Protea Species Research Articles

Anchored phylogenomics improves the resolution of evolutionary relationships in the rapid radiation of Protea L.

Estimating phylogenetic relationships in relatively recent evolutionary radiations is challenging, especially if short branches associated with recent divergence result in multiple gene tree histories. We combine anchored enrichment next-generation sequencing with species tree analyses to produce a robust estimate of phylogenetic relationships in the genus Protea (Proteaceae), an iconic radiation in South Africa. We sampled multiple individuals within 59 out of 112 species of Protea and 6 outgroup species for a total of 163 individuals, and obtained sequences for 498 low-copy, orthologous nuclear loci using anchored phylogenomics. We compare several approaches for building species trees, and explore gene tree-species tree discrepancies to determine whether poor phylogenetic resolution reflects a lack of informative sites, incomplete lineage sorting, or hybridization. Phylogenetic estimates from species tree approaches are similar to one another and recover previously well-supported clades within Protea, in addition to providing well-supported phylogenetic hypotheses for previously poorly resolved intrageneric relationships. Individual gene trees are markedly different from one another and from species trees. Nonetheless, analyses indicate that differences among gene trees occur primarily concerning clades supported by short branches. Species tree methods using hundreds of nuclear loci provided strong support for many previously unresolved relationships in the radiation of the genus Protea. In cases where support for particular relationships remains low, these appear to arise from few informative sites and lack of information rather than strongly supported disagreement among gene trees.

Knoxdaviesia capensis : dispersal ecology and population genetics of a flower-associated fungus

Abstract Protea-associated fungi are dispersed between flower heads by mites, beetles and possibly birds. For the ophiostomatoid fungus, Knoxdaviesia proteae, these vectors offer regular dispersal between distant floral hosts. Unlike K. proteae, Knoxdaviesia capensis occupies multiple Protea host species. In this study, we aimed to determine whether the generalist K. capensis shares the long-distance dispersal pattern with specialist K. proteae and whether it moves freely between different host species. We evaluated the genetic structure of K. capensis from five populations of a wide-spread host and between sympatric hosts. Twelve K. capensis-specific microsatellite markers were developed and applied to 90 individuals. K. capensis showed high genetic diversity and almost maximal genotypic diversity. All populations were poorly differentiated, indicating the presence of long-distance dispersal. No differentiation could be detected between sympatric host populations, suggesting free dispersal between different hosts. This implies that the beetle and bird vectors that pollinate Protea species show the same non-specific movement.

A bird pollinator shows positive frequency dependence and constancy of species choice in natural plant communities.

Animal pollinators mediate reproduction of many plant species. Foraging theory suggests that animal pollinators exhibit preferences for common plant species in natural communities (positive frequency-dependent foraging) and temporary single-species specialization (flower constancy) during foraging bouts. Positive frequency dependence may favor common plant species; flower constancy may enhance conspecific pollen transfer particularly in rare plant species. Previous experimental studies suggest that avian pollinators are unlikely to exhibit these behaviors. We studied foraging behavior of Cape Sugarbirds (Promerops cafer), the main avian pollinator of many Protea species, using focal-plant and focal-bird sampling, assisted by high-resolution maps of the spatiotemporal distribution of Protea individuals and their flowering status. We found that Sugarbird's visitation preference increased with species' relative floral abundance, and that individual Sugarbirds tended to visit single species in sequence. Flower constancy during foraging bouts was significantly higher than expected from random plant-animal encounters at the scale of pollinator movements. Positive frequency dependence may favor the reproduction of abundant plant species while flower constancy may be particularly important for rare plant species. This first simultaneous study of both behaviors in a natural plant-pollinator system shows that bird pollinators exhibit both types of behavior and, in this way, possibly influence plant community structure.

