Root Hemiparasitic Plants Research Articles

Controlled Transition in a Modified Model of Biomass Dynamics of Root Hemiparasitic Plants

Controlled Transition in a Modified Model of Biomass Dynamics of Root Hemiparasitic Plants

Root hemiparasites suppress invasive alien clonal plants: evidence from a cultivation experiment

Alien invasive plants threaten biodiversity by rapid spread and competitive exclusion of native plant species. Especially, tall clonal invasives can rapidly attain strong dominance in vegetation. Root-hemiparasitic plants are known to suppress the growth of clonal plants by the uptake of resources from their below-ground organs and reduce their abundance. However, root-hemiparasites’ ability to interact with alien clonal plants has not yet been tested. We explored the interactions between native root-hemiparasitic species, Melampyrum arvense and Rhinanthus alectorolophus and invasive aliens, Solidago gigantea and Symphyotrichum lanceolatum. We investigated the haustorial connections and conducted a pot experiment. We used seeds from wild hemiparasite populations and those cultivated in monostands of the invasive plants to identify a possible selection of lineages with increased compatibility with these alien hosts. The hemiparasitic species significantly suppressed the growth of the invasive plants. Melampyrum inflicted the most substantial growth reduction on Solidago (78%), followed by Rhinanthus (49%). Both hemiparasitic species reduced Symphyotrichum biomass by one-third. Additionally, Melampyrum reduced the shoot density of both host species. We also observed some transgenerational effects possibly facilitating the growth of hemiparasites sourced from subpopulations experienced with the host. Native root hemiparasites can effectively decrease alien clonal plants’ biomass production and shoot density. The outcomes of these interactions are species-specific and may be associated with the level of clonal integration of the hosts. The putative selection of lineages with higher performance when attached to the invasive novel hosts may increase hemiparasites’ efficiency in future biocontrol applications.

Host age affects the performance of the root hemiparasitic plant Rhinanthus alectorolophus.

Interactions between root hemiparasitic plants and their hosts are strongly affected by host identity, but may also depend on the condition of the host. An important determinant of host quality could be host age, as it may influence host size, allocation patterns, responses to infection, and the strength of competition for light between parasite and host. We investigated the effects of host species identity, host age and above-ground separation of hemiparasite and host on the interactions between the hemiparasite Rhinanthus alectorolophus and five host species in a factorial experiment. The host species were planted at six different times, from 10 weeks before the parasite was planted to 4 weeks after. Host age strongly influenced the performance of the parasite, but these effects also varied among host species. Parasites grew largest with hosts planted at the same time or 2 weeks earlier, but their performance strongly declined both with increasing host age and with the time they grew autotrophically. A large part of the variation due to host age but not of that due to host species identity could be related to the negative influence of host size at the likely time of parasite attachment. The low quality of older hosts was not due to light competition, suggesting that effective exploitation of these hosts was prevented by other factors like harder roots, stronger defense against parasite attack or competition for resources taken up by the host roots. Suppression of host growth by the parasites declined with increasing host age. The results indicate that the choice of host age may influence the results of studies on hemiparasites. They also highlight the importance for annual root hemiparasites of attachment in early spring, that is, at a time when their mostly perennial hosts produce fresh roots but are still poorly developed above ground.

Lamourouxia (Orobanchaceae) of Mexico

Lamourouxia is a Neotropical genus currently classified within the tribe Pedicularideae (Orobanchaceae), a clade of root hemiparasitic plants. It comprises 30 species endemic to the Americas. The genus was last studied as a whole in 1972. Some species have not been collected since that date. Half a century later, based on the revision of 1,284 herbarium specimens of Lamourouxia, 119 digitized specimens, and 43 observations of citizen science, here we present an update of the taxonomic classification, nomenclature, diversity, distribution, uses, and ecology of the Lamourouxia species in Mexico, the country with the highest species richness and highest number of endemic species of the genus (26 and 20 species, respectively). Typifications of valid names and synonyms are given. Also, it is presented the change of the name Lamourouxia barbata instead of L. lanceolata. New diagnostic characters, keys for the species, ecological data, and photographs of the species in the field are provided to facilitate the identification and study of the species of this fascinating genus of hemiparasitic plants.

Root hemiparasitic plants are associated with more even communities across North America.

