寄生植物对寄主的选择和影响

寄生植物对寄主的选择性与寄主营养物质的含量、合成的次生物质和硬度有关.多寄主存在的条件下,有利于寄生植物的生长发育.通过改变寄主光合产物的流向和影响寄主叶片的气孔调节,寄生植物对寄主生理和形态产生显著的影响.寄生植物的存在使植物群落的生物量、组成多样性和动态发生改变.大量研究显示,寄生植物对寄主的选择和影响与植食性动物对取食植物的选择和影响有很多相似之处.气候变化对寄生植物与寄主关系影响的研究还刚刚起步,寄生植物对寄主选择和影响的研究对有害寄生植物的防除和有益寄生植物的利用有重要的价值,应该重视和加强.     

寄生植物对寄主的选择和影响

寄生植物对寄主的选择性与寄主营养物质的含量、合成的次生物质和硬度有关．多寄主存在的条件下,有利于寄生植物的生长发育．通过改变寄主光合产物的流向和影响寄主叶片的气孔调节,寄生植物对寄主生理和形态产生显著的影响．寄生植物的存在使植物群落的生物量、组成多样性和动态发生改变．大量研究显示．寄生植物对寄主的选择和影响与植食性动物对取食植物的选择和影响有很多相似之处．气候变化对寄生植物与寄主关系影响的研究还刚刚起步,寄生植物对寄主选择和影响的研究对有害寄生植物的防除和有益寄生植物的利用有重要的价值,应该重视和加强．     

PHYLOGENETIC RELATIONSHIPS AMONG PAPER WASP SOCIAL PARASITES AND THEIR HOSTS (HYMENOPTERA: VESPIDAE; POLISTINAE)

Abstract— Cladistic analyses of data from allozyme polymorphisms in paper wasp social parasites and their hosts do not support the hypothesis that social parasites are most closely related to their hosts. Electrophoretic data are adduced for nine species of Polistes , including all three known species of social parasites ( Sulcopolistes ) and their hosts. Three different coding methods are investigated; in no case do the social parasites cluster most closely with their hosts. Rather, there is limited evidence that they form a monophyletic group. However, formal taxonomic recognition of Sulcopolistes is not justified, as it renders Polistes sensu stricto paraphyletic. Although the social parasites are not most closely related to their hosts, hosts and parasites belong in the same subgenus and share many characteristics that may have facilitated the exploitation and deception practised by the parasites on the hosts.     

Impact of forest size on parasite biodiversity: implications for conservation of hosts and parasites

Studies of biodiversity traditionally focus on charismatic megafauna. By comparison, little is known about parasite biodiversity. Recent studies suggest that co-extinction of host specific parasites with their hosts should be common and that parasites may even go extinct before their hosts. The few studies examining the relationship between parasite diversity and habitat quality have focused on parasites that require intermediate hosts and pathogens that require vectors to complete their life-cycles. Declines in parasite and pathogen richness in these systems could be due to the decline of any of the definitive hosts, intermediate hosts, or vectors. Here we focus on avian ectoparasites, primarily lice, which are host specific parasites with simple, direct, life-cycles. By focusing on these parasites we gain a clearer understanding of how parasites are linked to their hosts and their hosts’ environment. We compare parasite richness on birds from fragmented forests in southern China. We show that parasite richness correlates with forest size, even among birds that are locally common. The absence of some ectoparasite genera in small forests suggests that parasites can go locally extinct even if their hosts persist. Our data suggest that the conservation of parasite biodiversity may require preservation of habitat fragments that are sufficiently large to maintain parasite populations, not just their host populations.     

Nutritional ecology of endoparasitic insects and their hosts: An overview

The impact of insect endoparasites (parasitoids) on the physiology and behaviour of their hosts is reviewed within the context of the nutritional ecology of the parasitoids and their hosts. Alterations in the consumption, utilization and allocation of food by parasitized hosts are common, as are internal changes in their metabolic physiology. Gregarious parasitoid species frequently increase feeding by their host larvae whereas solitary parasitoid species often reduce feeding and growth of their hosts. Many parasitoid-associated changes in host physiology and behaviour are interpreted to be of adaptive significance to parasitoids. Substantial circumstantial evidence suggests, and a few direct tests of such adaptive significance indicate, that parasitoids alter their hosts in ways beneficial to their own fitness. However, most of the changes in parasitized hosts are of unknown cause and undocumented significance to the parasitoids. Several relevant hypotheses are presented, and these require extensive evaluation (often requiring novel experimental approaches) before a thorough understanding of parasitoid nutritional ecology is established.     

