Pollinator‐prey conflict in carnivorous plants

Most carnivorous plants utilize insects in two ways: the flowers attract insects as pollen vectors for sexual reproduction, and the leaves trap insects for nutrients. Feeding on insects has been explained as an adaptation to nutrient‐poor soil, and carnivorous plants have been shown to benefit from insect capture through increased growth, earlier flowering and increased seed production. Most carnivorous plant species seem to benefit from insect pollination, although many species autonomously self‐pollinate and some propagate vegetatively. However, assuming that outcross pollen is advantageous and is a more important determinant of reproductive success than the nutrients gained from prey, there should be a selective pressure on carnivorous plants not to feed on their potential pollen vectors. Therefore, it has been suggested that carnivorous plants are subject to a conflict, often called the pollinator‐prey conflict (PPC). The conflict results from a trade‐off of the benefits from feeding on potentially pollinating insects versus the need to use them as pollen vectors for sexual reproduction. In this review we analyze the conditions under which a PPC may occur, review the evidence for the existence of PPCs in carnivorous plants, and explore the mechanisms that may be in place to prevent or alleviate a PPC. With respect to the latter, we discuss how plant signals such as olfactory and visual cues may play a role in separating the functions of pollinator attraction and prey capture.     

Trade-offs between sexual and asexual reproduction in a monoecious species Sagittaria pygmaea (Alismataceae): the effect of different nutrient levels

Available resources could influence the trade-offs among different reproductive components in plants. Here, we created three nutrient levels to test the nutrient effects on trade-offs among sexual reproduction, clonal propagation and vegetative growth in a monoecious clonal herb Sagittaria pygmaea. The results of this study showed that the plant exhibited different trade-off patterns among different nutrient levels. When the nutrient level was low, there were weak trade-offs between sexual reproduction and vegetative growth and between clonal propagation and vegetative growth; when the nutrient level was moderate, we found a strong trade-off between sexual reproduction and clonal propagation; but when the nutrient level was high, we found no trade-offs among these three different reproductive components. These results indicated that the plant could adjust its trade-off patterns to fit the nutrient variation and suggested that trade-offs are unlikely to constrain the evolution of reproductive strategy in this species.     

Variation in resource abundance affects diet and feeding morphology in the pumpkinseed sunfish (Lepomis gibbosus)

Summary Growth responses and accumulation of N and P were studied in two pygmy south-west Australian species of Drosera following supplementary feeding of arthropods (collembolans, Hypogastrura vernalis and fruit flies, Drosophila melanogaster) and/or a balanced mineral nutrient supplement (N as nitrate) via the roots. One feeding experiment used glasshouse-raised germlings from vegetative propagules (gemmae) of the perennial Drosera closterostigma, the other three (two on D. closterostigma and one on the annual D. glanduligera) involved natural populations engaging in natural captures of indigenous prey. All experiments recorded highly significant increases in plant dry matter, N and P (all plant age groups) and in reproductive performance (adult plants only) from artificial feeding of arthropods, but no apparent benefits from minerals alone or additive effects of minerals above that due to insects. Unresponsiveness to mineral nutrients was suggested to relate to inability of the species to use nitrate, while up to three-fold growth and nutrient uptake response to insects indicated that growth of natural populations might be severely limited by inadequate catches of prey. It is concluded that the highly nutrient-poor conditions typical of the habitat of pygmy species of Drosera may have promoted marked specialization towards carnivory and an attendant decline in ability to utilize soil-derived sources of nutrients.     

The feeding ecology of a carnivorous plant (Pinguicula nevadense): prey analysis and capture constraints

Summary The taxonomic composition and size of arthropods captured by Pinguicula nevadense, an endemic carnivorous plant of the high-mountain zone of the Sierra Nevada (southern Spain), are analysed. The actual prey of P. nevadense and the available arthropods trapped by mimic-traps are compared, in order to identify the capture constraints of the plant. The results show that P. nevadense captures various arthropod taxa. Winged insects, especially Nematocera, make up the main component of the diet. The range of prey sizes in all P. nevadense populations studied is similar. The taxonomic composition of arthropods trapped by the mimic-traps is similar to that of the actual prey of P. nevadense. However, the plant captures prey only below a specific size threshold. These size constraints appear to be the principal factor determining the actual prey of this carnivorous plant.     