Root hemiparasitic plants both compete with and extract resources from host plants. By reducing the abundance of dominant plants and releasing subordinates from competitive exclusion, they can have an outsized impact on plant communities. Most research on the ecological role of hemiparasites is manipulative and focuses on a small number of hemiparasitic taxa. Here, we ask whether patterns in natural plant communities match the expectation that hemiparasites affect the structure of plant communities. Our data were collected on 129 national park units spanning the continental United States. The most common hemiparasite genera were Pedicularis, Castilleja, Krameria, and Comandra. We used null models and linear mixed models to determine whether hemiparasites were associated with changes in community richness and evenness. Hemiparasite presence did not affect community metrics. Hemiparasite abundance was positively associated with increasing evenness of herbaceous species, but not with species richness. The associations that we observed on a continental scale are consistent with evidence that the impacts of root hemiparasitic plants on evenness can be substantial and abundance dependent but that effects on richness are less pronounced. Hemiparasites mediate competitive exclusion in communities to facilitate species coexistence and merit consideration of inclusion in ecological theories of coexistence.

A Legume Host Benefits More from Arbuscular Mycorrhizal Fungi Than a Grass Host in the Presence of a Root Hemiparasitic Plant.

In nature, most plants parasitized by root hemiparasites are also colonized by mutualistic arbuscular mycorrhizal (AM) fungi, highlighting the prevalence of this tripartite interaction. AM colonization is generally found to improve the growth of parasitized legumes but has little impact on grass hosts parasitized by root hemiparasites, and the underlying mechanisms are still unclear. In this study, we conducted a pot experiment to test the influence of AM fungus (Glomus mosseae) on the growth and photosynthesis of leguminous Trifolium repens and gramineous Elymus nutans in the presence of a root hemiparasitic plant (Pedicularis kansuensis). The results showed that inoculation with AM fungi significantly improved the growth performance of parasitized legumes via enhancing their nutrient status and photosynthetic capacity, even though a larger P. kansuensis parasitized the legume host in the AM treatment. In contrast, AM colonization slightly improved the shoot DW of grass hosts by suppressing haustoria formation and the growth of P. kansuensis. Our results demonstrated that legume hosts benefit more from AM inoculation than grass hosts in the presence of hemiparasitic plants, and set out the various mechanisms. This study provides new clues for parsing the tritrophic interaction of AM fungi, parasitic plants, and host plants.

Diversity of Endophytic Bacteria in Parasitic and Non-Parasitic Centranthera grandiflora Benth. Based on High-Throughput Sequencing

The community of endophytic bacteria varies with the genotypes, nutritional status and growth environment of host plants, and in turn it also affects the growth, metabolism and biochemical synthesis of plants. Using the root, stem and leaf of parasitic and non-parasitic Centranthera grandiflora Benth. (PR, PS, PL and NR, NS, NL) as materials, the differences of endophytic bacteria community and diversity were analyzed by high-throughput sequencing. Alpha diversity analysis shows that the richness and diversity of endophytic bacteria in NR were lower than those in PR; while those in NS were higher than those in PS. At the phylum level, Proteobacteria was the dominant phyla, followed by Bacteroidetes and Actinobacteria; the relative abundance of Proteobacteria in each tissue of non-parasitic sample (NR 93.87%, NS 84.27%, NL 90.00%) was higher than that in parasitic sample (PR 77.06%, PS 78.28%, PL 84.96%). The relative abundance in roots increased the most, up to 16.84%. At the genus level, each sample had its own dominant group, Acinetobacter (37.90%) was the dominant in NR, and the relative abundance was 9.56 times than that in PR. The nutritional status and the endophytic bacteria community of host plants have an impact on the structure and diversity of endophytic bacteria in Centranthera grandiflora Benth.; the nutrients needed for Centranthera grandiflora Benth. growth may not only come from the host plant, but also from endophytic bacteria. The results aim to provide a theoretical basis for related study in the relationship between root hemiparasitic plants and their hosts.

Controlled Transition in a Model of Biomass Dynamics of Root Hemiparasitic Plants

Controlled Transition in a Model of Biomass Dynamics of Root Hemiparasitic Plants

Better alone? A demographic case study of the hemiparasite Castilleja tenuiflora (Orobanchaceae): A first approximation

