ORCID Profile
0000-0001-6310-2870
Current Organisation
Stellenbosch University
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Invasive Species Ecology | Evolutionary Biology | Biological Adaptation
Control of Pests, Diseases and Exotic Species at Regional or Larger Scales | Ecosystem Adaptation to Climate Change |
Publisher: American Association for the Advancement of Science (AAAS)
Date: 15-10-2021
Abstract: A global dataset shows that animal pollinators are crucial for reproduction in half of wild flowering plants.
Publisher: Wiley
Date: 21-05-2019
DOI: 10.1111/JBI.13602
Publisher: Springer Science and Business Media LLC
Date: 10-08-2020
DOI: 10.1038/S41467-020-17751-Y
Abstract: Land use change, by disrupting the co-evolved interactions between plants and their pollinators, could be causing plant reproduction to be limited by pollen supply. Using a phylogenetically controlled meta-analysis on over 2200 experimental studies and more than 1200 wild plants, we ask if land use intensification is causing plant reproduction to be pollen limited at global scales. Here we report that plants reliant on pollinators in urban settings are more pollen limited than similarly pollinator-reliant plants in other landscapes. Plants functionally specialized on bee pollinators are more pollen limited in natural than managed vegetation, but the reverse is true for plants pollinated exclusively by a non-bee functional group or those pollinated by multiple functional groups. Plants ecologically specialized on a single pollinator taxon were extremely pollen limited across land use types. These results suggest that while urbanization intensifies pollen limitation, ecologically and functionally specialized plants are at risk of pollen limitation across land use categories.
Publisher: Springer Science and Business Media LLC
Date: 20-11-2018
Abstract: Plant reproduction relies on transfer of pollen from anthers to stigmas, and the majority of flowering plants depend on biotic or abiotic agents for this transfer. A key metric for characterizing if pollen receipt is insufficient for reproduction is pollen limitation, which is assessed by pollen supplementation experiments. In a pollen supplementation experiment, fruit or seed production by flowers exposed to natural pollination is compared to that following hand pollination either by pollen supplementation (i.e. manual outcross pollen addition without bagging) or manual outcrossing of bagged flowers, which excludes natural pollination. The GloPL database brings together data from 2969 unique pollen supplementation experiments reported in 927 publications published from 1981 to 2015, allowing assessment of the strength and variability of pollen limitation in 1265 wild plant species across all biomes and geographic regions globally. The GloPL database will be updated and curated with the aim of enabling the continued study of pollen limitation in natural ecosystems and highlighting significant gaps in our understanding of pollen limitation.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2021
Publisher: Wiley
Date: 18-05-2017
DOI: 10.1111/NPH.14593
Abstract: Interactions between non‐native plants and their mutualists are often disrupted upon introduction to new environments. Using legume–rhizobium mutualistic interactions as an ex le, we discuss two pathways that can influence symbiotic associations in such situations: co‐introduction of coevolved rhizobia and utilization of, and adaptation to, resident rhizobia, hereafter referred to as ‘ecological fitting’. Co‐introduction and ecological fitting have distinct implications for successful legume invasions and their impacts. Under ecological fitting, initial impacts may be less severe and will accrue over longer periods as novel symbiotic associations and/or adaptations may require fine‐tuning over time. Co‐introduction will have more profound impacts that will accrue more rapidly as a result of positive feedbacks between densities of non‐native rhizobia and their coevolved host plants, in turn enhancing competition between native and non‐native rhizobia. Co‐introduction can further impact invasion outcomes by the exchange of genetic material between native and non‐native rhizobia, potentially resulting in decreased fitness of native legumes. A better understanding of the roles of these two pathways in the invasion dynamics of non‐native legumes is much needed, and we highlight some of the exciting research avenues it presents. Contents Summary 1354 I. Introduction 1354 II. Specificity and effectiveness of legume–rhizobium interactions and their impacts on non‐native legume establishment 1355 III. Co‐introduction and ecological fitting: two pathways to establish legume–rhizobium interactions during biological invasions 1357 IV. Consequences of co‐introduction of rhizobia and non‐native legumes for invasion impacts 1357 V. Concluding remarks and future directions 1359 Acknowledgements 1359 References 1359
Publisher: Wiley
Date: 20-11-2020
DOI: 10.1111/CLA.12436
