Adaptive radiation of shrubby tarweeds (Deinandra) in the California Islands parallels diversification of the Hawaiian silversword alliance (Compositae-Madiinae)

Phylogenetic analyses of nuclear rDNA transcribed spacers and cytogenetic studies of interspecific hybrids reported here uphold Carlquist's hypothesis (1965, Island Biology) that shrubby tarweeds (Deinandra) of Guadalupe Island, Mexico, are products of in situ radiation in the California Islands, where evidence of plant diversification has been equivocal. Based on the rDNA findings, the Guadalupe Island endemics (D. frutescens, D. greeneana subsp. greeneana, and D. palmeri) constitute a clade that arose since the late Pliocene, well after the origin of Guadalupe Island and diversification of annual, mainland Californian lineages of Deinandra. High interfertility and normal meiosis in F(1) hybrids between the three endemics contrast with reduced interfertility (to complete intersterility) and meiotic irregularities in F(1) hybrids between other, mostly mainland species of Deinandra. Cloned rDNA sequences provided no convincing evidence of introgression among the Guadalupe Island deinandras; morphological, phenological, and/or habitat differences among those taxa indicate ecological barriers to gene flow and a probable role for ecological divergence in diversification. Biosystematic and molecular phylogenetic data for shrubby tarweeds of Guadalupe Island and another secondarily woody, oceanic-island tarweed lineage, the Hawaiian silversword alliance, reveal strikingly similar evolutionary histories. Both groups violate Baker's Rule by stemming from self-incompatible ancestors in western North America, and each has undergone within-island diversification without evolution of strong sterility barriers among lineages. Evolutionary parallels between these Hawaiian and California Island lineages of Madiinae, first suggested by Carlquist, may reflect characteristics of tarweeds that facilitate insular colonization and adaptive radiation.     

Mitochondrial sequence variation in Carlos capensis (Neumann), a parasite of seabirds,collected on Torishima Island in Japan

Partial mitochondrial 16S ribosomal ribonucleic acid gene sequences in the ticks Carios capensis collected from black-footed albatross. Diomedea nigripes, colonies on Torishima Island, Japan (30 degrees 28'N, 140 degrees 18'E), were examined. The sequence was compared with those of C. capensis from Hawaii, South Carolina, and Texas. The sequences were all identical in ticks from Torishima and 2 from Hawaii. There were 2-3 transitions between the other Hawaiian and Texas ticks and Torishima specimens. Two transitions were also observed when compared with the ticks from South Carolina. The results suggest the possibility of gene flow between tick populations at each of the 2 geographic sites, which probably was accomplished by tick-infested migratory seabirds at their breeding sites. Sequence comparison analysis indicated that the C. capensis ticks are on the branch with C. marginatus and C. mexicanus ticks and not with Ornithodoros. This supports the revision suggested by Klompen and Oliver (1993).     

CHROMOSOME NUMBERS OF HAWAIIAN FLOWERING PLANTS AND THE SIGNIFICANCE OF CYTOLOGY IN SELECTED TAXA

Chromosome numbers are reported for 128 species of flowering plants indigenous or endemic to Hawaii, including first reports for 13 genera and 82 species. The special significance of reports for Ilex, Tribulus, Keysseria, Pisonia, Boerhavia, Jacquemontia, Claoxylon, Lipochaeta, Railliardia, and Dubautia are discussed. The cytological and morphological variation in Railliardia and Dubautia is considered and their treatment as congeners is advocated. The cytogeogruphic pattern in Dubautia and Railliardia and other factors suggest that the ancestral chromosome number of the Hawaiian tarweeds is n = 14. Their derivation from a western North American progenitor similar to Adenothamnus is considered plausible if not indeed likely.     

