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Tebbe J, Havenstein K, Forcada J, Tiedemann R, Caspers B, Hoffman JI. No evidence for a role of MHC class II genotype in the chemical encoding of heterozygosity and relatedness in Antarctic fur seals. Proc Biol Sci 2024; 291:20232519. [PMID: 38503331 PMCID: PMC10950461 DOI: 10.1098/rspb.2023.2519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 02/22/2024] [Indexed: 03/21/2024] Open
Abstract
Despite decades of research, surprisingly little is known about the mechanism(s) by which an individual's genotype is encoded in odour. Many studies have focused on the role of the major histocompatibility complex (MHC) owing to its importance for survival and mate choice. However, the salience of MHC-mediated odours compared to chemicals influenced by the rest of the genome remains unclear, especially in wild populations where it is challenging to quantify and control for the effects of the genomic background. We addressed this issue in Antarctic fur seals by analysing skin swabs together with full-length MHC DQB II exon 2 sequences and data from 41 genome-wide distributed microsatellites. We did not find any effects of MHC relatedness on chemical similarity and there was also no relationship between MHC heterozygosity and chemical diversity. However, multilocus heterozygosity showed a significant positive association with chemical diversity, even after controlling for MHC heterozygosity. Our results appear to rule out a dominant role of the MHC in the chemical encoding of genetic information in a wild vertebrate population and highlight the need for genome-wide approaches to elucidate the mechanism(s) and specific genes underlying genotype-odour associations.
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Affiliation(s)
- Jonas Tebbe
- Department of Evolutionary Population Genetics, Faculty of Biology, Bielefeld University, 33615 Bielefeld, Germany
- Department of Behavioural Ecology, Bielefeld University, 33501 Bielefeld, Germany
- Department of Animal Behaviour, Bielefeld University, 33501 Bielefeld, Germany
| | - Katja Havenstein
- Unit of Evolutionary Biology / Systematic Zoology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany
| | - Jaume Forcada
- British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, UK
| | - Ralph Tiedemann
- Unit of Evolutionary Biology / Systematic Zoology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam-Golm, Germany
| | - Barbara Caspers
- Department of Behavioural Ecology, Bielefeld University, 33501 Bielefeld, Germany
- Joint Institute for Individualisation in a Changing Environment (JICE), Bielefeld University and University of Münster, Bielefeld, Germany
| | - Joseph I. Hoffman
- Department of Evolutionary Population Genetics, Faculty of Biology, Bielefeld University, 33615 Bielefeld, Germany
- Department of Animal Behaviour, Bielefeld University, 33501 Bielefeld, Germany
- British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, UK
- Joint Institute for Individualisation in a Changing Environment (JICE), Bielefeld University and University of Münster, Bielefeld, Germany
- Center for Biotechnology (CeBiTec), Faculty of Biology, Bielefeld University, 33615 Bielefeld, Germany
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A Review of Suggested Mechanisms of MHC Odor Signaling. BIOLOGY 2022; 11:biology11081187. [PMID: 36009814 PMCID: PMC9405088 DOI: 10.3390/biology11081187] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 07/26/2022] [Accepted: 08/04/2022] [Indexed: 11/23/2022]
Abstract
Simple Summary Immune genes of the vertebrate MHC vary among individuals. Each individual collection is optimally diverse to provide resistance against some infectious diseases but not too diverse to cause autoimmune diseases. MHC-dependent mate choice aims for optimally complementary MHC alleles. Each potential partner signals through body odor his/her MHC alleles. Identifying the signal molecules was a long-lasting puzzle solved only recently after many deviations as described. Commensal microbiota which are controlled by the individual MHC genes differ among individuals. They were suspected repeatedly to provide the signal, though mice raised germ-free could still smell MHC genes. Carrier hypotheses came in various versions, centered around the specificity of each MHC molecule for binding peptides from diseases, shown to T lymphocytes to induce the immune response. Volatiles of various origins were suggested to fill the place of the peptide and thus reflect the identity of the MHC molecule. Finally, the bound peptides themselves were identified as the sought info-chemicals. Synthesized peptides affect mate choice as predicted. Specific olfactory neurons were shown to react to these peptides but only to the anchors that define the binding specificity. Even eggs choose sperm to produce offspring with optimal MHC, though the signaling pathway needs further research. Abstract Although an individual’s mix of MHC immune genes determines its resistance, finding MHC-dependent mate choice occurred by accident in inbred mice. Inbred mice prefer MHC dissimilar mates, even when the choice was restricted to urine. It took decades to find the info-chemicals, which have to be as polymorphic as the MHC. Microbiota were suggested repeatedly as the origin of the odor signal though germ-free mice maintained normal preference. Different versions of the ‘carrier hypothesis’ suggested MHC molecules carry volatiles after the bound peptide is released. Theory predicted an optimal individual MHC