Habitat adaptation rather than genetic distance correlates with female preference in fire salamanders (Salamandra salamandra)

Caspers B, Junge C, Weitere M, Steinfartz S. Habitat adaptation rather than genetic distance correlates with female preference in fire salamanders (Salamandra salamandra). Frontiers in Zoology. 2009;6(1):13.Background: Although some mechanisms of habitat adaptation of conspecific populations have been recently elucidated, the evolution of female preference has rarely been addressed as a force driving habitat adaptation in natural settings. Habitat adaptation of fire salamanders (Salamandra salamandra), as found in Middle Europe (Germany), can be framed in an explicit phylogeographic framework that allows for the evolution of habitat adaptation between distinct populations to be traced. Typically, females of S. salamandra only deposit their larvae in small permanent streams. However, some populations of the western post-glacial recolonization lineage use small temporary ponds as larval habitats. Pond larvae display several habitat-specific adaptations that are absent in stream-adapted larvae. We conducted mate preference tests with females from three distinct German populations in order to determine the influence of habitat adaptation versus neutral genetic distance on female mate choice. Two populations that we tested belong to the western post-glacial recolonization group, but are adapted to either stream or pond habitats. The third population is adapted to streams but represents the eastern recolonization lineage. Results: Despite large genetic distances with F-ST values around 0.5, the stream-adapted females preferred males from the same habitat type regardless of genetic distance. Conversely, pond-adapted females did not prefer males from their own population when compared to stream-adapted individuals of either lineage. Conclusion: A comparative analysis of our data showed that habitat adaptation rather than neutral genetic distance correlates with female preference in these salamanders, and that habitat-dependent female preference of a specific pond-reproducing population may have been lost during adaptation to the novel environmental conditions of ponds

Breeding state and season affect interspecific interaction types: indirect resource competition and direct interference

Indirect resource competition and interference are widely occurring mechanisms of interspecific interactions. We have studied the seasonal expression of these two interaction types within a two-species, boreal small mammal system. Seasons differ by resource availability, individual breeding state and intraspecific social system. Live-trapping methods were used to monitor space use and reproduction in 14 experimental populations of bank voles Myodes glareolus in large outdoor enclosures with and without a dominant competitor, the field vole Microtus agrestis. We further compared vole behaviour using staged dyadic encounters in neutral arenas in both seasons. Survival of the non-breeding overwintering bank voles was not affected by competition. In the spring, the numbers of male bank voles, but not of females, were reduced significantly in the competition populations. Bank vole home ranges expanded with vole density in the presence of competitors, indicating food limitation. A comparison of behaviour between seasons based on an analysis of similarity revealed an avoidance of costly aggression against opponents, independent of species. Interactions were more aggressive during the summer than during the winter, and heterospecific encounters were more aggressive than conspecific encounters. Based on these results, we suggest that interaction types and their respective mechanisms are not either–or categories and may change over the seasons. During the winter, energy constraints and thermoregulatory needs decrease direct aggression, but food constraints increase indirect resource competition. Direct interference appears in the summer, probably triggered by each individual’s reproductive and hormonal state and the defence of offspring against conspecific and heterospecific intruders. Both interaction forms overlap in the spring, possibly contributing to spring declines in the numbers of subordinate species

Chemical analysis reveals sex differences in the preen gland secretion of breeding Blue Tits

Caspers B, Marfull R, Dannenhaus T, Komdeur J, Korsten P. Chemical analysis reveals sex differences in the preen gland secretion of breeding Blue Tits. Journal of Ornithology. 2021;163(1):191–198.**Abstract** Acoustic and visual signals are well known to play important roles in social communication in birds. Growing evidence suggests that many bird species, including species of songbirds, additionally have a well-developed sense of smell. However, we are still at the beginning of understanding the potential importance of chemical communication in the social lives of birds, for example in mate choice. The secretion of the preen gland may be an important contributor to the chemical phenotype of birds. Here, we report on a first characterisation of the chemical composition of the preen gland secretion of the Blue Tit (Cyanistes caeruleus), a common songbird which is an often used model species in animal behaviour and ecology, in particular also in studies of sexual selection and (extra-pair) mate choice. We found sex differences in the composition of the preen gland secretion in breeding Blue Tits. Females further tended to have a larger number of putative compounds in their secretions compared to males. We briefly discuss the possible implications of these findings and speculate that the chemical composition of the preen gland secretion may be a sexually selected trait in Blue Tits. Our preliminary findings warrant follow-up research into the patterns of within- and among individual variation in the chemical composition of the preen gland secretion as well as the identification of the main chemical compounds involved.**Zusammenfassung**Chemische Analyse zeigt Geschlechtsunterschiede im Bürzeldrüsensekret brütender BlaumeisenSingvögel sind vor allem für ihren Gesang und ihre Gefiedermerkmale, die bei der sozialen Kommunikation eine bedeutende Rolle spielen, bekannt. Immer mehr Hinweise deuten aber darauf hin, dass viele Vogelarten, darunter auch Singvogelarten, zusätzlich einen gut entwickelten Geruchssinn haben. Welche Bedeutung die geruchliche Kommunikation im sozialen Leben der Vögel, zum Beispiel bei der Partnerwahl, spielt ist allerdings weitgehend noch unbekannt. Das Bürzeldrüsensekret könnte in diesem Zusammenhang einen wichtigen Beitrag zum chemischen Phänotyp der Vögel leisten. In unserer Studie haben wir uns die chemische Zusammensetzung des Bürzeldrüsensekrets der Blaumeise (Cyanistes caeruleus) in der Brutzeit angeschaut. Blaumeisen sind eine viel genutzte Modellart in der Verhaltensforschung und Verhaltensökologie, insbesondere auch in Studien zur sexuellen Selektion und (außerpaarigen) Partnerwahl. Anhand von chemischen Analysen mittels Gas-Chromatographie fanden wir heraus, dass es bei brütenden Blaumeisen einen Geschlechtsunterschied in der Zusammensetzung des Bürzeldrüsensekrets gibt. Weibchen neigen außerdem dazu, eine größere Anzahl von vermeintlichen Substanzen in ihren Sekreten zu haben als Männchen. Wir diskutieren hier kurz die möglichen Implikationen dieser Ergebnisse und spekulieren, dass die chemische Zusammensetzung des Bürzeldrüsensekrets ein sexuell selektiertes Merkmal bei Blaumeisen sein könnte. Unsere vorläufigen Ergebnisse rechtfertigen Folgeuntersuchungen, in denen die Identifikation der wichtigsten chemischen Verbindungen des Bürzeldrüsensekrets und die Variation innerhalb und zwischen Individuen in der chemischen Zusammensetzung des Drüsensekrets im Fokus stehen

