Globally plant species richness is a significant predictor of insect richness. Whether this is the result of insect diversity responding directly to plant diversity, or both groups responding in similar ways to extrinsic factors, has been much debated. Here we assess this relationship in the Cape Floristic Region (CFR), a biodiversity hotspot. The CFR has higher plant diversity than expected from latitude (i.e., abiotic conditions), but very little is known about the diversity of insects residing in this region. We first quantify diversity relationships at multiple spatial scales for one of the dominant plant families in the CFR, the Restionaceae, and its associated insect herbivore community. Plant and insect diversity are significantly positively correlated at the local scales (10–50 m; 0.1–3 km), but not at the regional scales (15–20 km; 50–70 km). The local scale relationship remains significantly positively correlated even when accounting for the influence of extrinsic variables and other vegetation attributes. This suggests that the diversity of local insect assemblages may be more strongly influenced by plant species richness than by abiotic variables. Further, vegetation age and plant structural complexity also influenced insect richness. The ratio of insect species per plant species in the CFR is comparable to other temperate regions around the world, suggesting that the insect diversity of the CFR is high relative to other areas of the globe with similar abiotic conditions, primarily as a result of the unusually high plant diversity in the region.
10 February 2017
Molecular Phylogenetics and Evolution
The Greater Cape Floristic Region (GCFR) in South Africa has been extensively investigated for its phenomenal angiosperm diversity. 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 diversification 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 diverged 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-diverged within this remarkable area.
4 January 2017
Fungal Genetics and Biology
MATKnoxdaviesia capensisK. proteaeProtea We hypothesise that this diversity is the result of outcrossing driven by a heterothallic MAT1MAT1MAT1-1MAT1-2MAT1-1MAT1-1-1MAT1-1-2MAT1-2MAT1-2-7 MAT1-2-1MATKnoxdaviesia MAT1-2-7MAT1-1-1Knoxdaviesia
12 December 2016
South African Journal of Botany
Papio hamadryas ursinus We recorded the extent of damage by rodents and baboons to inflorescences of the dominant shrub, Protea neriifolia, in 20 × 20 m plots in the Jonkershoek Nature Reserve near Stellenbosch. Damage was distributed patchily across the landscape. Rodents damaged up to 23% of the inflorescences per plot by feeding on styles and nectar. We observed the striped mouse (Rhabdomys pumilio) climbing up plants to feed on inflorescences. Up to 14% of inflorescences in some plots were destroyed by rodents gnawing through inflorescence stems. Baboons damaged or destroyed 12% to 29% of inflorescences at three study sites, but did not forage at all in the three remaining study sites. Among plant individuals affected by baboons or rodents, a mean proportion of 0.49 ± 0.31 (SD) of individuals' inflorescences were damaged or destroyed. Florivory by rodents and baboons can thus reduce the fecundity of P. neriifolia significantly. Protea inflorescences may be an important seasonal food source for certain rodents. In an evolutionary context, rodent florivory may have been an important selective force that caused certain Proteaceae species to shift to rodent pollination. Further work is needed to determine which rodent species feed on Protea inflorescences and whether rodent florivory is widespread in fynbos.
9 November 2016
de Jager M L | Willis-Jones E | Critchley S | Glover B J
Linear areas of contrasting floral colour, or ‘‘nectar guides’’, are recognized to enhance pollinator attraction. Few studies, however, have investigated the role of other types of floral marking in pollinator behaviour. In this study, we explore the impact of petal spots and petal rings on bumblebee foraging dynamics. Using model flowers with discrete spot or bullseye ring patterns we investigate the responses of Bombus terrestris foragers towards rewarding and unrewarding flowers. We find that the presence of petal spots and rings reduce the search time of pollinators to locate rewarding model flowers. Only the rewarding petal ring phenotype, however, is readily learned and significantly increases the foraging efficiency of experienced bees over four foraging bouts. Although the rewarding spot phenotype induces random foraging over this time frame, employing differential conditioning with a strong aversive stimulus over ten foraging bouts reveal that bees have the capacity to correctly identify rewarding spot phenotypes with more training. Once a strong association between petal marking and reward is formed, bees continue to respond to marked phenotypes even when unrewarding, suggesting rewardless plants that exhibit petal marking could potentially exploit their pollinators. We conclude that petal marking, whether organised discretely in a spot or in a continuous ring around the centre of a flower, have a significant and complex influence on pollinator foraging dynamics.
