Suitable Host Species Research Articles

Host adaptability of Microplitis manilae (Hymenoptera: Braconidae) in Noctuidae.

Biological control is an effective and sustainable method of integrated pest management. Microplitis manilae (Hymenoptera: Braconidae) is a common internal parasitoid wasp of the order Lepidoptera. To determine a suitable host species for the reproduction of parasitoids, it is essential to assess host suitability and parasitic potential of the parasitized pests. Herein, we investigated host selection and exploitation of M. manilae. We evaluated the parasitic efficacy of M. manilae in 4 pest species in the Spodoptera and Mythimna genera of the Noctuidae family. The results indicated that the parasitism rate of M. manilae on 3 species in the Spodoptera genus is higher than on Mythimna separata in the Mythimna genus, with M. manilae exhibiting a higher parasitism rate and shorter development duration on Spodoptera litura compared to other species. The parasitism rate for 1st instars hosts was 86.67 ± 0.04%, while the development duration was 14.1 ± 0.03 days. However, when parasitizing the 3rd instar of Spodoptera frugiperda, parasitoids showed a higher sex ratio, of 0.71 ± 0.05. Additionally, M. manilae had parasitic effect on M. separata, providing a new choice for its parasitism. The results identify the optimal host, which could enhance and reproduction rate and survival rate of M. manilae, thus facilitating their large-scale propagation. Understanding the parasitic effects of M. manilae on pests can further its field application, also plays a major role in promoting the development of biological control technologies and sustainable agricultural production.

Host Plant Modulated Physio-Biochemical Process Enhances Adaptive Response of Sandalwood (Santalum album L.) under Salinity Stress.

Salinity is one of the most significant abiotic stress that affects the growth and development of high-value tree species, including sandalwood, which can also be managed effectively on saline soils with the help of suitable host species. Therefore, the current investigation was conducted to understand the physiological processes and antioxidant mechanisms in sandalwood along the different salinity gradients to explore the host species that could support sandalwood growth in salt-affected agro-ecosystems. Sandalwood seedlings were grown with ten diverse host species with saline water irrigation gradients (ECiw~3, 6, and 9 dS m-1) and control (ECiw~0.82 dS m-1). Experimental findings indicate a decline in the chlorophyll content (13-33%), relative water content (3-23%), photosynthetic (27-61%) and transpiration rate (23-66%), water and osmotic potential (up to 137%), and ion dynamics (up to 61%) with increasing salinity levels. Conversely, the carotenoid content (23-43%), antioxidant activity (up to 285%), and membrane injury (82-205%) were enhanced with increasing salinity stress. Specifically, among the hosts, Dalbergia sissoo and Melia dubia showed a minimum reduction in chlorophyll content, relative water content, and plant water relation and gas exchange parameters of sandalwood plants. Surprisingly, most of the host tree species maintained K+/Na+ of sandalwood up to moderate water salinity of ECiw~6 dS m-1; however, a further increase in water salinity decreased the K+/Na+ ratio of sandalwood by many-fold. Salinity stress also enhanced the antioxidative enzyme activity, although the maximum increase was noted with host plants M. dubia, followed by D. sissoo and Azadirachta indica. Overall, the investigation concluded that sandalwood with the host D. sissoo can be successfully grown in nurseries using saline irrigation water and, with the host M. dubia, it can be grown using good quality irrigation water.

Assessing the Global Pest Risk of Aeolesthes sarta with Regards to the Host Specie Populus alba under Climate Change Scenarios