Coexistence of plant species in a biodiversity hotspot is stabilized by competition but not by seed predation

Understanding the mechanisms of species coexistence is a key task for ecology. Recent theory predicts that both competition and predation (which causes apparent competition among prey) can either promote or limit species coexistence. Both mechanisms cause negative interactions between individuals, and each mechanism promotes stable coexistence if it causes negative interactions to be stronger between conspecifics than between heterospecifics. However, the relative importance of competition and predation for coexistence in natural communities is poorly known. Here, we study how competition and apparent competition via pre‐dispersal seed predators affect the long‐term fecundity of Protea shrubs in the fire‐prone Fynbos biome (South Africa). These shrubs store all viable seeds produced since the last fire in fire‐proof cones. Competitive effects on cone number and pre‐dispersal seed predation reduce their fecundity and can thus limit recruitment after the next fire. In 27 communities comprising 49 990 shrubs of 22 Protea species, we measured cone number and per‐cone seed predation rate of 2154 and 1755 focal individuals, respectively. Neighbourhood analyses related these measures to individual‐based community maps. We found that conspecific neighbours had stronger competitive effects on cone number than heterospecific neighbours. In contrast, apparent competition via seed predators was comparable between conspecifics and heterospecifics. This indicates that competition stabilizes coexistence of Protea species, whereas pre‐dispersal seed predation does not. Larger neighbours had stronger competitive effects and neighbours with large seed crops exerted stronger apparent competition. For 97% of the focal plants, competition reduced fecundity more than apparent competition. Our results show that even in communities of closely related and ecologically similar species, intraspecific competition can be stronger than interspecific competition. On the other hand, apparent competition through seed predators need not have such a stabilizing effect. These findings illustrate the potential of ‘community demography’, the demographic study of multiple interacting species, for understanding plant coexistence.

In vitro mutagenicity and antimutagenicity of dichloromethane leaf extracts of seven Protea species using Ames test

In vitro mutagenicity and antimutagenicity of dichloromethane leaf extracts of seven Protea species using Ames test

New evidence for mammal pollination of Protea species (Proteaceae) based on remote-camera analysis

Flower visitation by small mammals is difficult to observe directly on account of their sensitivity to human presence and the nocturnal activity of some species. Their role in pollination has, thus, been inferred mostly from analysis of fur and faecal pollen loads of field-trapped animals. The development of motion-activated remote cameras allows for unprecedented insights into natural behaviours of small mammals on flowers. We used remote cameras to assess the identity of flower visitors, and the frequency and timing of their visitation to flower heads of four poorly studied Protea species (P. cordata, P. decurrens P. scabra and P. subulifolia) that were predicted to be rodent-pollinated on the basis of floral traits. Camera footage revealed that small mammals (typically three to six rodent species per Protea species) were frequent visitors to flower heads over one flowering season, making up 100% of visits to P. cordata and P. subulifolia, 98% of visits to P. decurrens, and 90% of visits to P. scabra. Rodents that are known pollinators of other ground Protea species, such as Acomys subspinosus, Micaelamys namaquensis and Rhabdomys pumulio, were observed to make contact with reproductive parts of the flowers, but further work would be required to demonstrate unequivocally that they are the main pollen vectors of these species. Mus minutoides was recorded for the first time to frequently visit inflorescences of P. subulifolia. Other visitors included genets that visited P. scabra inflorescences to lick nectar off florets, and birds that were relatively infrequent visitors to all species. Together with recent literature, the present study has shown that the utilisation of remote cameras in pollination studies provides an efficient, discreet method for observing vertebrate flower-visiting behaviour.

Knoxdaviesia proteae is not the only Knoxdaviesia-symbiont of Protea repens.

Two polyphyletic genera of ophiostomatoid fungi are symbionts of Proteaceae in southern Africa. One of these, Knoxdaviesia, includes two closely related species, K. proteae and K. capensis, that have overlapping geographical distributions, but are not known to share Protea host species. Knoxdaviesia capensis appears to be a generalist that occupies numerous hosts, but has never been found in P. repens, the only known host of K. proteae. In this study, extensive collections were made from P. repens and isolates were identified using DNA sequence comparisons. This led to the surprising discovery of K. capensis from P. repens for the first time. The fungus was encountered at a low frequency, suggesting that P. repens is not its preferred host, which may explain why it has not previously been found on this plant. The basis for the specialisation of K. proteae and K. capensis on different Protea species remains unknown.