Chemical fingerprints encode mother-offspring similarity, colony membership, relatedness and genetic quality in fur seals

Chemical communication underpins virtually all aspects of vertebrate social life, yet remains poorly understood because of its highly complex mechanistic basis. We therefore used chemical fingerprinting of skin swabs and genetic analysis to explore the chemical cues that may underlie mother–offspring recognition in colonially breeding Antarctic fur seals. By sampling mother–offspring pairs from two different colonies, using a variety of statistical approaches and genotyping a large panel of microsatellite loci, we show that colony membership, mother–offspring similarity, heterozygosity, and genetic relatedness are all chemically encoded. Moreover, chemical similarity between mothers and offspring reflects a combination of genetic and environmental influences, the former partly encoded by substances resembling known pheromones. Our findings reveal the diversity of information contained within chemical fingerprints and have implications for understanding mother–offspring communication, kin recognition, and mate choice

Multidimensionality of chemical information in male greater sac-winged bats (Saccopteryx bilineata)

Schneeberger K, Voigt C, Müller C, Caspers B. Multidimensionality of chemical information in male greater sac-winged bats (Saccopteryx bilineata). Frontiers in Ecology and Evolution. 2016;4: 83.The complexity of social signals is thought to depend on the complexity of social systems, but evidence from wild animals is scarce. Here, we investigated the chemical information provided by individual male greater sac-winged bats (Saccopteryx bilineata), a small, long-lived neotropical bat species with a harem-polygynous mating system. We analysed the chemical fingerprints of wing-sac liquids that are displayed by males in front of females. Specifically, we tested if fingerprints of 45 males included information about age (adult, juvenile), year of sampling, and distance between colonies. We confirmed age-specific differences in male-specific substances, but show furthermore that chemical fingerprints correlate with year of collection and distance between colonies. Thus, the wing-sac chemistry of male S. bilineata conveys a multitude of information, which can potentially be used by conspecifics, especially by females to assess the status of potential mates. Our study provides evidence for a multidimensionality of chemical information in a free-ranging mammal with high social complexity

Begging blue tit nestlings discriminate between the odour of familiar and unfamiliar conspecifics

1. Offspring often solicit, and compete for, limited parental care by elaborate begging behaviour. Kin selection theory predicts that competing offspring should modify the intensity of their begging depending on the degree of relatedness to their nest-or litter-mates. 2. Empirical evidence in birds, which are a key model in the study of parent-offspring interactions, indeed indicates that a lower level of relatedness between offspring in the nest correlates with more intense begging (i.e. more 'selfish' behaviour). This implies that competing nestlings can recognize kin, but the mechanism underlying such discrimination is unclear. Birds have long been thought to mainly rely on visual and auditory cues in their social communication, but there is now growing evidence for the importance of olfactory cues too. 3. To assess the potential importance of olfactory cues in modulating nestling begging behaviour, we experimentally tested in a free-living bird, the blue tit Cyanistes caeruleus, if nestlings discriminate and adjust their begging behaviour depending on their familiarity with a conspecific nestling odour stimulus. 4. We found that individuals responded with longer and more intense begging bouts to an unfamiliar compared with a familiar odour stimulus. 5. Our findings provide first evidence for a role of olfaction in modulating offspring begging behaviour in a wild bird population. Although our experiment cannot differentiate between the effects of familiarity and relatedness, it raises the interesting possibility that blue tit nestlings may also discriminate between odours of close kin and less related individuals, and adjust their begging behaviour accordingly. This hypothesis requires further testing