Parasitism ofAcyrthosiphon pisum byAllothrombium pulvinum (Acariformes: Trombidiidae): Host attachment site,host size selection,superparasitism and effect on host

Several aspects of parasitism of the pea aphid,Acyrthosiphon pisum (Harris), by the mite parasiteAllothrombium pulvinum Ewing, were examined in the laboratory. Larvae ofA. pulvinum were fastmoving mites that find their host by contact of their foretarsi with the host. They can attach to all parts of the host body, but insert their chelicerae only into weakly sclerotized parts such as intersegmental membranes. Of the attached larval mites, most (63.5–74.1%) were on the thorax of their hosts, regardless of host size. In hosts of small and medium size, the ventral side receives most parasitism, whereas in large hosts the lateral sites are most often attacked. Larval mites prefer large hosts when allowed to select between pairs of large and small hosts, but show no significant preference when allowed to choose between pairs of large and medium hosts or pairs of medium and small hosts. In two-choice tests, larval mites prefer previously parasitized hosts to umparasitized hosts, which results in superparasitism of the hosts. When the mite load is fiveA. pulvinum kills all small hosts within three days, and all medium hosts and 50% of large hosts within four days, the reproduction of surviving adult aphids were significantly reduced. Host-finding behavior, attachment site preference, host size selection, superparasitism, and effect on hosts are briefly reviewed for larval parasites of Trombidiidae. The potential role of larvalAllothrombium in integrated and biological aphid control is also discussed.     

Parasite local maladaptation in the Canarian lizard Gallotia galloti (Reptilia: Lacertidae) parasitized by haemogregarian blood parasite

Biologists commonly assume that parasites are locally adapted since they have shorter generation times and higher fecundity than their hosts, and therefore evolve faster in the arms race against the host's defences. As a result, parasites should be better able to infect hosts within their local population than hosts from other allopatric populations. However, recent mathematical modelling has demonstrated that when hosts have higher migration rates than parasites, hosts may diversify their genes faster than parasites and thus parasites may become locally maladapted. This new model was tested on the Canarian endemic lizard and its blood parasite (haemogregarine genus). In this host–parasite system, hosts migrate more than parasites since lizard offspring typically disperse from their natal site soon after hatching and without any contact with their parents who are potential carriers of the intermediate vector of the blood parasite (a mite). Results of cross-infection among three lizard populations showed that parasites were better at infecting individuals from allopatric populations than individuals from their sympatric population. This suggests that, in this host–parasite system, the parasites are locally maladapted to their host.     

Effect of delayed mating and prolonged engorgement on the reproductive fitness of female Amblyomma limbatum (Acari: Ixodidae) in marginal population areas

Reptile ticks mate while females are attached to their host. Following mating, females engorge, detach and then lay their eggs. This study examines whether the time that females of the reptile tick Amblyomma limbatum spend on hosts prior to mating and the time they take to engorge on hosts after mating influence their reproductive fitness, as measured by the number of viable eggs they produce. When compared with females that experienced no temperature-induced delay in mating, females attached for an initial period to hosts with body temperatures too low to induce mating had no decline in their reproductive fitness, once provided with suitable temperatures for mating. However, on hosts with suitable body temperatures for mating, female ticks that took longer to mate, took longer to engorge and had reduced reproductive fitness. In addition, females that spent more than 20 days feeding on hosts after mating had reduced reproductive fitness, irrespective of the time they spent on hosts prior to mating compared with females with shorter feeding periods. Thus, the time that A. limbatum females spent on hosts prior to mating and/or after mating has a significant bearing on the number viable progeny produced. The ecological implications of these results are discussed in relation to females colonizing marginal population areas at the edge of their distributional range.     

Local adaptation, resistance, and virulence in a hemiparasitic plant-host plant interaction

Abstract.— Coevolution may lead to local adaptation of parasites to their sympatric hosts. Locally adapted parasites are, on average, more infectious to sympatric hosts than to allopatric hosts of the same species or their fitness on the sympatric hosts is superior to that on allopatric hosts. We tested local adaptation of a hemiparasitic plant, Rhinanthus serotinus (Scrophulariaceae), to its host plant, the grass Agrostis capillaris . Using a reciprocal cross-infection experiment, we exposed host plants from four sites to hemiparasites originating from the same four sites in a common environment. The parasites were equally able to establish haustorial connections to sympatric and allopatric hosts, and their performance was similar on both host types. Therefore, these results do not indicate local adaptation of the parasites to their sympatric hosts. However, the parasite populations differed in average biomass and number of flowers per plant and in their effect on host biomass. These results indicate that the virulence of the parasite varied among populations, suggesting genetic variation. Theoretical models suggest that local adaptation is likely to be detected if the host and the parasite have different evolutionary potentials, different migration rates, and the parasite is highly virulent. In the interaction between R. serotinus and A. capillaris all the theoretical prerequisites for local adaptation may not be fulfilled.     

