33 research outputs found
Non-overlap of hosts used by three congeneric and sympatric loranthaceous mistletoe species in an Amazonian savanna: host generalization to extreme specialization
No full textTwo main hypotheses predominate in the literature on mistletoe-host specificity: (1) mistletoes are only likely to specialize on plant species on which they are frequently deposited; and (2) compatibility between mistletoes and plant species is a prerequisite for mistletoe-host parasitism. I explored these hypotheses by studying the seed deposition patterns and mistletoe-host compatibility in populations of three congeneric and sympatric mistletoe species of the genus Psittacanthus (P. biternatus, P. eucalyptifolius and P. plagiophyllus - Loranthaceae). I recorded the presence or absence of these mistletoe species in 15 tree species in a savanna patch in Amazonia. Among the five tree species that I found to be potential hosts (at least one tree individual infected), I also recorded if they had at least one mistletoe seed of any species attached to their branches. Finally, I planted seeds of all mistletoe species on the same individual trees in various hosts and non-host species and recorded seed survivorship and seedling establishment within 7 (P. plagiophyllus) to 12 months (P. biternatus and P. eucalyptifolius) after planting. There was no overlap among trees used as hosts by the three Psittacanthus species. Th e most specialized mistletoe species occurred in different host tree species with low relative abundance at the study site (Psittacanthus eucalyptifolius on Vatairea macrocarpa (Benth.) Ducke, and P. plagiophyllus on Anacardium occidentale L.). Mistletoe-host compatibility, and not seed deposition patterns, was the factor most likely to explain patterns of host use by Psittacanthus species at this study site.Duas hipóteses principais predominam na literatura sobre a especificidade entre ervas-de-passarinho e hospedeiros: (1) ervas-de-passarinho só poderão se especializar em espécies de plantas em que elas são frequentemente depositadas; e (2) compatibilidade entre as ervas-depassarinho e as espécies de plantas é um prerequisito para o parasitismo. Explorei estas hipóteses com o estudo dos padrões de deposição de sementes e a compatibilidade entre ervas-de-passarinho e hospedeiros em populações de três espécies de ervas-de-passarinho congenéricas e simpátricas do gênero Psittacanthus (P. biternatus, P. eucalyptifolius and P. plagiophyllus - Loranthaceae) e registrei a presença ou ausência destas três espécies em 15 espécies de árvores em uma mancha de savana na Amazônia. Entre as cinco espécies de árvores que eu encontrei infectadas, também registrei se elas possuíam pelo menos uma semente de erva-de-passarinho de qualquer das espécies aderida aos seus galhos. Finalmente, plantei sementes de todas as espécies de ervas-de-passarinho nas mesmas árvores em várias espécies de hospedeiros e não-hospedeiros e registrei a sobrevivência das sementes e o estabelecimento ao final de 7 (P. plagiophyllus) e 12 meses (P. biternatus e P. eucalyptifolius). Não houve sobreposição entre as árvores utilizadas como hospedeiros pelas três espécies de Psittacanthus. As espécies de ervas-de-passarinho mais especializadas ocorreram em diferentes espécies de hospedeiros com baixa abundância relativa na área de estudo (Psittacanthus eucalyptifolius em Vatairea macrocarpa (Benth.) Ducke, e P. plagiophyllus em Anacardium occidentale L.). A compatibilidade entre a erva-de-passarinho e o hospedeiro, e não o padrão de deposição de sementes, foi o fator mais propício a explicar os padrões de uso de hospedeiros por Psittacanthus neste local
Fire and host abundance as determinants of the distribution of three congener and sympatric mistletoes in an Amazonian savanna
No full textMost mistletoe species that live in savanna patches are subjected to frequent fires. Although having similar habits, even congener species may parasitize very different host species and show different degrees of specialization that may differentially affect their resistance to fire. We studied three congener mistletoe species with a diverse degree of specificity to their hosts: Psittacanthus biternatus, Psittacanthus eucalyptifolius and Psittacanthus plagiophyllus, the first being the most generalist species, and the last the most specialist. We investigated their prevalence (proportion of hosts infected) in 35 plots of an Amazonian savanna, with different fire histories. Our aim was to understand if they respond similarly to fire frequency and the abundance of their hosts. Additionally, we experimentally applied fire to individuals of the three species using a portable propane flamethrower to test for the influence of mistletoe species, plant size and quantity of heat pulses (single or double burn) on mistletoe survivorship. Prevalence varied greatly among species: 1.5 percent for P. biternatus, 4.8 percent for P. eucalyptifolius and 20 percent for P. plagiophyllus. Prevalence of P. plagiophyllus was negatively related to fire frequency, while for the other two species it was not. Psittacanthus biternatus had a higher probability of survival compared with the other two species, and larger plants were more likely to survive under single burn treatment and to regenerate through sprouting. Our results suggest that, due to complex interactions between fire, hosts and mistletoes, even sympatric species may respond differently to fire frequency and host abundance. © 2011 The Author(s) Journal compilation © 2011 Association for Tropical Biology and Conservation
Modeling occupancy of hosts by mistletoe seeds after accounting for imperfect detectability.