14 October 2016
Journal of Evolutionary Biology
Lapeirousia anceps Moegistorhynchus longirostris
Journal of Animal Ecology
Summary: Patterns of niche partitioning can result from local ecological interactions (e.g. interspecific competition) occurring within a contemporary time frame (realised niche partitioning). Alternatively they may represent the end-product of historical processes acting over long time frames (fundamental niche partitioning).
Niche partitioning is often detected by analysing patterns of resource use within communities, but experiments are rarely conducted to test whether patterns of non-overlapping resource use reflect realised or fundamental niche partitioning.
We studied a community of restio leafhoppers from the genus Cephalelus, and their host plants, the Restionaceae (restios). We used network and experimental approaches to determine whether network modularity (a measure of niche partitioning within local communities) reflects fundamental or realised niche partitioning. Using a weighted modularity index for two party networks (e.g. insect - plant) we determined whether the network of this community is modular (i.e. consists of groups of species interacting strongly, with weak interactions between groups). We also aimed to identify specific Cephalelus - restio modules (groups). Using knowledge of module membership to design experiments, we tested whether Cephalelus species from two different modules, C. uncinatus and C. pickeri, prefer and perform better on restios from their own modules versus restios from other modules. These experiments were performed under controlled conditions, eliminating the influences of competition and predation on host choices.
The Cephalelus – restio community was modular, implying niche partitioning. Cephalelus also preferred and performed better on restios from their own modules in the absence of local contemporary factors. Most niche partitioning in the investigated Cephalelus community, is not caused by local interactions, and thus host use patterns represent fundamental niches. Our findings highlight the importance of understanding local community structure in the light of processes extrinsic to the local community context.
5 May 2015
She's moving on to do a postdoc at University of Cape Town. We will miss her (and her cakes), but luckily she won't be too far away.
We wish you all the best Anina!
30 March 2016
Every year our lab does a group project where everyone who has time pitches in to do a fun paper together. Our 2015 group paper just got published in Plant Systematics and Evolution.
Well done to everyone involved, we're looking forward to next year's project!
de Jager, M., Newman, E., Theron, G., Botha, P., Barton, M. & Anderson, B. (2016) Pollinators can prefer rewarding models to mimics: consequences for the assumptions of Batesian floral mimicry. Plant Systematics and Evolution, 302:4, 409-418.
9 February 2016
Willem Augustyn has graduated with a PhD entitled: Evolutionary drivers of temporal and spatial host use patterns in restio leafhoppers Cephalelini (Cicadellidae)
Congratulations Dr Augustyn!
Willem will continue with us next year, focusing on turning all the chapters from his PhD into papers. He's done some really exciting work, and we look forward to seeing his papers come out.
30 December 2015
Abstract: Geographic variation in floral morphology is often assumed to reflect geographic variation in pollinator communities and associated divergence in selective pressures. We studied populations of Nerine humilis (Amaryllidaceae) to assess whether geographic variation in floral form is the result of local adaptation to different pollinator communities. We first tested for associations between floral traits and visitor communities, and found that populations with similar floral morphologies were visited by similar insect communities. Mean style length in each population was also closely associated with the mean body length of the local visitor community. A reciprocal translocation experiment demonstrated that native phenotypes set more seed than translocated phenotypes. Single visitation experiments showed that native flowers received more pollen, and set more seed per visit, than introduced phenotypes in both populations. This suggests that the effectiveness of pollinator visits is determined by the degree of mechanical fit between flowers and visitors. We provide strong evidence that the observed among-population variation in floral traits is an adaptive response to geographic variation in the pollinator community.