Production dependence of vegetative propagation inDisporum smilacinum A. Gray

The dependence of vegetative propagation on the production of individual plants was examined inDisporum smilacinum A. Gray on the basis of shading experiments and field surveys. This species typically showed four types of reproductive behavior: sterile plants producing one plantlet (no propagation), sterile plants producing more than two plantlets (vegetative propagation), fertile plants producing one plantlet (sexual reproduction) and fertile plants producing more than two plantlets (both sexual reproduction and vegetative propagation). The propagation ofD. smilacinum was clearly related to the annual net production of each individual plant. The probability of a mother plant producing more than two vegetative propagules (plantlets) increased with net production of the plant in the current year. The number of propagules per plant and runner length increased with net production. It was possible to explain the types of reproductive behavior of this species on the basis of both the initial plant size before sprouting and its net production during the growing season. There was a critical initial plant size for sexual reproduction and a critical level of production for vegetative propagation.     

Mineral allocation to reproduction in Sorhum bicolor and Sorghum halepense in relation to parental nutrient supply

Summary This experiment investigated the effect of parental nutrient shortage on the allocation of five nutrients to seeds and rhizomes in Sorghum halepense, a perennial, noxious weed, and to seeds in Sorghum bicolor, an annual, cultivated species. Plants from both species were grown from seeds and supplied with fertilizer at three concentrations. The allocation of biomass and nutrients (N, P, K, Ca and Mg) to reproductive and vegetative parts was determined. Relative biomass allocation to reproduction (either sexual or vegetative) remained constant in S. halepense in spite of large differences in total plant weight. In S. bicolor, however, biomass allocation to sexual reproductive structures decreased significantly with decreasing nutrient supply. Individual seed weight was not modified by parental nutrient supply in S. halepense, but it increased with decreasing nutrient availability in S. bicolor. Important differences in mineral allocation to seeds were found between the two species. While S. bicolor seeds were largely buffered from the differences in parental nutrient status, concentration of nutrients in S. halepense seeds decreased significantly with decreasing supply for all the nutrients analyzed except Ca. However, mineral nutrient concentration in S. halepense rhizomes remained remarkably constant despite differences in the external supply, evincing the priority given to vegetative reproduction at the expense of sexual reproduction. Overall, the pattern of nutrient allocation in S. bicolor seeds under different nutrient supply resembled the pattern observed in S. halepense rhizomes, but it had little resemblance to the pattern of nutrient allocation in S. halepense seeds. The results are discussed in terms of differences and similarities in the reproductive strategy of these two species.     

A new plant-animal mutualism involving a plant with sticky leaves and a resident hemipteran insect

We report on a new plant-animal mutualism in which the plant Roridula gorgonias, first suspected by Darwin (1875) to be carnivorous, is, at least in part, indirectly carnivorous. This plant has sticky leaves which trap many insects but it has no digestive enzymes. Instead, trapped invertebrates are rapidly consumed by a hemipteran Pameridea roridulae, only found on this plant. However, evidence from ¹⁵N experiments suggests that R. gorgonias does derive significant amounts of nitrogen from trapped prey, apparently via exudations of P. roridulae.     

Recent ecophysiological,biochemical and evolutional insights into plant carnivory

BackgroundCarnivorous plants are an ecological group of approx. 810 vascular species which capture and digest animal prey, absorb prey-derived nutrients and utilize them to enhance their growth and development. Extant carnivorous plants have evolved in at least ten independent lineages, and their adaptive traits represent an example of structural and functional convergence. Plant carnivory is a result of complex adaptations to mostly nutrient-poor, wet and sunny habitats when the benefits of carnivory exceed the costs. With a boost in interest and extensive research in recent years, many aspects of these adaptations have been clarified (at least partly), but many remain unknown.ScopeWe provide some of the most recent insights into substantial ecophysiological, biochemical and evolutional particulars of plant carnivory from the functional viewpoint. We focus on those processes and traits in carnivorous plants associated with their ecological characterization, mineral nutrition, cost–benefit relationships, functioning of digestive enzymes and regulation of the hunting cycle in traps. We elucidate mechanisms by which uptake of prey-derived nutrients leads to stimulation of photosynthesis and root nutrient uptake.ConclusionsUtilization of prey-derived mineral (mainly N and P) and organic nutrients is highly beneficial for plants and increases the photosynthetic rate in leaves as a prerequisite for faster plant growth. Whole-genome and tandem gene duplications brought gene material for diversification into carnivorous functions and enabled recruitment of defence-related genes. Possible mechanisms for the evolution of digestive enzymes are summarized, and a comprehensive picture on the biochemistry and regulation of prey decomposition and prey-derived nutrient uptake is provided.     

