Bot fly parasitism in mantled howler monkeys (Alouatta palliata): General patterns and climate influences

Parasitism is a strong selective pressure, and its study is crucial for predicting the persistence of host species. Mantled howler monkeys are infected by the larvae of the bot fly Cuterebra baeri. This parasitosis produces myiasis and may have negative impacts on host health, although systematic information on the dynamics of this host-parasite relationship is very limited. Currently, all available information on infection patterns of C. baeri comes from a single mantled howler monkey population (Barro Colorado Island, Panama). Therefore, in this study we describe temporal variation in infection patterns for a newly mantled howler monkey population and analyze the relationship between climate and infection likelihood. We assessed the presence of C. baeri nodules in 17 adult individuals in Los Tuxtlas for 10 months through direct observation and compiled data on ambient temperature and rainfall. Most subjects had nodules during the study and there were no differences between sexes in the number of nodules. Nodules were usually located in the neck. Prevalence and abundance of nodules peaked thrice during the study (February, April, and September), a pattern that was very similar to that of parasitism intensity (February, April, and August). Incidence closely tracked these peaks, increasing before and decreasing after them. The likelihood of nodule appearance increased when both mean and minimum temperature decreased in the 24-21 prior days to nodule appearance. It also increased with decreased rainfall in the 5-2 prior days to nodule appearance. Although only three of the eight analyzed climate variables had a significant effect on parasitosis, these results suggest that climate may affect pupal development and the access of larvae to hosts. Besides contributing data on C. baeri parasitism for a new mantled howler monkey population, our study provides novel information on the influence of environmental factors on the dynamics of host-parasite systems.

Environmental conditions influence host-parasite interactions and host fitness in a migratory passerine

The study of host-parasite co-evolution is a central topic in evolutionary ecology. However, research is still fragmented and the extent to which parasites influence host life history is debated. One reason for this incomplete picture is the frequent omission of environmental conditions in studies analyzing host-parasite dynamics, which may influence the exposure to or effects of parasitism. To contribute to elucidating the largely unresolved question of how environmental conditions are related to the prevalence and intensity of infestation and their impact on hosts, we took advantage of 25 years of monitoring of a breeding population of pied flycatchers, Ficedula hypoleuca, in a Mediterranean area of central Spain. We investigated the influence of temperature and precipitation during the nestling stage at a local scale on the intensity of blowfly (Protocalliphora azurea) parasitism during the nestling stage. In addition, we explored the mediating effect of extrinsic and intrinsic factors and blowfly parasitism on breeding success (production of fledglings) and offspring quality (nestling mass on day 13). The prevalence and intensity of blowfly parasitism were associated with different intrinsic (host breeding date, brood size) and extrinsic (breeding habitat, mean temperature) factors. Specifically, higher average temperatures during the nestling phase were associated with lower intensities of parasitism, which may be explained by changes in blowflies' activity or larval developmental success. In contrast, no relationship was found between the prevalence of parasitism and any of the environmental variables evaluated. Hosts that experienced high parasitism intensities in their broods produced more fledglings as temperature increased, suggesting that physiological responses to severe parasitism during nestling development might be enhanced in warmer conditions. The weight of fledglings was, however, unrelated to the interactive effect of parasitism intensity and environmental conditions. Overall, our results highlight the temperature dependence of parasite-host interactions and the importance of considering multiple fitness indicators and climate-mediated effects to understand their complex implications for avian fitness and population dynamics.

Differential effects of environmental climatic variables on parasite abundances in blue tit nests during a decade

Models on climate change have predicted an increase of temperature over the earth's surface with potential drastic effects on living organisms. We analyzed the relationships between climatic conditions (temperature, rainfall, and wind speed) and the abundance of blood‐sucking flying insects (biting midges and blackflies) and nest‐dwelling ectoparasites (mites, fleas, and blowflies) collected from blue tit nests during bird breeding seasons for a period of 10 years. Average temperature, rainfall, and wind speed showed significant differences among years. Temperature and wind speed increased during the period of study while rainfall decreased. Biting midge, blackfly, and blowfly abundances increased across years but not flea and mite abundances. Hatching date decreased and brood size increased across years. Independently of year variation, parasites were related to climatic variables. For example, biting midge, blowfly, mite, and flea abundances were positive and significantly related to average temperature. We also found a positive and significant relationship between abundances of Haemoproteus infections and biting midge abundances during the first year of life of birds out of nests. However, abundance and prevalence of Lankesterella infections in yearlings were positive and significantly related to mite abundances during the year of birth of birds. Leucocytozoon and Lankesterella infections were also significantly related to climatic variables and Haemoproteus and Lankesterella infections increased across years. In addition, body condition of adult females and males were negatively related to flea larvae and blowfly abundance respectively. Nestling body condition was also negatively related to biting midge abundance. Changes in climatic conditions across years could therefore affect several parasites of birds but also to birds themselves.