Abstract: Bombyliidae is a very species-rich and widespread family of parasitoid flies with more than 250 genera classified into 17 extant subfamilies. However, little is known about their evolutionary history or how their present-day ersity was shaped. Transcriptomes of 15 species and anchored hybrid enrichment (AHE) sequence captures of 86 species, representing 94 bee fly species and 14 subfamilies, were used to reconstruct the phylogeny of Bombyliidae. We integrated data from transcriptomes across each of the main lineages in our AHE tree to build a data set with more genes (550 loci versus 216 loci) and higher support levels. Our overall results show strong congruence with the current classification of the family, with 11 out of 14 included subfamilies recovered as monophyletic. Heterotropinae and Mythicomyiinae are successive sister groups to the remainder of the family. We examined the evolution of key morphological characters through our phylogenetic hypotheses and show that neither the "sand chamber subfamilies" nor the "Tomophthalmae" are monophyletic in our phylogenomic analyses. Based on our results, we reinstate two tribes at the subfamily level (Phthiriinae stat. rev. and Ecliminae stat. rev.) and we include the genus Sericosoma Macquart (previously incertae sedis) in the subfamily Oniromyiinae, bringing the total number of bee fly subfamilies to 19. Our dating analyses indicate a Jurassic origin of the family (165-194 Ma), with the sand chamber evolving early in bee fly evolution, in the late Jurassic or mid-Cretaceous (100-165 Ma). We hypothesize that the angiosperm radiation and the hothouse climate established during the late Cretaceous accelerated the ersification of bee flies, by providing an expanded range of resources for the parasitoid larvae and nectarivorous adults.
Publisher: Oxford University Press (OUP)
Date: 18-08-2015
Abstract: Establishing mutualistic interactions in novel environments is important for the successful establishment of some non-native plant species. These associations may, in turn, impact native species interaction networks as non-natives become dominant in their new environments. Using phylogenetic and ecological interaction network approaches we provide the first report of the structure of belowground legume–rhizobium interaction networks and how they change along a gradient of invasion (uninvaded, semi invaded and heavily invaded sites) by Australian Acacia species in South Africa’s Cape Floristic Region. We found that native and invasive legumes interact with distinct rhizobial lineages, most likely due to phylogenetic uniqueness of native and invasive host plants. Moreover, legume–rhizobium interaction networks are not nested, but significantly modular with high levels of specialization possibly as a result of legume–rhizobium co-evolution. Although network topology remained constant across the invasion gradient, composition of bacterial communities associated with native legumes changed dramatically as acacias increasingly dominated the landscape. In stark contrast to aboveground interaction networks (e.g. pollination and seed dispersal) we show that invasive legumes do not infiltrate existing native legume–rhizobium networks but rather form novel modules. This absence of mutualist overlap between native and invasive legumes suggests the importance of co-invading rhizobium–acacia species complexes for Acacia invasion success, and argues against a ubiquitous role for the formation and evolutionary refinement of novel interactions.
Publisher: Elsevier BV
Date: 12-2022
Publisher: Pensoft Publishers
Date: 25-07-2019
DOI: 10.3897/NEOBIOTA.49.34245
Abstract: Following their establishment in new communities, invasive species may cause evolutionary changes in resident native species. This is clearly true for phytophagous insects, which may adapt rapidly when utilising abundant and widespread introduced hosts. The balloon vines Cardiospermumhalicacabum and C.grandiflorum were introduced to South Africa approximately 100 years ago and are classified as minor and major weeds, respectively. Here we assess the potential evolutionary impact of these vines on native Leptocoris soapberry bug populations in Kruger National Park (KNP), using phylogenetic and morphometric analyses. We found that soapberry bugs associated with C.halicacabum are genetically and morphologically distinct from those associated with C.grandiflorum . This suggests that native soapberry bugs in KNP exhibit some degree of host preference, indicating that these vines may have had significant evolutionary consequences for these insects. The proboscis length of soapberry bugs feeding on C.halicacabum closely matched fruit size, often being longer than fruit size at the population level. These soapberry bugs are therefore well-suited to feeding on this introduced plant species.
Publisher: Microbiology Society
Date: 06-2014
Abstract: During a study to investigate the ersity of rhizobia associated with native legumes in South Africa’s Cape Floristic Region, a Gram-negative bacterium designated VG1C T was isolated from the root nodules of Aspalathus abietina Thunb. Based on phylogenetic analyses of the 16S rRNA and recA genes, VG1C T belongs to the genus Burkholderia , with the highest degree of sequence similarity to the type strain of Burkholderia sediminicola (98.5 % and 98 %, respectively). The DNA G+C content of strain VG1C T was 60.1 mol%, and DNA–DNA relatedness values to the type strain of closely related species were found to be substantially lower than 70 %. As evidenced by results of genotypic, phenotypic and chemotaxonomic tests provided here, we conclude that isolate VG1C T represents a novel rhizosphere-associated species in the genus Burkholderia , for which the name Burkholderia aspalathi sp. nov. is proposed, with the type strain VG1C T ( = DSM 27239 T = LMG 27731 T ).