Aeolesthes sarta or Trirachys sarta is a polyphagous long-horned beetle that has caused severe damage to the Populus alba forests/plantations in its regions of origin. Climate change could accelerate the introduction and spread of invasive pest species, potentially causing ecological damage and economic losses. Furthermore, globalization and increased trade can inadvertently transport pests across borders into regions where they do not already occur. Hence, it is crucial to identify areas where the climate is most suitable for the establishment of A. sarta’s and which areas of the world are suitable for the growth of P. alba under climate change scenarios. This study employed the CLIMEX model to estimate the potential global distribution of A. sarta and its correlation with its dominant host, P. alba, under current climatic conditions and potential future scenarios, namely the A1B and A2 climate change scenarios (CCSs). Under current climatic conditions, the model indicates that the establishment of a climatically suitable habitat for A. sarta extends beyond its current known range. The model estimated that, under the world’s current climatic conditions, 41.06% of the world can provide suitable areas (EI > 0) for the survival of A. sarta. For P. alba, under the current climatic conditions, suitable regions for the growth of P. alba are present in all continents (excluding Antarctica); under the world’s current climatic conditions, 53.52% of the world can provide suitable areas for the growth of P. alba (EI > 0). Climate change will significantly alter the number of suitable habitats for A. sarta development and P. alba growth globally. In future climatic conditions, the number areas capable of supplying suitable habitats (EI > 0) for A. sarta will slightly decrease to 40.14% (under A1B and A2 CCSs), while, for P. alba, the number areas capable of supplying suitable habitats will also marginally decrease to 50.39% (under A1B scenario), and this figure is estimated to drop to 48.41% (under A2 scenario) by the end century (2100). Asia, Europe, North America, South America, and Oceania have a high percentage of highly suitable areas for A. sarta development and P. alba growth under current climatic conditions; however, according to estimates of future climatic conditions, by the end century, only Asia, Europe, North America, and Oceania will have a high percentage of highly suitable areas for A. sarta development and P. alba growth. The range of highly suitable habitats is likely to increase in the northern hemisphere; however, this range is expected to shrink with regards to the southern hemisphere. The range contraction was higher under the A2 climate change scenario due to a higher warming trend than in the A1B scenario. Due to climate change, the range of A. sarta development shifted, as did the P. alba growth range, which, thanks to the suitable environmental conditions for the growth of P. alba, makes all those regions vulnerable to the introduction and development of A. sarta. Strict monitoring, prevention, and control measures at borders, airports, and seaports before the trade of P. alba and other suitable host species wood (logs/billets) are highly recommended to prevent the spread of A. sarta and ensure biodiversity security. It is expected that the A. sarta and P. alba climate models presented here will be useful for management purposes since both can be adapted to guide decisions about imparting resources to regions where the threat of pest invasion remains and away from regions where climate suitability is predicted to decrease in the future.

Potential host range of Cotesia vanessae (Hymenoptera: Braconidae), a parasitoid new to North America and a possible biological control agent of noctuid pest species.

The likelihood of parasitoids establishing in new geographic regions depends upon the availability of suitable host species. Identifying these hosts and the degree of their suitability is particularly important when they include species that are economically important as pests. In laboratory studies, we examined the suitability of 47 species of Lepidoptera as potential hosts of a parthenogenetic strain of the gregarious parasitoid Cotesia vanessae (Hymenoptera: Braconidae). Previously known from Eurasia and northern Africa, the first known recovery of C. vanessae in North America was in 2009. C. vanessae completed development in 34 species, of which three were known hosts (Noctuidae) and 31 (30 Noctuidae, 1 Nymphalidae) were not. Many of these noctuid species are economic pests. Parasitoid fitness was generally highest on species of Plusiinae (Noctuidae), measured as either percentage of successful parasitism, developmental time, or number and mass of F1 progeny. Closely related species were generally similar in their suitability as hosts. In some cases, parasitoid eggs or larvae were killed by the immune system of the parasitized host, but the host eventually failed to excrete food waste, did not pupate, and ultimately died. Such cases reached up to 100% mortality depending upon the lepidopteran species. The suitability of many species of noctuid pests as hosts for C. vanessae suggests that this parasitoid will become established widely throughout North America and may help to suppress populations of some pest species.

No evidence for persistent natural plague reservoirs in historical and modern Europe

Caused by Yersinia pestis, plague ravaged the world through three known pandemics: the First or the Justinianic (6th-8th century); the Second (beginning with the Black Death during c.1338-1353 and lasting until the 19th century); and the Third (which became global in 1894). It is debatable whether Y. pestis persisted in European wildlife reservoirs or was repeatedly introduced from outside Europe (as covered by European Union and the British Isles). Here, we analyze environmental data (soil characteristics and climate) from active Chinese plague reservoirs to assess whether such environmental conditions in Europe had ever supported "natural plague reservoirs". We have used new statistical methods which are validated through predicting the presence of modern plague reservoirs in the western United States. We find no support for persistent natural plague reservoirs in either historical or modern Europe. Two factors make Europe unfavorable for long-term plague reservoirs: 1) Soil texture and biochemistry and 2) low rodent diversity. By comparing rodent communities in Europe with those in China and the United States, we conclude that a lack of suitable host species might be the main reason for the absence of plague reservoirs in Europe today. These findings support the hypothesis that long-term plague reservoirs did not exist in Europe and therefore question the importance of wildlife rodent species as the primary plague hosts in Europe.

