Bidens

Bidens is a genus of flowering plants in the aster family, Asteraceae. The genus include roughly 230 species which are distributed worldwide. Despite their global distribution, the systematics and taxonomy of the genus has been described as complicated and unorganized. 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. The generic name refers to the same character; Bidens comes from the Latin bi and dens.

Phylogeny, taxonomy and diversity

Despite their global distribution, the systematics and taxonomy of the genus has been described as complicated and unorganized. The genus include roughly 230 species.
Bidens is closely related to the American genus Coreopsis, and the genera are sometimes difficult to tell apart; in addition, neither is monophyletic.

Species

Species include:Bidens alba DC. - romerilloBidens amplectens Sherff - Waianae kokoolau Bidens amplissima Greene - Vancouver Island beggarticksBidens aristosa Britt. - bearded beggarticks, long-bracted beggarticks, tickseed sunflower, western tickseedBidens asymmetrica Sherff - Koolau kokoolau, Ko'olau Range beggarticksBidens aurea Sherff - Arizona beggarticksBidens beckii - Beck's water-marigold, Henderson's water-marigold, Oregon water-marigoldBidens bidentoides Britt. - Delmarva beggarticksBidens bigelovii A.Gray - Bigelow's beggarticksBidens bipinnata L. - Spanish needles, hemlock beggarticks, gui zheng cao Bidens biternataBidens cabopulmensisBidens campylotheca Sch.Bip.- viper beggarticksBidens cernua L. - nodding beggarticks, nodding bur-marigoldBidens cervicata Sherff - Kauai beggarticksBidens chippii MesfinBidens conjuncta Sherff - bog beggarticksBidens connata Muhl. ex Willd. - purplestem beggarticksBidens coronata Britt. - crowned beggarticksBidens cosmoides Sherff - cosmosflower beggarticks, poola nuiBidens cynapiifolia Kunth - West Indian beggarticks, alfilerilloBidens discoidea Britt. - discoid beggarticks, small beggarticks, swamp beggarticks, few-bracted beggarticksBidens eatonii Fern. - Eaton's beggarticks, bident d'EatonBidens ferulifolia DC. - Apache beggarticks, fern-leaved beggarticksBidens forbesii Sherff - coastal bluff beggarticksBidens frondosa L. - devil's beggarticks, devil's pitchfork, devil's bootjack, pitchfork weed, common beggarticks, sticktights. Pitchfork weed is considered to be a weed in New Zealand. Bidens gardneri Baker - ridge beggarticksBidens hawaiensis A.Gray - Hawaii beggarticksBidens henryi SherffBidens heterodoxa Fern. & H.St.John - Connecticut beggarticks, bident différent Bidens heterosperma Gray - Rocky Mountain beggarticksBidens hillebrandiana O.Deg. - seacliff beggarticksBidens hyperborea Greene - estuary beggarticks, coastal beggarticks, northern estuarine beggarticks, seacliff beggarticksBidens laevis B.S.P. - smooth beggarticks, smooth bur-marigold, larger bur-marigold. Smooth beggarticks is a common fall flower in the southeastern United States. Bidens lemmonii Gray - Lemmon's beggarticksBidens leptocephala Sherff - few-flowered beggarticksBidens leptophyllaBidens macrocarpa Sherff - large-fruited beggarticksBidens macroptera MesfinBidens mannii T.G.J.RaynerBidens mauiensis Sherff - Maui beggarticksBidens maximowiczianaBidens menziesii Sherff - Mauna Loa beggarticksBidens meyeri V.A.Funk & K.R.WoodBidens micrantha Gaud. - grassland beggarticks

* B. micrantha ssp. kalealaha Nagata & Ganders - Kalealaha beggarticksBidens mitis Sherff - small-fruited beggarticksBidens molokaiensis Sherff - Molokai beggarticks, wedge beggarticks
Bidens × multiceps FassettBidens nudata Brandegee - Cape beggar's tick, Baja tickseedBidens parvifloraBidens pachyloma - Meskel FlowerBidens pilosa S.F.Blake - hairy beggarticksBidens polylepis S.F.BlakeBidens populifolia Sherff - Oahu beggarticksBidens radiataBidens reptans G.Don - manzanilla trepadorBidens sandvicensis Less. - shrubland beggarticksBidens schimperi Sch.Bip.Bidens simplicifolia C.H.WrightBidens socorrensisBidens squarrosa KunthBidens subalternans DC.Bidens tenuisecta A.Gray - slim-lobed beggarticksBidens torta Sherff - corkscrew beggarticksBidens trichosperma Britton - crowned beggarticksBidens tripartita L. - three-lobed beggarticks, three-part beggarticks, leafy-bracted beggarticks, trifid bur-marigoldBidens triplinervia Kunth
* B. triplinervia var. macrantha SherffBidens valida Sherff - Mt. Kahili beggarticksBidens vulgata Greene - big devil's beggarticks, tall beggarticks, tall bur-marigold, western sticktightBidens wiebkei Sherff - Wiebke's beggarticks

Formerly placed here

Distribution

Bidens includes roughly 230 species which are distributed worldwide throughout many tropical and warm temperate regions. Species occur in the Americas, Africa, Polynesia, Europe and Asia.
Bidens 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.

Human use and interactions

and hairy beggarticks are useful as honey plants. Several Bidens species are used as food by the caterpillars of certain Lepidoptera, such as the noctulian moth Hypercompe hambletoni and the brush-footed butterfly Vanessa cardui, the painted lady.
The Bidens mottle virus, a plant pathogen, was first isolated from B. pilosa, and it infects many other Asteraceae and plants of other families.
Native Hawaiians drink a special tea out of their leaves back when they were abundant in Hawaii.