Responses of nectar‐feeding birds to floral resources at multiple spatial scales

The responses of animal pollinators to the spatially heterogeneous distribution of floral resources are important for plant reproduction, especially in species‐rich plant communities. We explore how responses of pollinators to floral resources varied across multiple spatial scales and studied the responses of two nectarivorous bird species (Cape sugarbird Promerops cafer, orange‐breasted sunbird Anthobaphes violacea) to resource distributions provided by communities of co‐flowering Protea species (Proteaceae) in South African fynbos. We used highly resolved maps of about 125 000 Protea plants at 27 sites and estimated the seasonal dynamics of standing crop of nectar sugar for each plant to describe the spatiotemporal distribution of floral resources. We recorded avian population sizes and the rates of bird visits to > 1300 focal plants to assess the responses of nectarivorous birds to floral resources at different spatial scales. The population sizes of the two bird species responded positively to the amount of sugar resources at the site scale. Within sites, the effects of floral resources on pollinator visits to plants varied across scales and depended on the resources provided by individual plants. At large scales (radii > 25 m around focal plants), high sugar density decreased per‐plant visitation rates, i.e. plants competed for animal pollinators. At small scales (radii < 5 m around focal plants), we observed either competition or facilitation for pollinators between plants, depending on the sugar amount offered by individual focal plants. In plants with copious sugar, per‐plant visitation rates increased with increasing local sugar density, but visitation rates decreased in plants with little sugar. Our study underlines the importance of scale‐dependent responses of pollinators to floral resources and reveals that pollinators’ responses depend on the interplay between individual floral resources and local resource neighbourhood.

Using spatial gradient analysis to clarify species distributions with application to South African protea

Typical ecological gradient analyses consider variation in the response of plants along a gradient of covariate values, but generally constrain themselves to predetermined response curves and ignore spatial autocorrelation. In this paper, we develop a formal spatial gradient analysis. We adopt the mathematical definition of gradients as directional rates of change with regard to a spatial surface. We view both the response and the covariate as spatial surfaces over a region of interest with respective gradient behavior. The gradient analysis we propose enables local comparison of these gradients. At any spatial location, we compare the behavior of the response surface with the behavior of the covariate surface to provide a novel form of sensitivity analysis. More precisely, we first fit a joint hierarchical Bayesian spatial model for a response variable and an environmental covariate. Then, after model fitting, at a given location, for each variable, we can obtain the posterior distribution of the derivative in any direction. We use these distributions to compute spatial sensitivities and angular discrepancies enabling a more detailed picture of the spatial nature of the response–covariate relationship. This methodology is illustrated using species presence probability as a response to elevation for two species of South African protea. We also offer a comparison with sensitivity analysis using geographically weighted regression. We show that the spatial gradient analysis allows for more extensive inference and provides a much richer description of the spatially varying relationships.

Carnivorous mammals feed on nectar ofProteaspecies (Proteaceae) in South Africa and likely contribute to their pollination

Video S1 Footage from motion-triggered cameras of Carnivora visiting four Protea species (format and codec: mpeg4 + aac). Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Physiological and phenological responses of Protea ‘Pink Ice’ to elevated temperatures

Rising temperatures associated with global climate change may alter the physiology and phenology of Protea species and cultivars. Protea species are assumed to be well adapted to warm summers characteristic of their natural Mediterranean-type habitat, but their plasticity in responding to higher growth temperatures is not known. Using infrared lamps, a greenhouse-based temperature gradient was constructed, with temperatures ranging from ambient to ambient+3.1°C. Potted plants of Protea ‘Pink Ice’ (P. compacta R. Br×P. susannae Phill.) were grown at five positions along this gradient for 12 months under irrigation. Simultaneously, a field verification experiment in a nearby commercial ‘Pink Ice’ orchard was conducted under ambient temperature and ambient+2.9°C. Increased sclerophylly (leaf dry weight per unit area) with increasing temperature indicated leaf structural changes. While leaf area based gas exchange (net CO2 assimilation rate, stomatal conductance and dark respiration rate) did not differ across the temperature gradient, leaf weight based CO2 assimilation rate and dark respiration rate decreased significantly towards the upper end of the temperature range. The optimum temperature for net CO2 assimilation rate (Topt) showed seasonal adjustments, but increased in response to experimental warming only in the field experiment. Significant temperature elevation resulted in an earlier onset of spring bud break, but warming extended inflorescence initiation from the spring flush to the summer flush, leading to delayed flowering. Aboveground biomass allocation shifted from inflorescences to leaves and to a lesser degree to stems, with elevated temperatures, whereas root growth was stimulated in the middle of the warming range. The results of this study suggest that elevated temperature may prolong the vegetative growth period in some Protea cultivars where water is not limiting, at the expense of flower production. This could have significant economic and marketing consequences for commercial cut flower production systems. The findings are also of significance to ecologists studying the responses of Proteaceae to climate change.

