Molecular Phylogeny and Coevolution

Abstract Recent advances in molecular phylogenetic estimation in diverse organisms have improved our understanding of coevolution. From the phylogenies of interacting organisms, we can interpret the evolution of adaptive characters, and the history of interaction. Molecular approaches are generally more informative than these based solely on phenotypic characters. Molecular genetic method can be applied to organisms that have only simple morphological features and can be used for comparisons at any taxonomic level. Estimation of divergence time is also possible but still difficult because evolutionary rates of macromolecules are not always constant and suitable fossil records are often not available for calibrating rates of change. Here I review recent progress in the application of molecular techniques to the interpretation of coevolutionary relationships.     

An invasive species reverses the roles in a host-parasite relationship between bitterling fish and unionid mussels

The impact of multiple invading species can be magnified owing to mutual facilitation--termed 'invasional meltdown'--but invasive species can also be adversely affected by their interactions with other invaders. Using a unique reciprocal host-parasite relationship between a bitterling fish (Rhodeus amarus) and unionid mussels, we show that an invasive mussel reverses the roles in the relationship. Bitterling lay their eggs into mussel gills, and mussel larvae parasitize fish. Bitterling recently colonized Europe and parasitize all sympatric European mussels, but are unable to use a recently invasive mussel, Anodonta woodiana. The parasitic larvae of A. woodiana successfully develop on R. amarus, whereas larvae of European mussels are rejected by bitterling. This demonstrates that invading species may temporarily benefit from a coevolutionary lag by exploiting evolutionarily naive hosts, but the resulting relaxed selection may facilitate its exploitation by subsequent invading species, leading to unexpected consequences for established interspecific relationships.     

The impact of environmental change on host-parasite coevolutionary dynamics

Environmental factors are known to affect the strength and the specificity of interactions between hosts and parasites. However, how this shapes patterns of coevolutionary dynamics is not clear. Here, we construct a simple mathematical model to study the effect of environmental change on host-parasite coevolutionary outcome when interactions are of the matching-alleles or the gene-for-gene type. Environmental changes may effectively alter the selective pressure and the level of specialism in the population. Our results suggest that environmental change altering the specificity of selection in antagonistic interactions can produce alternating time windows of cyclical allele-frequency dynamics and cessation thereof. This type of environmental impact can also explain the maintenance of polymorphism in gene-for-gene interactions without costs. Overall, our study points to the potential consequences of environmental variation in coevolution, and thus the importance of characterizing genotype-by-genotype-by-environment interactions in natural host-parasite systems, especially those that change the direction of selection acting between the two species.     

Molecular characterization of an ancient Hepatozoon species parasitizing the 'living fossil' marsupial 'Monito del Monte' Dromiciops gliroides from Chile

The Microbiotheriid Dromiciops gliroides , also known as 'Monito del Monte', is considered to be a threatened species and the only living representative of this group of South American marsupials. During the last few years, several blood samples from specimens of 'Monito del Monte' captured at Chiloé island in Chile have been investigated for blood parasites. Inspection of blood smears detected a Hepatozoon species infecting red blood cells. The sequences of DNA fragments corresponding to small subunit ribosomal RNA gene revealed two parasitic lineages belonging to Hepatozoon genus. These parasite lineages showed a basal position with respect to Hepatozoon species infecting rodents, reptiles, and amphibians but are phylogenetically distinct from Hepatozoon species infecting the order Carnivora. In addition, the Hepatozoon lineages infecting D. gliroides are also different from those infecting other micro-mammals living in sympatry, as well as from some that have been described to infect an Australian species of bandicoot. The potential vector of this parasite appears to be the host-specific tick Ixodes neuquenensis because the sequencing of a long amplicon determined the presence of one of the two lineages found in the marsupial.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 568–576.     