Economical and Epidemiological Consequences of Seed Transmitted Plant Viruses. Review

Plant virus diseases greatly influence man’s economy by reducing the yield and quality of plant products. About one-quarter of the known plant viruses are transmitted through the seed. Seed transmission of plant viruses is an important means for the introduction of plant viruses into new localities where they may become established, spread rapidly, and can cause epidemics in the presence of suitable vectors and host species. Viruses may persist in seed for long periods so that commercial distribution of a seed-borne virus over long distances may occur. The location of the virus in seed determines the transmissibility of viruses through seed. The virus is considered to be externally seed transmitted when it is outside the functional seed and internally seed transmitted when it is within the tissue of the seed. Seed infection by the virus is epidemiologically important for the reason that it is the primary source of inoculums and forms the starting point for the initiation of the disease. Avoidance of virus inoculum from infected seeds; chemical seed disinfection, implementing the cultural practices like field sanitation, rouging, and crop rotation can reduce the virus disease incidence. The role of quarantines, resistant cultivars, healthy seed production, and certification schemes for healthy seed production are also critical measures for seed transmitted virus management. Keywords: Inoculum source; Management; Plant virus; Seed transmission DOI: 10.7176/RHSS/12-7-03 Publication date: April 30 th 2022

Higher mortality of the less suitable brown trout host compared to the principal Atlantic salmon host when infested with freshwater pearl mussel (Margaritifera margaritifera) glochidia

The freshwater pearl mussel (Margaritifera margaritifera) is a highly host-specific parasite, with an obligate parasitic stage on salmonid fish. Atlantic salmon (Salmo salar) and brown trout (Salmo trutta f. trutta and Salmo trutta f. fario) are the only hosts in their European distribution. Some M. margaritifera populations exclusively infest either Atlantic salmon or brown trout, while others infest both hosts with one salmonid species typically being the principal host and the other a less suitable host. Glochidial abundance, prevalence and growth are often used as parameters to measure host suitability, with the most suitable host species displaying the highest parameters. However, it is not known if the degree of host specialisation will negatively influence host fitness (virulence) among different host species. In this study we examined the hypothesis that glochidial infestation would result in differential virulence in two salmonid host species and that lower virulence would be observed on the most suitable host. Atlantic salmon and brown trout were infested with glochidia from two M. margaritifera populations that use Atlantic salmon as their principal host, and the difference in host mortality among infested and control (sham infested) fish was examined. Higher mortality was observed in infested brown trout (the less suitable host) groups, compared to the other test groups. Genetic assignment was used to identify offspring from individual mother mussels. We found that glochidia from individual mothers can infest both the salmonid hosts; however, some mothers displayed a bias towards either salmon or trout. We believe that the differences in host-dependent virulence and the host bias displayed by individual mothers were a result of genotype × genotype interactions between the glochidia and their hosts, indicating that there is an underlying genetic component for this parasite-host interaction.

Parasitoid-mediated indirect interactions between unsuitable and suitable hosts generate apparent predation in microcosm and modeling studies.

Parasitoids used as biological control agents often parasitize more than a single host species and these hosts tend to vary in suitability for offspring development. The population dynamics of parasitoids and hosts may be altered by these interactions, with outcomes dependent on the levels of suitability and acceptance of both host species. Parasitism of individuals of an unsuitable host species may indirectly increase populations of a suitable host species if eggs laid into unsuitable hosts do not develop into adult parasitoids. In this case, the unsuitable host is acting as an egg sink for parasitoids and this can reduce parasitism of suitable hosts under conditions of egg limitation. We studied parasitoid‐mediated indirect interactions between two aphid hosts, Aphis glycines (the soybean aphid) and A. nerii (the milkweed, or oleander aphid), sharing the parasitoid Aphelinus certus. While both of these aphid species are accepted by A. certus, soybean aphid is a much more suitable host than milkweed aphid is. We observed a drastic reduction of parasitoid offspring production (45%) on the suitable host in the presence of the unsuitable host in microcosm assays. Aphelinus certus females laid eggs into the unsuitable hosts (Aphis nerii) in the presence of the suitable host leading to egg and/or time limitation and reduced fitness. The impact of these interactions on the equilibrium population sizes of the three interacting species was analyzed using a consumer–resource modeling approach. Both the results from the laboratory experiment and the modeling approaches identified apparent predation between soybean aphid and milkweed aphid, in which milkweed aphid acts as a sink for parasitoid eggs leading to an increase in the soybean aphid population. The presence of soybean aphids had the opposite effect on milkweed aphid populations as it supported increases in parasitoid abundance and thus reduced the fitness and abundance of this aphid species.