AbstractCastilleja tenuiflora is a facultative root hemiparasitic plant that has colonized a disturbed lava field in central Mexico. To determine the effects of hemiparasitism on the population dynamics of the parasite, we identified a set of potential hosts and quantified their effects on the vital rates of C. tenuiflora during 2016–2018. Connections between the roots of the hemiparasite and the hosts were confirmed with a scanning electron microscope. Annual matrices considering two conditions (with and without potential hosts) were built based on vital rates for each year, and annual stochastic finite rate growth rates (λs) were calculated. Plants produced more reproductive structures with hosts than without hosts. A Life Table Response Experiment (LTRE) was performed to compare the contributions of vital rates between conditions. We identified 19 species of potential hosts for this generalist hemiparasite. Stochastic lambda with hosts λs = 1.02 (CI = 0.9999, 1.1) tended to be higher than without them λs = 0.9503 (CI = 0.9055, 0.9981). The highest elasticity values correspond to survival. LTRE indicated that the most important parameters are survival and fecundity; the total contribution of fecundity (0.0192) to the difference in growth was three times lower than that of survival (0.0603). Piqueria trinervia was the most abundant host, and C. tenuiflora had a higher lambda with it than with other species. Individuals can grow alone, but hosts can have a positive effect on the vital parameters of C. tenuiflora and on λ.

Effects of one haustorium-inducing quinone DMBQ on growth and development of root hemiparasitic plant Monochasma savatieri

ABSTRACT: Monochasma savatieri Franch. ex Maxim is a perennial, parasitic herb used in traditional Chinese medicine and its wild resources have decreased sharply in recent years due to destructively harvesting and habitat destruction. Haustorium formation is a key event of parasites, but the concentrations of haustorium-inducing factors vary with species and cultivation conditions. In this study, we investigated the effects of the 2,6-dimethoxy-p-benzoquinone (DMBQ) concentration and cultivation density on the growth traits, haustorium formation and biomass of M. savatieri in the absence of a host plant. The results showed that both the DMBQ concentration and cultivation density regulated growth traits, haustorium formation and biomass in M. savatieri. The number of haustoria was significantly positively correlated with seedling height, maximum root length, the number of root tips and total dry weight. Membership function analysis revealed an overall greater increase in growth traits, haustorium formation and biomass when M. savatieri was treated with 10 μmol·L-1DMBQ and grew solitarily. These results offer an understanding of growth in M. savatieri influenced by the DMBQ concentration and cultivation density, which may aid in the establishment of a comprehensive cultivation system for M. savatieri or similar plants.

Growth response of Monochasma savatieri to nitrogen, phosphorus, and potassium in the absence of a host plant: essential demand for nutrients of root hemiparasitic plants

Monochasma savatieri Franch. ex Maxim is a perennial, parasitic herb used in traditional Chinese medicine and its wild resources have declined sharply in recent years. For a long time, the research on fertilization of parasitic plants mostly focused on parasitic weeds. Despite its urgent need, there are few studies discussing the nutrient requirements of medicinal threatened parasitic plants. In this study, we investigated the growth response of M. savatieri to inorganic solutes. By using an orthogonal design in pot cultivation, the effects of nitrogen, phosphorus, and potassium on growth traits, haustoria formation, and biomass of M. savatieri were determined under greenhouse conditions. The results showed that M. savatieri had a rather significant growth response to different nutrients supplied. Nitrogen, phosphorus, and potassium significantly influenced growth traits, haustoria formation, and biomass of M. savatieri, but differ in the degree. M. savatieri experienced a more significant increase in nitrogen sufficient than phosphorus or potassium sufficient in terms of seedling height (SH), maximum root length, and biomass. There were significant positive correlations between tested parameters. The regression equation for SH, total leaf length, and number of haustoria both showed relatively high R2 values and could be sensitive available indicators. In the absence of hosts and haustoria-inducing factors, M. savatieri was capable of haustoria formation and autotrophic growth for a period of time. We concluded that M. savatieri had a certain demand for inorganic nutrients. The appropriate supply of inorganic nutrients promoted growth and development of M. savatieri.

Root hemiparasitism in Malania oleifera (Olacaceae), a neglected aspect in research of the highly valued tree species

Malania oleifera (Olacaceae) is a valued tree species, mostly because its seeds have high precious fatty acid content (particularly nervonic acid). However, seedling mortality rates are often high and regeneration of this tree has been problematic, which greatly hinders its utilization at a large scale. Cultivation difficulties of some tree species in the family Olacaceae have been attributed to their root hemiparasitic habit. Prompted by field observations and the taxonomic proximity of M. oleifera to root hemiparasites in Olacaceae, we hypothesized that tuberous structures observed on the roots of M. oleifera are parasitic organs known as haustoria. To test this hypothesis, we collected root samples from M. oleifera plants of various ages and growth conditions, investigated the morphological and anatomical features of tuberous structures and their connections to neighboring roots. Our analyses confirmed that M. oleifera are root hemiparasites. To the best of our knowledge, this is the first empirical report on root hemiparasitism in M. oleifera. Because life strategies of root hemiparasitic plants differ greatly from autotrophic plants, the root hemiparasitic habit needs to be taken into account for successful seedling regeneration of M. oleifera. This study establishes the foundation for investigations into a long-neglected but essential aspect in research of these highly valued tree species.

