Dodonaea

''Dodonaea'' is a genus of about 70 species of flowering plants, often known as hop-bushes, in the soapberry family, Sapindaceae. It has a cosmopolitan distribution in tropical, subtropical and warm temperate regions of Africa, the Americas, southern Asia and Australasia. By far the highest species diversity is in Australia. The genus is named after Rembert Dodoens, traditionally known as 'Dodonaeus'.

They are shrubs and small trees growing to tall. The leaves are alternate, simple or pinnate. The flowers are produced in short racemes. The fruit is a capsule, often with two or three wings.
''Dodonaea'' species are used as food plants by the larvae of some Lepidoptera species including '' Aenetus eximia'' and '' Aenetus ligniveren''.

Systematics

''Dodonaea'' is one of the largest genera in the Sapindaceae, and includes 70 species widely distributed in continental Australia. The only other species of the ''Dodonaea'' widely spread beyond mainland Australia, ''Dodonaea viscosa'', is believed to be one of the world's most greatly disseminated transoceanic plants.

The first attempts to distinguish infrageneric categories within genus ''Dodonaea'' were based on leaf morphology, specifically, two sections - ''Eu-Dodonaea'' (simple leaves) and ''Remberta'' (pinnate leaves) were differentiated. Later this sectional classification was expanded by Bentham, who included 39 species in five series - four simple-leaved series further divided on capsule-appendage morphology (series ''Cyclopterae, Platypterae, Cornutae and Apterae'') and one pinnate-leaved species (series ''Pinnatae'').

Later the genus has been reviewed extensively two times. Radlkofer identified ''Dodonaea'' as a part of the tribe ''Dodonaeeae'', within ''Dyssapindaceae'', together with ''Loxodiscus, Diplopeltis'' and ''Distichostemon''. ''Dodonaea'' and ''Distichostemon'' share similar morphological characteristics which include plants having regular flowers without petals and an intrastaminal disc. Therefore, these two genera are considered to be closely related.

54 ''Dodonaea'' species identified by Radlkofer were divided into three series (''Cyclopterae, Platypterae'' and ''Aphanopterae'') and six subseries. As classifiers were taken the presence or absence of an aril and leaves’ glandular structures.

Another revision of the genus was proposed by West, where ''Dodonaea'' were divided into six species groups by using a combination of characters. Species with the most primitive characters were classified in Group 1 and Group 6 included plants with the most derived states. For instance, the character of an aril possession was recognized as a derived trait.

The most recent molecular study of phylogenetic relationships within the genus revealed some discrepancy with the previously stated hypotheses of morphological evolution within ''Dodonaea'' which classified taxa by the combination of leaf, capsule and seed characters. As in preceding morphological research, species with compound leaves were identified in several clades, interspersed among species with simple leaves (e.g. ''D. humilis'' is the only species in Clade I with imparipinnate leaves). The breeding system has great variation across the phylogeny, and although most species are dioecious, sometimes some species may differ from this state being monoecious. Most genera in ''Sapindaceae'' are dioecious, however, most closely related to ''Dodonaea'' in the phylogeny (''Diplopeltis, Diplopeltis stuartii'' and ''Cossinia'') are monoecious. It has also been reported that whereas normally breeding system in ''Harpullia'' is dioecism, a few species have also been recognized as monoecious. It was stated that during evolution a general breeding-system across the phylogeny was dioecism, however, the polygamous state was intermediate or, might be partially reversible.

Molecular data supports an evidence that monophyly of ''Dodonaea'' includes all species of ''Distichostemon''. It is also supported by the morphological characters as synapomorphies of flowers with reduced petal number and with a highly reduced intrastaminal disk, the trait which is absent in staminate flowers. Both West and Radlkofer used an aril presence or absence as a character to define species groups. All the main clades of ''Dodonaea'' and also two species of ''Diplopeltis'' have small funicular arils. Seeds of D. viscosa have very small funicular aril, and are harvested by Pheidole sp. of ants and deposited in middens outside the nest after the elaiosome has been consumed.