Imperfect mimicry of host begging calls by a brood parasitic cuckoo: a cue for nestling rejection by hosts?

Coevolutionary interactions between avian brood parasites and their hosts often lead to the evolution of discrimination and rejection of parasite eggs or chicks by hosts based on visual cues, and the evolution of visual mimicry of host eggs or chicks by brood parasites. Hosts may also base rejection of brood parasite nestlings on vocal cues, which would in turn select for mimicry of host begging calls in brood parasite chicks. In cuckoos that exploit multiple hosts with different begging calls, call structure may be plastic, allowing nestlings to modify their calls to match those of their various hosts, or fixed, in which case we would predict either imperfect mimicry or divergence of the species into host-specific lineages. In our study of the little bronze-cuckoo (LBC) Chalcites minutillus and its primary host, the large-billed gerygone Gerygone magnirostris, we tested whether: (1) hosts use nestling vocalizations as a cue to discriminate cuckoo chicks; (2) cuckoo nestlings mimic the host begging calls throughout the nestling period; and (3) the cuckoo begging calls are plastic, thereby facilitating mimicry of the calls of different hosts. We found that the begging calls of LBCs are most similar to their gerygone hosts shortly after hatching (when rejection by hosts typically occurs) but become less similar as cuckoo chicks get older. Begging call structure may be used as a cue for rejection by hosts, and these results are consistent with gerygone defenses selecting for age-specific vocal mimicry in cuckoo chicks. We found no evidence that LBC begging calls were plastic.     

Experimental assemblage of novel plant–herbivore interactions: ecological host shifts after 40 million years of isolation

Geographic isolation is the first step in insect herbivore diet specialization. Such specialization is postulated to increase insect fitness, but may simultaneously reduce insect ability to colonize novel hosts. During the Paleocene‐Eocene, plants from the order Zingiberales became isolated either in the Paleotropics or in the Neotropics. During the Cretaceous, rolled‐leaf beetles diversified in the Neotropics concurrently with Neotropical Zingiberales. Using a community of Costa Rican rolled‐leaf beetles and their Zingiberales host plants as study system, we explored if previous geographic isolation precludes insects to expand their diets to exotic hosts. We recorded interactions between rolled‐leaf beetles and native Zingiberales by combining DNA barcodes and field records for 7450 beetles feeding on 3202 host plants. To determine phylogenetic patterns of diet expansions, we established 20 experimental plots in the field, in which we planted plots five exotic Zingiberales, recording beetles feeding on these exotic hosts. In the laboratory, using both native and exotic host plants, we reared a subset of insect species that had expanded their diets to the exotic plants. The original plant–herbivore community comprised 24 beetle species feeding on 35 native hosts, representing 103 plant–herbivore interactions. After exotic host plant introduction, 20 percent of the beetle species expanded their diets to exotic Zingiberales. Insects only established on exotic hosts that belong to the same plant family as their native hosts. Laboratory experiments show that beetles are able to complete development on these novel hosts. In conclusion, rolled‐leaf beetles are preadapted to expand their diets to novel host plants even after millions of years of geographic isolation.     

Ancient coevolution of baculoviruses and their insect hosts

If the relationships between baculoviruses and their insect hosts are subject to coevolution, this should lead to long-term evolutionary effects such as the specialization of these pathogens for their hosts. To test this hypothesis, a phylogeny of the Baculoviridae, including 39 viruses from hosts of the orders Lepidoptera, Diptera, and Hymenoptera, was reconstructed based on sequences from the genes lef-8 and ac22. The tree showed a clear division of the baculoviruses according to the order of their hosts. This division highlighted the need to reconsider the classification of the baculoviruses to include one or possibly two new genera. Furthermore, the specialization of distinct virus lineages to particular insect orders suggests ancient coevolutionary interactions between baculoviruses and their hosts.     

