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Parasites necessarily depend on their hosts, but the number of host species used by a parasite varies from one to hundreds. Estimating host range and identifying the preferred host species that influence distributional boundaries and confer greater advantage to the parasite has proven elusive. As well as the confounding effects of sampling effort, characterising host specificity and preference has been hindered by considering hostuse without accounting for availability. We selected three mistletoe species (Lysiana exocarpi, Amyema quandang, and Amyema lucasii) and sampled mistletoe-host interactions and host availability free from sampling bias. To quantify host specificity and identify preferred host species we applied specialist/generalist scores (G) and resource selection ratios ([omega]) respectively. Host specificity and preference were assessed at four scales. The generalist L. exocarpi was found to parasitise 31 plant species. Even at small scales, G values and host species turnover were high, with eight preferred hosts identified. Amyema quandang had a low G score with significant preference for half of its Acacia hosts. Amyema lucasii significantly preferred one host, consequently having low G values at all scales. By collecting potential host data and applying G scores and [omega], the parasite host spectrum can be quantitatively estimated rather than qualitatively described. Key words: host preference, host spectrum, host turn-over, parasitic plant, mistletoe. Les parasites dependent necessairement de leurs hotes, mais le nombre d'especes hotes utilisees par un parasite varie de un a plusieurs centaines. L'estimation de la gamme d'hotes et l'identification des especes d'hotes preferees qui influencent les limites de distribution et conferent un plus grand avantage au parasite se sont averees compliquees. Tout comme les effets confondants de l'effort d'echantillonnage, la caracterisation de la specificite et de la preference pour l'hote a ete genee par la consideration de l'utilisation de l'hote sans tenir compte de sa disponibilite. Les auteurs ont selectionne trois especes de guis (Lysiana exocarpi, Amyema quandang et Amyema lucasii) et echantillonne les interactions gui-hote et la disponibilite de l'hote sans biais d'echantillonnage. Pour quantifier la specificite pour l'hote et identifier les especes d'hotes preferees, ils ont applique respectivement les scores specialistes/generalistes (G) et les ratios de selection des ressources ([omega]). La specificite et la preference pour un hote ont ete evaluees a quatre echelles. Le gui generaliste L. exocarpi parasitait 31 especes de plantes. Meme a petites echelles, les valeurs de G et le renouvellement des especes hotes etaient eleves, huit hotes preferes ayant ete identifies. Amyema quandang presentait un faible score G, avec une preference significative pour la moitie des especes d'Acacia qui sont ses hotes. Amyema lucasii preferait de maniere significative un hote, ayant par consequent une faible valeur de G a toutes les echelles. En recoltant toutes les donnees sur les hotes potentiels et en appliquant les scores G et les [omega], le spectre d'hotes d'un parasite peut etre estime de maniere quantitative plutot que decrit qualitativement. [Traduit par la Redaction] Mots-cles : preference pour l'hote, spectre d'hotes, renouvellement de l'hote, plante parasite, gui., Introduction Parasites have a pervasive influence on ecosystems and, while their combined effects extend well beyond pairwise interactions with individual hosts, the magnitude and extent of their influence is often [...]

