Density-dependent sex ratio and sex-specific preference for host traits in parasitic bat flies

Authors marked in boldface are EvolEcol members.

Szentiványi T, Vincze O and Estók P 2017. Density-dependent sex ratio and sex-specific preference for host traits in parasitic bat flies. Parasites & Vectors 10: 405. pdf

DOI: 10.1186/s13071-017-2340-0



Deviation of sex ratios from unity in wild animal populations has recently been demonstrated to be far more prevalent than previously thought. Ectoparasites are prominent examples of this bias, given that their sex ratios vary from strongly female- to strongly male-biased both among hosts and at the metapopulation level. To date our knowledge is very limited on how and why these biased sex ratios develop. It was suggested that sex ratio and sex-specific aggregation of ectoparasites might be shaped by the ecology, behaviour and physiology of both hosts and their parasites. Here we investigate a highly specialised, hematophagous bat fly species with strong potential to move between hosts, arguably limited inbreeding effects, off-host developmental stages and extended parental care.


We collected a total of 796 Nycteribia kolenatii bat flies from 147 individual bats using fumigation and subsequently determined their sex. We report a balanced sex ratio at the metapopulation level and a highly variable sex ratio among infrapopulations ranging from 100% male to 100% female. We show that infrapopulation sex ratio is not random and is highly correlated with infrapopulation size. Sex ratio is highly male biased in small and highly female biased in large infrapopulations. We show that this pattern is most probably the result of sex-specific preference in bat flies for host traits, most likely combined with a higher mobility of males. We demonstrate that female bat flies exert a strong preference for high host body condition and female hosts, while the distribution of males is more even.


Our results suggest that locally biased sex ratios can develop due to sex-specific habitat preference of parasites. Moreover, it is apparent that the sex of both hosts and parasites need to be accounted for when a better understanding of host-parasite systems is targeted.

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New grant won & started

Our EvolEcol Group was recently financed by the Romanian Ministry of Research and Innovation for a grant entitled: Sex differences in life-history traits in birds and mammals: the significance of physiological state. The grant will run for 30 months. The main aim of the grant is to understand the physiological underpinnings of sexual differences in life histories among birds and mammals. Physiology will be characterized be immunological and oxidative physiological measures, and the level of insulin-like growth factor 1 (IGF-1). The grant involves 3 senior scientists (Péter L. Pap as PI, Orsolya Vincze and Csongor I. Vágási) and 1 MSc student (Janka Pénzes). For the IGF-1 level we collaborate with the group lead by Ádám Z. Lendvai at the University of Debrecen, Hungary. We post all the news related to this grant at this blog and our group’s twitter page.

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Paper on breeding effort, cohabitation with farm animals & feather-associated bacteria accepted in Journal of Avian Biology

Authors marked in boldface are EvolEcol members.

Fülöp A, Vágási CI and Pap PL 2017. Cohabitation with farm animals rather than breeding effort increases the infection with feather-associated bacteria in the barn swallow Hirundo rustica. Journal of Avian Biology (in press).

DOI: 10.1111/jav.01262


Abstract: Feather-associated bacteria are widespread inhabitants of avian plumage. However, the determinants of the between-individual variation in plumage bacterial loads are less well understood. Infection intensities can be determined by ecological factors, such as breeding habitat, and can be actively regulated by hosts via preening. Preening, yet, is a resource intensive activity, and thus might be traded-off against reproductive investment in breeding birds. Here, we studied barn swallows Hirundo rustica to assess the bacterial cost of reproduction in relation to nesting site micro-habitats. Barn swallows prefer to breed in the company of large-sized farm animals, although the presence of mammalian livestock in barns assures a warm and humid micro-climate that favours bacterial proliferation. Thus, we experimentally manipulated brood sizes of birds breeding in barns with, or without, farm animals and measured total cultivable bacteria (TCB) and feather-degrading bacteria (FDB) from the plumage. We found that the abundance of feather-associated bacteria (i.e. both TCB and FDB) in females, but not males, breeding in barns with livestock were significantly higher than in conspecifics breeding in empty barns. Plumage bacterial loads, however, were not affected by brood size manipulations in either sex. In addition, we report a negative relationship between both TCB and FDB and hatching date in females, and several sex and seasonal differences in plumage bacterial abundances. Our study is the first to show that breeding micro-habitat (i.e. livestock co-tenancy) has consequences for the abundance of feather-associated bacteria.


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A phylogenetic comparative analysis reveals correlations between body feather structure and habitat

Our paper in Functional Ecology is now edited.


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Our paper on body feather functional morphology is out in Functional Ecology

A phylogenetic comparative analysis reveals correlations between body feather structure and habitat.

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Paper about parental cooperation in a changing climate accepted in Global Ecology and Biogeography

Authors marked in boldface are EvolEcol members.

