Distribution Of Mistletoe Research Articles

Distribution of Dwarf Mistletoes (Arceuthobium spp., Viscaceae) in Durango, Mexico

ABSTRACT The dwarf mistletoes (Arceuthobium spp., Viscaceae) are an ecologically and economically important group of hemi-parasitic flowering plants that parasitize members of the Pinaceae in both the Old and New Worlds. There are two areas of maximum diversity for the dwarf mistletoes: northern California and Durango, Mexico. Here we provide additional information on the distribution of dwarf mistletoes in Durango based on field observations and herbarium collections. This information supplements data provided in a monograph on Arceuthobium published in 1996. Needed research on the dwarf mistletoes in Durango is also discussed. Key words: Arceuthobium, distribution, dwarf mistletoes, Durango, Mexico.

Parasites boost productivity: effects of mistletoe on litterfall dynamics in a temperate Australian forest

The importance of litter in regulating ecosystem processes has long been recognised, with a growing appreciation of the differential contribution of various functional plant groups. Despite the ubiquity of mistletoes in terrestrial ecosystems and their prominence in ecological studies, they are one group that have been overlooked in litter research. This study evaluated the litter contribution from a hemiparasitic mistletoe, Amyema miquelii (Lehm. ex Miq.) Tiegh., in an open eucalypt forest (Eucalyptus blakelyi, E. dwyeri and E. dealbata), at three scales; the forest stand, single trees and individual mistletoes. Litter from mistletoes significantly increased overall litterfall by up to 189%, the amount of mistletoe litter being proportional to the mistletoe biomass in the canopy. The high litter input was due to a much higher rate of mistletoe leaf turnover than that of host trees; the host litterfall and rate of leaf turnover was not significantly affected by mistletoe presence. The additional litter from mistletoes also affected the spatial and temporal distribution of litterfall due to the patchy distribution of mistletoes and their prolonged period of high litterfall. Associated with these changes in litterfall was an increase in ground litter mass and plant productivity, which reflects similar findings with root-parasitic plants. These findings represent novel mechanisms underlying the role of mistletoes as keystone resources and provide further evidence of the importance of parasites in affecting trophic dynamics.

Charting the Isophasic Endophyte of Dwarf Mistletoe Arceuthobium douglasii (Viscaceae) in Host Apical Buds

Dwarf mistletoes (Arceuthobium; Viscaceae) are highly specialized dioecious angiosperms parasitic on many gymnosperm hosts in the northern hemisphere. Several dwarf mistletoe species are capable of inducing an unusual form of isophasic infection in which the internal (endophytic) system proliferates even into the apical buds of its hosts. Studies of the internal endophytic system have, for the most part, focused on the parasite within secondary host tissues. The present anatomical and ultrastructural study characterizes the growth pattern of the isophasic endophytic system of Arceuthobium douglasii within the dormant apical buds of Pseudotsuga menziesii. Semi-thin serial sections from dwarf mistletoe-infected host apical buds were mounted, stained and micrographed. Graphic files were created from the serial micrographs and these files were stacked. These stacked files were utilized to describe the pattern of growth of the endophyte within the host tissue. The interface between cells of the mistletoe and host was also examined at the ultrastructural level by transmission electron microscopy. By utilizing a novel technique of superimposed graphics, the current study reveals an organized pattern of mistletoe distribution that penetrates further into host tissues than previously known. A consistent pattern of growth occurring even into the preformed leaves of the host is documented. The apparently non-intrusive growth of the parasite appears to be developmentally synchronized with that of the host. No symplastic connections were observed in the ultrastructural examination of the parasite/host interface within the apical buds of Pseudotsuga menziesii parasitized by A. douglasii or of Pinus contorta parasitized by A. americanum.

