in the tropics as a medicinal plant with numerous flavonoid compounds that have anti-microbial, anti-reverse transcriptase, and anti-inflammatory effects.
Dorstenia is part of the Dorstenieae tribe of the family Moraceae, and all three levels of classification are monophyletic from chloroplast and nuclear DNA phylogenies, with morphological characters that also support. The family Moraceae is a part of the monophyletic Rosales order, and within this order the Moraceae is most closely related to the Ulmaceae, Cannabaceae, and Urticaceae families of plants. Fossils of Ficus and Morus fruits have been found on the African continent, and are used to approximate the origin of family Moraceae to a maximum of 135 million years ago. In a recent study using fossil fruits, Bayesian molecular dating, and maximum likelihood, researchers attempted to reconstruct the ancestral history of Dorstenia with ITS (internal transcribed spacer) sequences from ribosomal DNA of 35 Dorstenia species and seven out-group species from the different tribes within the Moraceae. The goal was to resolve a long-standing issue within Dorstenia of if this genus diverged and radiated prior to the split of Africa and South American about 105 mya, and members of this genus are on separate continents by vicariance, or if this genus diverged post split and Dorstenia became established in the Neotropics by seed dispersal.
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