Parasite dynamics in North American monarchs predicted by host density and seasonal migratory culling.

Insect-pathogen dynamics can show seasonal and inter-annual variations that covary with fluctuations in insect abundance and climate. Long-term analyses are especially needed to track parasite dynamics in migratory insects, in part because their vast habitat ranges and high mobility might dampen local effects of density and climate on infection prevalence. Monarch butterflies Danaus plexippus are commonly infected with the protozoan Ophryocystis elektroscirrha (OE). Because this parasite lowers monarch survival and flight performance, and because migratory monarchs have experienced declines in recent decades, it is important to understand the patterns and drivers of infection. Here we compiled data on OE infection spanning 50 years, from wild monarchs sampled in the United States, Canada and Mexico during summer breeding, fall migrating and overwintering periods. We examined eastern versus western North American monarchs separately, to ask how abundance estimates, resource availability, climate and breeding season length impact infection trends. We further assessed the intensity of migratory culling, which occurs when infected individuals are removed from the population during migration. Average infection prevalence was four times higher in western compared to eastern subpopulations. In eastern North America, the proportion of infected monarchs increased threefold since the mid-2000s. In the western region, the proportion of infected monarchs declined sharply from 2000 to 2015, and increased thereafter. For both eastern and western subpopulations, years with greater summer adult abundance predicted greater infection prevalence, indicating that transmission increases with host breeding density. Environmental variables (temperature and NDVI) were not associated with changes in the proportion of infected adults. We found evidence for migratory culling of infected butterflies, based on declines in parasitism during fall migration. We estimated that tens of millions fewer monarchs reach overwintering sites in Mexico as a result of OE, highlighting the need to consider the parasite as a potential threat to the monarch population. Increases in infection among eastern North American monarchs post-2002 suggest that changes to the host's ecology or environment have intensified parasite transmission. Further work is needed to examine the degree to which human practices, such as mass caterpillar rearing and the widespread planting of exotic milkweed, have contributed to this trend.

Morphological and molecular characterization of Xyo pseudohystrix Travassos amp; Kloss, 1958 (Nematoda: Oxyuridomorpha: Hystrignathidae) from Odontotaenius disjunctus (Illiger, 1800) (Coleoptera: Passalidae) from USA and discussion on its taxonomic status.

The females of Xyo pseudohystrix Travassos Kloss, 1958 (Nematoda: Oxyuridomorpha: Hystrignathidae) are redescribed and illustrated with the aid of SEM. New features of the cephalic end, arrangement of the cervical spines and genital tract were observed. The taxonomic status of the species is discussed on the basis of discrepancies with the generic diagnosis of Xyo Cobb, 1898. Due to the lack of proper information on the genus the status of incertae sedis is proposed. The identity of the males was confirmed by molecular studies and the morphology of the specimens previously assigned by Christie (1932) as males of Hystrignathus rigidus Leidy, 1858 correspond to the current species. New locality records are given for the states of Georgia and Ohio, USA. The phylogenetic position of the species is inferred on the basis of the D2-D3 segment of the LSU rDNA and SSU rDNA.

Morphological and molecular characterization of Lepidonema magnum Morffe García, 2010 (Nematoda: Oxyuridomorpha: Hystrignathidae) from Passalus interstitialis Eschscholtz, 1829 (Coleoptera: Passalidae) from Cuba and new locality records for the species.

Lepidonema magnum Morffe García, 2010 (Nematoda: Oxyuridomorpha: Hystrignathidae) is redescribed and illustrated with the aid of SEM. New features of the cephalic end and genital tract of the females were observed. New locality records are given. The phylogenetic position of the species is inferred on the basis of the D2-D3 segment of the 28S LSU rDNA and 18S SSU rDNA. L. magnum forms a monophyletic clade formed by other hystrignathids: Coynema poeyi (Coy, García Álvarez, 1993), two species of Longior Travassos Kloss, 1958 and two Hystrignathus Leidy, 1850.

Do Healthy Monarchs Migrate Farther? Tracking Natal Origins of Parasitized vs. Uninfected Monarch Butterflies Overwintering in Mexico.

Long-distance migration can lower parasite prevalence if strenuous journeys remove infected animals from wild populations. We examined wild monarch butterflies (Danaus plexippus) to investigate the potential costs of the protozoan Ophryocystis elektroscirrha on migratory success. We collected monarchs from two wintering sites in central Mexico to compare infection status with hydrogen isotope (δ2H) measurements as an indicator of latitude of origin at the start of fall migration. On average, uninfected monarchs had lower δ2H values than parasitized butterflies, indicating that uninfected butterflies originated from more northerly latitudes and travelled farther distances to reach Mexico. Within the infected class, monarchs with higher quantitative spore loads originated from more southerly latitudes, indicating that heavily infected monarchs originating from farther north are less likely to reach Mexico. We ruled out the alternative explanation that lower latitudes give rise to more infected monarchs prior to the onset of migration using citizen science data to examine regional differences in parasite prevalence during the summer breeding season. We also found a positive association between monarch wing area and estimated distance flown. Collectively, these results emphasize that seasonal migrations can help lower infection levels in wild animal populations. Our findings, combined with recent declines in the numbers of migratory monarchs wintering in Mexico and observations of sedentary (winter breeding) monarch populations in the southern U.S., suggest that shifts from migratory to sedentary behavior will likely lead to greater infection prevalence for North American monarchs.