Preliminary Observations on Specific Adaptations of Exophilic Ixodid Ticks to Forests or Open Country Habitats

Some features of three-host exophilic ticks important for their survival differ at the generic level in relation to the types of their habitat. Ixodes and Haemaphysalis are typical forest genera, Hyalomma is an open country genus, whereas Dermacentor and Rhipicephalus, having some features of forest ticks, are closer to the ticks of open country. Forest ticks encounter rather stable and favorable temperature, humidity and illumination conditions as compared with open country ticks. A few differences determining every-day survival, host-seeking, and reproduction of ticks are considered. (1) Tolerance to desiccation is very low in forest ticks and much greater in ticks of open country. (2) Lack of eyes in forest ticks (having, however, epithelial photoreceptor cells) and formation of eyes as special morphological structures in ticks of open country. (3) Capability of mating and insemination of unfed specimens both on and off hosts in forest ticks (Ixodes) and insemination of partially engorged females only on hosts by fed males in open country ticks. (4) Reciprocal sexual dimorphism where in forest ticks females have a larger body than males and in open country ticks this correlation is opposite. (5) Linear dependence between female weight and number of eggs laid is established in forest ticks after the female weight becomes higher than 50% of mean engorgement weight whereas in open country ticks linear dependence begins to reveal itself much earlier. (6) In forest ticks the compensatory growth occurs only during adult feeding whereas in open country ticks such a growth occurs both during nymphal and adult feeding. The adaptive nature of the above differences and their evolutionary trends have been hypothesized. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of host lizard anemia on host choice and feeding rate of larval western black-legged ticks (Ixodes pacificus)

Although ticks are known to exhibit preferences among host species, there is little evidence that ticks select hosts within a species based on physiological condition. It may be beneficial for ticks to choose hosts that are easier to feed upon if the ticks can perceive indicative chemical or other signals from the host. For example, if ticks can detect host hematocrit they may choose hosts with high hematocrit, facilitating a faster blood meal. It may similarly be adaptive for ticks to avoid anemic hosts because it may be difficult for them to obtain an adequate meal and feeding duration may be extended. We tested the hypothesis that larval western black-legged ticks (Ixodes pacificus) detect host hematocrit using external cues and choose healthy over anemic hosts, allowing them to feed more quickly. We presented groups of larval ticks with pairs of healthy and anemic male western fence lizards (Sceloporus occidentalis), allowed them to select a host, and measured the feeding duration of the ticks. We found that the ticks did not exhibit a statistically significant preference for healthy over anemic lizards, but that the ticks fed to repletion significantly faster on healthy hosts than on anemic hosts. Larval ticks may not be able to detect external cues indicating the health of the host, at least not in terms of their hematocrit. The extended feeding duration likely reflects the extra time needed for the ticks to concentrate the blood meal of their anemic hosts.     

Patterns of recruitment and spawning in Hawaiian reef fishes

Synopsis Recruitment of juvenile fishes to five 25 m² quadrats on an extensive natural reef in Kona, Hawaii was monitored over 51 months. Pronounced between-year variability in recruit abundance was evident for some species. Many exhibited strikingly low levels of recruitment. Overall recruitment was highly seasonal with a major peak in June and July, and a generally smaller, secondary peak in February and March. Recruitment was minimal during early winter (October–December) and a review of other studies similarly indicates minimal recruitment in Hawaii during this period. Spawning in Hawaiian fishes generally begins during the winter months of relatively low temperatures, increases during late winter and early summer and declines rapidly as maximum summer water temperatures are reached (September–October). Seasonal changes in food availability, ocean currents or salinity seem unlikely to be responsible for observed patterns of recruitment and spawning. Rather, the patterns appear to be most closely tied to changes in water temperature or photoperiod. Loss of propagules to offshore-moving eddies or other unfavorable currents may be responsible for the low levels of juvenile recruitment found in this and other Hawaiian studies. In Kona, at least 6 species of fishes recruited in pulses during quarter or new moon phases. Four other species have been reported elsewhere in Hawaii to recruit during either new or full moon phases. Lunar spawning periodicity was present in fewer than half of the species so far examined, and no single adaptive function for lunar periodicity was applicable to all species.     

