The effect of host defoliation on hemiparasitic-host interactions between Rhinanthus serotinus and two Poa species

1999 ◽  
Vol 77 (4) ◽  
pp. 523-530 ◽  
Author(s):  
Susanna Puustinen ◽  
Veikko Salonen
Keyword(s):  
Host Species ◽  
Poa Pratensis ◽  
Parasitic Plant ◽  
Poa Annua ◽  
Total Biomass ◽  
Root Hemiparasite ◽  
Host Interactions ◽  
Relative Value ◽  
Grass Hosts ◽  
Host Parasite

We determined in a greenhouse experiment whether experimental defoliation of the host affects the performance of the parasitic plant and whether the effects on the success of the parasite depend on the host species. We also asked whether two species of grass hosts differ in response to simultaneous defoliation and hemiparasitic infection. The experiment had a complete 2 × 3 × 2 factorial design, with host species (Poa annua L. or Poa pratensis L.) combined with defoliation (undefoliated, 50% defoliated, or 100% defoliated) and hemiparasitic infection (parasitized or unparasitized). Defoliation reduced the final biomass of both host species. However, total biomass and the number of flowers produced by the hemiparasitic Rhinanthus serotinus (Schönh.) Oborny was reduced only when the host was P. annua and when the host was completely defoliated. Rhinanthus infection significantly decreased the final biomass of both host species. However, the two hosts differed in their responses: the biomass of undefoliated P. annua plants was reduced four times more than that of undefoliated P. pratensis plants. The results indicate that the relative value of different host species depends on the intensity of defoliation.Key words: root hemiparasite, host defoliation, host-parasite interaction, Poa annua, Poa pratensis, Rhinanthus serotinus.

The effects of seasonality on host–bat fly ecological networks in a temperate mountain cave

Parasitology ◽  
2016 ◽  
Vol 144 (5) ◽  
pp. 692-697 ◽  
Author(s):  
KARINA D. RIVERA-GARCÍA ◽  
CÉSAR A. SANDOVAL-RUIZ ◽  
ROMEO A. SALDAÑA-VÁZQUEZ ◽  
JORGE E. SCHONDUBE
Keyword(s):  
Species Composition ◽  
Host Species ◽  
Rainy Season ◽  
Ecological Networks ◽  
Host Interactions ◽  
Bat Flies ◽  
Bat Fly ◽  
Low Prevalence ◽  
Host Parasite

SUMMARYChanges in the specialization of parasite–host interactions will be influenced by variations in host species composition. We evaluated this hypothesis by comparing the composition of bats and bat flies within a roost cave over one annual. Five bat and five bat fly species occupied the cave over the course of the study. Bat species composition was 40% different in the rainy season compared with the dry–cold and dry–warm seasons. Despite the incorporation of three new bat species into the cave during the rainy season, bat fly species composition was not affected by seasonality, since the bats that arrived in the rainy season only contributed one new bat fly species at a low prevalence. Bat–bat fly ecological networks were less specialized in the rainy season compared with the dry–cold and dry–warm seasons because of the increase of host overlap among bat fly species during this season. This study suggests that seasonality promote: (1) differences in host species composition, and (2) a reduction in the specialization of host–parasite ecological networks.

EMBOLISM INCREASE AND ANATOMICAL MODIFICATIONS CAUSED BY A PARASITIC PLANT: PHORADENDRON CRASSIFOLIUM (SANTALACEAE) ON TAPIRIRA GUIANENSIS (ANACARDIACEAE)

IAWA Journal ◽  
2015 ◽  
Vol 36 (2) ◽  
pp. 138-151 ◽  
Author(s):  
Luíza Teixeira-Costa ◽  
Gregório Ceccantini
Keyword(s):  
Wood Anatomy ◽  
Direct Action ◽  
Xylem Sap ◽  
Wood Formation ◽  
Parasitic Plant ◽  
Hormonal Changes ◽  
Functional Changes ◽  
Host Trees ◽  
Xylem Sap Flow ◽  
Host Parasite