Mineral nutrition of carnivorous plants: A review

Plant carnivory is one of many possible adaptation strategies to unfavorable conditions, mostly low nutrient availability in wet, acid soils. The following issues concerning the mineral nutrition of carnivorous plants are reviewed: the relative importance of carnivory and root nutrition for growth; which nutrients (elements) from prey are of principal importance for growth; the relationship between mineral and organic nutrition based on carnivory; the interactions between carnivory and root mineral nutrition; and the importance of carnivory under natural conditions. Special attention is paid to aquatic carnivorous plants. Studies on mineral nutrition carried out in laboratory and/or greenhouse conditions are discussed separately from those carried out in field conditions. The emphasis of this review is on recapitulation of original data and conclusions of results from a variety of studies that approach carnivorous plants from an ecophysiological point of view.     

Phenology and life cycle of the annual, <Emphasis Type="Italic">Chamaesyce maculata</Emphasis> (L.) Small (Euphorbiaceae), with multiple overlapping generations in Japan

The phenology of germination, vegetative growth and sexual reproduction in the annual Chamaesyce maculata (L.) Small (Euphorbiaceae) were investigated in a natural population in western Japan. Seedlings emerged from mid-June to early October, with three peaks: mid-June, late July and late August. Plants that emerged in June commenced sexual reproduction from late July, and thereafter both vegetative growth and sexual reproduction occurred together until early November, the plants showing no switching from vegetative growth to sexual reproduction. Seedlings that emerged in June and July suffered high mortality, but most seedlings that emerged from August onward survived until the reproductive stage. The minimum size for reproduction was largest for plants that emerged early in the season, and it decreased with a delay in seedling emergence. The late emergence of seedlings that resulted in low reproductive output may be to some extent compensated for by the increased probability of survival in the seedling stage. A transplant experiment clarified that C. maculata can repeat a maximum of three overlapping generations within a year. Multiple generations per year were attained by non-dormant seeds produced in the first and second generations and clearly resulted in an increased reproductive output per year. The life cycle with multiple overlapping generations may have been acquired in habitats where unpredictable disturbance results in temporally unsuitable conditions for germination, vegetative growth and sexual reproduction of annual plants, but where suitable conditions frequently continue over a period longer than the single generation time of annual plants.     

Proteomic analysis of secreted protein induced by a component of prey in pitcher fluid of the carnivorous plant Nepenthes alata

The Nepenthes species are carnivorous plants that have evolved a specialized leaf organ, the 'pitcher', to attract, capture, and digest insects. The digested insects provide nutrients for growth, allowing these plants to grow even in poor soil. Several proteins have been identified in the pitcher fluid, including aspartic proteases (nepenthesin I and II) and pathogenesis-related (PR) proteins (β-1,3-glucanase, class IV chitinase, and thaumatin-like protein). In this study, we collected and concentrated pitcher fluid to identify minor proteins. In addition, we tried to identify the protein secreted in response to trapping the insect. To make a similar situation in which the insect falls into the pitcher, chitin which was a major component of the insect exoskeleton was added to the fluid in the pitcher. Three PR proteins, class III peroxidase (Prx), β-1,3-glucanase, and class III chitinase, were newly identified. Prx was induced after the addition of chitin to the pitcher fluid. Proteins in the pitcher fluid of the carnivorous plant Nepenthes alata probably have two roles in nutrient supply: digestion of prey and the antibacterial effect. These results suggest that the system for digesting prey has evolved from the defense system against pathogens in the carnivorous plant Nepenthes.     

