| 1. |
- Jakobsson, Anna, et al.
(författare)
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Competition for pollinators between invasive and native plants : Effects of spatial scale of investigation (note)
- 2009
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Ingår i: Ecoscience. - : Informa UK Limited. - 1195-6860. ; 16:1, s. 138-141
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Tidskriftsartikel (refereegranskat)abstract
- In this study we show that spatial scale of investigation affects the estimated strength of competition for pollinators between an invasive and a native plant species. The effect of the invasive herb Oxalis pes-caprae on pollinator visits to the native herb Diplotaxis erucoides was studied when the invader was (1) totally present, (2) present on a large scale (of hectares) but absent on a small scale (of square metres), and (3) totally absent. No difference in number of pollinator visits to D. erucoides was found between treatment 1 and 3, i.e., between total presence and total absence of the invader. However, when the invader was removed in the small scale while still remaining in the large scale, a higher number of visits to the native was recorded. Our study thus shows the importance of incorporating multiple spatial scales to allow for investigation of hierarchical effects on competition for pollinators, and it suggests that small-scale studies of effects of invasive plants on pollinator visitation might risk overstating negative effects of the invader.
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| 2. |
- Jakobsson, Anna, et al.
(författare)
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Distance-dependent effects of invasive Lupinus polyphyllus on pollination and reproductive success of two native herbs
- 2015
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 16:2, s. 120-127
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive understanding of the effects of invasive plants on native species requires identification of both the mechanisms of interaction and the spatial scale over which they act. Indirect interactions involving mobile organisms such as pollinators are likely to be scale-dependent, yet most studies examining effects of invasive species on pollination of native plants have considered effects across a single distance between interacting species. We examined the effects of the invasive herb Lupinus polyphyllus on pollination of two native herbs using multiple distances between the invasive and the natives. We recorded pollinator visitation and seed production in the native herbs Lotus corniculatus and Lychnis viscaria at 0, 5 m or 200 m away from L. polyphyllus. To reduce the influence of confounding factors, we used experimentally established populations of the invasive and potted individuals of the natives. In the immediate vicinity to L. polyphyllus, visitation to L. corniculatus was higher than 200 m away, and seed production per flower was higher than 5 m and 200 m away. In L. viscaria, bumblebee visitation was higher adjacent to L. polyphyllus than 5 m and 200 m away, but total pollinator visitation and reproductive success did not vary with distance. The results indicate that L. polyphyllus facilitates pollination of the native plants, and that this occurs at a very local spatial scale as effects dropped off already at a distance of 5 m. Presence of L. polyphyllus could benefit both pollinators and pollination of native herbs, and these positive effects should be considered along with likely negative effects due to resource competition. Moreover, the results illustrate the necessity to consider scale-dependent effects when assessing the impact of invasive flowering plants on native pollination interactions.
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| 3. |
- Jakobsson, Anna, et al.
(författare)
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Does the invasive Lupinus polyphyllus increase pollinator visitation to a native herb through effects on pollinator population sizes?
- 2014
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 174:1, s. 217-226
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Tidskriftsartikel (refereegranskat)abstract
- Invasive plants may compete with native species for abiotic factors as light, space and nutrients, and have also been shown to affect native pollination interactions. Studies have mainly focused on how invasive plants affect pollinator behaviour, i.e. attraction of pollinators to or away from native flowers. However, when an invasive plant provides resources utilized by native pollinators this could increase pollinator population sizes and thereby pollination success in natives. Effects mediated through changes in pollinator population sizes have been largely ignored in previous studies, and the dominance of negative interactions suggested by meta-analyses may therefore be biased. We investigated the impact of the invasive Lupinus polyphyllus on pollination in the native Lotus corniculatus using a study design comparing invaded and uninvaded sites before and after the flowering period of the invasive. We monitored wild bee abundance in transects, and visit rate and seed production of potted Lotus plants. Bumblebee abundance increased 3.9 times in invaded sites during the study period, whereas it was unaltered in uninvaded sites. Total visit rate per Lotus plant increased 2.1 times in invaded sites and decreased 4.4 times in uninvaded sites. No corresponding change in seed production of Lotus was found. The increase in visit rate to Lotus was driven by an increase in solitary bee visitation, whereas mainly bumblebees were observed to visit the invasive Lupinus. The mechanism by which the invasive increases pollinator visit rates to Lotus could be increased availability of other flower resources for solitary bees when bumblebees forage on Lupinus.
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| 4. |
- Jakobsson, Anna, et al.
(författare)
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Pollen transfer from invasive Carpobrotus spp. to natives - a study of pollinator behaviour and reproduction success
- 2008
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 141:1, s. 136-145
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Tidskriftsartikel (refereegranskat)abstract
- The influence of invasive plant species on native community composition is well-documented, but less is known about underlying mechanisms. Especially scarce is knowledge about effects on biotic interactions such as relationships between native plants and their pollinators. In this study we investigate if pollen transfer from the invasive and highly pollen productive Carpobrotus spp. affects seed production and/or seed quality in three native species. We monitored pollinator movements and pollen loads on pollinators and native stigmas, and in a field pollination experiment we investigated the effect of invasive pollen on reproduction. Invasive pollen adhered to pollinators, pollinators switched from Carpobrotus spp. to natives, invasive pollen was transferred to native stigmas, and it affected seed production in one species. Although all possible steps for interference with seed production were found to be qualitatively taken, invasive pollen has probably little impact on the native community because the frequency of invasive pollen transfer to natives was low. However, pollination interactions may change with plant abundance and our study provides evidence that pollen transfer from Carpobrotus spp. to natives does occur and have the potential to affect seed production. We found the species identity of shared pollinators to be of importance, higher flower constancy and lower capacity of pollen adherence are likely to result in less invasive pollen transfer.
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