Bidens

Bidens is a genus of flowering plants in the aster family, Asteraceae. The common names beggarticks, black jack, burr marigolds, cobbler's pegs, Spanish needles, stickseeds, tickseeds and tickseed sunflowers refer to the fruits of the plants, most of which are bristly and barbed, with two sharp pappi at the end. The generic name refers to the same character; Bidens comes from the Latin bis ("two") and dens ("tooth").

Propagation

The plants are zoochorous; their seeds will stick to clothing, fur or feathers, and be carried to new habitat. This has enabled them to colonize a wide range, including many oceanic islands. Some of these species occur only in a very restricted range and several are now threatened with extinction, notably in the Hawaiian Islands. Due to the absence of native mammals on these islands, some of the oceanic island taxa have reduced burrs, evolving features that seem to aid in dispersal by the wind instead.

Distribution

Bidens is distributed throughout the tropical and warm temperate regions of the world. Most species occur in the Americas, Africa, and Polynesia, and there are some in Europe and Asia.Bidens is closely related to the American genus Coreopsis, and the genera are sometimes difficult to tell apart; in addition, neither is monophyletic.