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

Smarter in the city? Lizards from urban and semi-natural habitats do not differ in a cognitive task in two syntopic species.

Urbanization occurs at a global scale, imposing dramatic and abrupt environmental changes that lead to biodiversity loss. Yet, some animal species can handle these changes, and thrive in such artificial environments. One possible explanation is that urban individuals are equipped with better cognitive abilities, but most studies have focused on birds and mammals and yielded varied results. Reptiles have received much less attention, despite some lizard species being common city dwellers. The Italian wall lizard, Podarcis siculus, and the common wall lizard, Podarcis muralis, are two successful lizards in anthropogenic habitats that thrive in urban locations. To test for differences in a cognitive skill between urban and semi-natural environments, we investigated inhibitory control through a detour task in syntopic populations of the two species, across 249 lizards that were tested in partially artificial field settings. Sophisticated inhibitory control is considered essential for higher degrees of cognitive flexibility and other higher-level cognitive abilities. In this task, we confronted lizards with a transparent barrier, separating them from a desired shelter area that they could only reach by controlling their impulse to go straight and instead detour the barrier. We found no differences between lizards in urban and semi-natural environments, nor between species, but females overall performed better than males. Moreover, 48% of the lizards in our study did not perform a correct trial in any of the 5 trials, hinting at the difficulty of the task for these species. This study is among the first to address lizard cognition, through their inhibitory control, as a potential explanation for success in cities and highlights one should be careful with assuming that urban animals generally have enhanced cognitive performance, as it might be taxa, task, or condition dependent

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

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

Bats, Bacteria, and Bat Smell V.2.0: Repeatable Sex-Specific Differences in Scent Organ Microbiota

Reproducibility is a fundamental principle in science, ensuring reliable and valid findings. However, replication studies are scarce, particularly in ecology, due to the emphasis on novelty for publication. We explored the possibility of replicating original findings in the field of microbial and chemical ecology by conducting a conceptual replication of a previous study analysing the sex-specific differences in the microbial communities inhabiting the wing sacs, a scent organ with crucial functions in olfactory communication, of greater sac-winged bat (Saccopteryx bilineata). In the original study, the skin swabs from the antebrachial wing sacs of the males and wing sac rudiments of the females were analysed using culture-dependent methods to test sex-specific differences. The authors demonstrated that males have lower microbial richness and different microbial composition than females. We attempted to reproduce these findings using 16S rRNA sequencing, which offers improved accuracy in pinpointing microbial members than culture-dependent methods because of advanced statistical methods. Our study validated the original study’s findings: Males had a lower microbial richness, and the community composition differed between the sexes. Furthermore, in the current study, males had an increased abundance of bacteria that might potentially be involved in odour production and degradation of malodorous substances and antimicrobial production. Our conceptual replication study corroborated that microbes can play a role in shaping their host’s olfactory phenotype and consequently influence sexual selection. Furthermore, the current study emphasises the importance of replication efforts and hopefully encourages a culture that values replication studies in scientific practice

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