Bayesian MCMC estimation of ''Dodonaea'' phylogeny supported the hypothesis that two species of ''Cossinia'' are sisters to ''Diplopeltis'' and ''Dodonaea''. Nevertheless, Diplopeltis is identified as a paraphyletic group. The monophyly of ''Dodonaea'' is well supported by Bayesian MCMC estimation (1.00 posterior probability, PP). Within the Clade I (1.00 PP) eight species are recognized as sister to the remaining ''Dodonaea''. ''Distichostemon'' is placed in the Clade II (1.00 PP). The phylogeny of remaining 53 species of ''Dodonaea'' (1.00 PP) is poorly supported (<0.95 PP).

''Dodonaea viscosa'' is placed within the Clade IV being closely related to ''D.biloba, D.procumbens'' and ''D.camfieldii''. It is known that ''D. viscosa'' and ''D. camfieldii'' evolved in Australia from their most recent common ancestor. ''D.viscosa'' is widely distributed in Australia today while ''D. camfieldii'' is restricted to New South Wales. The divergence of these taxa occurred approximately in the Late Pliocene to Early Pleistocene (2.7–1.4 Ma, 95% Highest Posterior Density, HPD). The molecular data shows evidence that a monophyletic ''D. viscosa'' includes two species, ''D. procumbens'' and ''D. biloba''.

Clade I: ''D. triquetra SE, D. triangularis MT, D. lanceolata MTEr, D. serratifolia SE, D. trifida SW, D. bursariifolia SWSE, D. amblyophylla SW.''

Clade II: ''Distichostemon arnhemicus MT, Distichostemon malvaceus MT, Distichostemon hispidulus var aridus MT, Distichostemon hispidulus var hspidulus MT, Distichostemon dodocandrus MT, Distichostemon barklyanus MT, Distichostemon filamentosus MT.''

Clade III a: ''D. humifusa SW, D. ceratocarpa SW, D. pinifolia SW, D. ericoides SWEr, D. D.ivaricata SW, D. caespitosa SW, D. tepperi SE, D. hexandra SE, D. stenophylla MT,D. pachyneura Er, D. rigidia Er, D. baueri SEEr.''

Clade III b: ''D. platyptera MT, D. adenophora ErSW, D. microzyga Er, D. polyzyga MT, D. physocarpa MT, D. madagascariensis Os, D. stenozyga ErSWSE, D. polyandra MTOs, D. concinna SW, D. larreoides E.''

Clade IV: ''D. vestita MT, D. procumbens SE, D. biloba SE, D. viscosa ErSWSEMTOs, D. camfieldii SE.''

Clade V: ''D. rupicola SE, D. boroniifolia SEMT, D. pinnata SE, D. multijuga SE, D. filiformis SE, D. macrossanii SE, D. oxyptera M.''

Clade VI: ''D. falcata SE, D. peduncularis SEMT, D. filifolia MT, D. uncinata MT, D. hackettiana SW, D. coriacea Er, D. hirsuta SE.''

Clade VII: ''D. truncatiales SE, D. rhombifolia SE, D. megazyga SE, D. tenuifolia SEMT, D. heteromorpha SE, D. inaequifolia SWEr, D. ptarmicaefolia SW, D. lobulata ErSWSE, D. aptera SW, D. intricata SE, D. sinuolata ssp sinuolata SE.''