A novel clade of cysteinyl leukotriene scavengers in soft ticks

Inflammation is an important vertebrate defense mechanism against ecto-parasites for which ticks have evolved numerous mechanisms of modulation. AM-33 and TSGP4, related lipocalins from the soft ticks Argas monolakensis and Ornithodoros savignyi bind cysteinyl leukotrienes with high affinity as measured by isothermal titration calorimetry. This was confirmed in a smooth muscle bioassay that measured contraction of guinea pig ileum induced by leukotriene C(4) where both proteins inhibited contraction effectively. Conservation of this function in two diverse soft tick genera suggests that scavenging of cysteinyl leukotrienes evolved in the ancestral soft tick lineage. In addition soft ticks also evolved mechanisms that target other mediators of inflammation that include scavenging of histamine, serotonin, leukotriene B(4), thromboxane A(2), ATP and inhibition of the complement cascade. Inhibitors of blood-coagulation and platelet aggregation were also present in the ancestral soft tick lineage. Because histamine and cysteinyl leukotrienes are mainly produced by mast cells and basophils, and these cells are important in the mediation of tick rejection reactions, these findings indicate an ancient antagonistic relationship between ticks and the immune system. As such, modulation of the hemostatic system as well as inflammation was important adaptive responses in the evolution of a blood-feeding lifestyle in soft ticks.     

Multiple cave invasions by species of the planthopper genus Oliarus in Hawaii (Homoptera: Fulgoroidea: Cixiidae)

Although geologically young, the Hawaiian Islands harbour a rich and remarkably diverse fauna of terrestrial troglobites: more than 70 cave species are known from Kauai, Oahu, Molokai, East Maui, and Hawaii Island. Among the more speciosc groups that have invaded the subterranean biome are the planthoppers (Homoptera Cixiidae) of the genus Oliarus. Five new obligately cavernicolous (troglobitic) Oliarus species which differ in their degree of troglomorphy and male genital structures, are described from lava tubes on the Hawaiian Islands: O. lorettae sp. nov. and O. makaiki sp. nov. from Hawaii Island, O. gagnei sp. nov. and O. ivaikau sp. nov. from Maui Island, and O. kalaupapae sp. nov. from Molokai Island. Short diagnoses of the two troglobitic species already known, 0. polyphemus Fennah, 1973 from Hawaii Island and 0. priola Fennah, 1973 from Maui are provided. Notes on the ecology and distribution of all cavernicolous species are given. Morphological evidence suggests that each of the seven cavernicolous Oliams species from Hawaii represents a separate, independent adaptive shift to underground environments. Potential relationships to the extant epigean species are discussed.     

The tick Ornithodoros papillipes count in Namangan and Andizhan Provinces and its determining factors

Analysis of the abundance of the tick O. papillipes in the Namangan and Andizhan districts was conducted on vast material. According to the tick abundance (from very high to very low) settlements were arranged into five groups. Most common are settlements with a high and average tick abundance. In most cases the agent of TRF was isolated from the ticks. Natural and anthropogenic factors determining the abundance rate of ticks in some settlements and possibilities of their practical use for the quick annihilation of TRF nidi are discussed.     

On the visual perception of the eyes in adult Hyalomma truncatum ticks (Acari: Ixodidae)

Adult Hyalomma truncatum ticks with uncovered and foil-covered eyes were exposed to an upright-positioned rectangle as a target giving a luminance contrast ratio of 5:1 at a sun-simulating radiation. The transmission rate of the foil was less than 0.003%. Significantly (p0.05) more locomotorally active ticks with uncovered eyes (36.6%) responded to the target than ticks with foil-covered eyes (7.3%). When the rectangle was illuminated by monochromatic light at wavelengths ranging between 420 and 648 nm, the target induced a positive scototaxis in ticks with uncovered eyes regardless of the wavelength range. In contrast, ticks with covered eyes did not exhibita positive scototaxis at wavelength ranges of 553–585 and 608–648 nm and very few ticks responded only to other wavelength ranges. The results indicate that the eyes are the only or at least the most essential sense organs in the visual system of adult H. truncatum ticks.     

Gluttony and sex in female ixodid ticks: how do they compare to other blood-sucking arthropods?

