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Effects of the Non-Pollinating Fig Wasps Ceratosolen galili and Sycophaga sycomori on Ceratosolen arabicus - the Pollinator of Ficus sycomorus

Barke, J. (2004) Effects of the Non-Pollinating Fig Wasps Ceratosolen galili and Sycophaga sycomori on Ceratosolen arabicus - the Pollinator of Ficus sycomorus. Master's Thesis / Essay, Biology.

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Mutualistic associations are prone to exploitation by 'exploitative species'. The fig tree Ficus sycomorus is in addition to its pollinator, the fig wasp Ceratosolen arabicus, associated to several species of fig wasps, which benefit from it and the pollination-mutualism but which do not reciprocate by pollinating the fig tree's flowers. The two 'non-pollinators' Ceratosolen ga/ui and Sycophaga sycomori are in comparison to other non-pollinators likely to affect the fitness of C. arabicus and hence the stability of this mutualism. Both non-pollinators are relatively abundant and share many ecological features with the pollinator. How can C. arabicus, C. galili and S. sycomori coexist? Do these nonpollinators compete with the pollinator for the resources of F. sycomorus (figs, female flowers and nutrients) or do they occupy different niches? In order to investigate how the three species of fig wasps can coexist, several aspects of their niche ecology were studied with regard to figs, collected in Nelspruit and Kruger National Park (South Africa). Some of these aspects were related to their foundresses, occupying the immature figs of F. sycomorus, whereas others were related to their male and female offspring, reared from the fig tree's mature figs. Among others, it has been investigated, (1) how common the foundresses and female offspring of the species are in the immature and mature figs respectively, (2) how numerous their foundresses occupy the immature figs during oviposition, (3) at what time the female offspring emerge from the mature figs and (4) how the immature figs become occupied by the foundresses and foundress species. The foundresses and female offspring of S. sycomori were much more common than the ones of C. arabicus and C. ga/ui. This indicates that S. sycomori, in contrast to C. ga/i/i, has a high potential to compete with the pollinator. The foundresses of C. galili and S. sycomori were more numerous during oviposition than C. arabicus. In contrast to both non-pollinators, the pollinator therefore is supposed to produce offspring with a strongly female biased sex ratio and thus to have a relatively high 'per capita growth rate'. The female offspring of C. arabicus emerged most commonly during the evening and the ones of C. ga/i/i during the morning. This indicates first that the females of both species time their emergence and second that this timing is in tune with the timing of their dispersal, which is known to take place during the night and day respectively. The females of S. sycomori emerged from the figs during both night and day. The occupation of the figs seemed to be correlated with the timing of the species dispersal. After all, figs occupied by the foundresses of both C. arabicus and C. ga/i/i were relatively rare and figs, inhabited by the foundresses of both C. arabicus and S. sycomori were relatively common. This gives S. sycomori a higher potential to compete with the pollinator than C. ga/i/i. Further, the figs were most commonly occupied by single foundress species, which limits the potential for all species to compete with one another. Finally, most figs that were occupied by C. arabicus contained one foundress, which i ndicates that the pollinator has a high capability to monopolize figs and thus a high potential to compete for figs. This research found some aspects of the species niche ecology to overlap but most others to differ. In general, S. sycomori seemed to have a higher potential to compete with the highly competitive pollinator, than C. ga/i/i.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:31
Last Modified: 15 Feb 2018 07:31

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