No evidence for host specialization or host-race formation in the European bitterling (Rhodeus amarus), a fish that parasitizes freshwater mussels

Coevolutionary relationships between parasites and hosts can elevate the rate of evolutionary changes owing to reciprocal adaptations between coevolving partners. Such relationships can result in the evolution of host specificity. Recent methodological advances have permitted the recognition of cryptic lineages, with important consequences for our understanding of biological diversity. We used the European bitterling (Rhodeus amarus), a freshwater fish that parasitizes unionid mussels, to investigate host specialization across regions of recent and ancient sympatry between coevolving partners. We combined genetic data (12 microsatellite and 2 mitochondrial markers) from five populations with experimental data for possible mechanisms of host species recognition (imprinting and conditioning). We found no strong evidence for the existence of cryptic lineages in R. amarus, though a small proportion of variation among individuals in an area of recent bitterling–mussel association was statistically significant in explaining host specificity. No other measures supported the existence of host‐specific lineages. Behavioural data revealed a weak effect of conditioning that biased behavioural preferences towards specific host species. Host imprinting had no effect on oviposition behaviour. Overall, we established that populations of R. amarus show limited potential for specialization, manifested as weak effects of host conditioning and genetic within‐population structure. Rhodeus amarus is the only species of mussel‐parasitizing fish in Europe, which contrasts with the species‐rich communities of bitterling in eastern Asia where several host‐specific bitterling occur. We discuss costs and constraints on the evolution of host‐specific lineages in our study system and more generally.     

Cryptic diversity and patterns of host specificity in trematode flatworms

The widespread utilization of molecular markers has revealed that a broad spectrum of taxa contain sets of morphologically cryptic, but genetically distinct lineages ( Bickford et al. 2007 ). The identification of cryptic taxa is important as an accurate appreciation of diversity is crucial for a proper understanding of evolutionary and ecological processes. An example is the study of host specificity in parasitic taxa, where an apparent generalist may be found to contain a complex of several more specific species ( Smith et al. 2006 ). Host specificity is a key life history trait that varies greatly among parasites ( Poulin & Keeney 2007 ). While some can exploit a wide range of hosts, others are confined to just a single species. Access to additional hosts increases the resources available to a parasite. However, physiological or ecological constraints can restrict the extension of host range. Furthermore, there may be a trade‐off between relaxed specificity and performance: generalism can decrease a parasites ability to adapt to each individual host species, and increase exposure to competition from other parasites ( Poulin 1998 ). Despite the central role that host specificity plays in parasite life history, relatively little is known about how host range is determined in natural systems, and data from field studies are required to evaluate among competing ideas. In this issue, an exciting paper by Locke et al. (2010) makes a valuable contribution toward the understanding of host specificity in an important group of trematode flatworms. Using molecular methods, Locke et al. reveal an almost four‐fold increase in the appreciated diversity of their focal group. In combination with a large and elegant sampling design this allows them to accurately assess host specificity for each taxon, and thus draw key insights into the factors that control host range in a dominant parasite group.     

Allopatric origin of cryptic butterfly species that were discovered feeding on distinct host plants in sympatry

Surveys of tropical insects are increasingly uncovering cryptic species – morphologically similar yet reproductively isolated taxa once thought to comprise a single interbreeding entity. The vast majority of such species are described from a single location. This leaves us with little information on geographic range and intraspecific variation and limits our ability to infer the forces responsible for generating such diversity. For example, in herbivorous and parasitic insects, multiple specialists are often discovered within what were thought to be single more generalized species. Host shifts are likely to have contributed to speciation in these cases. But when and where did those shifts occur, and were they facilitated by geographic isolation? We attempted to answer these questions for two cryptic species within the butterfly Cymothoe egesta that were recently discovered on different host plants in central Cameroon. We first used mtDNA markers to separate individuals collected on the two hosts within Cameroon and then extended our analysis to incorporate individuals collected across the entire pan‐Afrotropical range of the original taxon. To our surprise, we found that the species are almost entirely allopatric, dividing the original range and overlapping only in the narrow zone of West‐Central Africa where they were first discovered in sympatry. This finding, combined with analyses of genetic variation within each butterfly species, strongly suggests that speciation occurred in allopatry, probably during the Pleistocene. We discuss the implications of our results for understanding speciation among other cryptic species recently discovered in the tropics and argue that more work is needed on geographic patterns and host usage in such taxa.     