Reward quality predicts effects of bird-pollinators on the reproduction of African Protea shrubs

Pollination syndromes predict the principal animal pollinators of plant species from floral traits. However, the existence of discrete pollination syndromes and the relevance of these syndromes for the effects of animal pollinators on plant reproduction are controversial and a quantitative, trait-based approach may refine the concept of pollination syndromes. Thus far, however, very few studies have simultaneously analysed the importance of signalling, accessibility and reward traits of flowers for the effects of animal pollinators on plant reproduction of multiple species. The genus Protea is an ideal study system because the members of this genus exhibit remarkable variation in functional traits and Protea species are visited by several guilds of animal pollinators, such as birds and insects. We experimentally investigated seven Protea species from the South African fynbos to assess variability in reproduction (seed set, seed mass, germination) in response to pollinator exclusion (full-exclusion, bird-exclusion) and hand-pollination (self-pollen, cross-pollen). To generalise the findings of the experiment, we conducted a meta-analysis of the effects of bird-exclusion on seed set of 14 Protea species, associating effect sizes of bird-pollination with signalling (inflorescence length and diameter), accessibility (inflorescence and style length) and reward traits (length of pollen presenter, nectar volume and sugar concentration). All Protea species were self-compatible, but only two species were to a small degree capable of autonomous selfing. Protea species varied in their dependence on animal pollinators, including species depending exclusively on birds, insects, or both for seed production. Protea species exhibited continuous variation in the effects of bird-pollinators on reproduction, challenging the accuracy of categorical pollination syndromes for predicting pollinator effects on plant reproduction. The meta-analysis showed that the quality of floral rewards, especially nectar sugar concentration, predicts the dependence of Protea reproduction on bird pollinators, whereas the signalling and accessibility traits tested in this study were not important. Beyond revealing new insights into the pollination biology of Protea species, our findings underscore the usefulness of experimental approaches on multiple plant species to test the effects of pollinator guilds on plant reproduction and contribute to a trait-based understanding of the functional determinants of plant–pollinator interactions.

Arthropod Assemblages Associated with Wild and Cultivated Indigenous Proteas in the Grabouw area, Cape Floristic Region

Control of arthropod pests on indigenous flower crops often has particular challenges. Here we investigate the arthropod species associated with indigenous cultivated Protea species and cultivars in the Cape Floristic Region (CFR), South Africa. Arthropod individuals were collected from various commercial varieties of protea as well as from wild protea plants. Arthropod individuals were recorded directly on plants in the field (for disturbance-sensitive species), as well as from specific plant parts carefully enclosed in plastic bags and taken to the laboratory. Of the arthropod morphospecies recorded, 95.9 % were insects, and the rest mostly mites. A total of 37 % of the individuals could be identified to species level, along with 33 new species records of arthropods on protea plants. Taxonomically, Coleoptera, Lepidoptera, Hymenoptera and Diptera were the most abundant and speciose groups. Structurally complex plants and mixed stands of plant species harboured the most arthropod species. Morphospecies were sorted into guilds, as determined by previous studies. In general, guild structure reflected the complexity of structure of individual plants as well as the mixture of plant species and cultivars, with apparently strong natural enemy activity on complex plants and mixed groups. The free-living, flower visitor guild was the most abundant, with largely beetles contributing to this guild. Endophages were about equal in abundance across all cultivars but less on those with simple structures. From rank abundance curves, a total of 30 % of the arthropod species were categorized as abundant, with the rest (70 %) being rare. Most species were generalists on the various proteas, with some being species or cultivar specialists. A total of 7.26 % species recorded were major pests affecting commercial production of proteas in the CFR. This protea agroecosystem, being composed of plant types being grown in their general native area, resulted in about 93%of the arthropod species being restricted to the Proteaceae, with only 5.6%associated with other South African crops. Even though some of this arthropod assemblage is adverse for protea farming in theCFR, these commercial fields are nevertheless playing a role in biodiversity conservation in the fynbos. The wild proteas supported only intermediate arthropod abundance, suggesting strong, and probably complex, natural regulatory processes at work.