Genetic variation in a host-parasite association: potential for coevolution and frequency-dependent selection

Abstract.— Models of host‐parasite coevolution assume the presence of genetic variation for host resistance and parasite infectivity, as well as genotype‐specific interactions. We used the freshwater crustacean Daphnia magna and its bacterial microparasite Pasteuria ramosa to study genetic variation for host susceptibility and parasite infectivity within each of two populations. We sought to answer the following questions: Do host clones differ in their susceptibility to parasite isolates? Do parasite isolates differ in their ability to infect different host clones? Are there host clone‐parasite isolate interactions? The analysis revealed considerable variation in both host resistance and parasite infectivity. There were significant host clone‐parasite isolate interactions, such that there was no single host clone that was superior to all other clones in the resistance to every parasite isolate. Likewise, there was no parasite isolate that was superior to all other isolates in infectivity to every host clone. This form of host clone‐parasite isolate interaction indicates the potential for coevolution based on frequency‐dependent selection. Infection success of original host clone‐parasite isolate combinations (i.e., those combinations that were isolated together) was significantly higher than infection success of novel host clone‐parasite isolate combinations (i.e., those combinations that were created in the laboratory). This finding is consistent with the idea that parasites track specific host genotypes under natural conditions. In addition, correspondence analysis revealed that some host clones, although distinguishable with neutral genetic markers, were susceptible to the same set of parasite isolates and thus probably shared resistance genes.     

Infection success in novel hosts: an experimental and phylogenetic study of Drosophila-parasitic nematodes

Surprisingly little is known about what determines a parasite's host range, which is essential in enabling us to predict the fate of novel infections. In this study, we evaluate the importance of both host and parasite phylogeny in determining the ability of parasites to infect novel host species. Using experimental lab assays, we infected 24 taxonomically diverse species of Drosophila flies (Diptera: Drosophilidae) with five different nematode species (Tylenchida: Allantonematidae: Howardula, Parasitylenchus), and measured parasite infection success, growth, and effects on female host fecundity (i.e., virulence). These nematodes are obligate parasites of mushroom-feeding Drosophila, particularly quinaria and testacca group species, often with severe fitness consequences on their hosts. We show that the potential host ranges of the nematodes are much larger than their actual ranges, even for parasites with only one known host species in nature. Novel hosts that are distantly related from the native host are much less likely to be infected, but among more closely related hosts, there is much variation in susceptibility. Potential host ranges differ greatly between the related parasite species. All nematode species that successfully infected novel hosts produced infective juveniles in these hosts. Most novel infections did not result in significant reductions in the fecundity of female hosts, with one exception: the host specialist Parasitylenchus nearcticus sterilized all quinaria group hosts, only one of which is a host in nature. The large potential host ranges of these parasites, in combination with the high potential for host colonization due to shared mushroom breeding sites, explain the widespread host switching observed in comparisons of nematode and Drosophila phylogenies.     

The influence of thyroxine on the host-parasite relationship of Ancylostoma caninum in swiss albino mice

Bhai Ismail and Pandey A.K. 1981. The influence of thyroxine on the host-parasite relationship of Ancylostoma caninum in Swiss albino mice. International Journal for Parasitology11: 377–379. Thyroxine treatment, 1μg/0.3 ml saline/mouse/day for 21 days, significantly increased the susceptibility of female mice (P > 0.001) but not of males to Ancylostoma caninum infection, compared with their saline-treated controls. This accounted for the loss of the sex difference between the worm populations of male and female mice (0.001 < P < 0.005). More hyperthyroid females died following infection with A. caninum than control female mice. The possible reasons for higher susceptibility of female mice are discussed.     

Diversity and zoogeography of marine Tubificidae (Annelida,Oligochaeta) with notes on variation in widespread species

The specific and generic diversities of the marine Tubificidae (Annelida, Oligochaeta) of the NE Pacific are compared to those of the NE and NW Atlantic as well as to those of Heron Island, Australia. Diversity in the NE Pacific is relatively high when compared to that of the NE Atlantic. The Tubificidae of the NW Atlantic (limited to the eastern coast of the USA) show two distinct zoogeographic regions: Florida to Cape Hatteras; Cape Hatteras to Massachusetts. Diversity, both in terms of the number of species and number of genera, is approximately the same in these two regions, and is similar to that of both the NE Pacific and Heron Island. Evidence suggests that the widespread marine species, in particular Tubificoides pseudogaster, have a range of morphotypes across their distributions. The apparent wide distributions of these species may be due to a taxonomy unable to resolve the differences between the morphotypes. The tubificid oligochaete fauna of the NE Atlantic appears impoverished compared to the other regions examined. The NE Pacific, NW Atlantic, and Heron Island regions are not dominated by one group of species while the NE Atlantic fauna is dominated by Tubificoides benedeni and Clitellio arenarius.     