Phylogenetic evidence for the evolution of ecological specialization in Timema walking‐sticks

We used phylogenetic and ecological information to study the evolution of host‐plant specialization and colour polymorphism in the genus Timema, which comprises 14 species of walking‐sticks that are subject to strong selection for cryptic coloration on their host‐plants. Phylogenetic analysis indicated that this genus consists of three main lineages. Two of the lineages include highly generalized basal species and relatively specialized distal species, and one of the lineages comprises four specialized species. We tested for phylogenetic conservatism in the traits studied via randomizing host‐plant use, and the four basic Timema colour patterns, across the tips of the phylogeny, and determining if the observed number of inferred changes was significantly low compared to the distribution of numbers of inferred changes expected under the null model. This analysis showed that (1) host‐plant use has evolved nonrandomly, such that more closely related species tend to use similar sets of hosts and (2) colour pattern evolution exhibits considerable lability. Inference of ancestral states using maximum parsimony, under four models for the relative ease of gain and loss of plant hosts or colour morphs, showed that (1) for all models with gains of host‐plants even marginally more difficult than losses, and for most optimizations with gains and losses equally difficult, the ancestral Timema were generalized, feeding on the chaparral plants Ceanothus and Adenostoma and possibly other taxa, and (2) for all models with gains of colour morphs more difficult than losses, the ancestral Timema were polymorphic for colour pattern. Generation of null distributions of inferred ancestral states showed that the maximum‐parsimony inference of host‐plant generalization was most robust for the most speciose of the three main Timema lineages. Ancestral states were also inferred using maximum likelihood, after recoding host‐plant use and colour polymorphism as dichotomous characters. Likelihood analyses provided some support for inference of generalization in host‐plant use at ancestral nodes of the two lineages exhibiting mixtures of generalists and specialists, although levels of uncertainty were high. By contrast, likelihood analysis did not estimate ancestral colour morph patterns with any confidence, due to inferred rates of change that were high with respect to speciation rates. Information from biogeography, floristic history and the timing of diversification of the genus are compatible with patterns of inferred ancestral host‐plant use. Diversification in the genus Timema appears to engender three main processes: (1) increased specialization via loss of host‐plants, (2) retention of the same, single, host‐plant and (3) shifts to novel hosts to which lineages were ‘preadapted’ in colour pattern. Our evidence suggests that the radiation of this genus has involved multiple evolutionary transitions from individual‐level specialization (multiple‐niche polymorphism) to population‐level and species‐level specialization. Ecological studies of Timema suggest that such transitions are driven by diversifying selection for crypsis. This paper provides the first phylogeny‐based evidence for the macroevolutionary importance of predation by generalist natural enemies in the evolution of specialization.     

Sex and seasonal differences in hippocampal volume and neurogenesis in brood‐parasitic brown‐headed cowbirds (Molothrus ater)

Brown‐headed cowbirds (Molothrus ater) are one of few species in which females show more complex space use than males. Female cowbirds search for, revisit, and parasitize host nests and, in a previous study, outperformed males on an open field spatial search task. Previous research reported a female‐biased sex difference in the volume of the hippocampus, a region of the brain involved in spatial memory. Neurons produced by adult neurogenesis may be involved in the formation of new memories and replace older neurons that could cause interference in memory. We tested for sex and seasonal differences in hippocampal volume and neurogenesis of brood‐parasitic brown‐headed cowbirds and the closely related non‐brood‐parasitic red‐winged blackbird (Agelaius phoeniceus) to determine whether there were differences in the hippocampus that reflected space use in the wild. Females had a larger hippocampus than males in both species, but hippocampal neurogenesis, measured by doublecortin immunoreactivity (DCX+), was greater in female than in male cowbirds in the absence of any sex difference in blackbirds, supporting the hypothesis of hippocampal specialization in female cowbirds. Cowbirds of both sexes had a larger hippocampus with greater hippocampal DCX+ than blackbirds. Hippocampus volume remained stable between breeding conditions, but DCX+ was greater post‐breeding, indicating that old memories may be lost through hippocampal reorganization following breeding. Our results support, in part, the hypothesis that the hippocampus of cowbirds is specialized for brood parasitism. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1275–1290, 2016     