Diversity, Distribution and Host Range of Mistletoes in Godawari-Phulchoki Area, Kathmandu, Nepal

Diversity, Distribution and Host Range of Mistletoes in Godawari-Phulchoki Area, Kathmandu, Nepal

Distribution and dispersal of desert mistletoe is scale‐dependent, hierarchically nested

Spatial patterns are important to many ecological processes, and scale is a critical component of both patterns and processes. I examined the pattern and scale of the spatial distribution of infection of host plants by the desert mistletoe, Phoradendron californicum, in a landscape that spans several square kilometers. I also studied the relationship between mistletoe infection and seed dispersal. I found elevated seed rain in areas with a high prevalence of mistletoes and I found that a greater proportion of trees receive seeds than are infected, suggesting that mistletoes will be aggregated in space. Using nested analysis of variance and variograms, I found that mistletoe infections were distributed in hierarchical patches. Mistletoes were aggregated within trees and mistletoe prevalence was correlated at scales of <1500 m, and at scales >4000 m. Patterns at the largest scales were correlated with elevation: sites at higher elevations showed reduced mistletoe infection compared to those at lower elevations. I propose that at small scales, mistletoe distributions are primarily the result of aggregation of seed‐dispersing birds, and that the elevational effect could reflect the recent colonization of higher elevations by the mistletoes' mesquite hosts or the limits of the mistletoes' physiological tolerance to freezing‐induced cavitation.

WHERE DOES A FRUIT-EATING BIRD DEPOSIT MISTLETOE SEEDS? SEED DEPOSITION PATTERNS AND AN EXPERIMENT

The distribution of desert mistletoes (Phoradendron californicum) among mesquite (Prosopis velutina) hosts is significantly aggregated. We hypothesized that the aggregation of mistletoes among hosts is produced by the pattern of seed rain generated by seed dispersers. We tested whether frugivorous Phainopeplas (Phainopepla nitens) foraged preferentially, and hence deposited mistletoe seeds disproportionately, in already parasitized mesquites. We found that Phainopeplas favored parasitized tall trees as perching and feeding sites and deposited mistletoe seeds disproportionately on trees with these characteristics. To assess experimentally the effect of the presence of mistletoes on seed deposition, we removed mistletoes from host trees. Before mistletoe removal, seed deposition was equivalent and temporally correlated in pairs of control and removal trees. After removal, deposition was lower into removal trees than into unmanipulated trees. Although mistletoe removal resulted in lower seed deposition, it did not eliminate it. We inferred that seed deposition into parasitized hosts can result from deposition of seeds originating from within a host and from other infected hosts. We conclude that the response of seed-dispersing birds to mistletoes leads to disproportionate seed deposition into already parasitized trees and that the heterogeneous distribution of seeds among hosts created by birds contributes to the clumped distribution of mistletoes among hosts.

Where Does a Fruit-Eating Bird Deposit Mistletoe Seeds? Seed Deposition Patterns and an Experiment

The distribution of desert mistletoes (Phoradendron californicum) among mesquite (Prosopis velutina) hosts is significantly aggregated. We hypothesized that the aggregation of mistletoes among hosts is produced by the pattern of seed rain generated by seed dispersers. We tested whether frugivorous Phainopeplas (Phainopepla nitens) foraged preferentially, and hence deposited mistletoe seeds disproportionately, in already parasitized mesquites. We found that Phainopeplas favored parasitized tall trees as perching and feeding sites and deposited mistletoe seeds disproportionately on trees with these characteristics. To assess experimentally the effect of the presence of mistletoes on seed deposition, we removed mistletoes from host trees. Before mistletoe removal, seed deposition was equivalent and temporally correlated in pairs of control and removal trees. After removal, deposition was lower into removal trees than into unmanipulated trees. Although mistletoe removal resulted in lower seed deposition, it did not eliminate it. We inferred that seed deposition into parasitized hosts can result from deposition of seeds originating from within a host and from other infected hosts. We conclude that the response of seed-dispersing birds to mistletoes leads to disproportionate seed deposition into already parasitized trees and that the heterogeneous distribution of seeds among hosts created by birds contributes to the clumped distribution of mistletoes among hosts.

