Host Specificity of North AmericanRhabdiasspp. (Nematoda: Rhabdiasidae): Combining Field Data and Experimental Infections with a Molecular Phylogeny

2013 ◽  
Vol 99 (2) ◽  
pp. 277-286 ◽  
Author(s):  
Gabriel J. Langford ◽  
John Janovy
2008 ◽  
Vol 98 (5) ◽  
pp. 499-507 ◽  
Author(s):  
H.C. Zhang ◽  
G.X. Qiao

AbstractThree traditional tribes of Fordini, Pemphigini and Eriosomatini comprise Pemphiginae, and there are two subtribes in Fordini and Pemphigini, respectively. Most of the species in this subfamily live heteroecious holocyclic lives with distinct primary host specificity. The three tribes of Pemphigini (except Prociphilina), Eriosomatini and Fordini use three families of plants, Salicaceae (Populus), Ulmaceae (Ulums) and Anacardiaceae (Pistacia and Rhus), as primary hosts, respectively, and form galls on them. Therefore, the Pemphigids are well known as gall makers, and their galls can be divided into true galls and pseudo-galls in type. We performed the first molecular phylogenetic study of Pemphiginae based on molecular data (EF-1α sequences). Results show that Pemphiginae is probably not a monophylum, but the monophyly of Fordini is supported robustly. The monophyly of Pemphigini is not supported, and two subtribes in it, Pemphigina and Prociphilina, are suggested to be raised to tribal level, equal with Fordini and Eriosomatini. The molecular phylogenetic analysis does not show definite relationships among the four tribes of Pemphiginae, as in the previous phylogenetic study based on morphology. It seems that the four tribes radiated at nearly the same time and then evolved independently. Based on this, we can speculate that galls originated independently four times in the four tribes, and there is no evidence to support that true galls are preceded by pseudo-galls, as in the case of thrips and willow sawflies.


2020 ◽  
Vol 5 (1) ◽  
pp. 17-38 ◽  
Author(s):  
K. Seto ◽  
S. Van Den Wyngaert ◽  
Y. Degawa ◽  
M. Kagami

During the last decade, the classification system of chytrids has dramatically changed based on zoospore ultrastructure and molecular phylogeny. In contrast to well-studied saprotrophic chytrids, most parasitic chytrids have thus far been only morphologically described by light microscopy, hence they hold great potential for filling some of the existing gaps in the current classification of chytrids. The genus Zygorhizidium is characterized by an operculate zoosporangium and a resting spore formed as a result of sexual reproduction in which a male thallus and female thallus fuse via a conjugation tube. All described species of Zygorhizidium are parasites of algae and their taxonomic positions remain to be resolved. Here, we examined morphology, zoospore ultrastructure, host specificity, and molecular phylogeny of seven cultures of Zygorhizidium spp. Based on thallus morphology and host specificity, one culture was identified as Z. willei parasitic on zygnematophycean green algae, whereas the others were identified as parasites of diatoms, Z. asterionellae on Asterionella, Z. melosirae on Aulacoseira, and Z. planktonicum on Ulnaria (formerly Synedra). According to phylogenetic analysis, Zygorhizidium was separated into two distinct order-level novel lineages; one lineage was composed singly of Z. willei, which is the type species of the genus, and the other included the three species of diatom parasites. Zoospore ultrastructural observation revealed that the two lineages can be distinguished from each other and both possess unique characters among the known orders within the Chytridiomycetes. Based on these results, we accommodate the three diatom parasites, Z. asterionellae, Z. melosirae, and Z. planktonicum in the distinct genus Zygophlyctis, and propose two new orders: Zygorhizidiales and Zygophlyctidales.


