Pandanus

Here is the rewritten encyclopedia entry:

Known commonly as pandan, screw palm, or screw pine, *Pandanus* is a genus of monocots containing roughly 578 accepted species. These palm-like, dioecious trees and shrubs are native to the Old World tropics and subtropics. They belong to the order Pandanales and the family Pandanaceae, of which they are the largest genus.

The plants range from small shrubs under a meter tall to medium-sized trees reaching 20 meters, with broad canopies, heavy fruit, and a moderate growth rate. Their stout trunks are ringed with leaf scars and may be smooth, rough, or warty depending on the species. Mature plants can branch, and their roots form a pyramidal tract to hold the trunk. Many species produce thick, adventitious stilt roots near the base that branch and provide support as the tree grows top-heavy. At the top, one or more crowns of strap-shaped leaves appear; these may be spiny and vary from 30 centimeters to 2 meters long and 1.5 to 10 centimeters wide.

As dioecious plants, male and female flowers occur on separate individuals. Male flowers are 2–3 centimeters long, fragrant, and surrounded by narrow white bracts. Female flowers produce round, bract-surrounded fruits. The individual fruit is a drupe, and these merge into a globular multiple fruit 10–20 centimeters across, with many prism-like sections that resemble a pineapple. The fruit typically shifts from green to bright orange or red as it matures and can remain on the tree for over a year.

The oldest credible fossil of the genus, *Pandanus estellae*, comes from a silicified fruit found in Queensland, Australia, dating to the Oligocene epoch about 32–28 million years ago. Analyses of maternal DNA divide the genus into two large groups (Clade I and Clade II), each further split into two subgroups (Subclade Ia, Ib, IIa, and IIb). The split between the main clades occurred during the early Miocene, while the subgroup splits happened during the Middle Miocene Climatic Optimum. Nuclear target-capture genomics shows that the genus’s evolution was heavily shaped by reticulate evolution and transoceanic adaptive introgression across the Indian Ocean. A key lineage, Clade Ba (which includes the widespread *Pandanus tectorius*), acted as a genetic and biogeographical bridge connecting Asian and Afro-Malagasy populations through bidirectional gene flow. Geographically isolated “swamp” lineages across the Palaeotropics share similar morphological traits, but nuclear analysis reveals these are due to convergent evolution driven by similar climates, not hybrid origins.

Despite being called “pandanus palms,” these plants are not closely related to true palms. The genus name comes from the Malay word *pandan* for *Pandanus amaryllifolius*, the most commonly known species. This word derives from Proto-Austronesian *paŋudaN*, which became Proto-Malayo-Polynesian *paŋdan* and Proto-Oceanic *padran*. Cognates appear in many Austronesian languages—such as Atayal *pangran*, Tagalog *pandan*, Hawaiian *hala*, and Māori *whara*—reflecting the plant’s cultural importance. The genus is traditionally divided into six subgenera (Coronata, Kurzia, Lophostigma, Pandanus, Rykia, and Vinsonia), but molecular phylogenetic analyses show that all except Coronata are polyphyletic or paraphyletic, meaning they do not reflect true evolutionary history. Several species once placed in subgenera Acrostigma and Martellidendron are now in the separate genera *Benstonea* and *Martellidendron*.

*Pandanus* is a Paleotropical genus, with the greatest number of species found in Madagascar and Malaysia. These plants grow from sea level up to 3,300 meters. They are of cultural, health, and economic importance in the Pacific, second only to the coconut on atolls. They grow wild mainly in semi-natural vegetation in littoral habitats across the tropical and subtropical Pacific, tolerating drought, strong winds, and salt spray. They propagate readily from seed, and popular cultivars are widely propagated from branch cuttings. Species on exposed coastal headlands and beaches use thick stilt roots as anchors in loose sand. While distributed throughout tropical and subtropical islands and coastlines of the Atlantic, Indian, and Pacific Oceans, they are most numerous on low islands and barren atolls of Polynesia and Micronesia. Other species are adapted to mountain habitats and riverine forests. The tree is grown from shoots that form spontaneously in the axils of lower leaves. Pandanus fruits are eaten by animals including bats, rats, crabs, and elephants, but the vast majority of species are used by humans for food, clothing, basket weaving, and shelter.