Fragmentation, Disturbance, and Plant Distribution: Mistletoes in Woodland Remnants in the Western Australian Wheatbelt

Spatial heterogeneity and patchy distributions of species in intact landscapes are likely to lead to complex and unpredictable distribution patterns in remnants following fragmentation. We examined this proposition in relation to the mistletoe Amyema miquelii, which exhibits a clumped distribution in Eucalyptus salmonophloia woodlands in the Western Australian wheatbelt. We sampled mistletoe distribution and abundance in 14 woodland fragments ranging from 2.4 to 60.5 ha and in 14 sections of roadside corridors. These sites represent all known fragments and corridors containing E. salmonophloia in a 1680‐km2 study area. We found that large fragments were more likely to have mistletoes than small fragments, but that small fragments either contained many or few to no mistletoes, reflecting the way fragmentation “samples” the pre‐existing distribution. Superimposed on this sampling effect is the influence of disturbance. Fragments subjected to stock grazing contained no mistletoes. This indicates that grazing modified the habitat either for the mistletoe itself, through changed water relations, or for the frugivorous birds which may disperse mistletoe fruit, through removal of the shrubby understory. Only one A. miquelii plant was found on 26.3 km of roadside corridor, despite tree densities in corridors being similar to those in fragments. Roadside areas are generally considered good habitat for mistletoes, and their absence suggested that fruit‐dispersing birds either did not use the corridors or did not stay in them long enough to deposit mistletoe seeds. These results indicate that, in order to predict biotic responses to fragmentation, information on distribution patterns and scales of patchiness in the prefragmentation landscape is required and the effects of fragmentation per se are likely to be confounded by other factors such as disturbance. Furthermore, quantifying fragmentation effects is difficult because of the small sample sizes typical of highly fragmented landscapes.

Dispersal and Infection in Mistletoe Metapopulations

1 The influence of dispersal patterns on the local distribution and abundance of the mistletoe, Phrygilanthus sonorae (Loranthaceae) is investigated. 2 Mistletoe and host distributions were measured at several subsites at two field sites in Baja California. Dispersal patterns were determined both by bird observation and the locations of dispersed seeds. The observed correlations between patterns of dispersal and patterns of mistletoe infection are interpreted by treating the mistletoe population as a metapopulation of the mistletoes on individual trees. 3 Mistletoe seeds were dispersed artificially to test experimentally for differences in the establishment success of mistletoe seedlings between individuals within a host species or between host species. No evidence was found for individual differences in susceptibility of hosts within a site or for host specific races of Phrygilanthus sonorae. 4 Sites and subsites differed dramatically in frugivore sets, dispersal patterns and the relative density of host trees (relative to all large trees and shrubs in the community). 5 A number of patterns of mistletoe distribution are explained by dispersal. Within subsites, the proportion of a size class infected by mistletoes (cohort occupancy) increases with the size of the class.. This size-occupancy relationship is predicted from a metapopulation model with patch (tree) turnover. Subsites within sites differ in the slope of the size-occupancy relationship and in the overall proportion of hosts infected by mistletoes (overall occupancy). These differences between subsites are explained by differences in the proportion of mistletoe seeds that are dispersed off the parent host tree and the efficiency of the off-tree dispersal, but not by overall dispersal efficiency. 6 Differences in mistletoe establishment success, adult mistletoe mortality and host turnover do not explain the observed patterns of infection.

The Distribution of Mistletoes in South Africa: Patterns of Species Richness and Host Choice

We analysed distribution records of mistletoes (Loranthaceae and Viscaceae) in South Africa in terms of host taxa and geographic patterns. Few species are found in nutri- ent-poor Cape shrublands (fynbos) and in the southern ever- green forests on nutrient-poor sands. The most species-rich areas are the nutrient-rich mesic savannas (including Valley Bushveld, a subset of savanna). Mistletoe species richness is significantly correlated with the average nitrogen levels of the woody plants in any biome, suggesting that the overall nutri- ent status of a biome influences mistletoe species richness. The analysis of host-choice of mistletoes also indicates a non-random distribution; thirty-three genera in twenty-two plant families host from three to twenty-four different mistle- toe species, suggesting that parasitism is not related to phylo- genetic position. The most important host genera are Acacia (hosting twenty-four spp. mistletoes), followed by Combretum (fourteen), Maytenus (thirteen) and Rhus (twelve). The species richness of mistletoes on host genera is significantly correlated with mean host N, and in four of five areas sampled, the number of mistletoes on host trees was significantly correlated with host N.