Host Plant Choice Determined by Reproductive Interference between Closely Related Butterflies

AbstractA number of empirical studies have concluded that reproductive interference (RI) contributes to parapatric species distributions or sexual exclusion. However, the possibility that divergent host plant use in phytophagous insects is due to sexual exclusion has seldom been considered. Here, we present evidence that RI is responsible for different host plant use by two Pierid butterfly species, Pieris napi and Pieris melete. When a novel host species was introduced about 50 years ago, two Pierid butterfly species at first used both the ancestral host species and the novel one. Subsequently, P. napi shifted to use only the novel host, while P. melete shifted to specialize on the ancestral host. To explain these patterns, we investigated whether the two host species differ in suitability for larval growth and survival. Additionally, we tested whether RI occurred between the two butterfly species using large outdoor field cages. Courtship of females by conspecific and heterospecific males reduces the number of eggs laid by approximately half. However, RI is asymmetric and would generate selection on P. melete females to evolve to avoid the more suitable host species preferred by P. napi. Thus, our study suggests that sexual exclusion can explain the shift in host plant use by these two butterfly species.

Reviewing Fasciola hepatica transmission in the West Indies and novel perceptions from experimental infections of sympatric vs. allopatric snail/fluke combinations

Fasciolosis is an important food-borne parasitic disease affecting over two million people worldwide with economic losses related to cattle production of up to US$ 3 billion annually. Despite the long known presence of Fasciola hepatica in the Caribbean islands its transmission is not well known. This study reviews historical and recent data on fasciolosis in the West Indies, revealing for the first time the outcomes of sympatric and allopatric fluke/snail interactions in the area by exploring the susceptibility of four lymnaeid species after exposure to F. hepatica isolates from Cuba, the Dominican Republic and France. Overall, Galba cubensis showed a mean prevalence of 71.8% and appears to be the most suitable intermediate host species irrespective of the isolate used. Sympatric combinations (snail and parasite from the same country) were generally more compatible (higher susceptibility, parasite intensity and snail survival post-exposure) and only the allopatric interaction of French G. truncatula/Cuban F. hepatica attained 100% prevalence and mean intensity over 33 rediae/snail. However, certain Dominican populations of Pseudosuccinea columella showed high parasite intensities (>30 rediae/snail) when infected with Cuban flukes, highlighting the potential risks of biological introductions. Overall, high compatibility in most sympatric combinations compared to low or moderate compatibility in allopatric ones, suggests the existence of local adaptation from a long sustained interaction that has led to high rates of transmission. Interestingly, attempts to infect G. schirazensis with sympatric and allopatric flukes failed and coupled with the lowest survival rates which supposes a low risk of fasciolosis transmission in areas where this is the only snail species. Although there are significant gaps in the actual status of fasciolosis transmission from several islands in the West Indies these results show a permanent risk. We conclude that fasciolosis transmission is high in areas where the local snail, G. cubensis, occurs, and will be even higher in the presence of the invasive P. columella.

Prevalence and distribution of Babesia and Theileria species in roe deer from Spain.

Babesiosis and Theileriosis are important worldwide-distributed tick-borne diseases for human and animals. Their presence in a particular area depends on the presence of suitable tick-vector and host species as well as competent reservoirs such as roe deer, one of the most abundant wild cervids in Spain.Spleen samples from 174 roe deer hunted in Spain were analysed to determine the prevalence of Babesia and Theileria species. DNA of both piroplasms was firstly detected using a commercial qPCR. Then, positive samples were molecularly characterized at the 18S rRNA and ITS1 genes of Babesia spp. and Theileria spp. The possible influence of some factors such as ecological area, age and sex was also assessed.Overall, 89.7% of roe deer were positive to any of the two piroplasms. Theileria spp. was more prevalent (60.9%) than Babesia spp. (19.0%); species identification could not be achieved in 17.3% of positive samples. Babesia prevalence was significantly higher in young animals and in roe deer from Oceanic regions, in contrast to Theileria spp. Five species were identified: Theileria sp. OT3 (60.3%), Babesia capreoli (15.5%), Babesia venatorum (2.9%), Theileria sp. 3185/02 (0.6%) and Babesia bigemina (0.6%). The coinfection B. capreoli/T. sp. OT3 was the most common (4.6%) followed by B. venatorum/T. sp. OT3 (0.6%) and B. bigemina/T. sp. OT3 (0.6%).Our results reveal that Theileria spp. and Babesia spp. are prevalent piroplasms in roe deer from Spain. These cervids can act as reservoirs for several Babesia and Theileria species, including the zoonotic B. venatorum. This study represents the first description of B. venatorum and B. bigemina in roe deer from Spain.