Female Zebra Finches smell their eggs

Golüke S, Dörrenberg S, Krause ET, Caspers B. Female Zebra Finches smell their eggs. PLOS ONE. 2016;11(5): e0155513.Parental investment in unrelated offspring seems maladaptive from an evolutionary perspective, due to the costs of energy and resources that cannot be invested in related offspring at the same time. Therefore selection should favour mechanisms to discriminate between own and foreign offspring. In birds, much emphasis has been placed on understanding the visual mechanisms underlying egg recognition. However, olfactory egg recognition has almost been completely ignored. Here, we investigated whether female zebra finches (Taeniopygia guttata) are able to discriminate between their own and a conspecific egg based on olfactory cues alone. Zebra finches are colonial—breeding songbirds. Eggs are monomorphic, i.e. without any spotting pattern, and intraspecific brood parasitism frequently occurs. In a binary choice experiment, female zebra finches were given the choice between the scent of their own and a conspecific egg. After the onset of incubation, females chose randomly and showed no sign of discrimination. However, shortly before hatching, females preferred significantly the odour of their own egg. The finding that females are capable to smell their own egg may inspire more research on the potential of olfaction involved in egg recognition, especially in cases where visual cues might be limited

Chemical patterns of colony membership and mother- offspring similarity in Antarctic fur seals are reproducible

Tebbe J, Humble E, Stoffel MA, et al. Chemical patterns of colony membership and mother-offspring similarity in Antarctic fur seals are reproducible. PeerJ. 2020;8: e10131.Replication studies are essential for evaluating the validity of previous research findings. However, it has proven challenging to reproduce the results of ecological and evolutionary studies, partly because of the complexity and lability of many of the phenomena being investigated, but also due to small sample sizes, low statistical power and publication bias. Additionally, replication is often considered too difficult in field settings where many factors are beyond the investigator’s control and where spatial and temporal dependencies may be strong. We investigated the feasibility of reproducing original research findings in the field of chemical ecology by performing an exact replication of a previous study of Antarctic fur seals (Arctocephalus gazella). In the original study, skin swabs from 41 mother-offspring pairs from two adjacent breeding colonies on Bird Island, South Georgia, were analyzed using gas chromatography-mass spectrometry. Seals from the two colonies differed significantly in their chemical fingerprints, suggesting that colony membership may be chemically encoded, and mothers were also chemically similar to their pups, hinting at the possible involvement of phenotype matching in mother-offspring recognition. In the current study, we generated and analyzed chemical data from a non-overlapping sample of 50 mother-offspring pairs from the same two colonies 5 years later. The original results were corroborated in both hypothesis testing and estimation contexts, with p-values remaining highly significant and effect sizes, standardized between studies by bootstrapping the chemical data over individuals, being of comparable magnitude. However, exact replication studies are only capable of showing whether a given effect can be replicated in a specific setting. We therefore investigated whether chemical signatures are colony-specific in general by expanding the geographic coverage of our study to include pups from a total of six colonies around Bird Island. We detected significant chemical differences in all but a handful of pairwise comparisons between colonies. This finding adds weight to our original conclusion that colony membership is chemically encoded, and suggests that chemical patterns of colony membership not only persist over time but can also be generalized over space. Our study systematically confirms and extends our previous findings, while also implying more broadly that spatial and temporal heterogeneity need not necessarily negate the reproduction and generalization of ecological research findings

Timing matters: age-dependent impacts of the social environment and host selection on the avian gut microbiota

Background The establishment of the gut microbiota in early life is a critical process that influences the development and fitness of vertebrates. However, the relative influence of transmission from the early social environment and host selection throughout host ontogeny remains understudied, particularly in avian species. We conducted conspecific and heterospecific cross-fostering experiments in zebra finches (Taeniopygia guttata) and Bengalese finches (Lonchura striata domestica) under controlled conditions and repeatedly sampled the faecal microbiota of these birds over the first 3 months of life. We thus documented the development of the gut microbiota and characterised the relative impacts of the early social environment and host selection due to species-specific characteristics and individual genetic backgrounds across ontogeny by using 16S ribosomal RNA gene sequencing. Results The taxonomic composition and community structure of the gut microbiota changed across ontogenetic stages; juvenile zebra finches exhibited higher alpha diversity than adults at the post-breeding stage. Furthermore, in early development, the microbial communities of juveniles raised by conspecific and heterospecific foster parents resembled those of their foster family, emphasising the importance of the social environment. In later stages, the social environment continued to influence the gut microbiota, but host selection increased in importance. Conclusions We provided a baseline description of the developmental succession of gut microbiota in zebra finches and Bengalese finches, which is a necessary first step for understanding the impact of the early gut microbiota on host fitness. Furthermore, for the first time in avian species, we showed that the relative strengths of the two forces that shape the establishment and maintenance of the gut microbiota (i.e. host selection and dispersal from the social environment) change during development, with host selection increasing in importance. This finding should be considered when experimentally manipulating the early-life gut microbiota. Our findings also provide new insights into the mechanisms of host selection