Long-distance dispersal and recolonization of a fire-destroyed niche by a mite-associated fungus

The Fynbos Biome in the Core Cape Subregion of South Africa is prone to recurrent fires that can clear vast areas of vegetation. Between periods of fire, ophiostomatoid fungi colonize the fruiting structures of serotinous Protea species through arthropod-mediated dispersal. Using microsatellite markers, this study considered the process whereby a Protea-associated ophiostomatoid fungus, Knoxdaviesia proteae, recolonizes a burnt area. The genetic diversity, composition and structure of fungal populations from young P. repens plants in a recently burnt area were compared to populations from the adjacent, unburnt Protea population. The only difference between K. proteae populations from the two areas was found in the number of private alleles, which was significantly higher in the unburnt population. The population structure, although weak, indicated that most K. proteae individuals from recently burnt areas originated from the unburnt population. However, individuals from unsampled source populations were also detected. This, together with the lack of isolation-by-distance across the landscape, suggested that long-distance dispersal is important for K. proteae to recolonize burnt areas. Similarly, the high level of gene flow and low differentiation observed between two distantly separated K. proteae populations also supported the existence of long-distance dispersal. The genetic cohesiveness of populations over long distances and the genetic diversity within populations could be attributed to frequent multiple fungal migration events mediated primarily by arthropods but, potentially, also by birds.

Fire-mediated disruptive selection can explain the reseeder-resprouter dichotomy in Mediterranean-type vegetation.

Crown fire is a key selective pressure in Mediterranean-type plant communities. Adaptive responses to fire regimes involve trade-offs between investment for persistence (fire survival and resprouting) and reproduction (fire mortality, fast growth to reproductive maturity, and reseeding) as investments that enhance adult survival lower growth and reproductive rates. Southern hemisphere Mediterranean-type ecosystems are dominated by species with either endogenous regeneration from adult resprouting or fire-triggered seedling recruitment. Specifically, on nutrient-poor soils, these are either resprouting or reseeding life histories, with few intermediate forms, despite the fact that the transition between strategies is evolutionarily labile. How did this strong dichotomy evolve? We address this question by developing a stochastic demographic model to assess determinants of relative fitness of reseeders, resprouters and hypothetical intermediate forms. The model was parameterised using published demographic data from South African protea species and run over various relevant fire regime parameters facets. At intermediate fire return intervals, trade-offs between investment in growth versus fire resilience can cause fitness to peak at either of the extremes of the reseeder-resprouter continuum, especially when assuming realistic non-linear shapes for these trade-offs. Under these circumstances, the fitness landscape exhibits a saddle which could lead to disruptive selection. The fitness gradient between the peaks was shallow, which may explain why this life-history trait is phylogenetically labile. Resprouters had maximum fitness at shorter fire-return intervals than reseeders. The model suggests that a strong dichotomy in fire survival strategy depends on a non-linear trade-off between growth and fire persistence traits.

Drought Response Diversification in African Protea Species

Premise of research. Evolutionary radiations can be driven by physiological tolerances. Protea is a species-rich genus in the Cape Floristic Region of South Africa and provides the opportunity to examine whether drought response traits may have contributed to differentiation in this stress-tolerant genus. Commonly utilized drought responses might be indicative of traits important to species diversification in stressful environments. Methodology. We studied how greenhouse-grown plants of six white Protea species physiologically responded to drought stress. We measured leaf-level physiological traits such as stomatal conductance, temperature, pubescence, chlorophyll, and abscisic acid (ABA) content. Pivotal results. Most traits showed similar drought responses across all six species and 29 populations we examined. Only for foliar ABA content, leaf hair density, and foliar chlorophyll content did species respond to drought in different ways, indicating that some differences in plasticity might be important to this evolutionary radiation. Conclusions. Our data support stomatal conductance as a trait important to stress tolerance across a range of environmental conditions. Moreover, population variation in the plasticity of physiological traits might be important to evolutionary trajectories in this system.