Adaptive genetic differentiation in life-history traits between populations of <Emphasis Type="Italic">Mimulus guttatus</Emphasis> with annual and perennial life-cycles

The optimal allocation to sexual and vegetative reproduction as well as the optimal values of other life-history characteristics such as phenology, growth and mating system are likely to depend on the life-cycle of the organism. I tested whether plants of Mimulus guttatus originating from temporarily wet populations where the species has an enforced annual life-cycle have higher allocation to sexual reproduction, lower allocation to vegetative reproduction, more rapid phenology, faster growth, and floral traits associated with a self-fertilizing mating system than plants from permanently wet populations where the species has a perennial life-cycle. I grew a total of 1377 plants originating from three populations with an annual life-cycle and 11 populations with a perennial life-cycle in a greenhouse under permanently and temporarily wet conditions. Plants of M. guttatus in permanently wet conditions had significantly more vegetative reproduction and tended to have a faster growth than plants in the temporarily wet conditions, indicating plasticity in these life-history traits. Plants from populations with an annual life-cycle invested significantly more in sexual reproduction and significantly less in vegetative reproduction than the ones from populations with a perennial life-cycle. Moreover, this study showed that plants originating from populations with an annual life-cycle have a significantly faster development and floral traits associated with autonomous self-fertilization. In conclusion, this study suggests that there has been adaptive evolution of life history traits of M. guttatus in response to natural watering conditions that determine the life span of the species.     

An experimental test of the defensive role of sticky traps in the carnivorous plant Pinguicula moranensis (Lentibulariaceae)

It has been sustained that the sticky traps present in some carnivorous plants could have evolved from ancestor species bearing leaves covered with secreting glands formerly associated with a defensive function. In this study, we evaluated the interaction of the carnivorous plant Pinguicula moranensis with its insect herbivores to assess the defensive role of the glandular trichomes. Firstly, we estimated the standing levels of insect herbivory in field conditions. We also evaluated the response of herbivore insects to the removal of the secreting glands from the leaves of P. moranensis in field and laboratory conditions. The mean damage was 1.61%, and half of the sampled plants showed no damage. The low level of herbivory in the field suggests that P. moranensis has an efficient defense ability. In the field experiment, after 25 d of exposure to natural damage, treated glandless plants received 18 times more damage than control plants. In the laboratory, the consumption of glandless tissue was three times higher during a 6 h evaluation period. Overall, our results provide evidence that secreting trichomes in Pinguicula are not only associated with prey capture but also have a defensive role. The defensive function could have favored the evolution of the sticky traps, the most extended prey‐capture strategy among carnivorous plants.     

Environmental constraints on the growth,photosynthesis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert,Svalbard

Opportunities exist in high Arctic polar semidesert communities for colonisation of unvegetated ground by long-lived clonal plants such as Dryas octopetala. This can be achieved by lateral spread of vegetative ramets, or by sexual reproduction and seedling recruitment. The objectives of this study were (1) to determine whether these two means of proliferation show differential sensitivity to contrasting components of the abiotic environment (temperature, soil nutrient and water availability) and (2) to evaluate the potential for D. octopetala to respond to climate change by an increase in cover and biomass in polar semi-desert communities. Factorial environmental manipulations of growing season temperature, soil nutrient and water status were conducted over 3 years at a polar semi-desert community in Svalbard, Norway (78°56.12N, 11°50.4E) and both clonal and sexual reproductive performance, together with instantaneous net photosynthesis (P_n), were recorded during the third season (1993). D. octopetala capitalised rapidly on an amelioration in the availability of inorganic nutrients (N, P and K) by an expansion in leaf area and biomass supported by increased P_n per unit leaf weight, and by apparent luxury uptake of nutrients (particularly P). Several facets of sexual reproductive development and seed viability were markedly improved by elevated temperatures or soil nutrient availability. Thus although D. octopetala is a long-lived clonal plant, with many traits characteristic of stress resistance syndrome, it showed considerable phenotypic plasticity in response to environmental manipulations. The results support the hypothesis that clonal growth confers survival potential during unfavourable years, together with the ability to capitalise on nutrient flushes and recycle nutrients internally. Continued investment in sexual reproduction ensures that seed setting is successful during favourable years, even if these occur infrequently. Cimate warming in the high Arctic could thus result in changes in the cover, biomass and the relative significance of clonal versus sexual proliferation of D. octopetala (and thus the genetic diversity of the population) but the long-term responses will probably be constrained by lack of available nutrients.     