The coevolution of ixodid ticks and terrestrial vertebrates

Paleontologic and zoogeographic data speak in favour of Mesozoic origin of ixodid ticks. The absence of strict restrictions for the feeding on unusual species of hosts has caused the domination of polyphagy and oligophagy over monophagy among ixodid ticks. The same peculiarities of ixodid ecology are responsible for a restricted part or absence of phylogenetic parallelism with hosts in their evolution. Primary food relations with reptiles are, apparently, preserved only in the genus Aponomma and in many species of Amblyomma while hosts for most species of other genera are mammals and, to a lesser extent, birds. The number of potential hosts in these species can be much greater than that of real ones. Restrictions in the distribution of some species are connected rather with direct effect of unfavourable environmental factors on their nonparasitic stages of the life cycle than with the absence of suitable hosts. During the evolution of natural landscapes and at a shorter stages under the influence of successions or anthropogenic factors ixodids easily adapt themselves to feeding on new species of hosts. So the differentiation of primary and secondary hosts of these parasites is rather difficult.     

昆虫内共生菌在昆虫防御中的作用

共生菌在昆虫体内的生长、繁殖过程中起着十分重要的作用,如营养功能、解毒作用、调控生殖及与寄主适应性等等。近些年,一些学者提出了共生菌在寄主抵御天敌等逆境的胁迫时也具有重要的作用。其在寄主防御中的作用可分为3类:(1)昆虫体内共生菌能产生具有抗真菌作用的代谢物,能够抵御病原真菌的入侵,提高寄主的适应性。(2)昆虫抵御寄生蜂的作用与其体内的共生细菌密切相关。(3)共生菌也能产生有毒物质保护寄主免于被捕食。昆虫共生菌在寄主防御中的作用机制除了产生抗菌物质和聚酮类等有毒物质外,还可能通过与水平传播的寄生物(horizontal transmission parasites,HTPs)竞争寄主资源来直接保护寄主。对共生菌的作用的深入研究将有可能进一步明确其功能,并加以利用。     

The roles of ecological fitting, phylogeny and physiological equivalence in understanding realized and fundamental host ranges in endoparasitoid wasps

Co-evolutionary theory underpins our understanding of interactions in nature involving plant-herbivore and host-parasite interactions. However, many studies that are published in the empirical literature that have explored life history and development strategies between endoparasitoid wasps and their hosts are based on species that have no evolutionary history with one another. Here, we investigated novel associations involving two closely related solitary endoparasitoids that originate from Europe and North America and several of their natural and factitious hosts from both continents. The natural hosts of both species are also closely related, all being members of the same family. We compared development and survival of both parasitoids on the four host species and predicted that parasitoid performance is better on their own natural hosts. In contrast with this expectation, survival, adult size and development time of both parasitoids were similar on all (with one exception) hosts, irrespective as to their geographic origin. Our results show that phylogenetic affinity among the natural and factitious hosts plays an important role in their nutritional suitability for related parasitoids. Evolved traits in parasitoids, such as immune suppression and development, thus enable them to successfully develop in novel host species with which they have no evolutionary history. Our results show that host suitability for specialized organisms like endoparasitoids is closely linked with phylogenetic history and macro-evolution as well as local adaptation and micro-evolution. We argue that the importance of novel interactions and 'ecological fitting' based on phylogeny is a greatly underappreciated concept in many resource-consumer studies.     

SPECIES DIVERSITY AND COMMUNITY STRUCTURE OF SUCKING LICE IN YUNNAN, CHINA

Abstract  On the basis of investigating 9 counties (towns) in Yunnan Province of China, the species diversity and community structure of sucking lice on the body surface of small mammal hosts are studied in the paper. Species richness ( S ) is used to stand for the species diversity. The calculation of community diversity index and evenness are based on Shannon-Wiener's method. 2 745 small mammals captured from the investigated sites belong to 10 families, 25 genera and 41 species in 5 orders (Rodentia, Insectivora, Scandentia, Logomorpha and Carnivora) while 18165 individuals of sucking lice collected from the body surface of the small mammal hosts are identified into 4 families, 6 genera and 22 species. The species of sucking lice are much less than the species of their hosts. Most species of small mammals have their fixed sucking lice on their body surface. One species of small mammals usually have few species of sucking lice (1 to 4 species). The close species of the hosts in the taxonomy are found to have the same or similar dominant species of sucking lice on their body surface. The results reveal that the species diversity of sucking lice on small mammals is very low with a very simple community structure. The results also imply there may be a close co-evolution relationship between the lice and the hosts.     

