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Riverón S, Raoult V, Baylis AMM, Jones KA, Slip DJ, Harcourt RG. Pelagic and benthic ecosystems drive differences in population and individual specializations in marine predators. Oecologia 2021; 196:891-904. [PMID: 34173892 DOI: 10.1007/s00442-021-04974-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 06/13/2021] [Indexed: 11/24/2022]
Abstract
Individual specialization, which describes whether populations are comprised of dietary generalists or specialists, has profound ecological and evolutionary implications. However, few studies have quantified individual specialization within and between sympatric species that are functionally similar but have different foraging modes. We assessed the relationship between individual specialization, isotopic niche metrics and foraging behaviour of two marine predators with contrasting foraging modes: pelagic foraging female South American fur seals (Arctocephalus australis) and benthic foraging female southern sea lions (Otaria byronia). Stable isotope analysis of carbon and nitrogen was conducted along the length of adult female vibrissae to determine isotopic niche metrics and the degree of individual specialization. Vibrissae integrated time ranged between 1.1 and 5.5 years, depending on vibrissae length. We found limited overlap in dietary niche-space. Broader population niche sizes were associated with higher degrees of individual specialization, while narrower population niches with lower degrees of individual specialization. The degree of individual specialization was influenced by pelagic and benthic foraging modes. Specifically, South American fur seals, foraging in dynamic pelagic environments with abundant but similar prey, comprised specialist populations composed of generalist individuals. In contrast, benthic southern sea lions foraging in habitats with diverse but less abundant prey had more generalist populations composed of highly specialized individuals. We hypothesize that differences in specialization within and between populations were related to prey availability and habitat differences. Our study supports growing body of literature highlighting that individual specialization is a critical factor in shaping the ecological niche of higher marine predators.
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Affiliation(s)
- Sabrina Riverón
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.
| | - Vincent Raoult
- School of Environmental and Life Sciences, University of Newcastle, Ourimbah, Australia
| | - Alastair M M Baylis
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.,South Atlantic Environmental Research Institute, Stanley Cottage, PO Box 609, Stanley, FIQQ 1ZZ, Falkland Islands
| | - Kayleigh A Jones
- British Antarctic Survey, High Cross, Madingley Rd, Cambridge, CB3 0ET, UK.,University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| | - David J Slip
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia.,Taronga Conservation Society Australia, Bradley's Head Road, Mosman, NSW, 2088, Australia
| | - Robert G Harcourt
- Marine Predator Research Group, Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2113, Australia
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Lübcker N, Whiteman JP, Newsome SD, Millar RP, de Bruyn PJN. Can the carbon and nitrogen isotope values of offspring be used as a proxy for their mother's diet? Using foetal physiology to interpret bulk tissue and amino acid δ 15N values. CONSERVATION PHYSIOLOGY 2020; 8:coaa060. [PMID: 32765882 PMCID: PMC7397484 DOI: 10.1093/conphys/coaa060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 04/14/2020] [Accepted: 06/14/2020] [Indexed: 06/11/2023]
Abstract
The measurement of bulk tissue nitrogen (δ15N) and carbon isotope values (δ13C) chronologically along biologically inert tissues sampled from offspring can provide a longitudinal record of their mothers' foraging habits. This study tested the important assumption that mother-offspring stable isotope values are positively and linearly correlated. In addition, any change in the mother-offspring bulk tissues and individual amino acids that occurred during gestation was investigated. Whiskers sampled from southern elephant seal pups (Mirounga leonina) and temporally overlapping whiskers from their mothers were analyzed. This included n = 1895 chronologically subsampled whisker segments for bulk tissue δ15N and δ13C in total and n = 20 whisker segments for amino acid δ15N values, sampled from recently weaned pups (n = 17), juvenile southern elephant seals (SES) < 2 years old (n = 23) and adult female SES (n = 17), which included nine mother-offspring pairs. In contrast to previous studies, the mother-offspring pairs were not in isotopic equilibrium or linearly correlated during gestation: the Δ15N and Δ13C mother-offspring offsets increased by 0.8 and 1.2‰, respectively, during gestation. The foetal bulk δ15N values were 1.7 ± 0.5‰ (0.9-2.7‰) higher than mothers' δ15N values before birth, while the foetal δ13C increased by ~1.7‰ during gestation and were 1.0 ± 0.5‰ (0.0-1.9‰) higher than their mothers' δ13C at the end of pregnancy. The mother-offspring serine and glycine Δ15N differed by ~4.3‰, while the foetal alanine δ15N values were 1.4‰ lower than that of their mothers during the third trimester of pregnancy. The observed mother-offspring δ15N differences are likely explained by shuttling of glutamate-glutamine and glycine-serine amongst skeletal muscle, liver, placenta and foetal tissue. Foetal development relies primarily on remobilized endogenous maternal proteinaceous sources. Researchers should consider foetal physiology when using offspring bulk tissue isotope values as biomarkers for the mother's isotopic composition as part of monitoring programmes.