Distribution of Arceuthobium divaricatum and Phoradendron juniperinum (Viscaceae) on the South Rim of Grand Canyon, Arizona

The distribution and effects of the mistletoes Arceuthobium divaricatum Engelm. on Pinus edulis Engelm. and Phoradendron juniperinum Engelm. on Juniperus osteosperma (Torr.) Little on the pinyon-juniper vegetation type on the south rim of Grand Canyon National Park were investigated. Fire was the most limiting factor in the distribution of the mistletoes. The incidence of infection increased as trunk diameter and height increased in both pinyon and juniper. Arceuthobium divaricatum had the more serious impact on its host in respect to both vigor and mortality. Both mistletoes appear to be in equilibrium with their hosts at this time. Two mistletoes of the pinyon-juniper ecosystem of the Grand Canyon are Arceuthobium divaricatum Engelm. and Phoradendron juniperinum Engelm. Research on A. divaricatum and P. juniper- inum has been extremely limited because the trees infected have not been economically important as timber resources. With rising in- terest in utilization of the resources of the pinyon-juniper vegetation type, especially in a recreational capacity, effective management of these stands will be paramount in national parks and recreation areas (Clary 1975). Information on the site preferences and environmental factors that predispose the host trees to mistletoe infection will fa- cilitate management of diseased stands. This study was conducted to determine the distribution and effects of dwarf mistletoe on pinyon (Pinus edulis Engelm.) and true mistletoe on juniper (Juniperus osteosperma (Torr.) Little) on the South Rim at Grand Canyon Na- tional Park, Arizona.

Diversity, distribution and host range of mistletoe in protected and unprotected areas of Central Nepal Himalayas

Diversity, distribution and host range of mistletoe were assessed in protected and unprotected areas of the Central Nepal Himalayas. This study recorded ten mistletoe species. Occurrence of all ten mistletoe species within the Shivpuri Nagarjun National Park (SNNP) was a clear indication that national parks provide better habitat for mistletoe species richness and thus a better opportunity for biodiversity conservation than in unprotected areas. For these mistletoes, a total of 34 host species of 21 unrelated families were documented. Scurrula genus of the Loranthaceae family had the highest number of species, the highest number of host species, and the widest altitudinal distribution. Variation in climatic factors, edge effect, disperser behaviour, fragmented forests and the availability of suitable host species determine the occurrence of a particular mistletoe species in a particular habitat. Key words: Diversity: distribution: host range: mistletoe: Nepal DOI: 10.3126/banko.v20i2.4797 Banko Janakari Vol.20(2) 2010 pp.14-20

Diversity, Host Range and Distribution of Mistletoes along Steep Altitudinal Gradient of Tribhuvan Highway, Central Nepal

A total of 11 mistletoe species, eight belonging to five genera in the family Loranthaceae and three species belonging to two genera in the family Viscaceae were documented from 43 host species belonging to 24 unrelated host families along Tribhuvan highway, central Nepal. Wide host range of Scurrula species (Loranthaceae) showed that they were more generalist and successfully parasitized as many hosts as encountered, while Viscaceae mistletoes showed narrow host range and high degree of host specificity since they infected a limited number of hosts. The irregular and patchy distribution of mistletoe along the highway was governed by three major factors: forest structure, site mesoclimate and availability of suitable host species. Marginal fragmented forests located along the warm sunny slopes of highway were found as most suitable habitat. Warmer southern sunny slopes, between Sinbhanjyang to Bahise Dobhan, favoured wider altitudinal distribution range of mistletoe compared to cold and moist northern slopes.DOI: 10.3126/on.v8i1.4317

Distribution of Mistletoe

Distribution of Mistletoe