Effect of seasonality and microclimate on the variation in bat-fly load (Diptera: Streblidae) in a cave bat assemblage in a dry forest

Seasonality causes fluctuations in the availability of resources, affecting the presence and abundance of animal species. These fluctuations can have an impact on parasite-host relationships, which in turn can be exacerbated by microclimatic changes to which bat-flies are exposed. We characterized the bat-fly load and evaluated the effect of seasonality on five bat species in a dry forest. We evaluated variations in microclimatic conditions inside the cave Cerro Huatulco between seasons and the response of the bat-fly load. We collected 1165 bat-fly specimens belonging to 16 species from 688 bats. The obtained results indicate that the mean abundance and infestation intensity exhibited changes between seasons in Artibeus jamaicensis, Desmodus rotundus, Glossophaga soricina, and Pteronotus parnellii. In the case of the effect of microclimate conditions, we observed that prevalence is negatively correlated with temperature in G. soricina, while mean abundance and mean infestation intensity were negatively related to temperature in A. jamaicensis and G. soricina. The present study provides significant information about host-parasite relationships in a dry forest and discusses the relevance of abiotic and biotic factors that could affect host-parasite interactions, as well as the importance of each parasite load parameter for the understanding of this interaction.

Nest-type associated microclimatic conditions as potential drivers of ectoparasite infestations in African penguin nests

Nest design and characteristics can influence the microclimatic conditions in the nest. Nest-dwelling ectoparasites are sensitive to temperature and moisture and as such the conditions in the nest can influence parasite infestations. The endangered African penguin (Spheniscus demersus) breeds in different nest types and as yet little is known with regard to the microclimate and parasite infestation within these nests. This study characterized the microclimatic conditions in natural open, natural covered (with vegetation) and artificial nests, and assessed the relationship between nest characteristics (type, age, distance from the coast, orientation and entrance opening) and in-nest ectoparasite infestations and the health of African penguins in Stony Point, South Africa. Penguins (50 adults and 192 chicks) and their nests (n = 308) were sampled in 2016 and 2017. Soil temperature was higher in artificial than in natural nests, and soil and nest material moisture was lower in artificial and natural covered nests than natural open. Ectoparasite infestations were higher under warmer and drier conditions, in artificial nests and nests near the coastline. Penguin (adult and chick) body mass and chick body condition were lower in warmer nests and total plasma protein (in adults and checks) was lower in drier nests. Given the potential adverse effects of ectoparasites on host species, it is recommended that conservation agencies implement a monitoring programme to assess the ectoparasite infestation in artificial nests across multiple colonies. This information will facilitate a more holistic penguin conservation management plan that may prevent further detrimental effects on this endangered penguin species.

Can Community Structure Causally Determine Dynamics of Constituent Species? A Test Using a Host-Parasite Community

Structures of communities have been widely studied with the assumption that they not only are a useful bookkeeping tool but also can causally influence dynamics of the populations from which they emerge. However, convincing tests of this assumption have remained elusive because generally the only way to alter a community property is by manipulating its constituent populations, thereby preventing independent measurements of effects on those populations. There is a growing body of evidence that methods like convergent cross-mapping (CCM) can be used to make inferences about causal interactions using state space reconstructions of coupled time series, a method that relies on only observational data. Here we show that CCM can be used to test the causal effects of community properties using a well-studied Slovakian rodent-ectoparasite community. CCM identified causal drivers across the organizational scales of this community, including evidence that host dynamics were influenced by the degree to which the community at large was connected and clustered. Our findings add to the growing literature on the importance of community structures in disease dynamics and argue for a broader use of causal inference in the analysis of community dynamics.

Long-term variation in environmental conditions influences host-parasite fitness

Long-term data on host and parasite fitness are important for predicting how host-parasite interactions will be altered in an era of global change. Here, we use data collected from 1997 to 2013 to explore effects of changing environmental conditions on bird-blowfly interactions in northern New Mexico. The objectives of this study were to examine what climate variables influence blowfly prevalence and intensity and to determine whether blowflies and climate variables affect bird fledging success. We examined how temperature, precipitation, and drought affect two parasitic blowflies and their hosts, Western Bluebirds (Sialia mexicana) and Ash-throated Flycatchers (Myiarchus cinerascens). We found that blowfly prevalence did not change over time. Blowfly intensity increased over time in bluebird nests, but not in flycatcher nests. More blowflies result in slightly higher fledging success in bluebirds, but not flycatchers. There was a significant interaction between blowflies and precipitation on bluebird fledging success. For flycatchers, there was a significant interaction between blowflies and temperature and between blowflies and drought severity on fledging success. Given that the southwest is projected to be hotter and have more frequent and prolonged droughts, we predict that flycatchers may be negatively impacted by blowflies if these trends continue. Future work should focus on investigating the role of both blowflies and climate on fledging success. Climate patterns may negatively impact host fitness through altered parasite pressure.