Vincze O, Kosztolányi A, Barta Z, Küpper C, Alrashidi M, Amat JA, Argüelles Ticó A, Burns F, Cavitt J, Conway WC, Cruz-López M, Desucre-Medrano AE, dos Remedios N, Figuerola J, Galindo-Espinosa D, García-Peña GE, Gómez Del Angel S, Gratto-Trevor C, Jönsson P, Lloyd P, Montalvo T, Parra JE, Pruner R, Que P, Liu Y, Saalfeld ST, Schulz R, Serra L, St Clair JJH, Stenzel LE, Weston MA, Yasué M, Zefania S and Székely T 2017. Parental cooperation in a changing climate: fluctuating environments predict shifts in care division. Global Ecology and Biogeography (in press) doi:10.1111/geb.12540.



Parental care improves the survival of offspring and therefore has a major impact on reproductive success. It is increasingly recognized that coordinated biparental care is necessary to ensure the survival of offspring in hostile environments, but little is known about the influence of environmental fluctuations on parental cooperation. Assessing the impacts of environmental stochasticity, however, is essential for understanding how populations will respond to climate change and the associated increasing frequencies of extreme weather events. Here we investigate the influence of environmental stochasticity on biparental incubation in a cosmopolitan ground-nesting avian genus.




We assembled data on biparental care in 36 plover populations (Charadrius spp.) from six continents, collected between 1981 and 2012. Using a space-for-time approach we investigate how average temperature, temperature stochasticity (i.e. year-to-year variation) and seasonal temperature variation during the breeding season influence parental cooperation during incubation.


We show that both average ambient temperature and its fluctuations influence parental cooperation during incubation. Male care relative to female care increases with both mean ambient temperature and temperature stochasticity. Local climatic conditions explain within-species population differences in parental cooperation, probably reflecting phenotypic plasticity of behaviour.

Main conclusions

The degree of flexibility in parental cooperation is likely to mediate the impacts of climate change on the demography and reproductive behaviour of wild animal populations.

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Paper on functional morphology of body feathers accepted in Functional Ecology

Authors marked in boldface are EvolEcol members, authors with asterisk are undergrad students.

Pap PL, Vincze O, Wekerle B*, Daubner T*, Vágási CI, Nudds RL, Dyke GJ and Osváth G 2017. A phylogenetic comparative analysis reveals correlations between body feather structure and habitat. Functional Ecology (in press).

1. Body feathers ensure both waterproofing and insulation in waterbirds, but how natural variation in the morphological properties of these appendages relates to environmental constraints remains largely unexplored. Here, we test how habitat and thermal condition affect the morphology of body feathers using a phylogenetic comparative analysis of five structural traits [i.e., total feather length, the lengths of the pennaceous (distal) and plumulaceous (proximal) sections, barb density, and pennaceous barbule density] from a sample of 194 European bird species.
2. Body feather total length is shorter in aquatic than in terrestrial birds, and this difference between groups is due to the shorter plumulaceous feather section in aquatic birds. Indeed, a reduced plumulaceous section in feather length probably reflects the need to limit air trapped in the plumage to adjust the buoyancy of aquatic birds. In contrast, the high pennaceous barbule density of aquatic birds compared to their terrestrial counterparts reflects water resistance of the plumage in contact with water.
3. Our results show that birds living in environments with low ambient temperature have long plumulaceous feather lengths, low barb density, and low pennaceous barbule density. Data also suggest that plumage probably has limited function in reducing the heat absorption of species living in hot environments.
4. Our results have broad implications for understanding the suite of selection pressures driving the evolution of body feather functional morphology. It remains to be tested, however, how other feather traits, such as the density of plumage (feathers per unit area) and the relative number of different feather types, for example downy feathers, are distributed amongst birds with different water resistance and thermoinsulative needs.

Key-words: body feathers, feather lengths, functional morphology, thermal insulation, vane density, water repellence


Figure 1. Different parts of a body feather with distal pennaceous and proximal plumulaceous sections delimited by a white stripe across the rachis at the base of the barb in which the length was at least 33% plumulaceus. The black lines define the boundary of the pennaceous and plumulaceous sections of the vane (a,b). Upper figures show two typical species with the ratio of the pennaceous feather section to plumulaceous part. In the Common Raven (Corvus corax), a terrestrial species, the plumulaceous part is longer (a), while in the Common Moorhen (Gallinula chloropus), an aquatic bird, this feather part is reduced in length (b). Lower figures illustrate a section of pennaceous vane with the rachis and barb to which the barbules attach. The density of pennaceous barbules are lower in terrestrial species, such as the Common Buzzard (Buteo buteo) (c) than in aquatic birds, represented here by the Northern Pintail (Anas acuta) (d). Scale bars for figures (a) and (b) are 1 cm, and for (c) and (d) are 0.5 mm.

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