A neglected alliance in battles against parasitic plants: arbuscular mycorrhizal and rhizobial symbioses alleviate damage to a legume host by root hemiparasitic Pedicularis species.

Despite their ubiquitous distribution and significant ecological roles, soil microorganisms have long been neglected in investigations addressing parasitic plant-host interactions. Because nutrient deprivation is a primary cause of host damage by parasitic plants, we hypothesized that beneficial soil microorganisms conferring nutrient benefits to parasitized hosts may play important roles in alleviating damage. We conducted a pot cultivation experiment to test the inoculation effect of an arbuscular mycorrhizal fungus (Glomus mosseae), a rhizobium (Rhizobium leguminosarum) and their interactive effects, on alleviation of damage to a legume host (Trifolium repens) by two root hemiparasitic plants with different nutrient requirements (N-demanding Pedicularis rex and P-demanding P.tricolor). Strong interactive effects between inoculation regimes and hemiparasite identity were observed. The relative benefits of microbial inoculation were related to hemiparasite nutrient requirements. Dual inoculation with the rhizobium strongly enhanced promotional arbuscular mycorrhizal effects on hosts parasitized by P.rex, but reduced the arbuscular mycorrhizal promotion on hosts parasitized by P.tricolor. Our results demonstrate substantial contribution of arbuscular mycorrhizal and rhizobial symbioses to alleviating damage to the legume host by root hemiparasites, and suggest that soil microorganisms are critical factors regulating host-parasite interactions and should be taken into account in future studies.

Water-stress physiology of Rhinanthus alectorolophus, a root-hemiparasitic plant.

Root-hemiparasitic plants of the genus Rhinanthus acquire resources through a water-wasting physiological strategy based on high transpiration rate mediated by the accumulation of osmotically active compounds and constantly open stomata. Interestingly, they were also documented to withstand moderate water stress which agrees with their common occurrence in rather dry habitats. Here, we focused on the water-stress physiology of Rhinanthus alectorolophus by examining gas exchange, water relations, stomatal density, and biomass production and its stable isotope composition in adult plants grown on wheat under contrasting (optimal and drought-inducing) water treatments. We also tested the effect of water stress on the survival of Rhinanthus seedlings, which were watered either once (after wheat sowing), twice (after wheat sowing and the hemiparasite planting) or continuously (twice and every sixth day after that). Water shortage significantly reduced seedling survival as well as the biomass production and gas exchange of adult hemiparasites. In spite of that drought-stressed and even wilted plants from both treatments still considerably photosynthesized and transpired. Strikingly, low-irrigated plants exhibited significantly elevated photosynthetic rate compared with high-irrigated plants of the same water status. This might relate to biochemical adjustments of these plants enhancing the resource uptake from the host. Moreover, low-irrigated plants did not acclimatize to water stress by lowering their osmotic potential, perhaps due to the capability to tolerate drought without such an adjustment, as their osmotic potential at full turgor was already low. Contrary to results of previous studies, hemiparasites seem to close their stomata in response to severe drought stress and this happens probably passively after turgor is lost in guard cells. The physiological traits of hemiparasites, namely the low osmotic potential associated with their parasitic lifestyle and the ability to withstand drought and recover from the wilting likely enable them to grow in dry habitats. However, the absence of osmotic adjustment of adults and sensitivity of seedlings to severe drought stress demonstrated here may result in a substantial decline of the hemiparasitic species with ongoing climate change.