Consequences of preformation for dynamic resource allocation by a carnivorous herb,Pinguicula vulgaris (Lentibulariaceae)

When resource availability changes frequently and unpredictably, natural selection favors flexible resource allocation; however, such versatility may be compromised in perennial plants that differentiate leaves or flowers a year in advance of their development (preformation). We investigated resource allocation by the carnivorous perennial Pinguicula vulgaris to determine whether increased resource availability changes within-season allocation to growth, vegetative propagation, and reproduction. In response to resource supplementation (feeding with fruit flies), plants attained a mass 60% greater than that of unfed plants after a single growing season. Feeding also enhanced vegetative propagation, which is closely associated with growth, without modifying relations between these two vegetative functions. In contrast, feeding did not alter the size of vegetative rosettes or the within-season incidence of either flowering or fruiting. This lack of immediate responses occurred because floral and leaf primordia differentiated up to 10 mo before resource supplementation and flower development. However, enhanced resource status likely affected future reproduction indirectly through resource effects on plant size. Large plants produced more floral primordia and between-year changes in fruiting status corresponded to changes in plant size. These results illustrate that preformation can delay responses to enhanced resources by perennial plants.     

ABIOTIC REGULATION OF INVESTMENT IN SEXUAL VERSUS VEGETATIVE REPRODUCTION IN THE CLONAL KELP LAMINARIA SINCLAIRII (LAMINARIALES,PHAEOPHYCEAE)1

Clonal kelp taxa may reproduce both sexually and vegetatively resulting in a potential trade‐off in the allocation of acquired carbon and nitrogen resources. Such trade‐offs may dictate a different response of clonal kelps to varying environmental conditions relative to aclonal kelp taxa. Laboratory temperature and nutrient manipulation experiments demonstrated that investment in sexual and vegetative reproduction in Laminaria sinclairii (Harv. ex Hook. f. et Harv.) Farl., C. L. Anderson et D. C. Eaton was regulated by different abiotic factors. Sorus production (investment in sexual reproduction) and blade growth were significantly higher at 12°C compared to 17°C, regardless of nutrient concentration. Net carbon storage and depletion in rhizomes were observed in the low‐ and high‐temperature treatments, respectively, suggesting that carbon stores were not responsible for increased growth. Rhizome elongation (investment in vegetative reproduction), on the other hand, was significantly higher in 12 μM NO₃^? than in 2 μM NO₃^?, irrespective of temperature. This increase in rhizome growth was concurrent with elevated rhizome percent tissue nitrogen levels also observed in treatments with higher nutrients, again indicating a growth response to treatment independent of previous nutrient stores. These results suggest that regulation of growth and investment in sexual reproduction in L. sinclairii is similar to that in aclonal kelps (i.e., warmer temperatures result in decreased reproductive output). Additionally, depletion of carbon and nitrogen from rhizomes in suboptimal conditions confirms the role of clonal kelp rhizomes in carbon and nutrient storage.     

The role of multiple partners in a digestive mutualism with a protocarnivorous plant

Background and aims

The protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) is similar to bromeliads in that this plant has a rosette-like structure that allows rainwater to accumulate in leaf axils (i.e. phytotelmata). Although the rosettes of P. bromelioides are commonly inhabited by predators (e.g. spiders), their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. In this study it is predicted that these plants can derive nutrients from recycling processes carried out by termites and from predation events that take place inside the rosette. It is also predicted that bacteria living in phytotelmata can accelerate nutrient cycling derived from predators.

Methods

The predictions were tested by surveying plants and animals, and also by performing field experiments in rocky fields from Serra do Cipó, Brazil, using natural abundance and enriched isotopes of ¹⁵N. Laboratory bioassays were also conducted to test proteolytic activities of bacteria from P. bromelioides rosettes.

Key Results

Analyses of ¹⁵N in natural nitrogen abundances showed that the isotopic signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. Linear mixing models showed that predatory activities on the rosettes (i.e. spider faeces and prey carcass) resulted in overall nitrogen contributions of 26·5 % (a top-down flux). Although nitrogen flux was not detected from termites to plants via decomposition of labelled cardboard, the data on ¹⁵N in natural nitrogen abundance indicated that 67 % of nitrogen from P. bromelioides is derived from termites (a bottom-up flux). Bacteria did not affect nutrient cycling or nitrogen uptake from prey carcasses and spider faeces.