Cryptic diversity in the pen shell Atrina pectinata (Bivalvia: Pinnidae): high divergence and hybridization revealed by molecular and morphological data

Cryptic species have been increasingly revealed in the marine realm through an analytical approach incorporating multiple lines of evidence (e.g., mtDNA, nuclear genes and morphology). Illustrations of cryptic taxa improve our understanding of species diversity and evolutionary histories within marine animals. The pen shell Atrina pectinata is known to exhibit extensive morphological variations that may harbour cryptic diversity. In this study, we investigated A. pectinata populations along the coast of China and one from Japan to explore possible cryptic diversity and hybridization using a combination of mitochondrial (cytochrome c oxidase subunit I, mtCOI) and nuclear (ribosomal internal transcribed spacer, nrITS) genes as well as morphology. Phylogenetic analyses of mtCOI ‘DNA barcoding gene’ sequences resolved six divergent lineages with intralineage divergences between 0.4% and 0.8%. Interlineage sequence differences ranged from 4.3% to 22.0%, suggesting that six candidate cryptic species are present. The nrITS gene revealed five deep lineages with Kimura 2‐parameter distances of 3.7–30.3%. The five nuclear lineages generally corresponded to mtCOI lineages 1–4 and (5 + 6), suggestive of five distinct evolutionary lineages. Multiple nrITS sequences of significant variance were found within an individual, clearly implying recent hybridization events between/among the evolutionary lineages, which contributed to cytonuclear discordance. Morphologically, five morphotypes matched the five genetic lineages, although the intermediates may well blur the boundaries of different morphotypes. This study demonstrates the importance of combining multiple lines of evidence to explore species cryptic diversity and past evolutionary histories.     

We do not select,nor are we choosy: reproductive biology of Strepsiptera (Insecta)

The cryptic entomophagous parasitoids in the order Strepsiptera exhibit specific adaptations to each of the 34 families that they parasitize, offering rich opportunities for the study of male–female conflict. We address the compelling question as to how the diversity of Strepsiptera (where cryptic speciation is common) arose. Studying 13 strepsipteran families, including fossil taxa, we explore the genitalic structures of males, the free‐living females of the Mengenillidia (suborder), and the endoparasitic females of the Stylopidia (suborder). Inferring from similarity between aedeagi of males either between congeners, heterogeners, or between species within the same taxonomic family, the same of which is true of the cephalothoraces of females, we predict that male–female conflict and a co‐evolutionary morphological arms race between sexes is not likely to exist in most species of Strepsiptera. We then review the non‐genitalic structures that play a role during sexual communication, and present details of copulatory behaviour. We conclude that Strepsiptera fall within the synchronous sensory exploitation model where short‐lived males take advantage of a pre‐existing sensory system involving pheromone signals emitted by females.     

EVALUATING PATTERNS OF CONVERGENT EVOLUTION AND TRANS‐SPECIES POLYMORPHISM AT MHC IMMUNOGENES IN TWO SYMPATRIC STICKLEBACK SPECIES

The immunologically important major histocompatibility complex (MHC) harbors some of the most polymorphic genes in vertebrates. These genes presumably evolve under parasite‐mediated selection and frequently show inconsistent allelic genealogies, where some alleles are more similar between species than within species. This phenomenon is thought to arise either from convergent evolution under parallel selection or from the preservation of ancient allelic lineages beyond speciation events (trans‐species polymorphism, TSP). Here, we examine natural populations of two sympatric stickleback species (Gasterosteus aculeatus and Pungitius pungitius) to investigate the contribution of these two mechanisms to the evolution of inconsistent allelic genealogies at the MHC. Overlapping parasite taxa between the two host species in three different habitats suggest contemporary parallel selection on the MHC genes. Accordingly, we detected a lack of species‐specific phylogenetic clustering in the immunologically relevant antigen‐binding residues of the MHC IIB genes which contrasted with the rest of the coding and noncoding sequence. However, clustering was not habitat‐specific and a codon‐usage analysis revealed patterns of similarity by descent. In this light, common descent via TSP, in combination with intraspecies gene conversion, rather than convergent evolution is the more strongly supported scenario for the inconsistent genealogy at the MHC.     