The central issue dealt with here is the role of copulation in the control of feeding behaviour in ticks and some haematophagous insects. Female ticks of the family Ixodidae normally engorge to approximately 100 x their unfed body weight, and then drop from the host, produce and lay eggs, and die. Virgins, on the other hand, normally do not exceed 5-40% (depending on species) of the normal engorged body weight. But instead of detaching voluntarily at that point most virgins remain fixed to the host for extended periods, waiting for males to find them so they can complete engorgement. Virgin haematophagous insects, and virgin ticks of the family Argasidae display little, if any, reduction in blood meal size compared to mated females, at least not during the first ovarian cycle. During subsequent ovarian cycles, meal size in some virgin insects may be somewhat reduced depending on how many eggs are retained in the reproductive tract, but the reduction is not nearly to the same extent as that observed for virgin ixodid females. The stimulatory effect of copulation on engorgement in the latter is caused by a pair of proteins (voraxin alpha and beta) produced in the testis and transferred to the female with the spermatophore. Here, I propose why it might be adaptive for an ixodid female to remain small until mated. The hypothesis is suggested from the facts that ixodid ticks remain attached to the host for days (rather than minutes), and that virgin ticks, above a certain critical weight, lose all opportunity for producing viable offspring should they be groomed off the host prematurely, or should the host die while ticks are still attached.     

Hyalomma truncatum (Acari; Ixodidae): investigations into the scototaxis of unfed adult ticks

Under controlled test conditions, unfed male and female Hyalomma truncatum ticks exhibited a positive scototaxis to stationary, two-dimensional targets. Upright-positioned rectangles were the most attractive targets. The attractiveness of these targets increased with their size. Significantly more ticks responded scototactically positively to the targets under a luminance contrast ratio of 5:1, as compared with other luminance contrast ratios. Targets with an elevation angle of 13° were occupied more frequently than objects with higher elevation angles. Scototaxis was the same towards a stationary and a sinusoid oscillating target. When an upright-positioned rectangle was combined with a CO₂ gradient, the number of ticks that migrated into the CO₂ gradient and contacted the target did not increase significantly. The interval between exposure and first locomotion of the ticks, however, was significantly shorter under the influence of a CO₂ gradient than in all other experiments without a CO₂ gradient. A temperature gradient simulating a natural host (cattle) did not alter the scototaxis. The results of these investigations suggest that the positive scototaxis exhibited by adult H. truncatum ticks is not likely to be part of their appetence behaviour but rather searching behaviour to find adequate protection from harsh climatic conditions.     

Detection of Wolbachia in the tick Ixodes ricinus is due to the presence of the hymenoptera endoparasitoid Ixodiphagus hookeri

The identification of micro-organisms carried by ticks is an important issue for human and animal health. In addition to their role as pathogen vectors, ticks are also the hosts for symbiotic bacteria whose impact on tick biology is poorly known. Among these, the bacterium Wolbachia pipientis has already been reported associated with Ixodes ricinus and other tick species. However, the origins of Wolbachia in ticks and their consequences on tick biology (known to be very diverse in invertebrates, ranging from nutritional symbionts in nematodes to reproductive manipulators in insects) are unknown. Here we report that the endoparasitoid wasp Ixodiphagus hookeri (Hymenoptera, Chalcidoidea, Encyrtidae)--strictly associated with ticks for their development--infested at almost 100% prevalence by a W. pipientis strain belonging to a Wolbachia supergroup that has already been reported as associated with other hymenopteran parasitoids. In a natural population of I. ricinus that suffers high parasitism rates due to I. hookeri, we used specific PCR primers for both hymenopteran and W. pipientis gene fragments to show that all unfed tick nymphs parasitized by I. hookeri also harbored Wolbachia, while unparasitized ticks were Wolbachia-free. We demonstrated experimentally that unfed nymphs obtained from larvae exposed to I. hookeri while gorging on their vertebrate host also harbor Wolbachia. We hypothesize that previous studies that have reported W. pipientis in ticks are due to the cryptic presence of the endoparasitoid wasp I. hookeri. This association has remained hidden until now because parasitoids within ticks cannot be detected until engorgement of the nymphs brings the wasp eggs out of diapause. Finally, we discuss the consequences of this finding for our understanding of the tick microbiome, and their possible role in horizontal gene transfer among pathogenic and symbiotic bacteria.     

