Nadine Schubert

Olfactory cues play a vital role in mammalian social communication, conveying fitness-relevant information such as genetic quality and relatedness. Kin recognition through scent can help avoid inbreeding and guide nepotistic behaviors, enhancing fitness. In banded mongooses, synchronized breeding disrupts familiarity-based kin recognition, potentially increasing reliance on phenotype matching, where individuals compare genetically determined odors to assess similarity. We tested whether banded mongooses use odors to assess genetic diversity and relatedness based on (i) major histocompatibility complex (MHC) genotypes and (ii) neutral microsatellite loci. Results showed individuals responded differently to odors from unfamiliar conspecifics based on MHC diversity and relatedness. Specifically, less MHC-diverse and less related individuals attracted more interest, suggesting odor cues are used to evaluate intruder or competitor threat levels. Neutral genetic diversity did not affect odor responses and was not correlated with MHC diversity, indicating responses to MHC diversity are independent of overall genetic diversity. No effect of MHC similarity was observed, possibly due to sample size limitations. Our findings suggest MHC diversity may signal genetic quality, whereas other genomic regions might contribute to assessing relatedness. These results provide a foundation for further research into the role of MHC and other genes in social communication in species where phenotype matching offers adaptive benefits.

Background: The major histocompatibility complex’s (MHC) role in the vertebrate adaptive immune response and its exceptional polymorphism make it a key target for studying adaptive gene evolution. However, studies on carnivore MHC often focus on populations with severe bottlenecks or conservation concerns, leading to small sample sizes and unreliable generalizations about MHC diversity. Furthermore, many studies focus on one MHC class and do not cover the whole peptide binding groove of the MHC molecule. Here, we characterize MHC class I (MHC-I) exon 2 and 3, encoding the α1- and α2-domains, as well as MHC-II DRB exon 2 for a large sample ( N = 285–384) of a wild carnivore of least conservation concern but with high levels of inbreeding, the banded mongoose. Results: MHC-I showed higher allelic and supertype diversity and polymorphism compared to MHC-II, consistent with findings in humans where MHC-I experiences stronger diversifying selection. MHC-I exon 3 exhibited the lowest diversity, likely due to its specific role in forming the peptide binding groove. Diversifying selection was stronger on MHC-I exon 2 (α1 domain) than exon 3 (α2 domain). Despite frequent inbreeding, banded mongooses showed MHC diversity comparable to other carnivores of least concern using phylogenetic mixed models. Phylogenetic analysis indicated a longer evolutionary trajectory for MHC-II compared to MHC-I and species-specific gene duplication of nonclassical MHC-I sequences clustering with classical sequences. Trans-species polymorphism in nonclassical MHC-I sequences suggested homology or convergent evolution. Conclusions: This study is the first to characterize both MHC classes of a social, wild carnivore using high-throughput sequencing and a large sample size. Despite frequent inbreeding, banded mongooses exhibit MHC diversity comparable to other carnivores of least conservation concern, challenging assumptions that inbreeding universally reduces genetic diversity. Higher diversity and selection on MHC-I exon 2 emphasize its role in immune defense, while lower diversity in exon 3 highlights functional divergence between the exons. The longer evolutionary trajectory of MHC-II reveals differences in dynamics between MHC classes. Species-specific gene duplication and trans-species polymorphism in nonclassical MHC-I sequences suggest complex evolutionary mechanisms. These findings advance understanding of MHC evolution in wild carnivores, with implications for conservation genetics, particularly regarding the effects of social structure and inbreeding on immune gene diversity.

Parasite infections affect males and females differently across a wide range of species, often due to differences in immune responses. Generally, females tend to have stronger immune defences and lower parasite loads than males. The major histocompatibility complex (MHC) plays a crucial role in the adaptive immune response, and extensive research has explored how variation in this region influences infection and fitness outcomes. However, studies of sex‐specific relationships between MHC variation and infection are scarce, perhaps because MHC genes are located on the autosomes, which are shared by both sexes. Here, we provide evidence of sexually antagonistic selection in a wild, group‐living mammal—the banded mongoose. Using genetic and life history data collected from over 300 individuals across 25 years, we found that both MHC class I (MHC‐I) and MHC class II (MHC‐II) diversity influence lifetime reproductive success differently in males and females. Specifically, higher MHC diversity is linked to increased fitness in males but decreased fitness in females. Furthermore, MHC diversity did not differ between the sexes, indicating an unresolved genetic sexual conflict. Our findings demonstrate that sexually antagonistic selection acts on the MHC and may operate across both MHC classes but differently. This study contributes to the growing body of evidence that sex is a significant factor in shaping host immunity and fitness.