Partitioning of herbivore hosts across time and food plants promotes diversification in the Megastigmus dorsalis oak gall parasitoid complex

Communities of insect herbivores and their natural enemies are rich and ecologically crucial components of terrestrial biodiversity. Understanding the processes that promote their origin and maintenance is thus of considerable interest. One major proposed mechanism is ecological speciation through host‐associated differentiation (HAD), the divergence of a polyphagous species first into ecological host races and eventually into more specialized daughter species. The rich chalcid parasitoid communities attacking cynipid oak gall wasp hosts are structured by multiple host traits, including food plant taxon, host gall phenology, and gall structure. Here, we ask whether the same traits structure genetic diversity within supposedly generalist parasitoid morphospecies. We use mitochondrial DNA sequences and microsatellite genotypes to quantify HAD for Megastigmus (Bootanomyia) dorsalis, a complex of two apparently generalist cryptic parasitoid species attacking oak galls. Ancient Balkan refugial populations showed phenological separation between the cryptic species, one primarily attacking spring galls, and the other mainly attacking autumn galls. The spring species also contained host races specializing on galls developing on different host‐plant lineages (sections Cerris vs. Quercus) within the oak genus Quercus. These results indicate more significant host‐associated structuring within oak gall parasitoid communities than previously thought and support ecological theory predicting the evolution of specialist lineages within generalist parasitoids. In contrast, UK populations of the autumn cryptic species associated with both native and recently invading oak gall wasps showed no evidence of population differentiation, implying rapid recruitment of native parasitoid populations onto invading hosts, and hence potential for natural biological control. This is of significance given recent rapid range expansion of the economically damaging chestnut gall wasp, Dryocosmus kuriphilus, in Europe.     

A chromosome-scale Gastrodia elata genome and large-scale comparative genomic analysis indicate convergent evolution by gene loss in mycoheterotrophic and parasitic plants

Mycoheterotrophic and parasitic plants are heterotrophic and parasitize on fungi and plants, respectively, to obtain nutrients. Large-scale comparative genomics analysis has not been conducted in mycoheterotrophic or parasitic plants or between these two groups of parasites. We assembled a chromosome-level genome of the fully mycoheterotrophic plant Gastrodia elata (Orchidaceae) and performed comparative genomic analyses on the genomes of G. elata and four orchids (initial mycoheterotrophs), three parasitic plants (Cuscuta australis, Striga asiatica, and Sapria himalayana), and 36 autotrophs from various angiosperm lineages. It was found that while in the hemiparasite S. asiatica and initial mycoheterotrophic orchids, approximately 4–5% of the conserved orthogroups were lost, the fully heterotrophic G. elata and C. australis both lost approximately 10% of the conserved orthogroups, indicating that increased heterotrophy is positively associated with gene loss. Importantly, many genes that are essential for autotrophs, including those involved in photosynthesis, the circadian clock, flowering time regulation, immunity, nutrient uptake, and root and leaf development, were convergently lost in both G. elata and C. australis. The high-quality genome of G. elata will facilitate future studies on the physiology, ecology, and evolution of mycoheterotrophic plants, and our findings highlight the critical role of gene loss in the evolution of plants with heterotrophic lifestyles.     

Hidden diversity in the non‐caryophyllaceous plant‐parasitic members of Microbotryum (Pucciniomycotina: Microbotryales)