Life history and life table analysis of the predator Hyperaspis polita (Coccinellidae) on the mealybug Nipaecoccus viridis (Pseudococcidae)

The ladybird Hyperaspis polita (Coleoptera: Coccinellidae) occurs in the coastal areas of East Mediterranean and dry lands in southwest Asia. It is one of the important predatory coccinellids in southern Iran including Khuzestan Province. In this study, we examined life history traits and life table parameters of H. polita fed on the important citrus pest Nipaecoccus viridis (Pseudococcidae) in the laboratory, using the age-stage, two-sex life table. Experiments were performed under controlled conditions (25 and 30 ± 1 °C, 65 ± 5% RH and 14:10 h, L: D). Total preadult developmental period was significantly shorter at 30 (30.5 d (days) males, 30.1 d females) compared to 25 °C (40.0 d males, 40.4 d females). The oviposition period was not significantly different at both examined temperatures. However, the mean female fecundity for the total life span ranged from 180 to 368 eggs at 25 and 30 °C, respectively. The values for the intrinsic rate of increase (r = 0.089 d−1), finite rate of increase (λ = 1.093 d−1), and net reproductive rate (R0 = 102.6) were higher at 30 °C. On the other hand, the mean generation time (T) was shorter for the cohort reared at 30 (51.9 d) than at 25 °C (86.2 d). When literature on H. polita is considered, we suggest N. viridis as suitable host species for efficient mass-rearing of H. polita in the insectary in Khuzestan.

Parasite-induced colour alteration of intermediate hosts increases ingestion by suitable final host species

Abstract Parasites with complex life cycles often alter the phenotypic appearance of their intermediate hosts in order to facilitate ingestion by the final host. However, such manipulation can be costly as it might increase ingestion by less suitable or dead-end hosts as well. Species-specific parasitic manipulation is a way to enhance the transmission to suitable final hosts. Here, we experimentally show that the altered body colouration of the intermediate host Gammarus pulex caused by its acanthocephalan parasite Pomphorhynchus laevis differently affects predation by different fish species (barbel, perch, ruffe, brown trout and two populations of three-spined stickleback) depending on their suitability to act as final host. Species that were responsive to colour manipulation in a predation experiment were more susceptible to infection with P. laevis than unresponsive species. Furthermore, three-spined stickleback from different populations responded to parasite manipulation in opposite directions. Such increased ingestion of the intermediate host by preferred and suitable hosts suggests fine-tuned adaptive parasitic manipulation and sheds light on the ongoing evolutionary arms race between hosts and manipulative parasites.

Brood parasitism of rosefinches by cuckoos: suitable host or accidental parasitism?

The arms race between avian brood parasites and their hosts is a classic model of co-evolution. Parasitic breeding by the common cuckoo (Cuculus canorus) in the nests of the Chinese beautiful rosefinch (Carpodacus davidianus) was found from May to July 2017 in Saihanba National Forest Park, Heibei, China. To understand whether the rosefinch is a suitable host species for the common cuckoo, egg recognition, chick recognition, brood rearing, and brood diets were studied. The results showed that rosefinches fully accepted non-mimetic white model eggs and parakeet (Melopsittacus undulatus) eggs, and also did not reject the similar-looking eggs of cinereous tits (Parus cinereus). Chinese beautiful rosefinches did not demonstrate any ability to recognize or discriminate between parasitic eggs or nestlings, and provisioned nestlings of cinereous tit, coal tit (Periparus ater), dusky warbler (Phylloscopus fuscatus), and common cuckoo within their nests. However, Chinese beautiful rosefinches were unable to rear the parasitic nestlings; dissections of deceased nestlings revealed that the food provided by Chinese beautiful rosefinch parents was largely composed of plant seeds and young plant shoot materials. This suggested that the high cross-fostered nestling mortality was due to unsuitable food provisioning from the host parents to the parasitic chicks. Therefore, we concluded that the Chinese beautiful rosefinch is not a suitable host for the common cuckoo, and this parasitic breeding system does not represent a co-evolutionary relationship.