Species

*'' Dodonaea adenophora'' Miq.
*'' Dodonaea amblyophylla'' Diels
*'' Dodonaea aptera'' Miq. — coast hop-bush (Western Australia)
*'' Dodonaea baueri'' Endl.
*'' Dodonaea biloba''J.G.West
*''Dodonaea boroniifolia'' G.Don
*'' Dodonaea bursariifolia'' F.Muell.
*'' Dodonaea caespitosa'' Diels
*'' Dodonaea camfieldii'' Maiden & Betche
*'' Dodonaea ceratocarpa'' Endl.
*'' Dodonaea concinna'' Benth.
*'' Dodonaea coriacea'' (Ewart & O.B.Davies) McGill.
*'' Dodonaea divaricata'' Benth.
*'' Dodonaea ericifolia'' G.Don
*'' Dodonaea ericoides'' Miq.
*'' Dodonaea falcata''J.G.West
*'' Dodonaea filifolia''Hook.
*'' Dodonaea filiformis'' Link
*'' Dodonaea glandulosa''J.G.West
*'' Dodonaea hackettiana'' W.Fitzg.
*'' Dodonaea heteromorpha''J.G.West
*'' Dodonaea hexandra'' F.Muell.
*'' Dodonaea hirsuta'' Maiden & Betche
*'' Dodonaea hispidula'' Endl.
*'' Dodonaea humifusa'' Miq.
*'' Dodonaea humilis'' Endl.
*'' Dodonaea inaequifolia'' Turcz.
*'' Dodonaea intricata''J.G.West – Gawler Ranges hop bush
*'' Dodonaea lanceolata'' F.Muell.
*'' Dodonaea larreoides'' Turcz.
*'' Dodonaea lobulata'' F.Muell. – lobed-leaved hop-bush, lobed hop-bush, lobed leaf hop bush
*'' Dodonaea macrossanii'' F.Muell. & Scort.
*'' Dodonaea madagascariensis'' Radlk.
*'' Dodonaea megazyga'' (F.Muell.) F.Muell. ex Benth.
*'' Dodonaea microzyga'' F.Muell.
*''Dodonaea multijuga'' G.Don.
*'' Dodonaea oxyptera'' F.Muell.
*'' Dodonaea pachyneura'' F.Muell.
*'' Dodonaea peduncularis'' Lindl.
*'' Dodonaea petiolaris'' F.Muell.
*'' Dodonaea physocarpa'' F.Muell.
*'' Dodonaea pinifolia'' Miq.
*'' Dodonaea pinnata'' Sm.
*'' Dodonaea platyptera'' F.Muell.
*'' Dodonaea polyandra'' Merr. & L.M.Perry
*'' Dodonaea polyzyga'' F.Muell.
*''Dodonaea procumbens'' F.Muell.
*'' Dodonaea ptarmicifolia'' Turcz.
*'' Dodonaea rhombifolia'' N.A.Wakef.
*'' Dodonaea rigida'' J.G.West
*'' Dodonaea rupicola'' C.T.White
*'' Dodonaea serratifolia'' McGill.
*'' Dodonaea sinuolata'' J.G.West
*'' Dodonaea spatulata'' Sm.
*'' Dodonaea stenophylla'' F.Muell.
*'' Dodonaea stenozyga'' F.Muell.
*''Dodonaea subglandulifera''J.G.West
*'' Dodonaea tenuifolia'' Lindl.
*'' Dodonaea tepperi'' F.Muell. ex Tepper
*'' Dodonaea triangularis'' Lindl.
*'' Dodonaea trifida'' F.Muell.
*'' Dodonaea triquetra'' J.C.Wendl.
*'' Dodonaea truncatiales'' F.Muell.
*'' Dodonaea uncinata'' J.G.West
*'' Dodonaea vestita'' Hook.
*''Dodonaea viscosa'' Jacq. (Pantropical)
** ''Dodonaea viscosa'' subsp. ''angustifolia'' (L.f.) J.G.West
**''Dodonaea viscosa'' subsp. ''angustissima'' (DC.) J.G.West
**''Dodonaea viscosa'' subsp. ''cuneata'' (Sm.) J.G.West
**''Dodonaea viscosa'' subsp. ''viscosa''

Formerly placed here:
*'' Combretum caffrum'' (Eckl. & Zeyh.) Kuntze (as ''D. caffra'' Eckl. & Zeyh.)

References

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{{Taxonbar, from=Q2719945

Sapindaceae genera
Taxa named by Philip Miller
Dioecious plants