Abstract

Members of the fungal genus Microbotryum are well‐known parasites on eudicotyledonous plant hosts. However, recent studies focused exclusively on Microbotryum species being parasites in the anthers of Caryophyllaceae in which strong host‐specificity was confirmed by molecular analyses. Consequently, species numbers have risen considerably as multi‐host parasites were split up in so‐called cryptic species. We subjected three non‐caryophyllaceous Microbotryum groups to molecular phylogenetic analyses to see whether we would confirm multi‐host morphospecies or if host‐specific cryptic species in these selected groups could be revealed as well (i.e. a group of non‐caryophyllaceous anther smuts, parasites on different Fallopia species, and parasites on Polygonum bistorta and Polygonum vi‐viparum). We applied a multiple analysis strategy to correct for varying alignment effects on a two‐locus dataset (ITS and LSU rDNA). The results obtained by the different approaches are uniform; high host‐specificity exists in the non‐ caryophyllaceous anther smuts, but overlapping host ranges occur in the parasites of Fallopia species. Results for the parasites of Polygonum are similar, with Microbotryum bistortarum being separated into three lineages and M. marginale forming a lineage on P. bistorta which apparently is conspecific with M. bistortarum p.p. Our study shows that phylogenetic patterns within Microbotryum are much more complicated than deduced from morphological observations alone. Even though Microbotryum species are highly host‐specific, it is impossible to identify species based solely on host taxa affiliation. Species status is reinstated for the anther smut on Salvia pratensis.     

Host‐driven divergence in the parasitic plant Orobanche minor Sm. (Orobanchaceae)

Many parasitic angiosperms have a broad host range and are therefore considered to be host generalists. Orobanche minor is a nonphotosynthetic root parasite that attacks a range of hosts from taxonomically disparate families. In the present study, we show that O. minor sensu lato may comprise distinct, genetically divergent races isolated by the different ecologies of their hosts. Using a three‐pronged approach, we tested the hypothesis that intraspecific taxa O. minor var. minor and O. minor ssp. maritima parasitizing either clover (Trifolium pratense) or sea carrot (Daucus carota ssp. gummifer), respectively, are in allopatric isolation. Morphometric analysis revealed evidence of divergence but this was insufficient to define discrete, host‐specific taxa. Intersimple sequence repeat (ISSR) marker‐based data provided stronger evidence of divergence, suggesting that populations were isolated from gene flow. Phylogenetic analysis, using sequence‐characterized amplified region (SCAR) markers derived from ISSR loci, provided strong evidence for divergence by clearly differentiating sea carrot‐specific clades and mixed‐host clades. Low levels of intrapopulation SCAR marker sequence variation and floral morphology suggest that populations on different hosts are probably selfing and inbreeding. Morphologically cryptic Orobanche taxa may therefore be isolated from gene flow by host ecology. Together, these data suggest that host specificity may be an important driver of allopatric speciation in parasitic plants.     

Biogeography and host‐related factors trump parasite life history: limited congruence among the genetic structures of specific ectoparasitic lice and their rodent hosts

Parasites and hosts interact across both micro‐ and macroevolutionary scales where congruence among their phylogeographic and phylogenetic structures may be observed. Within southern Africa, the four‐striped mouse genus, Rhabdomys, is parasitized by the ectoparasitic sucking louse, Polyplax arvicanthis. Molecular data recently suggested the presence of two cryptic species within P. arvicanthis that are sympatrically distributed across the distributions of four putative Rhabdomys species. We tested the hypotheses of phylogeographic congruence and cophylogeny among the two parasite lineages and the four host taxa, utilizing mitochondrial and nuclear sequence data. Despite the documented host‐specificity of P. arvicanthis, limited phylogeographic correspondence and nonsignificant cophylogeny was observed. Instead, the parasite–host evolutionary history is characterized by limited codivergence and several duplication, sorting and host‐switching events. Despite the elevated mutational rates found for P. arvicanthis, the spatial genetic structure was not more pronounced in the parasite lineages compared with the hosts. These findings may be partly attributed to larger effective population sizes of the parasite lineages, the vagility and social behaviour of Rhabdomys, and the lack of host‐specificity observed in areas of host sympatry. Further, the patterns of genetic divergence within parasite and host lineages may also be largely attributed to historical biogeographic changes (expansion‐contraction cycles). It is thus evident that the association between P. arvicanthis and Rhabdomys has been shaped by the synergistic effects of parasite traits, host‐related factors and biogeography over evolutionary time.     