Occurrence of Contracaecum bancrofti larvae in fish in the Murray-Darling Basin.

There is a paucity of information on the diversity and occurrence of freshwater fish parasites in Australia. This study investigates the distribution and occurrence of a parasitic nematode of the genus Contracaecum in freshwater fish from south-eastern Australia. Fish (n = 508) belonging to nine species and eight families were collected from eight wetlands associated with the Murrumbidgee River floodplain in the southern Murray-Darling Basin and subjected to laboratory examination. Third-stage nematode larvae were found in eight of the nine fish species. The exception was the fly-specked hardeyhead (Craterocephalus stercusmuscarum), although only one specimen of this species was examined. Nematode larvae were identified as Contracaecum bancrofti using a combined morphological and molecular approach. The parasite was most prevalent in weather loach (Misgurnus anguillicaudatus; 34.8%) and Australian smelt (Retropinna semoni; 21.4%), followed by carp (Cyprinus carpio; 9.5%), of which the former and latter are non-native species. Contracaecum prevalence differed between locations, with Two Bridges having the highest number of infected fish. This may be due to the higher number of suitable host species collected at these localities. Contracaecum spp. are parasites with low host specificity that have also been reported in Australian marine fish, humans and piscivorous birds. The high parasite prevalence in the two abundant non-native fish species in the region suggests that they act as a suitable host for this endemic parasite, resulting in the increase in the parasite population. It would be interesting to study host-parasite interactions in this area, especially if introduced fish populations declined dramatically in the attempt to eradicate them or control their population.

Do cuckoos imprint on hosts, micro-habitats, or nest sites? Parasitism preferences in the common cuckoo (Cuculus canorus)

Diverse nest-building behaviors used for constructing delicate and diverse kinds of nests constitute one of the most impressive and typical traits for birds. However, some bird species do not possess nest-building behavior but lay eggs in nests of other species. Such obligate brood parasites account for only 1% of all bird species in the world, but their extraordinary behavior has resulted in numerous studies. Unlike nesting birds, brood parasites such as cuckoos need to find suitable nests for parasitism rather than suitable habitat for nesting. Previous studies hypothesized that cuckoos may achieve this by imprinting on the habitats or nest sites they have experienced, or on host species by whom they have been reared, or simply by natal philopatry. Here, we test for host recognition mechanisms in a coevolutionary system constituted by the common cuckoo (Cuculus canorus) and its two sympatric hosts Daurian redstart (Phoenicurus auroreus) and Verditer flycatcher (Eumyias thalassinus) that build open cup-shaped nests in similar nest sites. Redstarts are partial rejecters of cuckoo eggs and they are parasitized by cuckoos with a parasitism rate of 16.2%, while flycatchers accept cuckoo eggs but no survival of parasite chicks in its nests and also no single case of parasitism was detected. Our results are consistent with the host imprinting hypothesis that cuckoos choose suitable hosts for parasitism by preference for them during the nestling period. The unique system consisting of common cuckoos (Cuculus canorus) and their two potential redstart (Phoenicurus auroreus) and flycatcher hosts (Eumyias thalassinus) provided persuasive evidence to show that common cuckoos have a host preference rather than a nest site preference based on micro-habitat characteristics or just random nest site selection for locating host nests and choosing a suitable host species.

Host range, host specificity, regional host preferences and genetic variability of Korthalsella Tiegh. (Viscaceae) mistletoes in New Zealand