Identification of four genes expressed by feeding, female Ixodes scapularis including three with sequence similarity to previously recognized genes

We created a cDNA library from feeding, female Ixodes scapularis ticks and screened the library with a subtracted probe to eliminate most genes common to feeding female and mating male I. scapularis ticks. Four unique genes were identified in this screen. One gene, Is 9, (represented by 16 cDNAs) was more highly expressed in female ticks. This gene encodes a putative glycine-rich protein, which matched a number of glycine-rich proteins including attachment cement proteins from Rhipicephalus appendiculatus. A second gene, Is 10 (represented by one cDNA) was also more highly expressed in female ticks, but did not match any other sequences in the GenBank database. The third gene, Is 11 (represented by one cDNA) was very similar to Drosophila sp. hsp68 and hsp70 genes and was expressed about equally in male and female ticks. The fourth gene, Is 12 (represented by two cDNAs) was also about equally expressed in male and female ticks, and was similar to a salivary gland gene from Ixodes ricinis. This gene also showed limited similarity to some cuticle genes from insects.     

Experimental study of micro-habitat selection by ixodid ticks feeding on avian hosts

Mechanisms of on-host habitat selection of parasites are important to the understanding of host-parasite interactions and evolution. To this end, it is important to separate the factors driving parasite micro-habitat selection from those resulting from host anti-parasite behaviour. We experimentally investigated whether tick infestation patterns on songbirds are the result of an active choice by the ticks themselves, or the outcome of songbird grooming behaviour. Attachment patterns of three ixodid tick species with different ecologies and host specificities were studied on avian hosts. Ixodes arboricola, Ixodes ricinus and Ixodes frontalis were put on the head, belly and back of adult great tits (Parus major) and adult domestic canaries (Serinus canaria domestica) which were either restricted or not in their grooming capabilities. Without exception, ticks were eventually found on a bird’s head. When we gave ticks full opportunities to attach on other body parts – in the absence of host grooming – they showed lower attachment success. Moreover, ticks moved from these other body parts to the host's head when given the opportunity. This study provides evidence that the commonly observed pattern of ticks feeding on songbirds’ heads is the result of an adaptive behavioural strategy. Experimental data on a novel host species, the domestic canary, and a consistent number of published field observations, strongly support this hypothesis. We address some proximate and ultimate causes that may explain parasite preference for this body part in songbirds. The link found between parasite micro-habitat preference and host anti-parasite behaviour provides further insight into the mechanisms driving ectoparasite aggregation, which is important for the population dynamics of hosts, ectoparasites and the micro-pathogens for which they are vectors.     

Novel Immunomodulators from Hard Ticks Selectively Reprogramme Human Dendritic Cell Responses

Hard ticks subvert the immune responses of their vertebrate hosts in order to feed for much longer periods than other blood-feeding ectoparasites; this may be one reason why they transmit perhaps the greatest diversity of pathogens of any arthropod vector. Tick-induced immunomodulation is mediated by salivary components, some of which neutralise elements of innate immunity or inhibit the development of adaptive immunity. As dendritic cells (DC) trigger and help to regulate adaptive immunity, they are an ideal target for immunomodulation. However, previously described immunoactive components of tick saliva are either highly promiscuous in their cellular and molecular targets or have limited effects on DC. Here we address the question of whether the largest and globally most important group of ticks (the ixodid metastriates) produce salivary molecules that specifically modulate DC activity. We used chromatography to isolate a salivary gland protein (Japanin) from Rhipicephalus appendiculatus ticks. Japanin was cloned, and recombinant protein was produced in a baculoviral expression system. We found that Japanin specifically reprogrammes DC responses to a wide variety of stimuli in vitro, radically altering their expression of co-stimulatory and co-inhibitory transmembrane molecules (measured by flow cytometry) and their secretion of pro-inflammatory, anti-inflammatory and T cell polarising cytokines (assessed by Luminex multiplex assays); it also inhibits the differentiation of DC from monocytes. Sequence alignments and enzymatic deglycosylation revealed Japanin to be a 17.7 kDa, N-glycosylated lipocalin. Using molecular cloning and database searches, we have identified a group of homologous proteins in R. appendiculatus and related species, three of which we have expressed and shown to possess DC-modulatory activity. All data were obtained using DC generated from at least four human blood donors, with rigorous statistical analysis. Our results suggest a previously unknown mechanism for parasite-induced subversion of adaptive immunity, one which may also facilitate pathogen transmission.     