Progress in the study of ecology, zoogeography, group, control repellent and medical usage of Hirudinea in China

Hirudinea in China were reviewed. The ecological distribution of Hirudinea, the population dynamics of H. hainana, the adaptation of H. hainana to temperature, soil humidity and pH, the response of H. hainana to temperature, relative humidity and light, and the effects of human activities on H. hainana populations were discussed. The land-leeches' behavior ecology, including (1) the locomotion of H. hainana such as shortening, oscillating, rotating, sucking cleaning, rubbing and foraging behaviors; (2) the factors influencing these behaviors; (3) the ecological significance, was also discussed. The ecology of freshwater leeches including (1) behavior in paddy fields of Ninghsien, Zhejiang Province, China; (2) relationship between population dynamics of Whitmania laevis and chemical factors in paddy fields of Guangzhou, China; (3) chemical environment of blood-sucking Hirudinaria manillensis in paddy fields of Guangzhou was described. The study also discussed the foraging, growth dynamics, life recycle and biology of reproduction of blood-sucking land-leech H. hainana and freshwater leech Hirudinaria manillensis, the taxonomy and the zoogeography. In addition, the morphology including histology and anatomy of the organic system of H. hainana was described. The Hirudinea can be classified into 2 subclasses (Branchiobdellidea and Euhirudinea), 3 orders (Branchiobdellida, Rhynchobdellida and Arhynchobdellida), 9 families, 33 genera and 111 species. The response of leeches to pesticides, including toxicity (LD50, LD95) of different pesticides to H. hainana, was presented. Medical usage of the leech Hirudin from salivary glands as anticoagulant material was discussed. Hirudin (from Hirudo medicinalis), Haemadin (from land-leech), and hementi (from Hementeria ghilianii) were identified and isolated.     

Coevolution: Mathematical analysis of host-parasite interactions

An SIS epidemic transmitted by two similar strains of parasite acting on a host population of three genotypes which differ in their reaction to the disease is modelled and analyzed. Singular perturbation techniques are used to reduce the original system of nine differential equations to a coupled system of two equations describing the slowtime coevolution of gene frequency and parasite strain frequency.Karen Christine Beck died June 25, 1983 at home.Born February 8, 1952 in Madison, Wisconsin, She received a B.A. degree in 1974 from Luther College, Decorah, Iowa and a Ph.D. in mathematics in 1980 from the University of Iowa. Since that time she has been an instructor in the Mathematics Department at the University of Utah. She was to become an Assistant Professor at the University of Texas, Arlington, beginning Autumn, 1983. Dr. Beck's areas of specialization in mathematics were Mathematical Analysis and Mathematical Biology. She published numerous research articles that resolved various problems in these areas.     