ABSTRACTThe distribution of parasitic plants is governed by the availability and distribution of suitable host species. Here we report the distributions, host associations and genetic variability of the three endemic New Zealand species of Korthalsella (Viscaceae) mistletoes. These species differ in their primary host and in the breadth of secondary and tertiary hosts. Korthalsella salicornioides is the most host-specific, with 96% of the total records from the primary (Leptospermum scoparium s.l. [Myrtaceae]) and secondary (Kunzea robusta [Myrtaceae]) hosts, but 26 host taxa (six genera in five families) recorded overall. Korthalsella clavata and K. lindsayi are more generalist species, parasitising 44 taxa (19 genera in 14 families) and 42 taxa (13 genera in 11 families), respectively. For K. clavata, Coprosma propinqua (Rubiaceae) and C. dumosa are the primary and secondary hosts, respectively, representing 66% of the total records. For K. lindsayi, Melicope simplex (Rutaceae) is the primary host (26% of records), whereas Coprosma crassifolia, Lophomyrtus obcordata (Myrtaceae), Myrsine australis (Primulaceae) and M. divaricata are secondary hosts. The only overlap among hosts is at the tertiary level, with K. clavata and K. lindsayi sharing Coprosma rigida and C. virescens, and among hosts that are rarely parasitised. Korthalsella salicornioides is the most widely distributed species occurring widely on the North and South Islands, while K. clavata is rare in the North Island and K. lindsayi is rare in the western regions of the South Island. Comparative sequencing of nuclear internal transcribed spacers and plastid trnQ–rps16 for the three mistletoes revealed that within-species genetic structure is geographic rather than host-based. Additionally, some plastid haplotypes and ITS sequence types shared between K. clavata and K. lindsayi may result from local hybridisation and introgression between the two species in a few locations.

Modelling the effects of habitat and hosts on tick invasions

AbstractMany tick species are invading new areas because of anthropogenic changes in the landscape, shifting climatic variables and increasing populations of suitable host species and tick habitat. However, the relative influences of habitat and hosts in tick dispersal and tick population establishment remain in question. A spatially explicit agent-based model was developed to explore the spatio-temporal dynamics of a generic tick population in the years immediately following the introduction of ticks into a novel environment. The general model was then adapted to investigate a case study of two recent tick species invasions into the Mid-Atlantic United States. The recent simultaneous range expansions of two ixodid tick species, Ixodes affinis and Amblyomma maculatum, provided an opportunity to determine if invasion patterns observed in the field could be replicated in silico on a small scale. The models presented here indicated that for generalist parasites, habitat connectivity is a better indicator tha...

The establishment threat of the obligate brood-parasitic Pin-tailed Whydah (Vidua macroura) in North America and the Antilles

ABSTRACT The Pin-tailed Whydah (Vidua macroura) is a generalist obligate brood parasitic bird native to Africa, frequently found in the pet trade, which has successfully established exotic populations in 2 biodiversity hotspots in the Americas. We analyze the species' potential future distribution by identifying key locations in the continental United States, Hawaii, and the Antilles that contain suitable climatic characteristics, host species, and habitat requirements. We used species distribution modeling (MaxEnt) to depict the geographic patterns of possible Pin-tailed Whydah establishment and compared the predictive power of models that included combinations of climatic data (“climate”), land cover (“habitat”), and localities of historical and one known novel host (“hosts”). The preferred model, the “hosts” model, was the highest performing. The most important variable characterizing Pin-tailed Whydah distribution in the preferred model was the presence of a frequent historical host that is also estab...

Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) differ in their suitability as hosts for the endangered freshwater pearl mussel (Margaritifera margaritifera) in northern Fennoscandian rivers

Abstract European populations of the freshwater pearl mussel (FPM, Margaritifera margaritifera) have collapsed across much of the species’ geographic range and, despite many types of conservation intervention, the number of successful restoration efforts has been low. The goal of this study was to determine whether there were population‐specific differences in the suitability of Atlantic salmon (Salmo salar) and brown trout (S. trutta) as hosts for the parasitic glochidium larvae of FPM. We predicted that such differences would depend on the historical occurrence of these salmonid species in FPM habitats. We studied the potential host specificity both in the field and in laboratory by exposing salmonid fish to FPM glochidia originating from nine populations in different types of streams and rivers within three large river basins in northern Fennoscandia. The exposures showed remarkable population‐specific differences in the suitability of host species. In large main channels, previously colonised by Atlantic salmon but mostly now dammed for hydropower production, the occurrence of FPM glochidia was always highest on salmon. Moreover, glochidia on salmon were often larger than the conspecifics on brown trout. Conversely, in small tributaries with no salmon history, brown trout was generally the best, or the only suitable, host for FPM. The adaptation of certain FPM populations to salmon is a highly significant finding, which offers — together with the hydropower dam construction and the salmonid stocking practices that often favour brown trout — an explanation for the collapse of FPM populations living in former Atlantic salmon rivers. This study illustrates the indirect but substantial effects that dams and changes in fish communities may induce, and emphasises the need to determine the most suitable host species for each FPM population in order to inform conservation and management actions.