Parasitic plants are capable of causing a variety of effects to their hosts, including alterations in the process of wood formation. However, the majority of studies dealing with parasitic plant anatomy have focused on the host–parasite interface and the direct action of the haustorium, which is the organ responsible for attaching the parasite to the host. Considering this gap, we studied the anatomical and functional effects caused by a mistletoe species, Phoradendron crassifolium (Santalaceae), on the wood anatomy of the host tree Tapirira guianensis (Anacardiaceae). Both parasitized and non-parasitized branches were collected from host trees. Traditional wood anatomy procedures were employed, along with functionality experiments using the ascent of safranin solution through the xylem. Prior to the analysis, all sampled branches were divided in “upstream” and “downstream” portions, considering the direction of xylem sap flow inside the plant body. This design was chosen in order to avoid biased results derived from normal ontogeny-related wood anatomical and functional changes. Our results showed that infested wood expressed a higher density of embolized vessels, narrower vessel lumen diameter, higher vessel density, taller and wider rays, and fibers with thinner cell walls. All these responses were most conspicuous in the downstream sections of the parasitized branches. We propose that the wood anatomical and functional alterations were induced by the combination of water stress caused by water use by the parasite and consequent low turgor in differentiating cambial derivates; by unbalanced auxin/cytokinin concentrations originating at the infestation region due to phloem disruptions caused by the parasite’s penetration and action; and by higher than usual ethylene levels. Further analysis of hydraulic conductivity and hormonal changes in host branches are necessary to test this hypothesis.

scholarly journals Do parasites adopt different strategies in different intermediate hosts? Host size, not host species, influences Coitocaecum parvum (Trematoda) life history strategy, size and egg production

Parasitology ◽  
2012 ◽  
Vol 140 (2) ◽  
pp. 275-283 ◽  
Author(s):  
R. RUIZ DANIELS ◽  
S. BELTRAN ◽  
R. POULIN ◽  
C. LAGRUE
Keyword(s):  
Host Species ◽  
Egg Production ◽  
Life History Strategy ◽  
Host Size ◽  
Life Strategy ◽  
Amphipod Species ◽  
Intermediate Hosts ◽  
Host Interactions ◽  
Resource Limitations ◽  
Coitocaecum Parvum

SUMMARYHost exploitation induces host defence responses and competition between parasites, resulting in individual parasites facing highly variable environments. Alternative life strategies may thus be expressed in context-dependent ways, depending on which host species is used and intra-host competition between parasites. Coitocaecum parvum (Trematode) can use facultative progenesis in amphipod intermediate hosts, Paracalliope fluviatilis, to abbreviate its life cycle in response to such environmental factors. Coitocaecum parvum also uses another amphipod host, Paracorophium excavatum, a species widely different in size and ecology from P. fluviatilis. In this study, parasite infection levels and strategies in the two amphipod species were compared to determine whether the adoption of progenesis by C. parvum varied between these two hosts. Potential differences in size and/or egg production between C. parvum individuals according to amphipod host species were also investigated. Results show that C. parvum life strategy was not influenced by host species. In contrast, host size significantly affected C. parvum strategy, size and egg production. Since intra-host interactions between co-infecting parasites also influenced C. parvum strategy, size and fecundity, it is highly likely that within-host resource limitations affect C. parvum life strategy and overall fitness regardless of host species.

scholarly journals How host phenology impacts multi-season epidemic cycles

2021 ◽  
Author(s):  
Hannelore MacDonald ◽  
Dustin Brisson
Keyword(s):  
Mathematical Model ◽  
Population Dynamics ◽  
Population Cycles ◽  
Seasonal Activity ◽  
Host Interactions ◽  
Host Phenology ◽  
Demographic Impact ◽  
Host Parasite ◽  
Parasite Populations ◽  
Parasite Dynamics

Parasite-host interactions can result in periodic population dynamics when parasites over-exploit host populations. The timing of host seasonal activity, or host phenology, determines the frequency and demographic impact of parasite-host interactions which may govern if the parasite can sufficiently over-exploit their hosts to drive population cycles. We describe a mathematical model of a monocyclic, obligate-killer parasite system with seasonal host activity to investigate the consequences of host phenology on host-parasite dynamics. The results suggest that parasites can reach the densities necessary to destabilize host dynamics and drive cycling in only some phenological scenarios, such as environments with short seasons and synchronous host emergence. Further, only parasite lineages that are sufficiently adapted to phenological scenarios with short seasons and synchronous host emergence can achieve the densities necessary to over-exploit hosts and produce population cycles. Host-parasite cycles can also generate an eco-evolutionary feedback that slows parasite adaptation to the phenological environment as rare advantageous phenotypes are driven to extinction when introduced in phases of the cycle where host populations are small and parasite populations are large. The results demonstrate that seasonal environments can drive population cycling in a restricted set of phenological patterns and provides further evidence that the rate of adaptive evolution depends on underlying ecological dynamics.