中国蛭类动物生态地理类群特征及其防护医用研究进展

综述中国蛭类研究如下内容:(1)生态学.山蛭生态学,包括山蛭的生态分布,海南山蛭(H. hainana)的种群动态,对温度、土壤湿度和pH值的适应,以及对温、光、湿的综合反应和人类经济活动对其种群数量的影响;山蛭行为生态学,山蛭的运动包括慢缩短、快缩短、身体摆动和转动、洗刷运动、亲吻运动、觅食行为6程序,影响山蛭行为的一些因素以及对环境因素刺激的生态学意义;淡水水蛭生态学,包括浙江水田蛭类生活习性、广州水生光润金线蛭种群数量动态与水体化学因子关系、广州水田吸血菲牛蛭生活水体化学环境;山蛭和水生吸血菲牛蛭的觅食、生长动态、生命周期和生殖生物学;(2)形态学、分类学和动物地理学.形态学包括山蛭机能组织学、山蛭器官系统解剖;分类学,中国蛭类动物有2亚纲(蛭蚓亚纲、真蛭亚纲)、3目(蛭蚓目、吻蛭目、无吻目)、9科、33属、111种,占世界蛭类物种数约1/6;动物地理学,包括世界山蛭科属动物地理,中国山蛭科动物地理、中国医蛭科动物地理.(3)蛭类的防治和驱避,淡水吸血蛭类防治所用农药种类,不同农药对海南山蛭的毒力( LD50、LD95)及使用,并比较了12种驱避剂对海南山蛭的驱避效果.(4)蛭类的医学利用,蛭素是蛭类唾液腺分泌的一种抗凝物质,蛭素有水蛭素(Hirudin)、山蛭素(Haemadin)和吻蛭素(Hementin).记述了蛭素的分离、纯化和功能以及有关分子生物学内容.     

Progress in the study of ecology, zoogeography, group, control repellent and medical usage of Hirudinea in China

Hirudinea in China were reviewed. The ecological distribution of Hirudinea, the population dynamics of H. hainana, the adaptation of H. hainana to temperature, soil humidity and pH, the response of H. hainana to temperature, relative humidity and light, and the effects of human activities on H. hainana populations were discussed. The land-leeches' behavior ecology, including (1) the locomotion of H. hainana such as shortening, oscillating, rotating, sucking cleaning, rubbing and foraging behaviors; (2) the factors influencing these behaviors; (3) the ecological significance, was also discussed. The ecology of freshwater leeches including (1) behavior in paddy fields of Ninghsien, Zhejiang Province, China; (2) relationship between population dynamics of Whitmania laevis and chemical factors in paddy fields of Guangzhou, China; (3) chemical environment of blood-sucking Hirudinaria manillensis in paddy fields of Guangzhou was described. The study also discussed the foraging, growth dynamics, life recycle and biology of reproduction of blood-sucking land-leech H. hainana and freshwater leech Hirudinaria manillensis, the taxonomy and the zoogeography. In addition, the morphology including histology and anatomy of the organic system of H. hainana was described. The Hirudinea can be classified into 2 subclasses (Branchiobdellidea and Euhirudinea), 3 orders (Branchiobdellida, Rhynchobdellida and Arhynchobdellida), 9 families, 33 genera and 111 species. The response of leeches to pesticides, including toxicity (LD50, LD95) of different pesticides to H. hainana, was presented. Medical usage of the leech Hirudin from salivary glands as anticoagulant material was discussed. Hirudin (from Hirudo medicinalis), Haemadin (from land-leech), and hementi (from Hementeria ghilianii) were identified and isolated.     

Ecological zoogeography of the bats of Paraguay

Aim To relate the composition of bat assemblages in Paraguay to environmental factors (vegetation) and to test the hypothesis that the observed patterns of distribution of Paraguayan mammals is ultimately due to soils and geological features. Location Paraguay. Methods Museum specimens were used to create a data base of 3762 individuals of forty-eight species collected in twenty-six 50 × 50 km sites distributed throughout the country. Proportion of each of sixteen vegetation types per site was estimated from vegetation maps. Vegetation and bat data were related using canonical correspondence analysis (CCA) and Mantel tests. The same analyses were performed with the bat data grouped in terms of trophic strategies. Results A significant relationship was found between composition of vegetation and composition of bat assemblages. CCA ordination arranged plant associations and bat assemblages into three distinct groups: Dry Chaco, Floodable Lands and Eastern Paraguay, which correspond to the major characteristics of the Paraguayan vegetation, geology and soils. Frugivorous bats were restricted to Eastern Paraguay and Floodable Lands, whereas most insectivore and omnivore species occur across the entire country. However, the maximum abundance of insectivorous and omnivorous species within each genus indicates that there is at least a partial segregation of species to one of the three regions, and in those cases where the maximum abundance of congeneric species coincide, those species differ considerably in size. Main conclusions The Paraguayan bat fauna is a composite of species from various South American biomes, with no endemic species. However, species are not randomly distributed across the country despite the lack of geographical barriers and the high dispersal capabilities of bats. Instead, species presence at any given site is strongly associated with vegetation patterns that are ultimately the result of the geological history of the area. This correlation can be explained partially in terms of habitat suitability and resource availability. Additionally, results suggest that interspecific interactions are also an important component in determining the composition of a given bat assemblage.     

