Does farming with native honeybees affect bird pollination in Cape fynbos?

S. Geerts, A. Pauw
2009 South African Journal of Botany  
Does alien plant invasion cause declines in plant species richness? The broadly accepted connection between invasive species and diversity declines has recently been subjected to rigorous scrutiny. However, to answer this question one has to consider different spatial as well as different temporal scales. At a global scale naturalized species are undoubtedly contributing to decline of species richness by causing or facilitating the extinction of native species. At sub-global scales however, the
more » ... establishment of naturalized species may cause changes in species composition but the net outcome on species richness is uncertain. A comparative study of plant and bird species on oceanic islands showed that species richness for land birds remained relatively unchanged with the number of naturalizations being roughly equal to the number of extinctions. Even more surprising was the fact that species richness for vascular plants had increased dramatically, with the number of naturalizations greatly exceeding those of extinctions. It can therefore be argued that at smaller scales the losses due to extinction of native species have on average been more than offset by the colonization of invading species. However, we have to take into account the different timescales between invasions and extinctions. With plant species especially, the process of extinction may occur over a much longer timescale than invasion and it is not unlikely that many plant species will become extinct in the future as a direct consequence of current processes. Up until now, on a sub-global scale, the number of naturalizations of alien plant species greatly exceeds the number of extinctions of native plant species. As part of this review, we wanted to address the question of whether invasion by alien species necessarily leads to an extinction of native species and consequently to a decline of native species richness and on which scale. To address this question however, it is crucial to understand which factors are responsible for a decrease of native species richness. The review thus also addresses the question of if there is a decline in species richness, which factors are responsible for that decline. Tef (Eragrostis tef (Zucc.) Trotter) is an important small seeded cereal of high economic importance as a food and forage crop. The crop is nutritious both for human consumption and as animal feed for its high content of essential amino acids comparing to most other common cereals. However, it is a crop that has remained mostly unattended by scientists in the past to expand its domestication by improving yield and grain quality. The yield of this crop is very low, which ranges between 1.0-3.0 t/ha mostly being produced in East Africa mainly Ethiopia as an important cereal grain source and its close relatives (Eragrostis spp.) are grown in South Africa as forage for animals. The low yield compared to other cereals is due to lack of genetically high yielding varieties. One of the greatest drawbacks in improving yield has been the positive high genetic correlation of grain yield to plant height. The crop however already suffers form inherent extreme lodging problem, which accounts a yield reduction by more than 20% from the current production. This huge loss is yet without taking into account the potential limitation already imposed by this agronomic trait to further increasing yield genetically and also to using high input like fertilizer use and irrigation. Thus lodging is now a major setback to tef improvement demanding scientific intervention. This study involves identification of major genes that play a key role in the control of plant height and regulating these genes to develop genetically dwarf varieties that can be employed to develop high yielding varieties with improved standing ability. Such a process has been demonstrated successfully and within reasonable time constraints for other cereals. Moreover, the approach will also lay the foundation for future genetic improvement of the crops through biotechnology. Outside of their natural range, honeybees (Apis mellifera) are known to have detrimental effects on indigenous plants and pollinators. Within their natural range (e.g. Africa), no studies have tested for possible negative effects of honeybee farming, although beekeeping potentially elevates the abundance of honeybees above far above natural levels. Therefore, we ask: Does honeybee farming affect nectar-feeding birds and birdpollinated plants in fynbos? Beehives were introduced into natural fynbos areas to experimentally increase bee numbers. We chose a common protea species (Protea repens), utilized by 401 SAAB Annual Meeting Abstracts
doi:10.1016/j.sajb.2009.02.051 fatcat:aobkhw57irffpnhouyfpjrxiuy