Mistletoe is increasingly being reported as a horticultural pest, infecting many species grown commercially for fruit, nuts, and other food products. Unlike mistletoe impacts on forestry, the published research on mistletoe in horticulture is scant, with management guidelines reliant on anecdotes, un-replicated trials on unrelated species, and often in different countries and growing systems. We have integrated the existing work to summarize information on the most effective control strategies for mistletoe in horticulture, and call attention to the paucity of empirical research. Despite grower interest in growth regulators and herbicides, limited trials suggest chemical treatment of mistletoe is ineffective, consistent with findings from forestry and ornamental trees. Although labour-intensive, ongoing mechanical removal is the most effective strategy to minimize mistletoe impacts but, without information available on effects of mistletoe infection on yield or tree mortality, cost-effectiveness calculations are not possible. Given the range of herbivores that consume mistletoe tissues, biological control may be useful, both to prevent initial infection and also reduce impacts on infected hosts in commercial plantations. To catalyse more research on mistletoes in horticulture, we articulate six priorities for further work, emphasizing the utility of tree crops as model systems to address questions regarding mistletoe ecology and host-parasite dynamics more broadly. Key words: integrated pest management, plantation, orchard, host quality, monoculture. Le gui est de plus en plus victime de ceux qui le considerent comme un parasite en horticulture, contaminant de nombreuses especes cultivees commercialement pour les fruits, les noix et autres produits alimentaires. Contrairement aux impacts du gui en sylviculture, les recherches scientifiques publiees sur le gui en horticulture sont peu nombreuses, sa gestion reposant sur des anecdotes, des essais non repetes sur des especes sans rapport les unes avec les autres, souvent dans des pays et des modes de culture differents. Nous integrons les travaux existants afin de resumer les informations sur les meilleures strategies de lutte contre le gui en horticulture et soulignons la rarete des recherches empiriques. Malgre l'interet des producteurs pour les regulateurs de croissance et les herbicides, des essais limites suggerent que le traitement chimique du gui est inefficace, en concordance avec les resultats obtenus en foresterie et chez les arbres ornementaux. Bien qu'exigeant une importante main d'oeuvre, l'elimination mecanique en continu demeure la strategie la plus efficace pour minimiser l'impact du gui, mais sans la disponibilite d'informations sur les effets de l'infection par le gui sur le rendement ou la mortalite des arbres, les calculs du rapport cout-efficacite ne sont pas possibles. Compte tenu du spectre des herbivores qui consomment les tissus du gui, la lutte biologique pourrait etre utile afin de prevenir a la fois une infection initiale et pour reduire les impacts sur les hotes deja infectes dans des plantations commerciales. Afin de catalyser plus de recherches sur le gui en horticulture, nous formulons six priorites pour les travaux ulterieurs, soulignant l'utilite de cultures arboricoles comme systemes modeles pour aborder les questions concernant l'ecologie du gui et les dynamiques hote-parasite en general. [Traduit par la Redaction] Mots-cles : gestion integree des parasites, plantation, verger, qualite de l'hote, monoculture., Introduction Horticulture is a rapidly expanding industry, accounting for 35% and 39% of the total valueofcrops for the USA and Europe, respectively. In addition to accounting for an increasing proportion [...]

Mistletoes have a fraught public relations history. Vilified as toxic tree-killing weeds, they have long been targeted for removal by arborists and forest managers concerned with tree health. Research on mistletoe ecology has revealed their positive influence on diversity and community structure via complex networks of interactions. In areas where mistletoe has traditionally been removed, managers are now asking whether these parasitic plants can return on their own or whether they should be reintroduced. To evaluate the practicalities of mistletoe restoration, we inoculated 28 London plane trees Platanus × acerfolia (Aiton) Willd. in inner Melbourne with creeping mistletoe Muellerina eucalyptoides (DC.) Barlow, a locally rare species. Branch dimensions and aspect had no discernible effect on germination or seedling emergence, but trees where access to possums (Trichosurus vulpecula (Kerr, 1792) and Pseudocheirus peregrinus (Boddaert, 1785)) was restricted were 30% more likely to host seedlings. Five years after inoculation, seven mistletoes successfully established on five trees, with two mistletoes bearing fruit. Communications with residents and city users elicited positive feedback, catalysing four additional inoculation trials in urban and forest settings elsewhere. In addition to representing a cost-effective means of enhancing habitat values, mistletoe restoration is useful for addressing open questions about mistletoe ecology and educating the community about the functional roles these parasitic plants play. [ABSTRACT FROM AUTHOR]

Keystone plant species are commonly used for restoring degraded terrestrial sites because, despite being encountered in low abundances in natural communities, they interact with multiple species across multiple niche dimensions. Nevertheless, the demographic characteristics of these "great interactors" are often disregarded in restoration planning, which may bring unintended consequences for restoration trajectories once the outcome of species relationships interplays between positive and negative effects depending on the density of interacting species. Therefore, while replanting keystone species at their characteristically low densities may re‐entangle food webs and allow novel plant and animal recruitment, restoring them at high densities can assemble asymmetrical relationships strong enough to affect sympatric plant species establishment, survival, and reproduction. Here, we explore the negative consequences of overusing keystone plant species in sites undergoing restoration and provide specific guidelines for practitioners to maximize the benefits of keystone plants in restoration initiatives. [ABSTRACT FROM AUTHOR]

Abstract: In 2001, I synthesised published information on mistletoe--animal interactions, demonstrating the pervasive influence these hemiparasites have on community composition and proposing that mistletoes represent keystone resources. Although the review [...]