Potential seed dispersal distances of native and non-native fleshy fruiting shrubs in the South African Mediterranean climate region

Mokotjomela, Thabiso Michael; Musil, C.F.; Esler, Karen J.

doi:10.1007/s11258-013-0237-3

Cited by 29 publications

(42 citation statements)

References 75 publications

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“…Avian frugivores play a key role in seed dispersal of many plant species worldwide (Cain et al 2000;Renne et al 2000;Vivian-Smith and Gosper 2010;Jordaan et al 2011a;Mokotjomela et al 2013bMokotjomela et al , 2015. The process of seed dispersal by avian frugivores usually involves the consumption of pulp and regurgitation or excretion of intact seeds (D'Avila et al 2010;Fedriani et al 2011;Czarnecka et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…This process is mutually beneficial as plants benefit from seed dispersal away from the parent plant to locations with fewer pathogens (Wenny 2001;Aslan 2011;Fricke et al 2013) while frugivores benefit from important food resources and energy rewards (Jordaan et al 2011b; Mokotjomela et al 2013a). Avian frugivores consume both native and invasive fruit and therefore can facilitate the rapid spread of fruiting invasive species (Davis 2011;Mokotjomela et al 2013b).…”

Section: Introductionmentioning

confidence: 99%

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Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

et al. 2015

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Avian frugivores play a key role in seed dispersal of many plant species, including invasive alien plants. We assessed the effect of gut passage on the germination of selected invasive alien plant species in South Africa. Fruits of four fleshly-fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava, and Morus alba, were fed to two species of indigenous turacos, Knysna (Tauraco corythaix) and purple-crested (Gallirex porphyreolophus) turacos, and to invasive roseringed parakeets (Psittacula krameri). Seed retention time was determined as this can influence both seed dispersal and germination success. Germination success of ingested seeds was compared with that of manually de-pulped seeds, as well as to seeds in whole fruit. The germination success of seeds of all the invasive plant species increased significantly after ingestion by both turaco species compared with seeds from whole fruits. Germination success of manually de-pulped seeds did not differ significantly from that of turaco ingested seeds. In contrast, seed passage through the digestive tract of rose-ringed parakeets significantly reduced germination success and viability of ingested invasive plant species. Our results suggest that Knysna and purple-crested turacos are legitimate seed dispersers of fleshy-fruited invasive plants, while rose-ringed parakeets are mainly seed predators. Although seed predation by rose-ringed parakeets negatively affects the reproductive success of these plants, it is unlikely that this will suppress the spread of these invasive alien plants in South Africa as they are already well established. Furthermore, they can facilitate dispersal by seed regurgitation and dropping uneaten fruits away from the parent plant. Similar trends could be expected for indigenous seeds that rose-ringed parakeets feed on and therefore these birds remain a negative influence within invaded ecosystems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

et al. 2015

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“…, Mokotjomela et al . ). Benefits of avian endozoochory include dormancy release and enhanced germination (Howe & Smallwood , Schupp et al .…”

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confidence: 97%

“…, Mokotjomela et al . ). However, dispersal distances are also influenced by spatial distributions of fruit or seed resources (Mokotjomela et al .…”

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The potential for birds to disperse the seeds of Acacia cyclops, an invasive alien plant in South Africa

Mokotjomela

Hoffmann

Downs

2015

Ibis

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Rooikrans Acacia cyclops is an aggressive invasive tree that threatens natural resources in South Africa. The seeds of A. cyclops have a prominent aril which attracts birds that ingest the seeds and disperse them endozoochorously. Two biological control agents, a Seed Weevil Melanterius servulus and a Flower‐galling Midge Dasineura dielsi, were released on A. cyclops in 1991 and 2002, respectively. Together these agents have substantially reduced seed production and generally far lower numbers of seeds are now available to birds. A consequence of this transition from historically bounteous quantities of seeds to scanty seed availability is that birds may no longer associate with the trees and seed dispersal may be disproportionately reduced. To assess whether this has happened, seed attrition was measured by comparing the amount of seeds that disappeared from two groups of branches, one available to birds and the other enclosed in bird netting. Other types of granivores (mainly field mice) were excluded from both groups of branches with a plastic funnel placed around the stems. Mature seeds were also harvested and fed to caged bird species to determine gut retention times and germination rates of ingested seeds. Attrition rates of seeds showed that birds continue to remove seeds but that only a proportion of the crop is taken. Only two frugivorous species (Knysna Turaco Tauraco corythaix and Red‐winged Starling Onychognathus morio) and two granivorous species (Red‐eyed Dove Streptopelia semitorquata and Laughing Dove Streptopelia sengalensis) ingested A. cyclops seeds during feeding trials. Ingestion by birds enhanced seed germination except for those ingested by Laughing Doves. There were no apparent effects of length of gut passage time and avian body size on seed germination rates. Despite the diminished seed resource due to biological control agents, birds continue to disperse A. cyclops seeds.

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Determining the critical recruitment needs for the declining population of Olea europaea subsp. africana (Mill.) P.S. Green in Free State, South Africa

Vukeya

Mokotjomela

Powrie

et al. 2023

Ecology and Evolution

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Olea europaea subsp. africana (Mill.) P.S. Green (medium-sized tree species known as "African wild olive"), provides important ecological goods and services for sustaining frugivores in the grassland biome in South Africa. We speculate that O. europaea subsp. africana's population has been declining due to habitat loss and exploitation for domestic benefits suggesting an unrecognized conservation threat. Therefore, the study aimed to investigate the anthropogenic conservation threats for O. europaea subsp. africana in the Free State, South Africa and to determine the potential importance of seed dispersal effectiveness in the restoration of the species in the study area. Overall, the results showed that 39% of the natural habitat range has been transformed by human-mediated activities. Agricultural activities accounted for 27%, while mining activities and human settlement accounted for 12%, of natural habitat loss. In support of the study predictions, seeds of O. europaea subsp. africana had significantly higher germination and germinated faster after passing through the mammal gut (i.e., 28% and 1.49 per week), compared to other seed treatments (i.e., over 39 weeks). However, there were no statistically significant differences between seed germination of the bird-ingested seeds, with intact fruits as the experimental control, although both were significantly greater than the de-pulped seeds. Potential seed dispersal distances by birds were relatively larger, ranging from 9.4 km to 53 km, than those of mammals (1.5 km-4.5 km). We propose that the O. europaea subsp. africana's habitat range may have been declining, and since it is a keystone plant species, we recommend that the complementary seed dispersal services by birds and mammals could be important for its recruitment and restoration in the degraded habitat.

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Potential seed dispersal distances of native and non-native fleshy fruiting shrubs in the South African Mediterranean climate region

Cited by 29 publications

References 75 publications

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

The potential for birds to disperse the seeds of Acacia cyclops, an invasive alien plant in South Africa

Determining the critical recruitment needs for the declining population of Olea europaea subsp. africana (Mill.) P.S. Green in Free State, South Africa

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