Genisteae

Argyrolobium zanonii, copyright Philippe Gerbet.

Belongs within: Papilionoideae.
Contains: Lupinus, Genistinae.

The Genisteae are a group of woody shrubs primarily found in temperate regions with the highest diversity around the Mediterranean.

In a bunch, in a bunch!
Published 26 May 2008
Cytisus scoparius, a widespread broom species, and the most widespread as an invasive species. Photo by Paul Slichter.

The Genisteae are the tribe of about 450 species of mostly Holarctic leguminous plants that includes brooms*, gorse and lupins**. The first of these are the Palaearctic brooms—elsewhere, I wrote about the New Zealand brooms, which belong to a different legume tribe, the Galegeae, and whose broom-like appearance is convergent with that of the Genisteae brooms. However, a number of species of Genisteae have been transported by humans to many temperate regions around the world (including New Zealand), and many are familiar weed species outside their native ranges.

*The shrubs, obviously, not the things you sweep with. Though brooms the plants were often used for the making of brooms the implements, which is probably the origin of the name of one or the other.

**Monty Python fans are permitted to start humming now.

Argyrolobium zanonii, a Mediterranean species of the possibly polyphyletic genus Argyrolobium that is one of best contenders for inclusion in the Genisteae. Photo from here.

Phylogenetically, Genisteae can be divided into three well-divided groups (Ainouche et al. 2003). The probably paraphyletic Argyrolobium group includes five genera of mostly southern African and South American plants that lie outside the clade formed by the Palaearctic members of Genisteae. Previously members of this group were included in the sister tribe Crotalarieae, and their position remains unsettled. In particular, it has been suggested that Argyrolobium itself may be polyphyletic, with some species belonging to Crotalarieae and others to Genisteae. With the Argyrolobium group included, the Genisteae are characterised by a basically two-lipped calyx with a trifid lower lip, and the presence of quinolizidine alkaloids of a-pyridone type (chemical characters have proven to be very useful in plant systematics, with many groups characterised by the production of particular secondary metabolites).

Lupinus polyphyllus, a lupin species native to western North America. Photo from Wikimedia.

The genus Lupinus (the lupins) form a distinct group from the remainder of the Palaearctic Genisteae. Lupinus is by far the largest genus of Genisteae, including about half the species and the only genus to have made it to the New World, where it is found in both North and South America. Most lupins are readily distinguished from other Genisteae by their palmate, divided leaves. While the flowers are not particularly edible (despite the rumoured possibilities of lupin soup, roast lupin, steamed lupin, braised lupin in lupin sauce, lupin in the basket with sauted lupins, lupin meringue pie, lupin sorbet…), the beans of some species are eaten pickled (raw beans generally contain toxic alkaloids) in Mediterranean areas or Latin America. Lupins have been widely grown as stock feed and as ornamentals, and include many of the aforementioned weed species.

Valley in Victoria (Australia) overrun by the vile Ulex europaeus. Photo by Kate Blood.

The remaining genera of Genisteae form the subtribe Genistinae. Diversity of Genistinae is centred around the Mediterranean, with the three best-known genera being the brooms in Genista and Cytisus, and gorse in Ulex (Ulex and the closely related, possibly synonymous, genus Stauracanthus have been placed in a separate subtribe Ulicinae, but Ainouche et al., 2003, demonstrated that these genera fell within Genistinae). A number of other broom genera are recognised, but classifications may differ on which genera are recognised as including which species. The Genistinae also includes the tree genus Laburnum (Käss & Wink 1997). Members of the Genistinae are characterised by adaptations for arid habitats such as very small or absent leaves and photosynthetic stems. Ulex species have the leaves modified into long spines. The species Ulex europaeus (commonly called simply “gorse”) was introduced into New Zealand for use in hedges, a role which it apparently fulfils admirably in Britain. Unfortunately, the imported gorse plants found the New Zealand climate much more to their liking than that of their native Britain, and are currently one of New Zealand’s most widespread and visible weed species. Yours truly has many unwelcome memories of hot summer days spent grubbing up gorse plants.

A South American paradox
Published 28 September 2009
Aspects of Sellocharis paradoxa (Papilionaceae) as illustrated by Polhill (1976): “1, habit; 2, node with stem cut away to show leaf-arrangement; 3, flower; 4, calyx, opened out; 5, standard; 6, wing; 7, keel; 8, stamens, spread out; 9, anthers; 10, pistil; 11, same with ovary-wall cut away to show ovules”.

The southern Brazilian leguminous subshrub Sellocharis paradoxa was first described in 1889, but for a very long time was known solely from the original isotypes*. It has only been rediscovered in scrubby grasslands and rockfields of the Brazilian state of Rio Grande do Sul within the last ten years or so (Conterato et al. 2007). Without having seen the original description, I can’t tell you for certain what earned Sellocharis the name of ‘paradoxa‘, but I suspect it was probably the unique arrangement of its leaves. As you can see in the figure above, S. paradoxa has its leaves arranged in regular whorls of five to seven. The individual “leaves” are more similar to the leaflets of other leguminous plants, and Polhill (1976) tentatively suggested that that might be what they were – that instead of having whorls of six leaves, S. paradoxa might have only a single leaf that had lost its basal stalk so completely that it had merged with the main stem.

*For the non-botanists among you, “isotypes” are two or more type specimens that have been taken from the same original individual, such as two branches from a single tree.