Publisher: The Royal Society
Date: 22-03-2014
Abstract: The costs that species suffer when deceived are expected to drive learned resistance, although this relationship has seldom been studied experimentally. Flowers that elicit mating behaviour from male insects by mimicking conspecific females provide an ideal system for such investigation. Here, we explore interactions between a sexually deceptive daisy with multiple floral forms that vary in deceptiveness, and the male flies that pollinate it. We show that male pollinators are negatively impacted by the interaction, suffering potential mating costs in terms of their ability and time taken to locate genuine females within deceptive inflorescences. The severity of these costs is determined by the amount of mating behaviour elicited by deceptive inflorescences. However, inexperienced male flies exhibit the ability to learn to discriminate the most deceptive inflorescences as female mimics and subsequently reduce the amount of mating behaviour they exhibit on them with increased exposure. Experienced males, which interact with sexually deceptive forms naturally, exhibit similar patterns of reduced mating behaviour on deceptive inflorescences in multiple populations, indicating that pollinator learning is widespread. As sexually deceptive plants are typically dependent on the elicitation of mating behaviour from male pollinators for pollination, this may result in antagonistic coevolution within these systems.
Publisher: Oxford University Press (OUP)
Date: 28-03-2017
DOI: 10.1093/AOB/MCX028
Publisher: Elsevier BV
Date: 10-2009
Publisher: Elsevier BV
Date: 05-2017
Publisher: Oxford University Press (OUP)
Date: 19-09-2013
DOI: 10.1093/AOB/MCT189
Publisher: Wiley
Date: 31-07-2012
Publisher: Wiley
Date: 19-09-2014
DOI: 10.1111/DDI.12261
Publisher: The Royal Society
Date: 19-08-2014
Abstract: Phenotypic integration, the coordinated covariance of suites of morphological traits, is critical for proper functioning of organisms. Angiosperm flowers are complex structures comprising suites of traits that function together to achieve effective pollen transfer. Floral integration could reflect shared genetic and developmental control of these traits, or could arise through pollinator-imposed stabilizing correlational selection on traits. We sought to expose mechanisms underlying floral trait integration in the sexually deceptive daisy, Gorteria diffusa , by testing the hypothesis that stabilizing selection imposed by male pollinators on floral traits involved in mimicry has resulted in tighter integration. To do this, we quantified patterns of floral trait variance and covariance in morphologically ergent G. diffusa floral forms representing a continuum in the levels of sexual deception. We show that integration of traits functioning in visual attraction of male pollinators increases with pollinator deception, and is stronger than integration of non-mimicry trait modules. Consistent patterns of within-population trait variance and covariance across floral forms suggest that integration has not been built by stabilizing correlational selection on genetically independent traits. Instead pollinator specialization has selected for tightened integration within modules of linked traits. Despite potentially strong constraint on morphological evolution imposed by developmental genetic linkages between traits, we demonstrate substantial ergence in traits across G. diffusa floral forms and show that ergence has often occurred without altering within-population patterns of trait correlations.
Publisher: Elsevier BV
Date: 07-2022
Publisher: Public Library of Science (PLoS)
Date: 16-04-2013
Publisher: Elsevier BV
Date: 04-2010
Publisher: Oxford University Press (OUP)
Date: 17-09-2015
DOI: 10.1111/BOJ.12334
Publisher: Springer Science and Business Media LLC
Date: 19-12-2010
DOI: 10.1007/S00442-010-1879-7
Abstract: The co-occurrence of plant species within a community is influenced by local deterministic or neutral processes as well as historical regional processes. Floral trait distributions of co-flowering species that share pollinators may reflect the impact of pollinator preference and constancy on their assembly within local communities. While pollinator sharing may lead to increased visitation rates for species with similar flowers, the receipt of foreign pollen via interspecific pollinator movements can decrease seed set. We investigated the pattern of community flower colour assembly as perceived by native honeybee pollinators within 24 local assemblages of co-flowering Oxalis species within the Greater Cape Floristic Region, South Africa. To explore the influence of pollinators on trait assembly, we assessed the impact of colour similarity on pollinator choices and the cost of heterospecific pollen receipt. We show that flower colour is significantly clustered within Oxalis communities and that this is not due to historical constraint, as flower colour is evolutionarily labile within Oxalis and communities are randomly structured with respect to phylogeny. Pollinator observations reveal that the likelihood of pollinators switching between co-flowering species is low and increases with flower colour similarity. Interspecific hand pollination significantly reduced seed set in the four Oxalis species we investigated, and all were dependant on pollinators for reproduction. Together these results imply that flower colour similarity carries a potential fitness cost. However, pollinators were highly flower constant, and remained so despite the extreme similarity of flower colour as perceived by honeybees. This suggests that other floral traits facilitate discrimination between similarly coloured species, thereby likely resulting in a low incidence of interspecific pollen transfer (IPT). If colour similarity promotes pollinator attraction at the community level, the observed clustering of flower colour within communities might result from indirect facilitative interactions.