Adaptation, specificity and host-parasite coevolution in mites (ACARI)

Parasitism by mites is widespread and involves all the classes of vertebrates, from fishes to mammals. Owing to their small size and their great plasticity, mites are able to adapt to a wide range of habitats. Most of the species are ectoparasites but endoparasitism, especially in the respiratory tract, is common in birds and mammals. The morphological modifications appearing during the process adaptation to parasitic life, especially in Myobiidae, are analysed. Two kinds of characters are particularly important: the constructive specialized characters, consisting of the production of new structures, especially attachment organs allowing the mite to attach to the skin and the hair of the host, and regressive characters. Regression of the external structures is the most important phenomenon appearing in the process of evolution of parasitic mites. The importance of the regression in the parasite is correlated with the degree of evolution of the host. Host and parasite have a parallel evolution, but they go in opposite directions. The author surmises that the regressive evolution is related to the immunological reactions of the host that tend to reject the parasite. To escape from this rejection the parasite tends to select the less antigenic and therefore the most regressed phenotype. Specificity is generally strict in permanent parasites. Coevolution of host and parastie is studied-in the family Myobiidae which parasitizes marsupials, insectivores, bats and rodents. The concordance between the radiations of the mites and that of their hosts is very high.     

中国瓦娄蜗牛属系统发育关系和动物地理学初探(肺螺亚纲,柄眼目,瓦娄蜗牛科)

运用支序分析方法和Hennig86软件探讨了柄眼目瓦娄蜗牛科瓦娄蜗牛属中国种类的系统发育关系。中国瓦娄蜗牛属种类现已知16种,主要分布于中国北部,也分布在亚洲北部和西部,欧洲大部以及北美东南部。选择Acan-thinual属的代表种A．aculeata作为外群。系统分析所用特征为瓦娄蜗牛届的19个形态学特征。运用命令mh^*;和bb^*;对原始数据集进行运算,并进行逐步加权处理,结果共得到步长＝102,CI值＝61,RI值＝83的同等简约树一株。选择该树作为支序分析的首选支序图。支序分析的结果初步将中国瓦娄蜗牛属的16个种分为两群：西部瓦娄蜗牛群和东部瓦娄蜗牛群。运用扩散-隔离分析方法对该属的动物地理学进行了分析和讨论,认为瓦娄蜗牛居中国种类现有分布格局的形成可能是在中新世以前主要由该属的祖先在其起源地内蒙古一带逐步向现有分布地扩散的结果。     

Cretaceous Promecognathinae (Goleoptera: Garabidae): a new genus, phylogenetic reconstruction and zoogeography

A fossil carabid (Coleoptera) belonging to the subfamily Promecognathinae is described from Cretaceous crater lake deposits at Orapa, Botswana. The specimen, which is the first ever fossil promecognathine, is placed in a new genus Palaeoxinidium. The fossil supports a Cretaceous age determination for the sediments, and it indicates that the Orapa crater was, at least in part, heavily vegetated at the time of deposition. Cladistic analysis of the fossil and extant Promecognathinae indicates that the fossil represents the sister group of the extant taxa and that the latter, in turn, comprise a pair of sister groups. It is, therefore, proposed that the Promecognathinae should be divided into two tribes: the Palaeoaxinidiini, represented by the fossil, and the Promecognathini, represented by the extant groups. The Promecognathini should be subdivided further into the subtribes Promecognathina and Axinidiina, represented by the American and African species, respectively. Three alternative zoogeographic hypotheses that explain the distributions of the fossil and extant promecognathines are discussed and tests for the hypotheses are proposed.