<em>British Engineers and Africa, 1875–1914</em>, by Casper Andersen

Reviewed by: British Engineers and Africa, 1875–1914 by Casper Andersen Jessica Ratcliff (bio) British Engineers and Africa, 1875–1914, by Casper Andersen; pp. xi + 229. London and Brookfield, VT: Pickering & Chatto, 2011. £60.00, $99.00. In 1910, at the prestigious address of 1 Great George Street, Westminster, the Institute of Civil Engineers (ICE) built a luxurious new headquarters and fitted it out with great columns, extravagant chandeliers, broad mahogany staircases, and stately halls and meeting rooms. The façade was ornamented with floral symbols of Britain and the Empire: “the Tudor rose, thistle and daffodil representing Britain (including Ireland); the maple leaf for Canada; for New Zealand the silver fern; a protea species for South Africa; the golden wattle for Australia; a palm leaf for all the Crown Colonies; and lotus flowers to represent India” (46). Material for the building included timber and other products from various parts of the Empire, symbolizing, as was explained in the pages of the trade journal African Engineering, “the close relationship of those who constitute the Institution of Civil Engineers in all parts of the world” (qtd. in Andersen 46). The international and colonial contingent of ICE membership had indeed grown steadily since its founding in 1871, and by 1912 twenty-two percent of the ICE members resided in the colonies, 376 of them (five percent) in Africa. Through active correspondence and publishing, and the organization of international conferences and committees, the ICE did manage to sustain and grow a professional network throughout the Empire, even while other factors—the grand new headquarters, for one—ensured that the [End Page 293] center of power for the profession remained firmly in London. At the helm of the profession was the so-called Great George Street Clique: the consulting engineers to whom Government would turn when seeking expertise for, say, a rail line into Rhodesia, or a dam across the Nile. To this professional elite in London, Africa represented many things: a rhetorical space to display engineering-as-civilization, a testing ground for young recruits, a stage for the self-styled explorer engineer, and most of all a vast new market for lucrative contracts. Casper Andersen covers these themes and much more in this important study of the ways in which the civil engineering profession in London shaped and was shaped by Britain’s colonial entanglement with Africa. The book’s title, British Engineers and Africa, suggests a broad scope, and some readers might be disappointed to find that in fact Andersen has limited himself, firstly, to the engineering community in London—the subject is not engineers in Africa but engineers and Africa—and secondly to a subset of that category, the domain of the civil engineer. Most of the book relates through different channels back to the ICE, which emerges as the center of gravity of this study. As Andersen ably demonstrates, this aspect of engineering history is worthy of such close study. Andersen’s choice of subject is especially valuable in that it brings into focus the interpersonal and fine-fibered, but still very consequential, relationships between private engineering firms and various imperial offices of government. Given that much of the historiography of technology and imperialism has focused on the military’s engineering branches such as the Royal Engineers, the Royal Artillery, and the Ordnance Survey, Andersen’s story of the civil engineering firms and empire is particularly welcome. Throughout the book, Andersen employs a wide range of analytical approaches, drawing on the work of, among others, Christine MacLeod, Ben Marsden and Crosbie Smith, Felix Driver, John Darwin, Simon J. Potter, and Andrew S. Thompson. It is Thompson whom Andersen follows most closely, by “exploring the ways in which empire ‘struck back’ at the engineering profession, while knowing that it was more likely to do so in complex, unequal ways” (3). Andersen’s methodological approach is almost prosopographical; considerable effort has gone into analyzing the civil engineering community around Great George Street as well as the membership of the ICE, producing several impressive tables breaking down various features of these groups. In terms of sources, the work draws heavily from popular trade journals such as Engineer, Feilden’s Magazine, African Engineering, and...

Adaptive responses to directional trait selection in the Miocene enabled Cape proteas to colonize the savanna grasslands