Olfactory cues are critical in mammalian social communication, conveying fitness-relevant information such as relatedness, genetic quality, and compatibility. Recognizing kin through scent can help avoid inbreeding depression and guide nepotistic behaviors, enhancing both direct and indirect fitness. While many species use familiarity to identify relatives, others rely on phenotype matching, where animals assess genetic similarity by comparing their own genetically determined odor with that of others. In banded mongooses, synchronized breeding disrupts familiarity cues, increasing reliance on alternative mechanisms for kin discrimination and mate selection. We tested whether banded mongooses use odors to assess genetic diversity and relatedness based on (1) major histocompatibility complex (MHC) genotypes and (2) neutral microsatellite loci that reflect genetic diversity and relatedness. We found that individuals respond differently to odors from unfamiliar individuals based on MHC diversity and genetic relatedness. Specifically, individuals show more interest in less MHC diverse and less related unfamiliar conspecifics, suggesting odor cues are used to evaluate threat level of intruders or competitors. Genetic diversity had no impact on responses to odors and was not significantly associated with MHC diversity, implying that responses to MHC diversity did not result from an underlying correlation with over-all genetic diversity. We also found no effect of MHC similarity, which might be caused by the limited sample size for this analysis. Our findings show that MHC diversity might signal the genetic quality of individuals, but regions of the genome other than MHC may be used to assess relatedness. These findings provide the basis for future research on the involvement of the MHC and other genes in social communication in species where phenotype matching is likely to be advantageous.

Parasite infections affect males and females differently across a wide range of species, often due to differences in immune responses. Generally, females tend to have stronger immune defenses and lower parasite loads than males. The major histocompatibility complex (MHC) plays a crucial role in the adaptive immune response, and extensive research has explored how variation in this region influences infection and fitness outcomes. However, studies of sex-specific relationships between MHC variation and infection are scarce, perhaps because MHC genes are located on the autosomes, which are shared by both sexes. Here, we provide evidence of sexually antagonistic selection in a wild, group-living mammal—the banded mongoose. Using genetic and life history data collected from over 300 individuals across 25 years, we found that particularly MHC class I (MHC-I) but also MHC class II (MHC-II) diversity influence lifetime reproductive success differently in males and females. Specifically, higher MHC diversity is linked to increased fitness in males but decreased fitness in females. Furthermore, MHC diversity did not differ between the sexes, indicating an unresolved genetic sexual conflict. Our findings demonstrate that sexually antagonistic selection acts on the MHC and may operate across both MHC classes but differently. This study contributes to the growing body of evidence that sex is a significant factor in shaping host immunity and fitness.

The major histocompatibility complex’s (MHC) role in the vertebrate adaptive immune response and its exceptional polymorphism make it a key target for studying adaptive gene evolution. However, previous studies on carnivore MHC have mostly focused on populations which experienced a severe bottleneck or are of general conservation concern. Hence, sample sizes are often small and generalizations about MHC diversity are unreliable. Furthermore, studies often focus on one MHC class and do not cover the whole peptide binding groove of the MHC molecule. Here, we characterize MHC class I (MHC-I) exon 2 and 3, encoding both the α1- and α2-domain of the MHC-I molecule, as well as MHC-II DRB exon 2 for a large sample (N = 282-485) of a wild mammal of least conservation concern, the banded mongoose. We found that MHC-I generally showed higher allelic diversity and polymorphism compared to MHC-II, which is in line with findings in humans that show higher diversifying selection acting on MHC-I. However, MHC-I exon 3 showed the lowest diversity, possibly due to its different role in generating the peptide binding groove of the class I molecule compared to exon 2. Moreover, we found selection to act more strongly on MHC-I exon 2 (domain α1) than exon 3 (domain α2). Despite frequent inbreeding, phylogenetic comparative analysis showed banded mongooses to have MHC diversity levels comparable with other carnivores of least concern. Phylogenetic analysis indicated a longer evolutionary trajectory for MHC-II compared to MHC-I as well as species-specific gene duplication of nonclassical sequences of MHC-I clustering with classical sequences. Trans-species polymorphism was detected for nonclassical MHC-I sequences suggesting homology or convergent evolution for these genes. Our study is the first to characterize both MHC classes of a social, wild carnivore using a high throughput sequencing approach with a large sample size and thereby provides the basis for further investigation of MHC structure and function within the banded mongoose and other carnivores.

