Urticaceae species can be shrubs (e.g.Pilea), lianas, herbs (e.g.Urtica,Parietaria), or, rarely, trees (Dendrocnide,Cecropia). Theirleaves are usually entire and bearstipules. Urticating (stinging) hairs are often present. They have usually unisexual flowers and can be bothmonoecious ordioecious. They arewind-pollinated. Most disperse theirpollen when thestamens are mature and their filaments straighten explosively, a peculiar and conspicuously specialised mechanism.
While the stings delivered by Urticaceae species are often unpleasant, they seldom pose any direct threat to health, and deaths directly attributed to stinging are exceedingly rare; species known to cause human fatalities includeDendrocnide cordata[4][5] andUrtica ferox.[6]
TheAPG II system puts the Urticaceae in the order Rosales, while older systems consider them part of theUrticales, along withUlmaceae,Moraceae, andCannabaceae. APG still considers "old" Urticales a monophyletic group, but does not recognise it as an order on its own.
Thefossil record of Urticaceae is scattered and mostly based on dispersed fruits. Twelve species based on fossilachenes are known from theLate Cretaceous ofCentral Europe. Most were assigned to the extant generaBoehmeria (three species),Debregeasia (one species) andPouzolzia (three species), while three species were assigned to theextinct genusUrticoidea.[7] A Colombian fossil flora of theMaastrichtian stage has yielded leaves that resemble leaves of the tribe Ceropieae.[8] In theCenozoic fossil leaves from theYpresianAllenby Formation preserve distincttrichomes, and have been attributed to the TribeUrticeae in the fossil record. The leaves had originally been identified asRubus by earlier workers on theEocene Okanagan Highlands, but Devoreet al (2020) interpreted the preserved hairs along the stem and major veins as stinging trichomes, rather than simple hairs or thorns.[9]
Myrothecium leaf spot, a fungal disease caused byMyrothecium roridum which affects plants throughout the Urticaceae, as well as other angiosperms[24][25]
^Else Marie Friis; Peter R. Crane; Kaj Raunsgaard Pedersen (18 Aug 2011).Early Flowers and Angiosperm Evolution. Cambridge University Press.ISBN978-0-521-59283-3.
^Treiber, E. L.; Gaglioti, A. L.; Romaniuc-Neto, S.; Madriñán, S.; Weiblen, G. D. (2016). "Phylogeny of the Cecropieae (Urticaceae) and the evolution of an ant-plant mutualism".Systematic Botany.41 (1):56–66.doi:10.1600/036364416X690633.S2CID28743975.
^Kim C, Deng T, Chase M, Zhang D-G, Nie Z-L, Sun H. (2015). "Generic phylogeny and character evolution in Urticeae (Urticaceae) inferred from nuclear and plastid DNA regions".Taxon.64 (1):65–78.doi:10.12705/641.20.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Treiber EL, Gaglioti EL, Romaniuc-Neto S, Madriñán S, Weiblen GD. (2016). "Phylogeny of the Cecropieae (Urticaceae) and the evolution of an ant–plant mutualism".Systematic Botany.41 (1):56–66.doi:10.1600/036364416X690633.S2CID28743975.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Deng Tao; Kim C; Zhang D-G; Zhang J-W; Li Z-M; Nie Z-L; Sun H. (2013). "Zhengyia shennongensis: A new bulbiliferous genus and species of the nettle family (Urticaceae) from central China exhibiting parallel evolution of the bulbil trait".Taxon.62 (1):89–99.doi:10.1002/tax.621008.JSTOR24389315.
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