Fast and abundant in vitro spontaneous haustorium formation in root hemiparasitic plant Pedicularis kansuensis Maxim. (Orobanchaceae)

Haustorium formation is the characteristic feature of all parasitic plants and a vital process for successful parasitism. Previous investigations on haustorium initiation and development are constricted to induced processes by host-derived signals or synthetic analogs. Spontaneous haustorium formation in the absence of host signals, a process representing an early stage in the evolution of parasitic plants, remains largely unexplored. Lack of fast and frequent formation of spontaneous haustoria greatly hinders full understanding of haustorium formation in root hemiparasites. In this study, seedlings of Pedicularis kansuensis Maxim., a facultative root hemiparasitic species in Orobanchaceae observed to produce many spontaneous haustoria, were grown in autoclaved water agar in the absence of any known haustorium-inducing stimulants. We aimed to test the temporal and developmental pattern of spontaneous haustorium formation. Also, effects of sucrose supply and root contact on spontaneous haustorium formation were tested. Spontaneous haustoria were observed starting from six days after germination, much earlier than previously reported root hemiparasites. A majority of the spontaneous haustoria formed on lateral roots. Percentage of seedlings with spontaneous haustoria was 28.8% when grown on water agar plates, with a mean of four haustoria per seedling two weeks after germination. Haustorium formation by seedlings grown in water agar amended with 2% sucrose was more than twice of those without sucrose amendment. Singly grown seedlings were able to develop spontaneous haustoria at similar levels as those grown with another conspecific seedling. In view of the fast and abundant formation of spontaneous haustoria, P. kansuensis may be developed as an excellent experimental system in future investigations for unraveling endogenous regulation of haustorium initiation and development in root hemiparasitic plants.

N-P fertilization did not reduce AMF abundance or diversity but alter AMF composition in an alpine grassland infested by a root hemiparasitic plant

Fertilization has been shown to have suppressive effects on arbuscular mycorrhizal fungi (AMF) and root hemiparasites separately in numerous investigations, but its effects on AMF in the presence of root hemiparasites remain untested. In view of the contrasting nutritional effects of AMF and root hemiparasites on host plants, we tested the hypothesis that fertilization may not show strong suppressive effects on AMF when a plant community was infested by abundant hemiparasitic plants. Plants and soil samples were collected from experimental field plots in Bayanbulak Grassland, where N and P fertilizers had been applied for three continuous years for control against a spreading root hemiparasite, Pedicularis kansuensis. Shoot and root biomass of each plant functional group were determined. Root AMF colonization levels, soil spore abundance, and extraradical hyphae length density were measured for three soil depths (0–10 cm, 10–20 cm, 20–30 cm). Partial 18S rRNA gene sequencing was used to detect AMF diversity and community composition. In addition, we analyzed the relationship between relative abundance of different AMF genera and environmental factors using Spearman's correlation method. In contrast to suppressive effects reported by many previous studies, fertilization showed no significant effects on AMF root colonization or AMF species diversity in the soil. Instead, a marked increase in soil spore abundance and extraradical hyphae length density were observed. However, fertilization altered relative abundance and AMF composition in the soil. Our results support the hypothesis that fertilization does not significantly influence the abundance and diversity of AMF in a plant community infested by P. kansuensis.

N-P Fertilization Inhibits Growth of Root Hemiparasite Pedicularis kansuensis in Natural Grassland.

Fertilization has been shown to affect interactions between root hemiparasitic plants and their host plants, alleviating damage to the hosts by parasitism. However, as a majority of studies were conducted in pot cultivation, the influence of fertilizer application on root hemiparasites and the surrounding plant community in field conditions as well as relevant mechanisms remain unclear. We manipulated soil nutrient resources in a semi-arid subalpine grassland in the Tianshan Mountains, northwestern China, to explore the links between fertilization and plant community composition, productivity, survival, and growth of a weedy root hemiparasite (Pedicularis kansuensis). Nitrogen (at a low rate, LN, 30 kg N ha-1 year-1 as urea; or at a high rate, HN, 90 kg N ha-1 year-1 as urea) and phosphorus [100 kg ha-1 year-1 as Ca(H2PO4)2⋅H2O] were added during two growing seasons. Patterns of foliar nutrient balances were described with isometric log ratios for the different plant functional groups receiving these fertilization regimes. Fertilization with LN, HN, and P reduced above-ground biomass of P. kansuensis, with above-ground biomass in the fertilization treatments, respectively, 12, 1, and 39% of the value found in the unfertilized control. Up to three times more above-ground biomass was produced in graminoids receiving fertilizers, whereas forb above-ground biomass was virtually unchanged by the fertilization regimes and forb species richness was reduced by 52% in the HN treatment. Fertilization altered foliar nutrient balances, and distinct patterns emerged for each plant functional group. Foliar [C | P,N] balance in the plant community was negatively correlated with above-ground biomass (P = 0.03). The inhibited competitiveness of P. kansuensis, which showed a much higher [C | P,N] balance, could be attributed to reduced C assimilation rather than mineral nutrient acquisition, as shown by significant increase in foliar N and P concentrations but little increase in C concentration following fertilization.