Searching Before It Is Too Late: A Survey of Blood Parasites in Ctenosaura melanosterna, a Critically Endangered Reptile of Honduras.

For species at risk of extinction, any parasites they have would be expected to face a similar fate. In such cases, time is running out for efforts to identify and study their parasitic fauna before they are gone. We surveyed the hemoparasite fauna of 50 black-chested, spiny-tailed iguanas (Ctenosaura melanosterna), a critically-endangered species, on an island off the coast of Honduras. Blood samples from captured animals were tested for hemoparasites by thin blood smear and molecular analyses. Based on microscopy, two parasites were identified, a Plasmodium sp. in 14% of iguanas and a Hepatozoon sp. in 32%. For both parasites, parasitemia levels were <0.1%. Prevalence and parasitemias of Hepatozoon declined with increasing host size, a pattern differing from most prior studies of saurian reptiles. From a subset of iguanas with microscopy-confirmed Plasmodium infections, sequence analysis of 454 bp of the cytochrome b gene indicated that the Plasmodium species was distinct from known Plasmodium and was most closely related to P. chiricahuae (96.5% similarity) followed by P. mexicanum (95.8% similarity). Efforts to amplify the Hepatozoon parasite using PCR were not successful. Additional surveys and studies of this host-parasite system would be valuable, both to science and to the management of this endangered animal.

Are female monarch butterflies declining in eastern North America? Evidence of a 30-year change in sex ratios at Mexican overwintering sites.

Every autumn the entire eastern North American population of monarch butterflies (Danaus plexippus) undergoes a spectacular migration to overwintering sites in the mountains of central Mexico, where they form massive clusters and can number in the millions. Since their discovery, these sites have been extensively studied, and in many of these studies, monarchs were captured and sexes recorded. In a recent effort to compile the sex ratio data from these published records, a surprising trend was found, which appears to show a gradual decline in proportion of females over time. Sex ratio data from 14 collections of monarchs, all spanning 30 years and totaling 69 113 individuals, showed a significant negative correlation between proportion of females and year (r = -0.69, p = 0.007). Between 1976 and 1985, 53 per cent of overwintering monarchs were female, whereas in the last decade, 43 per cent were female. The relationship was significant with and without weighting the analyses by sampling effort. Moreover, analysis of a recent three-year dataset of sex ratios revealed no variation among nine separate colonies, so differences in sampling location did not influence the trend. Additional evidence from autumn migration collections appears to confirm that proportions of females are declining, and also suggests the sex ratio is shifting on breeding grounds. While breeding monarchs face a number of threats, one possibility is an increase in prevalence of the protozoan parasite, Ophryocystis elektroscirrha, which recent evidence shows affects females more so than males. Further study will be needed to determine the exact cause of this trend, but for now it should be monitored closely.

Blood parasites of House Finches (Carpodacus mexicanus) from Georgia and New York.

This study investigated the ecology of hematozoan parasites in two eastern populations of House Finch (Carpodacus mexicanus). Blood smears were obtained from birds captured in Georgia during 2001-2003 (n = 757) and New York during 2001 (n = 282) and evaluated for the presence of hematozoans. Low-density infections of Haemoproteus fringillae and Plasmodium relictum were confirmed at each location. Infections were observed year-round in Georgia, but primarily between June and November in New York. Overall, hematozoa were more prevalent in House Finches from Georgia than New York (P

Stress responses and disease in three wintering house finch (Carpodacus mexicanus) populations along a latitudinal gradient.

In laboratory studies, stress hormones have been shown to impair immune functions, and increase susceptibility to diseases. However, the interactions between stress hormones and disease have rarely been studied in free-ranging populations. In this study, we measured concentrations of the avian stress hormone corticosterone across four winter months (December-March) over two years in three eastern North American house finch populations (Carpodacus mexicanus) along a latitudinal gradient. Because Mycoplasma gallisepticum infections appear in these populations in late winter, we hypothesized that the timing of the disease outbreaks could be mediated by changes in corticosterone concentrations. We found a significant increase in baseline and stress-induced plasma corticosterone concentrations in house finches without Mycoplasma symptoms in late winter; when the prevalence of Mycoplasma infection peaks. We also found that house finches with Mycoplasma symptoms had elevated stress-induced corticosterone concentrations. High baseline concentrations were associated with a low body condition and a high fat load. We found that the relationship between corticosterone concentrations and the latitude of the study population changed between years. The first year, corticosterone concentrations were lowest in the southern latitude, but became higher in the second year when average winter temperatures were low. A causal understanding of the implications for this variation in corticosterone concentrations for Mycoplasma disease dynamics awaits further studies.