Strain diversity of Borrelia burgdorferi in ticks dispersed in North America by migratory birds

The role of migratory birds in the dispersal of Ixodes scapularis ticks in the northeastern U.S. is well established and is presumed to be a major factor in the expansion of the geographic risk for Lyme disease. Population genetic studies of B. burgdorferi sensu stricto, the agent of Lyme disease in this region, consistently reveal the local presence of as many as 15 distinct strain types as designated by major groups of the ospC surface lipoprotein. Recent evidence suggests such strain diversity is adaptive to the diverse vertebrate hosts that maintain enzootic infection. How this strain diversity is established in emergent areas is unknown. To determine whether similar strain diversity is present in ticks imported by birds, we examined B. burgdorferi strains in I. scapularis ticks removed from migrants at an isolated island site. Tick mid‐guts were cultured and isolates underwent DNA amplification with primers targeting ospC. Amplicons were separated by gel electrophoresis and sequenced. One hundred thirty‐seven nymphal ticks obtained from 68 birds resulted in 24 isolates of B. burgdorferi representing eight ospC major groups. Bird‐derived ticks contain diverse strain types of B. burgdorferi, including strain types associated with invasive Lyme disease. Birds and the ticks that feed on them may introduce a diversity of strains of the agent of Lyme disease to emergent areas.     

Stepping stone speciation in Hawaii’s flycatchers: molecular divergence supports new island endemics within the elepaio

The elepaio (Chasiempis sandwichensis) is a monarch flycatcher endemic to the Hawaiian Islands of Kauai, Oahu, and Hawaii. Elepaio vary in morphology among and within islands, and five subspecies are currently recognized. We investigated phylogeography of elepaio using mitochondrial (ND2) and nuclear (LDH) markers and population structure within Hawaii using ND2 and microsatellites. Phylogenetic analyses revealed elepaio on each island formed reciprocally monophyletic groups, with Kauai ancestral to other elepaio. Sequence divergence in ND2 among islands (3.02–2.21%) was similar to that in other avian sibling species. Estimation of divergence times using relaxed molecular clock models indicated elepaio colonized Kauai 2.33 million years ago (95% CI 0.92–3.87 myr), Oahu 0.69 (0.29–1.19) myr ago, and Hawaii 0.49 (0.21–0.84) myr ago. LDH showed less variation than ND2 and was not phylogenetically informative. Analysis of molecular variance within Hawaii showed structure at ND2 (fixation index = 0.31), but microsatellites showed no population structure. Genetic, morphological, and behavioral evidence supports splitting elepaio into three species, one on each island, but does not support recognition of subspecies within Hawaii or other islands. Morphological variation in elepaio has evolved at small geographic scales within islands due to short dispersal distances and steep climatic gradients. Divergence has been limited by lack of dispersal barriers in the extensive forest that once covered each island, but anthropogenic habitat fragmentation and declines in elepaio population size are likely to decrease gene flow and accelerate differentiation, especially on Oahu.     

Mid-ocean isolation and the evolution of Hawaiian reef fishes

The Hawaiian fish fauna has close affinities with the fauna of the Indo-west Pacific from which it is derived, but is depauperate. It is characterized by a large number of endemic species (30% of inshore fishes), which are often the most abundant species in their families in Hawaii. Although there is evidence of local adaptation, there has been no radiation of species within the island chain, as occurs in the terrestrial biota of isolated islands. Three major factors have contributed to these trends: (1) the geographic isolation of the islands, and oceanographic features, especially current patterns; (2) the life history characteristics of the fishes, especially their dispersal capabilities; and (3) the extent of adaptive differentiation to environmental conditions after they reached Hawaii.     

Linkage relationships among 12 enzyme loci in cattle fever ticks of the genus Boophilus

Electrophoretic variation at 12 enzyme loci in cattle fever ticks were examined for mode of inheritance and linkage relationships. All variants exhibited codominant Mendelian inheritance, and PGI and GOT were sex-linked. Four pairs of enzyme loci were linked (PGI and GOT, ACON-A and alpha GPD, MDH-1 and LDH, and EST-3 and EST-4). Four additional enzyme loci (ACON-C, MDH-2, PEP, and PP) did not show linkage to any other locus tested, giving eight presumptive linkage groups that have enzyme markers in the genus Boophilus.