A hemiparasite in the forest understorey: photosynthetic performance and carbon balance of Melampyrum pratense.

Melampyrum pratense is an annual root-hemiparasitic plant growing mostly in forest understorey, an environment with unstable light conditions. While photosynthetic responses of autotrophic plants to variable light conditions are in general well understood, light responses of root hemiparasites have not been investigated. We carried out gas exchange measurements (light response and photosynthetic induction curves) to assess the photosynthetic performance of M.pratense in spring and summer. These data and recorded light dynamics data were subsequently used to model carbon balance of the hemiparasite throughout the entire growth season. Summer leaves had significantly lower rates of saturated photosynthesis and dark respiration than spring leaves, a pattern expected to reflect the difference between sun- and shade-adapted leaves. However, even the summer leaves of the hemiparasite exhibited a higher rate of light-saturated photosynthesis than reported in non-parasitic understorey herbs. This is likely related to its annual life history, rare among other understorey herbs. The carbon balance model considering photosynthetic induction still indicated insufficient autotrophic carbon gain for seed production in the summer months due to limited light availability and substantial carbon loss through dark respiration. The results point to potentially high importance of heterotrophic carbon acquisition in M.pratense, which could be of at least comparable importance as in other mixotrophic plants growing in forests - mistletoes and partial mycoheterotrophs. It is remarkable that despite apparent evolutionary pressure towards improved carbon acquisition from the host, M.pratense retains efficient photosynthesis and high transpiration rate, the ecophysiological traits typical of related root hemiparasites in the Orobanchaceae.

DNA barcoding as a tool for identification of host association of root-hemiparasitic plants

Root hemiparasites are green plants which attach to roots of other plants and extract solutes from the host-root xylem parasitically. They frequently act as keystone species by affecting competitive relations in plant communities and altering mineral nutrient cycling. Understanding their ecology has been hindered by the difficulty to identify host associations of hemiparasitic plants growing in natural conditions. Direct examination of host associations is only possible at sites with specific soil types (e.g. sandy substrates) that allow host roots to be traced to the shoot to identify the host species. We investigated the possibility of using a DNA barcoding-based approach to identify host associations of root hemiparasites growing naturally. Host associations of Melampyrum nemorosum, Rhinanthus major and Rhinanthus minor were investigated. Their root systems were washed free of soil to reveal haustorial connections. Host-root fragments were subjected to DNA extraction and the plastid DNA trnL intron was sequenced. The functioning of haustoria was examined in semi-thin anatomical sections. The analysis of the DNA of host roots yielded a ca 60% success rate. The Rhinanthus species were confirmed to attack mostly grasses and legumes. By contrast, Melampyrum nemorosum attached mainly to plants of Rosaceae and Asteraceae. In addition, both conspecific and heterospecific connections between the hemiparasites were frequently observed. Our study demonstrates the usefulness of the DNA barcoding approach for identifying host associations of root hemiparasites at sites where tracing host roots to their shoot is not possible due to soil structure or high rooting density.

Spatial analysis of root hemiparasitic shrubs and their hosts: a search for spatial signatures of above- and below-ground interactions

Root hemiparasitic plants take up resources from the roots of neighbouring plants, which they use for fuelling their own growth. While taking up resources from the hosts below-ground, they may simultaneously compete with the hosts for sunlight. Suppression caused by the parasitism could result in openings in the vegetation structure and increased mortality levels. On the other hand, the root hemiparasites may also be constrained by the hosts, restricting the parasites to a limited number of locations within a community. These vegetation alterations and location restrictions can be referred to as spatial signatures of the root hemiparasites. In order to search for such spatial signatures, we investigated a population of a predominant Acacia species in Australia co-occurring with established root hemiparasitic shrubs, using intensity estimates of the Acacia and dead shrubs to be indicators of parasite populations. We find evidence that the root hemiparasitic shrubs, like herbaceous root hemiparasites, prefer growing at distances from neighbouring plants that fulfil resource requirements both below-ground and above-ground. Assuming that root hemiparasites are limited by their hosts, we present an optimal host density and distance to host hypothesis (‘Goldilocks hypothesis’) to account for such a vegetation pattern. Although mortality appeared to primarily result from intraspecific competition and shoot parasitism, the root parasitism could explain some of the mortality in open areas. It is likely that both processes occur simultaneously. In spite of differing annual and perennial life strategies among root hemiparasites, root parasitism across systems may follow these two general processes in the formation of vegetation patterns.