Parasitology ◽  
2001 ◽  
Vol 123 (1) ◽  
pp. 67-70 ◽  
Author(s):  
S. KOCK

The avian schistosomatid Trichobilharzia ocellata plays an important role as causative agent of cercarial dermatitis of humans in Europe. In order to improve the taxonomic knowledge on this parasite, studies of miracidial chemo-orientation as well as experimental infections of different snail species were conducted using strains of T. ocellata and T. franki. Both schistosomes exhibited a high intermediate host specificity. The miracidia clearly preferred the SCW (snail-conditioned water) of the respective natural intermediate host to SCW of other sympatric snail species. T. ocellata proved to be capable of infecting Lymnaea stagnalis and Stagnicola palustris, but could not develop in Radix ovata or R. auricularia. T. franki established an infection in specimens of R. auricularia and R. ovata, but not in L. stagnalis or S. palustris. The results imply that the intermediate host spectrum of T. ocellata is limited to L. stagnalis and S. palustris. Findings of T. ocellata (or Cercaria ocellata) that originated from snails of the genus Radix are likely to have actually belonged to species such as T. franki or T. regenti. The assumption that T. szidati is synonymous to T. ocellata is also discussed.


Biologia ◽  
2012 ◽  
Vol 67 (3) ◽  
Author(s):  
Anna Skoracka ◽  
Lechosław Kuczyński

AbstractFor the majority of eriophyoid species, host ranges have been established purely on the basis of collection records, usually without quantitative data. The aim of this study was to: (1) quantitatively examine published literature to explore whether relevant analyses of field-collected quantitative data were used to assess host specificity of herbivores; (2) propose a protocol for data analysis that could be applied to plant-feeding mites; (3) analyse host specificity of the grass-feeding Aceria species as a case study. Field data were collected in Central and Northern Europe over a period of 11 years, and included 73 grass species. For the eight Aceria species found, infestation parameters and host specificity indexes were assessed. Accumulation curves were calculated to study how the sampling effort influenced estimates of host specificity indexes. A literature analysis showed that among the studies that declared an aim of estimating the host range only 56% of them applied any quantitative analysis or informed on estimation reliability. The analysis of field-collected data and its interpretation showed the most complete and reliable conclusions about the host specificity of Aceria species when all indices were considered and, if available, other information about the mite’s ecology and biology. It was shown that estimates of host specificity could be strongly affected by sampling effort, and that several hundreds of samples should be collected for measuring the host specificity of grass-infesting mites, at least. Recommendations regarding host specificity estimation on the basis of field data are given.


2006 ◽  
Vol 73 (4) ◽  
pp. 1120-1125 ◽  
Author(s):  
Diego Libkind ◽  
Alejandra Ruffini ◽  
Maria van Broock ◽  
Leonor Alves ◽  
Jos� Paulo Sampaio

ABSTRACT Phaffia rhodozyma (sexual form, Xanthophyllomyces dendrorhous) is a basidiomycetous yeast that has been found in tree exudates in the Northern Hemisphere at high altitudes and latitudes. This yeast produces astaxanthin, a carotenoid pigment with biotechnological importance because it is used in aquaculture for fish pigmentation. We isolated X. dendrorhous from the Southern Hemisphere (Patagonia, Argentina), where it was associated with fruiting bodies of Cyttaria hariotii, an ascomycetous parasite of Nothofagus trees. We compared internal transcribed spacer (ITS)-based phylogenies of P. rhodozyma and its tree host (Betulaceae, Corneaceae, Fagaceae, and Nothofagaceae) and found them to be generally concordant, suggesting that different yeast lineages colonize different trees and providing an explanation for the phylogenetic distance observed between the type strains of P. rhodozyma and X. dendrorhous. We hypothesize that the association of Xanthophyllomyces with Cyttaria derives from a previous association of the yeast with Nothofagus, and the sister relationship between Nothofagaceae and Betulaceae plus Fagaceae correlates with the phylogeny of X. dendrorhous strains originating from these three plant families. The two most basal strains of X. dendrorhous are those isolated from Cornus, an ancestral genus in the phylogenetic analysis of the host trees. Thus, we question previous conclusions that P. rhodozyma and X. dendrorhous represent different species since the polymorphisms detected in the ITS and intergenic spacer sequences can be attributed to intraspecific variation associated with host specificity. Our study provides a deeper understanding of Phaffia biogeography, ecology, and molecular phylogeny. Such knowledge is essential for the comprehension of many aspects of the biology of this organism and will facilitate the study of astaxanthin production within an evolutionary and ecological framework.


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