THE BITTERLING–MUSSEL COEVOLUTIONARY RELATIONSHIP IN AREAS OF RECENT AND ANCIENT SYMPATRY

Host–parasite relationships are often characterized by the rapid evolution of parasite adaptations to exploit their host, and counteradaptations in the host to avoid the costs imposed by parasitism. Hence, the current coevolutionary state between a parasite and its hosts is predicted to vary according to the history of sympatry and local abundance of interacting species. We compared a unique reciprocal coevolutionary relationship of a fish, the European bitterling (Rhodeus amarus) and freshwater mussels (Unionidae) between areas of recent (Central Europe) and ancient (Turkey) sympatry. Bitterling parasitize freshwater mussels by laying their eggs in the gills of mussel and, in turn, mussel larvae (glochidia) parasitize the fish. We found that all bitterling from both regions avoided one mussel species. Preferences among other mussel species tended to be related to local mussel abundance rather than duration of sympatry. Individual fish were not consistent in their oviposition choices, precluding the evolution of host‐specific lineages. Mussels were demonstrated to have evolved strong defenses to bitterling parasitism in the area of ancient sympatry, but have no such defenses in the large areas of Europe where bitterling are currently invasive. Bitterling avoided glochidia infection irrespective of the duration of sympatry.     

Host switching in cowbird brood parasites: how often does it occur?

Avian obligate brood parasites lay their eggs in nests of host species, which provide all parental care. Brood parasites may be host specialists, if they use one or a few host species, or host generalists, if they parasitize many hosts. Within the latter, strains of host‐specific females might coexist. Although females preferentially parasitize one host, they may occasionally successfully parasitize the nest of another species. These host switching events allow the colonization of new hosts and the expansion of brood parasites into new areas. In this study, we analyse host switching in two parasitic cowbirds, the specialist screaming cowbird (Molothrus rufoaxillaris) and the generalist shiny cowbird (M. bonariensis), and compare the frequency of host switches between these species with different parasitism strategies. Contrary to expected, host switches did not occur more frequently in the generalist than in the specialist brood parasite. We also found that migration between hosts was asymmetrical in most cases and host switches towards one host were more recurrent than backwards, thus differing among hosts within the same species. This might depend on a combination of factors including the rate at which females lay eggs in nests of alternative hosts, fledging success of the chicks in this new host and their subsequent success in parasitizing it.     

Patterns of parental care in Neotropical glassfrogs: fieldwork alters hypotheses of sex‐role evolution

Many animals provide parental care to offspring. Parental sex‐roles vary extensively across taxa, and such patterns are considered well documented. However, information on amphibians is lacking relative to other vertebrate groups. We combine natural history observations with functional and historical analyses to examine the evolution of egg care in glassfrogs (Centrolenidae). Parental care was considered rare and predominately provided by males. Our field observations of 40 species revealed that care occurs throughout the family, and the caregiving sex changes across lineages. We discovered that a brief period of maternal care is widespread and occurs in species previously thought to lack care. Using a combination of female‐removal experiments, prey‐choice tests with egg‐eating katydids, and parental disturbance‐tolerance assays, we confirm the adaptive benefits of short‐term maternal care in wild Cochranella granulosa and Teratohyla pulverata. To examine historical transitions between caregiving sexes, we assembled a molecular phylogeny and estimated ancestral care states using our data and the literature. We assessed patterns indicative of sex‐specific constraints by testing whether transitions between the sexes are associated with changes in care levels. Our analyses support that male‐only care evolved 2–3 times from female‐only care, and this change is associated with substantial increases in care levels – a pattern supporting the hypothesis that male‐only care evolved via constraints on maternal expenditure. Many groups of amphibians remain poorly studied, with emerging evidence indicating that care patterns are more diverse than currently appreciated. Natural history remains fundamental to uncovering this diversity and generating testable hypotheses of sex‐role evolution.     

Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach

Studies of host-parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.     

Non‐monophyly of Bostrychia simpliciuscula (Ceramiales,Rhodophyta): Multiple species with very similar morphologies,a revised taxonomy of cryptic species

