The spectacular Proteaceae family

Residents of the Western Cape are privileged to live amongst such floral beauty. Nature reserves managed by CapeNature offer numerous opportunities to experience the exceptional biodiversity of this biodiversity hotspot region we call home. Many species of the iconic Proteaceae family are flowering right now.

The family Proteaceae was named in 1767 by Carl Linnaeus after Proteus, one of the gods in Greek mythology who had the ability to constantly change his form. The name Proteaceae and Protea thus echo the variability of many different plant forms found within the large family. The Proteaceae is one of the most spectacular plant families in South Africa. The first record of any plant ever described in southern Africa was Protea neriifolia, described by Clusius, 50 years before Jan van Riebeeck landed at the Cape of Good Hope (Vogts 1960).

The Core Cape Subregion of South Africa (also referred to as the Greater Cape Floristic Region) is one of the world’s most remarkable hotspots of biodiversity. The region comprises an estimated 9 400 species of vascular plants of which almost 70% are endemic. It is home to six endemic or near-endemic families, of which the Proteaceae is one of the most well-known.

Fourteen genera of the Proteaceae occur in southern Africa, namely Aulax (featherbushes - 3 taxa), Brabejum (Wild Almond being the single taxon), Diastella (silkypuffs - 9 taxa), Faurea (beechwoods - 5 taxa), Leucadendron (conebushes - 98 taxa), Leucospermum (pincushions – 54 taxa), Mimetes (pagodas – 13 taxa), Orothamnus (Marsh Rose being the single taxon), Paranomus (sceptres - 19 taxa), Protea (sugarbushes – 87 taxa), Serruria (spiderheads – 59 taxa), Sorocephalus (clusterheads - 11 taxa), Spatalla (spoons - 20 taxa), and Vexatorella (vexators - 5 taxa) (Rebelo 1995; SANBI 2020). Two genera are dioecious, namely Aulax and Leucadendron (Figure 1). Growth forms in the Proteaceae differ vastly, from prostrate shrubs (Figure 2) to tall trees. All species have compound flower heads, called inflorescence.

Pollination of Proteas

Most species of Proteaceae are pollinated by birds, e.g., the national flower which is the King Protea (Protea cynaroides), the common and well-known sugarbush (P. repens), and most of the bearded Proteas (P. neriifolia, P. laurifolia, P. magnifica, P. lorifolia). Bird pollinated species mostly have brightly coloured involucral bracts to attract birds of which the most important are the sugarbirds and sunbirds (Figure 3). Several species are pollinated by rodents, including gerbils, mice, rats and shrews. An interesting fact is the one species, P. punctata (Figure 4), which has implemented a pollination shift to being pollinated primarily by long-proboscid flies and butterflies (Johnson et al. 2012). Another interesting species is Leucospermum arenarium which is listed as Critically Endangered. This species depends on rodents for pollination and presents its viscous nectar in an exposed position on petal tips to allow rodents easy access without destroying the inflorescences (Johnson & Pauw 2014). Some species are pollinated by bees, e.g., Diastella thymelaeoides ssp. meridiana (Figure 5). The inflorescences of bee-pollinated species are considerably smaller in size than those of bird-pollinated species. There are also 10 wind-pollinated members of the Proteaceae in southern Africa, all of which are Leucadendron species. These species are odourless and do not secrete nectar.

Some species of Proteaceae exude a ‘yeasty’ scent, which is a typical trait of plants pollinated by small mammals (Kühn et al. 2017). Visits by small mammals do not however preclude visits by other pollinators, such as sunbirds and insects. The mammal-pollinated flowers are more open-shaped and with a diameter wider than the length of the inflorescence, e.g., Protea canaliculata, P. sulphurea, and P. humiflora.

Figure 1: Leucadendron sp. (Image: Scott Ramsay)

Figure 2: Leucospermum prostratum (Image: Steve Gildenhuys)

Figure 3: Protea eximia [Acknowledgement: iNaturalist © capietours (CC BY-NC 4.0)]

Figure 4: Protea punctata (Image: Charleen Brunke)

Figure 5: Diastella thymelaeoides ssp. meridiana (Image: Ruida Pool-Stanvliet)

Figure 6: Mimetes cucullatus (Image: Scott Ramsay)

Figure 7: Protea nitida [Acknowledgement: iNaturalist © pleistocene (CC BY-NC 4.0)]

References:

Johnson, C.M. & Pauw, A. 2014. Adaptation for rodent pollination in Leucospermum arenarium (Proteaceae) despite rapid pollen loss during grooming. Annals of Botany 113: 931–938.

Johnson, S.D., Newman, E. & Anderson, B. 2012. Preliminary observations of insect pollination in Protea punctata (Proteaceae). South African Journal of Botany 83: 63–67.

Kühn, N., Midgley J. & Steenhuisen, S.-L. 2017. Reproductive biology of three co-occurring, primarily small-mammal pollinated Protea species (Proteaceae). South African Journal of Botany 113: 337–345.

Rebelo, T. 1995. Proteas: A field guide to the Proteas of Southern Africa. Cape Town: Fernwood Press.

SANBI. 2020. Red List of South African Plants version 2020.1. Downloaded from Redlist.sanbi.org on 2022/05/18.

Vogts, M. 1960. The South African Proteaceae: the need for more research. South African Journal of Science, pp. 297-305. URL: https://journals.co.za/doi/pdf/10.10520/AJA00382353_4709