Directional selection occurs when the agent of selection changes direction or strength such that fitness of a dominant trait is relaxed or even annulled, and simultaneously the fitness of a rare opposing trait is intensified or even becomes essential. The value of this concept in evolutionary ecology was demonstrated by mapping fire- and growth-related traits and regional affinity onto a molecular-based chronogram for 91 species of Protea that is widespread in the shrubland and grassland biomes of southern Africa. The crown clade arose 22–34 million years ago (Oligocene) in the Cape shrublands that was increasingly winter wet, nutrient and water-limited, and moderately fireprone. This environment favoured nonsprouting and resprouting shrubs, on-plant seed storage (serotiny) and strong sclerophylly. Adjoining grasslands developed 7–19 million years ago (mid-late Miocene) that were summer wet, carbon-limited and highly fireprone. This favoured resprouting only, seed release at maturity, and taller plants with large leaves and weak sclerophylly. Thus, for successful migration from the shrublands to grasslands, the dominant ancestral condition of serotiny was replaced by almost universal nonserotiny in response to a change in fire type, and the dominant ancestral condition of nonsprouting by universal (lignotuberous) resprouting in response to more frequent fire. Taller plants with epicormic resprouting and larger, softer leaves were also promoted, due to the change in fire type, growing season and declining pCO2, but appeared 4–6 million years later. Thus, adaptive radiation via directional selection in the novel grassland environment required a suite of adaptive responses to various selection pressures that led to species radiation in the vast habitat available now constrained by stabilizing selection. The biology of grasses in savanna grasslands may well have changed during the Miocene/Pliocene but so did the woody plants that invaded them.

Effects of Volatile Compounds Emitted by Protea Species (Proteaceae) on Antennal Electrophysiological Responses and Attraction of Cetoniine Beetles

Evolutionary shifts in pollination systems within a plant genus are commonly associated with changes in floral scent, reflecting selection mediated through the sensory systems of various pollinators. The most common cetoniine beetle pollinator of grassland Protea species in South Africa, Atrichelaphinis tigrina, previously has been shown to have a strong preference for the fruity floral scent of these plants over the weak scent of their bird-pollinated congeners. However, it is not known which of the many compounds found in the scent of beetle pollinated Protea species play a role for pollinator attraction. Electroantennograms (EAG) from A. tigrina beetles were recorded in response to 15 compounds emitted by Protea flower heads. EAG responses to all 15 compounds were significantly greater than those to the paraffin solvent in which they were diluted. The greatest responses were observed for aromatics (anisole, methyl benzoate, methyl salicylate, benzaldehyde) followed by the monoterpene β-linalool, which can comprise up to 66 % of fruity Protea scents. Five compounds that elicited EAG responses (benzaldehyde, β-linalool, (E/Z)-linalool oxide (furanoid), methyl benzoate, and methyl salicylate) were tested in commercially available yellow bucket traps in the field to test their attractiveness to beetles. Traps baited with methyl benzoate, β-linalool, (E/Z)-linalool oxide (furanoid), and methyl salicylate caught significantly more insects than did those containing paraffin only. Methyl benzoate also was more specifically attractive to A. tigrina than was (E/Z)-linalool oxide (furanoid) and paraffin baited controls. A second field experiment using a combination of linalool vs. paraffin baited yellow or green traps showed that trap color had a significant effect on the number of trapped beetles. Yellow traps yielded a ten-fold higher number of insect catches than did green traps. However, the combination of yellow color and the scent compound linalool yielded the highest number of catches. This study has shown that the cetoniine beetle A. tigrina can detect a variety of floral compounds and is attracted to compounds comprising a large proportion of the blend that makes up fruity Protea scents, adding support for the hypothesis that change in scent chemistry during the shift from bird to cetoniine beetle pollination in this genus were mediated by beetle sensory preferences.

Direct and indirect selection on floral pigmentation by pollinators and seed predators in a color polymorphic South African shrub

The coexistence of different color morphs is often attributed to variable selection pressures across space, time, morph frequencies, or selection agents, but the routes by which each morph is favored are rarely identified. In this study we investigated factors that influence floral color polymorphisms on a local scale in Protea, within which approximately 40% of species are polymorphic. Previous work shows that seed predators and reproductive differences likely contribute to maintaining polymorphism in four Protea species. We explored whether selection acts directly or indirectly on floral color in two populations of Protea aurea, using path analysis of pollinator behavior, nectar production, seed predation, color, morphology, and maternal fecundity fitness components. We found that avian pollinators spent more time on white morphs, likely due to nectar differences, but that this had no apparent consequences for fecundity. Instead, the number of flowers per inflorescence underpinned many of the reproductively important differences between color morphs. White morphs had more flowers per inflorescence, which itself was positively correlated with nectar production, seed predator occurrence, and total long-term seed production. The number of seeds per plant to survive predation, in contrast, was not directly associated with color or any other floral trait. Thus, although color differences may be associated with conflicting selection pressures, the selection appears to be associated with the number of flowers per inflorescence and its unmeasured correlates, rather than with inflorescence color itself.