As befits its unusual morphology, the relationships of Sellocharis paradoxa are similarly mysterious. The most similar genus is Anarthrophyllum, a genus of Andean ‘cushion plants’ in which the stipules of the often trifoliate leaves surround the stem, often forming a sheath, and most authors seem to have assumed a relationship between the two genera. Flower morphology and the presence of α-pyridone alkaloids in Anarthrophyllum suggest a position in the Genisteae, the tribe including brooms, gorse and lupins. Within the Genisteae, the flowers of Anarthrophyllum and Sellocharis are most similar to those of the basal Argyrolobium group. A large-scale molecular analysis of Papilionaceae placed Anarthrophyllum as sister to the clade of Lupinus and Genistinae (Wojciechowski et al., 2004), which is consistent with the previously suggested position of the Argyrolobium group (Ainouche et al. 2003) though no other members of the group were included in the later analysis. However, Polhill (1976) noted that, if one interprets the ‘leaves’ of Sellocharis as leaflets of a single divided leaf, then they bear a certain resemblance to the leaves of lupins and may indicate a relationship to that genus instead.

A genistean position for Sellocharis and Anarthrophyllum is still not un-problematic. As described in the previous post, the Genisteae is a primarily Old World lineage. Lupinus is the only other genus of Genisteae found in the Americas, and as it is found in both the Old and New Worlds it could be a later invader of the latter. Nevertheless, other genera of the Argyrolobium group are found in southern Africa, and the ancestors of Sellocharis may have come from there as other organisms are known to have done (the ancestors of the New World monkeys being perhaps the most famous example). Also potentially problematic is that the number and morphology of chromosomes in Sellocharis is very distinct from those of any other Genisteae; however, the authors who described Sellocharis‘ karyotype (Conterato et al. 2007) only referred to its differences from Genisteae without comparing it to members of other tribes. Hopefully, now that Sellocharis paradoxa has been re-found, more progress can be made on establishing just what it is.

Systematics of Genisteae

Characters (from Ainouche et al. 2003): Stamen filaments joined into closed tube with distinctly dimorphic anthers; leaves simple, unifoliolate or digitately three–many-foliolate; seeds exarillate, or if arillate only on short side; calyx-lobes variously inited with basically two-lipped calyx.

<==Genisteae
    |--Dichilus lebeckioidesAB03, CP13
    |--MelolobiumAB03
    `--+--+--LupinusAB03
       |  `--+--GenistinaeAB03
       |     `--LaburnumCP13
       |          |--L. anagyroidesCP13
       |          `--L. vulgareC08
       `--+--AnarthrophyllumCP13
          |    |--A. desideratumCP13
          |    `--A. patagoniumSB06
          `--ArgyrolobiumAB03
               |--A. harveyanumAB03
               |--A. marginatumAB03
               |--A. velutinumCP13
               `--A. zanoniiAB03
Genisteae incertae sedis:
  SellocharisAB03
  AdenocarpusCP13
    |--A. foliolosusES06
    `--A. viscosusES06
  Gonocytisus pterocladusCP13, H97
  HesperolaburnumCP13
  LembotropisCP13
  Petteria ramentaceaCP13, GR98
  PodocytisusCP13
  PolhilliaCP13
  Retama raetamCP13, RBA00

*Type species of generic name indicated

References

[AB03] Ainouche, A., R. J. Bayer, P. Cubas & M.-T. Misset. 2003. Phylogenetic relationships within tribe Genisteae (Papilionoideae) with special reference to genus Ulex. In: Bruneau, B. B. K. A. (ed.) Advances in Legume Systematics vol. 10. Higher Level Systematics pp. 239–252. Royal Botanic Gardens: Kew.

[CP13] Cardoso, D., R. T. Pennington, L. P. de Queiroz, J. S. Boatwright, B.-E. Van Wyk, M. F. Wojciechowski & M. Lavin. 2013. Reconstructing the deep-branching relationships of the papilionoid legumes. South African Journal of Botany 89: 58–75.

[C08] Cheel. 1908. Notes and exhibits. Proceedings of the Linnean Society of New South Wales 33: 287.

Conterato, I. F., S. T. Sfoggia Miotto & M. T. Schifino-Wittman. 2007. Chromosome number, karyotype, and taxonomic considerations on the enigmatic Sellocharis paradoxa Taubert (Leguminosae, Papilionoideae, Genisteae). Botanical Journal of the Linnean Society 155 (2): 223–226.

[ES06] Erber, D., & M. Schöller. 2006. Revision of the Cryptocephalus-species of the Canary Islands and Madeira (Insecta, Coleoptera, Chrysomelidae, Cryptocephalinae). Senckenbergiana Biologica 86 (1): 85–107.

[GR98] Greuter, W., & T. Raus (eds.) 1998. Med-Checklist notulae, 17. Willdenowia 28: 163–174.

[H97] Heenan, P. B. 1997. Wood anatomy of the Carmichaelia (Fabaceae) complex in New Zealand. New Zealand Journal of Botany 35: 395–415.

Käss, E., & M. Wink. 1997. Phylogenetic relationships in the Papilionoideae (family Leguminosae) based on nucleotide sequences of cpDNA (rbcL) and ncDNA (ITS 1 and 2). Molecular Phylogenetics and Evolution 8 (1): 65–88.

Polhill, R. M. 1976. Genisteae (Adans.) Benth. and related tribes (Leguminosae). Botanical Systematics 1: 143–368.

[RBA00] Rifai, L. B., M. Abu Baker & Z. S. Amr. 2000. Ecology, distribution and status of the rock hyrax, Procavia capensis syriaca, in Jordan. Zoology in the Middle East 21: 19–26.

[SB06] Sarno, R. J., M. S. Bank, H. S. Stern & W. L. Franklin. 2006. Effects of age, sex, season, and social dynamics on juvenile guanaco subordinate behavior. Journal of Mammalogy 87 (1): 41–47.

Wojciechowski, M. F., M. Lavin & M. J. Sanderson. 2004. A phylogeny of legumes (Leguminosae) based on analysis of the plastid matK gene resolves many well-supported subclades within the family. American Journal of Botany 91: 1846–1862.

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