No full textThe detection of an organism in a given site is widely used as a state variable in many metapopulation and epidemiological studies. However, failure to detect the species does not necessarily mean that it is absent. Assessing detectability is important for occupancy (presence-absence) surveys; and identifying the factors reducing detectability may help improve survey precision and efficiency. A method was used to estimate the occupancy status of host trees colonized by mistletoe seeds of Psittacanthus plagiophyllus as a function of host covariates: host size and presence of mistletoe infections on the same or on the nearest neighboring host (the cashew tree Anacardium occidentale). The technique also evaluated the effect of taking detectability into account for estimating host occupancy by mistletoe seeds. Individual host trees were surveyed for presence of mistletoe seeds with the aid of two or three observers to estimate detectability and occupancy. Detectability was, on average, 17% higher in focal-host trees with infected neighbors, while decreased about 23 to 50% from smallest to largest hosts. The presence of mistletoe plants in the sample tree had negligible effect on detectability. Failure to detect hosts as occupied decreased occupancy by 2.5% on average, with maximum of 10% for large and isolated hosts. The method presented in this study has potential for use with metapopulation studies of mistletoes, especially those focusing on the seed stage, but also as improvement of accuracy in occupancy models estimates often used for metapopulation dynamics of tree-dwelling plants in general
Correction: Modeling Occupancy of Hosts by Mistletoe Seeds after Accounting for Imperfect Detectability.
No full text[This corrects the article DOI: 10.1371/journal.pone.0127004.]
Towards best-practice management of mistletoes in horticulture
No full textMistletoe 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.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Summary of model selection for predicting both the occupancy and detectability of hosts (<i>Anacardium occidentale</i>) by seeds of the mistletoe <i>Psittacanthus plagiophyllus</i>.
No full text<p>Models were organized in decreasing order of importance. Only five of the 36 models and their respective resulting values are presented.</p><p>Summary of model selection for predicting both the occupancy and detectability of hosts (<i>Anacardium occidentale</i>) by seeds of the mistletoe <i>Psittacanthus plagiophyllus</i>.</p
Comparison of occupancy estimates of seeds of <i>Psittacanthus plagiophyllus</i> between two models: one using naïve estimates fitted with a logistic regression (logit (p) = 0.251 + 0.18 (host crown) - 1.64(neighbor)), and other using occupancy estimates accounted for detectability (first model of Table 1).
No full text<p>Comparison of occupancy estimates of seeds of <i>Psittacanthus plagiophyllus</i> between two models: one using naïve estimates fitted with a logistic regression (logit (p) = 0.251 + 0.18 (host crown) - 1.64(neighbor)), and other using occupancy estimates accounted for detectability (first model of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127004#pone.0127004.t001" target="_blank">Table 1</a>).</p
Seeds of <i>P</i>. <i>plagiophyllus</i> attached to a branch of <i>A</i>. <i>occidentale</i> (Photo: Leidielly Ghizoni).
No full text<p>Seeds of <i>P</i>. <i>plagiophyllus</i> attached to a branch of <i>A</i>. <i>occidentale</i> (Photo: Leidielly Ghizoni).</p
Occupancy (A) and detection probability (B) of mistletoe seeds of <i>Psittacanthus plagiophyllus</i> deposited on the host <i>Anacardium occidentale</i> according to proximity to infected hosts host size (host crown diameter).
No full text<p>Central markers represent means, and lines represent 95% confidence intervals. Both graphs were traced with estimates from the model Ψ (size+neighborhood), p (size+neighborhood).</p
Above-ground biomass estimation for a shrubby mistletoe in an Amazonian savanna
No full textMistletoes are considered keystone species on woodlands and savannas worldwide, providing a food resource for a diversified fauna, as well as a nutrient-enriched litter. Infections can be large (∼1-3 m) and, in some parts of the Amazonian savannas, parasitize up to 70% of hosts locally. Despite these facts, biomass of mistletoes is rarely investigated. Here we constructed allometric models to predict the biomass stock of the shrubby mistletoe Psittacanthus plagiophyllus in an Amazonian savanna. In addition, we determined whether host size could be used as a proxy for mistletoe biomass. Finally, we compared the biomass of mistletoes with that of trees, to evaluate their relative importance. We have shown that: (1) biomass of leaves (46.1% ± 13.5%) are as important as of stems (47.8% ± 13.5%), and relative contribution of stems increases as plant grows; (2) the model including width, breadth and vertical depth was the best (SE = 0.39, R2 = 0.9) for predicting individual mistletoe biomass; (3) mistletoe load and biomass per host had a positive, but weak (R2 = 0.11 and 0.09, respectively), relationship with host size, and thus such host information is a poor predictor of mistletoe biomass; and (4) in comparison with trees, mistletoes constituted less than 0.15% (0.5-22 kg ha-1) of the total above-ground biomass, suggesting that this life-form is irrelevant to the local biomass stock despite its unequivocal biological importance. © Cambridge University Press 2019