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Affiliation(s)
- Nico Lübcker
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, Pretoria, 0028, South Africa
| | - John P Whiteman
- Department of Biological Sciences, Old Dominion University, 5115 Hampton Boulevard, Norfolk, VA, 23529, USA
- Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Seth D Newsome
- Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Robert P Millar
- Centre for Neuroendocrinology and Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, 0001, South Africa
- Department of Integrative Biomedical Sciences, Neurosciences Institute and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Anzio Road, Observatory 7925, South Africa
| | - P J Nico de Bruyn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, Pretoria, 0028, South Africa
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Delport TC, Power ML, Harcourt RG, Webster KN, Tetu SG. Colony Location and Captivity Influence the Gut Microbial Community Composition of the Australian Sea Lion (Neophoca cinerea). Appl Environ Microbiol 2016; 82:3440-3449. [PMID: 27037116 PMCID: PMC4959163 DOI: 10.1128/aem.00192-16] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/19/2016] [Indexed: 02/01/2023] Open
Abstract
UNLABELLED Gut microbiota play an important role in maintenance of mammalian metabolism and immune system regulation, and disturbances to this community can have adverse impacts on animal health. To better understand the composition of gut microbiota in marine mammals, fecal bacterial communities of the Australian sea lion (Neophoca cinerea), an endangered pinniped with localized distribution, were examined. A comparison of samples from individuals across 11 wild colonies in South and Western Australia and three Australian captive populations showed five dominant bacterial phyla: Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Fusobacteria The phylum Firmicutes was dominant in both wild (76.4% ± 4.73%) and captive animals (61.4% ± 10.8%), while Proteobacteria contributed more to captive (29.3% ± 11.5%) than to wild (10.6% ± 3.43%) fecal communities. Qualitative differences were observed between fecal communities from wild and captive animals based on principal-coordinate analysis. SIMPER (similarity percentage procedure) analyses indicated that operational taxonomic units (OTU) from the bacterial families Clostridiaceae and Ruminococcaceae were more abundant in wild than in captive animals and contributed most to the average dissimilarity between groups (SIMPER contributions of 19.1% and 10.9%, respectively). Differences in the biological environment, the foraging site fidelity, and anthropogenic impacts may provide various opportunities for unique microbial establishment in Australian sea lions. As anthropogenic disturbances to marine mammals are likely to increase, understanding the potential for such disturbances to impact microbial community compositions and subsequently affect animal health will be beneficial for management of these vulnerable species. IMPORTANCE The Australian sea lion is an endangered species for which there is currently little information regarding disease and microbial ecology. In this work, we present an in-depth study of the fecal microbiota of a large number of Australian sea lions from geographically diverse wild and captive populations. Colony location and captivity were found to influence the gut microbial community compositions of these animals. Our findings significantly extend the baseline knowledge of marine mammal gut microbiome composition and variability.
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Affiliation(s)
- Tiffany C Delport
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Michelle L Power
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Robert G Harcourt
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Koa N Webster
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Sasha G Tetu
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, New South Wales, Australia
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