10 September 2015
This prestigious award adds to an already impressive list awards and scholarships for Ethan including he Ernst and Ethel Eriksen Trust Scholarship (2013-2015); the NRF Innovation Scholarship (2014-2015); National Geographic Young Explorers Grant (2013 & 2014) and the NRF Scarce Skills Scholarship (2012-2013).
We are very proud and lucky to have Ethan in our lab. Ethan will soon be heading to the University of Montpellier in France as part of the Erasmus Mundus exchange programme, but will return to the lab in 2016 to finalise his PhD.
August 28, 2015
Photo: Marinus de Jager
Sexual reproduction is necessary to generate genetic diversity and, in ascomycete fungi, this process is controlled by a mating type (MAT) locus with two complementary idiomorphs. Knoxdaviesia capensis and K. proteae (Sordariomycetes; Microascales; Gondwanamycetaceae) are host-specific saprophytic fungi that show high population diversity within their Protea plant hosts in the Cape Floristic Region of South Africa. We hypothesise that this diversity is the result of outcrossing driven by a heterothallic mating system and sought to describe the MAT1 loci of both species. The available genome assembly of each isolate contained only one of the MAT1 idiomorphs necessary for sexual reproduction, implying that both species are heterothallic. Idiomorph segregation during meiosis, a 1:1 ratio of idiomorphs in natural populations and mating experiments also supported heterothallism as a sexual strategy. Longrange PCR and shot-gun sequencing to identify the opposite idiomorph in each species revealed no sequence similarity between MAT1-1 and MAT1-2 idiomorphs, but the homologous idiomorphs between the species were almost identical. The MAT1-1 idiomorph contained the characteristic MAT1-1-1 and MAT1-1-2 genes, whereas the MAT1-2 idiomorph consisted of the genes MAT1-2-7 and MAT1-2-1. This gene content was similar to that of the three species in the Ceratocystidaceae (Microascales) with characterized MAT loci. The Knoxdaviesia MAT1-2-7 protein contained and alpha domain and predicted intron, which suggests that this gene arose from MAT1-1-1 during a recombination event. In contrast to the Ceratocystidaceae species, Knoxdaviesia conformed to the ancestral Sordariomycete arrangement of flanking genes and is, therefore, a closer reflection of the structure of this locus in the Microascalean ancestor.
South African Journal of Botany
Rodents are important pollinators and seed predators of fynbos Proteaceae, but their role as florivores has received little attention. Chacma baboons (Papio hamadryas ursinus) are known to feed on Proteaceae inflorescences, however, their effect on plant reproduction has not been quantified. We recorded the extent of damage by rodents and baboons to inflorescences of the dominant shrub, Protea neriifolia, in 20 × 20 m plots in the Jonkershoek Nature Reserve near Stellenbosch. Damage was distributed patchily across the landscape. Rodents damaged up to 23% of the inflorescences per plot by feeding on styles and nectar. We observed the striped mouse (Rhabdomys pumilio) climbing up plants to feed on inflorescences. Up to 14% of inflorescences in some plots were destroyed by rodents gnawing through inflorescence stems. Baboons damaged or destroyed 12% to 29% of inflorescences at three study sites, but did not forage at all in the three remaining study sites. Among plant individuals affected by baboons or rodents, a mean proportion of 0.49 ± 0.31 (SD) of individuals' inflorescences were damaged or destroyed. Florivory by rodents and baboons can thus reduce the fecundity of P. neriifolia significantly. Protea inflorescences may be an important seasonal food source for certain rodents. In an evolutionary context, rodent florivory may have been an important selective force that caused certain Proteaceae species to shift to rodent pollination. Further work is needed to determine which rodent species feed on Protea inflorescences and whether rodent florivory is widespread in fynbos.
9 November 2016