Competition and the response of three plant species to a salinity gradient

1991 ◽  
Vol 69 (11) ◽  
pp. 2497-2502 ◽  
Author(s):  
N. C. Kenkel ◽  
A. L. McIlraith ◽  
C. A. Burchill ◽  
G. Jones
Keyword(s):  
Salt Tolerance ◽  
Interspecific Competition ◽  
Poa Pratensis ◽  
Salinity Gradient ◽  
Belowground Biomass ◽  
Peak Performance ◽  
Total Biomass ◽  
Salinity Response ◽  
Hordeum Jubatum ◽  
Puccinellia Nuttalliana

Three grasses (Poa pratensis, Hordeum jubatum, and Puccinellia nuttalliana) were grown in monoculture and three-species mixture at each of eight salinity levels in a controlled environment chamber. In monoculture, all species grew best when no salts were added to the nutrient medium. When salts were added the species showed differing degrees of salt tolerance. Percent decreases in total biomass with increasing salinity and shifts in aboveground to belowground biomass ratios suggested increased salt tolerance in the order P. pratensis < H. jubatum < P. nuttalliana. In mixture, all species showed a significant change in salinity response when compared with their responses in monoculture. Interspecific competition resulted in P. pratensis being suppressed at all but the lowest salinities. Hordeum jubatum showed the least suppression at intermediate salinities, while P. nuttalliana was least suppressed at the highest salinities. These results indicate that interspecific competition results in a shift in the peak performance of more salt-tolerant species toward the high end of the salinity gradient. The species distributions in our experimental mixtures reflected those observed in the field, suggesting that competition plays an important role in structuring inland saline plant communities. Key words: halophyte, glycophyte, community, Hordeum jubatum, Puccinellia nuttalliana, Poa pratensis.

Predicting the potential distribution ofVexillata(Nematoda: Ornithostrongylidae) and its hosts (Mammalia: Rodentia) within America

2012 ◽  
Vol 87 (4) ◽  
pp. 400-408 ◽  
Author(s):  
E.A. Martínez-Salazar ◽  
T. Escalante ◽  
M. Linaje ◽  
J. Falcón-Ordaz
Keyword(s):  
Environmental Factor ◽  
Species Distribution ◽  
Host Species ◽  
Potential Distribution ◽  
Species Distribution Modelling ◽  
Distribution Modelling ◽  
Distributional Patterns ◽  
Suitable Habitats ◽  
Temperature Seasonality ◽  
Host Parasite

AbstractSpecies distribution modelling has been a powerful tool to explore the potential distribution of parasites in wildlife, being the basis of studies on biogeography.Vexillataspp. are intestinal nematodes found in several species of mammalian hosts, such as rodents (Geomyoidea) and hares (Leporidae) in the Nearctic and northern Neotropical regions. In the present study, we modelled the potential distribution ofVexillataspp. and their hosts, using exclusively species from the Geomyidae and Heteromyidae families, in order to identify their distributional patterns. Bioclimatic and topographic variables were used to identify and predict suitable habitats forVexillataand its hosts. Using these models, we identified that temperature seasonality is a significant environmental factor that influences the distribution of the parasite genus and its host. In particular, the geographical distribution is estimated to be larger than that predicted for its hosts. This suggests that the nematode has the potential to extend its geographical range and also its spectrum of host species. Increasing sample size and geographical coverage will contribute to recommendations for conservation of this host–parasite system.

Composition patterns and network structure of epiphyte–host interactions in Chilean and New Zealand temperate forests

2021 ◽  
Author(s):  
A Taylor ◽  
A Saldaña ◽  
G Zotz ◽  
C Kirby ◽  
I Díaz ◽  
...  
Keyword(s):  
New Zealand ◽  
Host Species ◽  
Species Interactions ◽  
Temperate Forests ◽  
Null Model ◽  
Host Interactions ◽  
Host Trees ◽  
Specific Host ◽  
Random Patterns ◽  
Epiphyte Species

Ecological networks are becoming increasingly used as a framework to study epiphyte–host interactions. However, efforts to quantify the properties of epiphyte–host networks have produced inconsistent results. Epiphyte–host interactions in New Zealand and Chilean temperate forests were quantified to test for non-random patterns in nestedness, negative co-occurrences, number of links, and network specialisation. Results showed that three out of five New Zealand networks were significantly more nested than null model expectations, compared with just one out of four Chilean networks. Epiphytes co-occurred more often than null model expectations in one New Zealand network and one in Chile. In all cases, the number of links maintained by each epiphyte and host species was consistent with null model expectations. Lastly, two New Zealand networks and one in southern Chile were significantly less specialised than null model expectations, with all remaining networks returning low specialisation scores. As such, aside from the tendency for greater nestedness in New Zealand networks, most epiphyte species were distributed on their host trees at random. We attribute the result of nestedness in New Zealand to the abundance of large nest epiphytes (Astelia spp. in particular), which may facilitate the sequential colonisation of epiphyte species on developing host trees. The lack of negative co-occurrences suggests that negative species interactions are not an important determinant of species assemblage structure. Low network specialisation scores suggest that epiphytes are selecting for specific host traits, rather than specific host species for colonisation.

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