Patterns of association between crucifers and their flower-mimic pathogens: host jumps are more common than coevolution or cospeciation

Morphological and molecular phylogenies of animal parasites have often shown parallel cladogenesis, supporting hypotheses of coevolution. Few studies of the phylogenetic history for plants and their pathogens exist. Gene-for-gene interactions suggest that plant pathogens ought to have similar phylogenetic histories as their hosts. However, high dispersability combined with an inability to choose to leave if an inappropriate host has been landed on could increase the likelihood of host jumps and thus decrease phylogenetic congruence between plant pathogens and their hosts. In this study, I examined the pattern of association between the flower-mimicking crucifer rusts and their hosts by comparing independent host phylogenies (based on both cpDNA trnL-F introns and nuclear internal transcribed spacer [ITS] sequences) with that of their rust pathogens (based on ITS sequences). The expectation was that if the pathogens coevolved or cospeciated with their hosts, then their phylogenies should be congruent. Host-tracking coevolution can be differentiated from cospeciation by examining the times of divergence: If the pathogens are younger than the hosts, then it is likely that host tracking has occurred. For the crucifer rusts and their hosts, there was little evidence of parallel cladogenesis, suggesting that both cospeciation and coevolutionary tracking are rare. Instead, the most common pattern was one of host jumps to geographically associated taxa. There are at least three factors that may have contributed to the geographic structuring of the data. First, along the east-west transect stretching from the Rocky Mountains to California, large differences in rainfall and the timing of rainfall may reduce long-distance gene flow. Second, although dispersal of infectious spores is by wind, sexual reproduction of these fungi depends on insects, which move short distances. Third, host shifts are most likely to occur to geographically available taxa. Any species that grows adjacent to infected plants will be exposed to millions of spores, and the probability of eventual infection by a new mutant increases with greater exposure. Thus, patterns of association between the crucifers and their flower-mimic pathogens reflect jumps to geographically available hosts, which are not necessarily those that are most closely related.     

噬菌体与宿主菌间的角逐

噬菌体和它们的宿主菌组成了地球上教目最庞大的微生物种群,噬菌体靠寄生宿主菌来扩增繁衍。但在漫长的进化中,噬菌体与宿主菌间不单是捕食关系,它们间还形成了复杂的相互对抗机制,其中抵抗防御机制的抗防御机制也会促使抗．抗防御机制的产生。从生态学角度来看,噬菌体和宿主菌间的共进化保持着动态平衡。本文综述近年来这一领域的研究,为更清楚地了解噬菌体与宿主菌间的关系和应用提供了参考。     

Wolbachia属共生菌及其对节肢动物宿主适合度的影响

Wolbachia是广泛分布于节肢动物体生殖组织内呈母质遗传的一类共生细菌。近30多年来,大量的研究主要集中于Wolbachia对宿主生殖方式的调控方面;近年来的研究发现,Wolbachia对节肢动物宿主的适合度具有不同程度的影响。现对Wolbachia的宿主分布、存在部位及其对节肢动物宿主种群适合度的影响等方面进行了综述,探讨了Wolbachia在该领域的研究意义和潜在的应用价值。     

Host choice decisions in the polyembryonic wasp Copidosoma koehleri (Hymenoptera: Encyrtidae)

Female parasitoids often reject hosts of poor quality, where the survival and fitness of their offspring are expected to be low. In polyembryonic parasitoid wasps, a clone of genetically identical embryos develops from one egg in a host. In the wasp Copidosoma koehleri, each female clone produces one soldier larva that attacks competing clones inside the host. Aggression by soldiers is directed usually towards unrelated clones. Accordingly, it may be predicted that females will prefer nonparasitized over parasitized hosts, especially if the latter have been parasitized previously by a mated unrelated female, as a result of the reduced chances of survival for their offspring inside these hosts. In accordance with these predictions, females prefer nonparasitized hosts over self‐parasitized hosts when they are presented simultaneously. By contrast to the predictions, females prefer hosts parasitized by an unrelated conspecific over nonparasitized hosts when presented simultaneously. Females do not distinguish hosts parasitized by conspecifics from self‐parasitized hosts when presented simultaneously. They reject self‐parasitized hosts significantly more often than hosts parasitized by conspecifics when each host type is presented alone. Females faced with two previously parasitized hosts are not affected in their choice by the mating status (i.e. virgin or mated) of the previous parasitizing females. The combined results suggest that females are limited in their ability to assess the risk that their offspring will be attacked by a soldier, or that this risk is balanced by the relative advantages of ovipositing in a host parasitized by conspecifics. A possible advantage may be increased out‐breeding opportunities for the emerging offspring.