The discovery of a plethora of cryptic species in many algal groups has led to speculation as to the causes of this observation and has affected taxonomy, with reluctance to give names to species that look identical. While this is defensible for monophyletic cryptic species complexes, both our understanding of similar morphologies (crypsis) and nomenclature is challenged when we encounter non‐monophyletic ‘cryptic’ species. Bostrychia simpliciuscula is a wide‐ranging species in which multiple cryptic species are known. Our increased sampling shows that this species consists of four lineages that do not form a clade, but lineages are sister to species with different morphologies. Careful morphological examination shows that characters, especially branched monosiphonous laterals and rhizoid morphology in haptera, are able to distinguish these four lineages into two groups, that are still not monophyletic. The similar morphologies in these lineages could be due to convergence, but not developmental constraints or lack of time to diverge morphologically; or possibly maintenance of a generalized body plan. These lineages appear to have specific biogeographic patterns and these will be used to propose a new taxonomy. B. simpliciuscula is now confined to the tropics. Another of these lineages matches a previously described species, B. tenuissima, that was synonymized with B. simpliciuscula and is from cold temperate Australasia, and is resurrected. Another lineage is found in Japan in which a previous name is also available, B. hamana‐tokidae; the last lineage is found in central New South Wales, morphologically it resembles B. tenuissima, with which it overlaps in distribution around Sydney, and is named as a new species, B. kingii sp. nov.     

Zur Parasitologie und postparasitischen Entwicklung der neotropischen Wassermilbe Arrenurus valencius (Hydrachnellae,Acari), nebst einigen faunistischen Angaben zum See “Laguna Chichoj”; in Guatemala

During two visits to Guatemala in 1974 and 1975 observations were made on the fauna in Eichhomia growth of the small lake “Laguna Chichoj”;. Chemical and physical data and faunistic finds are reported. Particular attention was paid to the water mite Arrenurus (Arrenurus) valencius MARSHALL, 1919. Adults of this species occur commonly in the Eichhornia growth. The larvae parasitize adult Ischnura ramburi crédula (Zygoptera, Odonata). This fits the known pattern according to which nearly all species of the subgenus Arrenurus are parasites of dragonflies belonging to both the Zygoptera as well as Anisoptera (Münchberg 1935, Mitchell 1959, Böttger 1965, Cassagne‐Méjean 1966, Cook 1974, Stechmann 1977). Also the first mentions in the literature on tropical species of the subgenus Arrenurus pointed to Odonata as specific hosts (Münchberg 1958, 1959, 1960).

Ischnura ramburi credula is quite abundant in Eichhornia growth. Both sexes are infested by water mites, the males carrying a maximum of 111, the females of 66 parasites. The average were 24 parasites per male and 16 per female. For both sexes the extensity of infestation was an equal 90%.

The parasites are located predominantly at the ventral side of the thorax and the first abdominal segments. During the parasitic phase the volume of the larvae increases considerably: body length and width double. Separation from the host ‐ notwithstanding a few exceptions ‐ does not take place when after a few days of parasitic existence the amount of food necessary for further development has been ingested but only at the moment of death of the host. This raises the chances of the parasites of returning to the water: the host dragonflies live near the shore and regularly dying individuals fall on the surface of the water or among the Eichhornia plants.

Larvae which had left their dead host in the laboratory have been reared through the Postlarval Resting Stage I, the deutonymph stage and the Postlarval Resting Stage II up to the adult. The deutonymphs are carnivorous like the adults; they prey on ostracods with predilection.     

Reproductive isolation due to prezygotic isolation and postzygotic cytoplasmic incompatibility in parasitoid wasps

The reproductive barriers that prevent gene flow between closely related species are a major topic in evolutionary research. Insect clades with parasitoid lifestyle are among the most species‐rich insects and new species are constantly described, indicating that speciation occurs frequently in this group. However, there are only very few studies on speciation in parasitoids. We studied reproductive barriers in two lineages of Lariophagus distinguendus (Chalcidoidea: Hymenoptera), a parasitoid wasp of pest beetle larvae that occur in human environments. One of the two lineages occurs in households preferably attacking larvae of the drugstore beetle Stegobium paniceum (“DB‐lineage”), the other in grain stores with larvae of the granary weevil Sitophilus granarius as main host (“GW‐lineage”). Between two populations of the DB‐lineage, we identified slight sexual isolation as intraspecific barrier. Between populations from both lineages, we found almost complete sexual isolation caused by female mate choice, and postzygotic isolation, which is partially caused by cytoplasmic incompatibility induced by so far undescribed endosymbionts which are not Wolbachia or Cardinium. Because separation between the two lineages is almost complete, they should be considered as separate species according to the biological species concept. This demonstrates that cryptic species within parasitoid Hymenoptera also occur in Central Europe in close contact to humans.