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.YMPEV.2016.12.004
Abstract: The Greater Cape Floristic Region (GCFR) in South Africa has been extensively investigated for its phenomenal angiosperm ersity. A key emergent pattern is the occurrence of older plant lineages in the southern Fynbos biome and younger lineages in the northern Succulent Karoo biome. We know practically nothing, however, about the evolutionary history of the animals that pollinate this often highly-specialized flora. In this study, we explore the evolutionary history of an important GCFR fly pollinator, Megapalpus capensis, and ask whether it exhibits broadly congruent genetic structuring and timing of ersification to flowering plants within these biomes. We find that the oldest M. capensis lineages originated in Fynbos during the Miocene, while younger Succulent Karoo lineages erged in the Pliocene and correspond to the proposed age of this recent biome. A strong signature of population expansion is also recovered for flies in this arid biome, consistent with recent colonization. Our first investigation into the evolutionary history of GCFR pollinators thus supports a recent origin of the SK biome, as inferred from angiosperm phylogenies, and suggests that plants and pollinators may have co- erged within this remarkable area.
Publisher: Wiley
Date: 02-12-2019
Publisher: Elsevier BV
Date: 11-2022
Publisher: Wiley
Date: 29-06-2019
DOI: 10.1111/NPH.15935
Abstract: The role of pollination in the success of invasive plants needs to be understood because invasives have substantial effects on species interactions and ecosystem functions. Previous research has shown both that reproduction of invasive plants is often pollen limited and that invasive plants can have high seed production, motivating the questions: How do invasive populations maintain reproductive success in spite of pollen limitation? What species traits moderate pollen limitation for invaders? We conducted a phylogenetic meta-analysis with 68 invasive, 50 introduced noninvasive and 1931 native plant populations, across 1249 species. We found that invasive populations with generalist pollination or pollinator dependence were less pollen limited than natives, but invasives and introduced noninvasives did not differ. Invasive species produced 3× fewer ovules/flower and >250× more flowers per plant, compared with their native relatives. While these traits were negatively correlated, consistent with a tradeoff, this did not differ with invasion status. Invasive plants that produce many flowers and have floral generalisation are able to compensate for or avoid pollen limitation, potentially helping to explain the invaders' reproductive successes.
Publisher: Wiley
Date: 28-02-2013
DOI: 10.1111/EVO.12070
Abstract: Divergent mate preferences and subsequent genetic differentiation between populations has been demonstrated, but its effects on interspecific interactions are unknown. Associated species exploiting these mate preferences, for ex le, may erge to match local preferences. We explore this idea in the sexually deceptive, fly-mimicking daisy, Gorteria diffusa, by testing for association between genetic structure in the fly pollinator (a proxy for mate preference ergence) and geographic ergence in floral form. If genetic structure in flies influences interactions with G. diffusa, we expect phylogeographically distinct flies to be associated with different floral forms. Flies associated with forms exploiting only feeding behavior often belonged to several phylogeographic clades, whereas flies associated with forms exploiting male-mating behavior always belonged to distinct clades, indicating the possibility of pollinator-mediated floral ergence through phylogeographic variation in mating preferences of male flies. We tested this hypothesis with reciprocal presentations using male flies from distinct clades associated with separate floral forms. Results show that males from all clades exhibit similar preferences, making pollinator driven ergence through geographic variation in mate preference unlikely. Males, however, showed evidence of learned resistance to deceptive traits, suggesting antagonistic interactions between plants and pollinators may drive deceptive floral trait evolution in G. diffusa.
Publisher: Elsevier BV
Date: 09-2019
Publisher: Wiley
Date: 10-04-2018
Start Date: 08-2022
End Date: 08-2025
Amount: $291,000.00
Funder: Australian Research Council
View Funded Activity