Wildlife tagging provides critical insights into animal movement ecology, physiology, and behavior amid global ecosystem changes. However, the stress induced by capture, handling, and tagging can impact post-release locomotion and activity and, consequently, the interpretation of study results. Here, we analyze post-tagging effects on 1585 individuals of 42 terrestrial mammal species using collar-collected GPS and accelerometer data. Species-specific displacements and overall dynamic body acceleration, as a proxy for activity, were assessed over 20 days post-release to quantify disturbance intensity, recovery duration, and speed. Differences were evaluated, considering species-specific traits and the human footprint of the study region. Over 70% of the analyzed species exhibited significant behavioral changes following collaring events. Herbivores traveled farther with variable activity reactions, while omnivores and carnivores were initially less active and mobile. Recovery duration proved brief, with alterations diminishing within 4–7 tracking days for most species. Herbivores, particularly males, showed quicker displacement recovery (4 days) but slower activity recovery (7 days). Individuals in high human footprint areas displayed faster recovery, indicating adaptation to human disturbance. Our findings emphasize the necessity of extending tracking periods beyond 1 week and particular caution in remote study areas or herbivore-focused research, specifically in smaller mammals.

Genes of the major histocompatibility complex (MHC) have long been linked to odor signaling and recently researchers’ attention has focused on MHC structuring of microbial communities and how this may in turn impact odor. However, understanding of the mechanisms through which the MHC could affect the microbiota to produce a chemical signal that is both reliable and strong enough to ensure unambiguous transmission of behaviorally important information remains poor. This is largely because empirical studies are rare, predictions are unclear, and the underlying immunological mechanisms governing MHC–microbiota interactions are often neglected. Here, we review the immunological processes involving MHC class II (MHC-II) that could affect the commensal community. Focusing on immunological and medical research, we provide background knowledge for nonimmunologists by describing key players within the vertebrate immune system relating to MHC-II molecules (which present extracellular-derived peptides, and thus interact with extracellular commensal microbes). We then systematically review the literature investigating MHC–odor–microbiota interactions in animals and identify areas for future research. These insights will help to design studies that are able to explore the role of MHC-II and the microbiota in the behavior of wild populations in their natural environment and consequently propel this research area forward.

With urban areas growing worldwide comes an increase in artificial light at night (ALAN), causing a significant impact on wildlife behaviour and its ecological relationships. The effects of ALAN on nocturnal and protected European hedgehogs (Erinaceus europaeus) are unknown but their identification is important for sustainable species conservation and management. In a pilot study, we investigated the influence of ALAN on the natural movement behaviour of 22 hedgehogs (nine females, 13 males) in urban environments. Over the course of four years, we equipped hedgehogs at three different study locations in Berlin with biologgers to record their behaviour for several weeks. We used Global Positioning System (GPS) tags to monitor their spatial behaviour, very high-frequency (VHF) loggers to locate their nests during daytime, and accelerometers to distinguish between active and passive behaviours. We compared the mean light intensity of the locations recorded when the hedgehogs were active with the mean light intensity of simulated locations randomly distributed in the individual’s home range. We were able to show that the ALAN intensity of the hedgehogs’ habitations was significantly lower compared to the simulated values, regardless of the animal’s sex. This ALAN-related avoidance in the movement behaviour can be used for applied hedgehog conservation.