diversity to maximize resistance. The optimally complementary mate should be and is preferred as several studies show. Thus, the odor signal needs to transmit the exact information of the sender’s MHC alleles, as do MHC ligand peptides but not microbiota. The ‘MHC peptide hypothesis’ assumes that olfactory perception of the peptide ligand provides information about the MHC protein in a key-lock fashion. Olfactory neurons react only to the anchors of synthesized MHC peptides, which reflect the binding MHC molecule’s identity. Synthesized peptides supplemented to a male’s signal affect choice in the predicted way, however, not when anchors are mutated. Also, the human brain detects smelled synthesized self-peptides as such. After mate choice, the lottery of meiosis of randomly paired oocyte and sperm haplotypes would often produce MHC non-optimal offspring. In sticklebacks, eggs select MHC-compatible sperm, thus prefer the best combination close to the population optimum.
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Bracamonte SE, Hofmann MJ, Lozano-Martín C, Eizaguirre C, Barluenga M. Divergent and non-parallel evolution of MHC IIB in the Neotropical Midas cichlid species complex. BMC Ecol Evol 2022; 22:41. [PMID: 35365100 PMCID: PMC8974093 DOI: 10.1186/s12862-022-01997-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 03/21/2022] [Indexed: 01/09/2023] Open
Abstract
Background Ecological diversification is the result of divergent natural selection by contrasting habitat characteristics that favours the evolution of distinct phenotypes. This process can happen in sympatry and in allopatry. Habitat-specific parasite communities have the potential to drive diversification among host populations by imposing selective pressures on their host's immune system. In particular, the hyperdiverse genes of the major histocompatibility complex (MHC) are implicated in parasite-mediated host divergence. Here, we studied the extent of divergence at MHC, and discuss how it may have contributed to the Nicaraguan Midas cichlid species complex diversification, one of the most convincing examples of rapid sympatric parallel speciation. Results We genotyped the MHC IIB for individuals from six sympatric Midas cichlid assemblages, each containing species that have adapted to exploit similar habitats. We recovered large allelic and functional diversity within the species complex. While most alleles were rare, functional groups of alleles (supertypes) were common, suggesting that they are key to survival and that they were maintained during colonization and subsequent radiations. We identified lake-specific and habitat-specific signatures for both allelic and functional diversity, but no clear pattern of parallel divergence among ecomorphologically similar phenotypes. Conclusions Colonization and demographic effects of the fish could have contributed to MHC evolution in the Midas cichlid in conjunction with habitat-specific selective pressures, such as parasites associated to alternative preys or environmental features. Additional ecological data will help evaluating the role of host–parasite interactions in the Midas cichlid radiations and aid in elucidating the potential role of non-parallel features differentiating crater lake species assemblages. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-022-01997-9.
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Affiliation(s)
- Seraina E Bracamonte
- Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006, Madrid, Spain
| | - Melinda J Hofmann
- Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006, Madrid, Spain
| | - Carlos Lozano-Martín
- Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006, Madrid, Spain
| | - Christophe Eizaguirre
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Marta Barluenga
- Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006, Madrid, Spain.
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Whitlock KE, Palominos MF. The Olfactory Tract: Basis for Future Evolution in Response to Rapidly Changing Ecological Niches. Front Neuroanat 2022; 16:831602. [PMID: 35309251 PMCID: PMC8927807 DOI: 10.3389/fnana.2022.831602] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 02/01/2022] [Indexed: 01/10/2023] Open
Abstract
Within the forebrain the olfactory sensory system is unique from other sensory systems both in the projections of the olfactory tract and the ongoing neurogenic potential, characteristics conserved across vertebrates. Olfaction plays a crucial role in behaviors such as mate choice, food selection, homing, escape from predators, among others. The olfactory forebrain is intimately associated with the limbic system, the region of the brain involved in learning, memory, and emotions through interactions with the endocrine system and the autonomic nervous system. Previously thought to lack a limbic system, we now know that teleost fishes process emotions, have exceptional memories, and readily learn, behaviors that are often associated with olfactory cues. The association of neuromodulatory hormones, and more recently, the immune system, with odor cues underlies behaviors essential for maintenance and adaptation within natural ecological niches. Increasingly anthropogenic perturbations affecting ecosystems are impacting teleost fishes worldwide. Here we examine the role of the olfactory tract as the neural basis for the integration of environmental cues and resulting behaviors necessary for the regulation of biotic interactions that allow for future adaptation as the climate spins out of control.
