An overview of plant–pollinator relationships in southern Africa

Abstract

A particularly rich array of pollination systems is represented in the flora of southern Africa. Hopliine beetles, long-proboscid flies, satyrine butterflies, hawk moths, birds and rodents appear to assume greater importance as pollinators than they do in other temperate regions. These 'alternative' pollination systems may have developed because the bee-fauna of southern Africa is not particularly rich relative to the flora. Pollination by moths, for example, is relatively frequent in the eastern half of southern Africa where bee diversity is lowest. Pollination systems in southern Africa are relatively specialized and shifts between pollinators have been shown to be an important driving force in plant diversification and speciation. Changes in land-use, particularly afforestation and ploughing of grasslands, invasion of alien plants, overgrazing and urban developments have disrupted these mutualisms with mostly unknown consequences for ecosystem functioning. Future research will be directed at expanding our knowledge of pollination systems, with a strong focus on the conservation of mutualistic ecological interactions.Résumé. La flore Sud Africaine est particulièrement riche en systèmes de pollinisation. Ainsi les scarabés de la famille des Hopliinae, les mouches a long proboscis, les papillons de la famille des Satyrinae, les sphingides, les oiseaux et les rongeurs ont un rô le plus important comme pollinisateurs que celui qu'ils jouent dans les autres régions tempérées du globe. Ces systèmes de pollinisation alternatifs se seraient développés parce que la faune des abeilles Sud Africaine n'est pas très riche au regard de la flore. Ainsi, la pollinisation par les papillons de nuit est relativement fréquente dans l'Est de l'Afrique du Sud où la diversité des abeilles est plus faible. En Afrique du Sud les systèmes de pollinisation sont relativement spécialisés et on a montré que des changements de pollinisateurs pouvaient jouer un rô le important dans la diversification des plantes et leur spéciation. Des modifications de la gestion des terres, en particulier la déforestation, le labour des prairies, l'introduction de plantes invasives, le surpâturage et le développement des villes out perturbé ces associations mutualistes et ont des consequences inconnues sur le fonctionnement des écosystèmes. Les recherches futures devront approfondir les connaissances sur les systèmes de pollinisation, et s'intéresser en particulier au maintien des interactions écologiques mutualistes.

Pollinator Diversity: Distribution, Ecological Function, and Conservation

“…In some parts of the world, such as southern Africa (Johnson 2004), bee diversity is much lower than one might expect. This seems to have resulted in the evolution of plants exploiting "unusual" (from a north-temperate perspective) pollinators such as groups of beetles, wasps and rodents that rarely act as specialized pollinators elsewhere in the world (Johnson 2004, Ollerton et al 2003, 2006, Shuttleworth and Johnson 2009.…”

“…Pollination systems that involve "unusual" or "unexpected" taxa such as flower chafers, spider hunting wasps, lizards or rodents, are still considered exceptional despite the fact that such "oddities" can be locally dominant (Ollerton et al 2003, Shuttleworth and Johnson 2009, Olesen and Valido 2003, Johnson 2004) and may in fact be much more widespread than we realise -they are not just "tropical novelties". This then begs the question of just how "different" plant-pollinator interactions are in the tropics compared to higher latitudes, a topic that has received growing interest in the past few years and which I explore in section 3.…”

“…This seems to have resulted in the evolution of plants exploiting "unusual" (from a north-temperate perspective) pollinators such as groups of beetles, wasps and rodents that rarely act as specialized pollinators elsewhere in the world (Johnson 2004, Ollerton et al 2003, 2006, Shuttleworth and Johnson 2009. Similarly, Australian plants have evolved pollinator relationships with a wide diversity of "nonstandard" pollinators (Armstrong 1979).…”

Pollination ecosystem services in South African agricultural systems

“…A high abundance of honeybees is not uncommon; honeybees are known to be present in many agricultural systems worldwide 25,66 -either because managed hives have been used or because there are wild or feral honeybees 55 . Honeybees in South Africa are indigenous and ubiquitous in natural [67][68][69] and agricultural systems 55,70 and are an important pollinator to a wide range of indigenous plant species 68,71 . Consequently, assessing the ecological importance of wild honeybees within the agricultural matrix and their contribution to sustainable pollination services is essential.…”

“…Larger bees, such as the carpenter bee (Xylocopa caffra), are considered to be more suited to the large flowers of legumes and are more effective as a consequence of their foraging behaviour, during which they trip the flower and affect pollination. 68,[73][74][75] However, in crops where honeybees are abundant, synergistic effects (increasing the movement and rate of visitation of honeybees) of non-Apis have been shown to improve pollination efficiency and the potential to increase crop yields. 26,27,55 These findings suggest the possible benefits of integrated management of non-Apis and honeybees.…”