Conclusions

The results suggest that P. bromelioides derive nitrogen from associated predators and termites, despite differences in nitrogen cycling velocities, which seem to have been higher in nitrogen derived from predators (leaves) than from termites (roots). This is the first study that demonstrates partitioning effects from multiple partners in a digestion-based mutualism. Despite most of the nitrogen being absorbed through their roots (via termites), P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism.     

Sticky plant captures prey for symbiotic bug: is this digestive mutualism?

Many plants capture and kill insects but, until relatively recently, only carnivorous plants with digestive enzymes were known to gain directly from the nutrients of those insects. Recent studies show that some carnivorous plants lack digestive enzymes and have evolved digestive mutualisms with symbiotic insects that digest their prey for them. Rhododendron macrosepalum, a plant with sticky leaves that captures insects, has an association with symbiotic Mirid bugs that consume the insects captured. Here, we determine what the nature of the relationship is between Mirid and plant. We find that R. macrosepalum has no digestive enzymes of its own but that it does not seem to have the ability to absorb hemipteran faeces through its leaf cuticle. Naturally occurring levels of ¹⁵N and ¹⁴N were used to determine that R. macrosepalum gains no nitrogen through its association with the Mirid bugs and that it obtains all of its nitrogen from the soil. The Mirids, on the other hand, seem to obtain nitrogen from insects captured by the plant, as well as from plant tissues. The relationship between plant and Mirid is not a digestive mutualism but more likely an antagonistic relationship. This study adds to our understanding of how digestive mutualisms evolve and shows that insect capture alone, or in combination with a symbiotic insect relationship does not necessarily make a plant ‘carnivorous’.     

Element Stoichiometry of a Mixotrophic Protist Grown Under Varying Resource Conditions

ABSTRACT. The balance of essential elements (e.g. carbon [C], nitrogen [N], and phosphorus [P]) between consumers and their resources influences not only the growth and reproduction of the consumers but also the nutrients they regenerate. Flagellate protists are significant predators of aquatic bacteria and directly influence nutrient flow to higher trophic levels and, through excretion, influence the mineral element composition of dissolved nutrients. Because the element stoichiometry of protists is poorly characterized, we varied the resource composition of the bacterium Pseudomonas fluorescens and used it to grow the mixotrophic bacterivorous flagellate Ochromonas danica. Using a mass balance approach, the element composition of O. danica was found to vary depending upon the nutrient composition of the prey and ranged between 482:36:1 and 80:12:1 (C:N:P molar). Homeostasis plots suggested that flagellate protists weakly regulate their element composition and are likely to regenerate different elements depending upon the nature of the element limiting growth of their prey.     

Resource competition and fire‐regulated nutrient demand in carnivorous plants of wet pine savannas

Question: What are the mechanisms by which fire reduces competition for both a short‐lived and a long‐lived species in old‐growth ground‐cover plant communities of wet pine savannas (originally Pinus palustris, replaced by P. elliottii)? Location: Outer coastal plain of southeastern Mississippi, USA. Methods: I reviewed previous competition experiments and proposed a new hypothesis to explain the relationship between fire, competition, and species co‐existence in wet longleaf pine savannas. The first study is about growth and seedling emergence responses of a short‐lived carnivorous plant, Drosera capillaris, to reduction in below‐ground competition and above‐ plus below‐ground competition. The second study deals with growth and survival responses of a long‐lived perennial carnivorous plant, Sarracenia alata, to neighbour removal and prey‐exclusion to determine if a reduction in nutrient supply increased the intensity of competition in this nutrient‐poor system. Results: Fire increased seedling emergence of the short‐lived species by reducing above‐ground competition through the destruction of above‐ground parts of plants and the combustion of associated litter. Prey exclusion did not increase competitive effects of neighbours on the long‐lived species. However, because the experiment was conducted in a year without fire, shade reduced nutrient demand, which may have obviated competition for soil nutrients between Sarracenia alata and its neighbours. Conclusion: Repeated fires likely interact with interspecific differences in nutrient uptake to simultaneously reduce both above‐ground competition and competition for nutrients in old‐growth ground cover communities in pine savannas. Restoration practitioners should consider the possibility that the composition of the plant community is just as important as fire in ensuring that frequent fires maintain species diversity.