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Affiliation(s)
- Kathleen E. Whitlock
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Universidad de ValparaísoValparaíso, Chile
- Instituto de Neurociencia, Universidad de ValparaísoValparaíso, Chile
- *Correspondence: Kathleen E. Whitlock
| | - M. Fernanda Palominos
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Universidad de ValparaísoValparaíso, Chile
- Instituto de Neurociencia, Universidad de ValparaísoValparaíso, Chile
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Clemens BJ, Schreck CB. An assessment of terminology for intraspecific diversity in fishes, with a focus on "ecotypes" and "life histories". Ecol Evol 2021; 11:10772-10793. [PMID: 34429881 PMCID: PMC8366897 DOI: 10.1002/ece3.7884] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/03/2021] [Accepted: 06/23/2021] [Indexed: 12/15/2022] Open
Abstract
Understanding and preserving intraspecific diversity (ISD) is important for species conservation. However, ISD units do not have taxonomic standards and are not universally recognized. The terminology used to describe ISD is varied and often used ambiguously. We compared definitions of terms used to describe ISD with use in recent studies of three fish taxa: sticklebacks (Gasterosteidae), Pacific salmon and trout (Oncorhynchus spp., "PST"), and lampreys (Petromyzontiformes). Life history describes the phenotypic responses of organisms to environments and includes biological parameters that affect population growth or decline. Life-history pathway(s) are the result of different organismal routes of development that can result in different life histories. These terms can be used to describe recognizable life-history traits. Life history is generally used in organismal- and ecology-based journals. The terms paired species/species pairs have been used to describe two different phenotypes, whereas in some species and situations a continuum of phenotypes may be expressed. Our review revealed overlapping definitions for race and subspecies, and subspecies and ecotypes. Ecotypes are genotypic adaptations to particular environments, and this term is often used in genetic- and evolution-based journals. "Satellite species" is used for situations in which a parasitic lamprey yields two or more derived, nonparasitic lamprey species. Designatable Units, Evolutionary Significant Units (ESUs), and Distinct Population Segments (DPS) are used by some governments to classify ISD of vertebrate species within distinct and evolutionary significant criteria. In situations where the genetic or life-history components of ISD are not well understood, a conservative approach would be to call them phenotypes.
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Affiliation(s)
| | - Carl B. Schreck
- Department of Fisheries and WildlifeOregon State UniversityCorvallisORUSA
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Gahr CL, Boehm T, Milinski M. Male validation factor for three-spined stickleback ( Gasterosteus aculeatus) mate choice likely evolutionarily conserved since 50 thousand years. ETHOL ECOL EVOL 2021. [DOI: 10.1080/03949370.2020.1789748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Christoph L. Gahr
- Department of Evolutionary Ecology, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Thomas Boehm
- Department of Developmental Immunology, Max-Planck-Institute for Immunobiology and Epigenetics, Freiburg, Germany
| | - Manfred Milinski
- Department of Evolutionary Ecology, Max Planck Institute for Evolutionary Biology, Plön, Germany
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Griebel IA, Dawson RD. Nestling tree swallows (
Tachycineta bicolor
) alter begging behaviour in response to odour of familiar adults, but not their nests. Ethology 2020. [DOI: 10.1111/eth.13015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ilsa A. Griebel
- Ecosystem Science and Management Program University of Northern British Columbia Prince George BC Canada
| | - Russell D. Dawson
- Ecosystem Science and Management Program University of Northern British Columbia Prince George BC Canada
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Achorn AM, Rosenthal GG. It’s Not about Him: Mismeasuring ‘Good Genes’ in Sexual Selection. Trends Ecol Evol 2020; 35:206-219. [DOI: 10.1016/j.tree.2019.11.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 11/24/2019] [Accepted: 11/26/2019] [Indexed: 01/18/2023]
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