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Majaliwa MM, Hughey LF, Stabach JA, Songer M, Whyle K, Alhashmi AEA, Al Remeithi M, Pusey R, Chaibo HA, Ngari Walsoumon A, Hassan Hatcha M, Wacher T, Ngaba C, Newby J, Leimgruber P, Mertes K. Experience and social factors influence movement and habitat selection in scimitar-horned oryx (Oryx dammah) reintroduced into Chad. Mov Ecol 2022; 10:47. [PMID: 36357952 PMCID: PMC9650856 DOI: 10.1186/s40462-022-00348-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
Reintroduced animals-especially those raised in captivity-are faced with the unique challenge of navigating a wholly unfamiliar environment, and often make erratic or extensive movements after release. Naïveté to the reintroduction landscape can be costly, e.g., through increased energy expenditure, greater exposure to predation, and reduced opportunities to forage. Integration with an extant population may provide opportunities for social information transfer. However, in the absence of interactions with residents, it is unclear how individual and social learning may affect an animal's ability to track resources in an unfamiliar landscape. We use integrated step selection functions (iSSFs) to address these knowledge gaps, by evaluating the extent to which environmental factors, individual experience (time since release), and social information-sharing (group size) influence movement decisions by scimitar-horned oryx (Oryx dammah) reintroduced into their native range for the first time in ca. 30 years. We found that both experience and social factors influenced the habitat selection and movement behavior of reintroduced oryx. Of four candidate iSSFs, the model that included environmental, experience, and group size variables performed best in both dry and wet periods. Statistically significant interaction terms between environmental variables and experience were generally larger than similar terms for group size, indicating that experience may affect habitat selection by reintroduced oryx more strongly than social factors. These findings may inform the management of recovering wildlife populations, update widely-held expectations about how released ungulates acclimate to novel landscapes, and demonstrate the utility of long-term monitoring of reintroduced populations.
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Affiliation(s)
- M M Majaliwa
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA
- School of Mathematics and Statistics, University of Glasgow, Glasgow, G12 8QQ, UK
| | - L F Hughey
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA
| | - J A Stabach
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA
| | - M Songer
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA
| | - K Whyle
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA
| | - A E A Alhashmi
- Terrestrial and Marine Biodiversity, Environment Agency, Abu Dhabi, United Arab Emirates
| | - M Al Remeithi
- Terrestrial and Marine Biodiversity, Environment Agency, Abu Dhabi, United Arab Emirates
| | - R Pusey
- Terrestrial and Marine Biodiversity, Environment Agency, Abu Dhabi, United Arab Emirates
| | - H A Chaibo
- Direction de la Conservation de la Faune et des Aires Protégées, N'Djamena, Chad
| | - A Ngari Walsoumon
- Direction de la Conservation de la Faune et des Aires Protégées, N'Djamena, Chad
| | - M Hassan Hatcha
- Direction de la Conservation de la Faune et des Aires Protégées, N'Djamena, Chad
| | - T Wacher
- Conservation Programmes, Zoological Society of London, London, UK
| | - C Ngaba
- SaharaConservation, Saint-Maur-des-Fossés, France
| | - J Newby
- SaharaConservation, Saint-Maur-des-Fossés, France
| | - P Leimgruber
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA
| | - K Mertes
- Conservation Ecology Center, Smithsonian's National Zoo and Conservation Biology Institute, Front Royal, VA, USA.
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2
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Mertes K, Jarzyna MA, Jetz W. Hierarchical multi-grain models improve descriptions of species' environmental associations, distribution, and abundance. Ecol Appl 2020; 30:e02117. [PMID: 32154624 DOI: 10.1002/eap.2117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 12/17/2019] [Accepted: 01/06/2020] [Indexed: 06/10/2023]
Abstract
The characterization of species' environmental niches and spatial distribution predictions based on them are now central to much of ecology and conservation, but implicitly requires decisions about the appropriate spatial scale (i.e., grain) of analysis. Ecological theory and empirical evidence suggest that range-resident species respond to their environment at two characteristic, hierarchical spatial grains: (1) response grain, the (relatively fine) grain at which an individual uses environmental resources, and (2) occupancy grain, the (relatively coarse) grain equivalent to a typical home range. We use a multi-grain (MG) occupancy model, aided by fine-grain remotely sensed imagery, to simultaneously estimate species-environment associations at both grains, conduct grain optimization to measure response grain, and apply this analysis framework to an example species: a medium-sized bird (Tockus deckeni) in a heterogeneous East African landscape. Based on home range analysis of movement data, we calculate an occupancy grain of 1 km for T. deckeni. Using a grain optimization procedure across 32 grains from 10 to 500 m, we identify 60 m as the most strongly supported response grain for a suite of environmental variables, slightly coarser than opportunistic behavioral observations would have suggested. Validation confirms that the accuracy of the optimized MG occupancy model substantially exceeds that of equivalent single-grain (SG) occupancy models. We further use a simulation approach to assess the potential impacts of accounting for the multi-scale structure of species' environmental requirements on estimates of population size. We find that the more strongly supported MG approach consistently predicts a minimum population size in the study landscape that is much lower than that provided by the SG model. This suggests that SG approaches commonly used in conservation applications could lead to overly optimistic abundance and population estimates, and that the MG approach may be more appropriate for supporting species conservation goals. More generally, we conclude that multi-grain approaches of the sort presented, and increasingly enabled by growing high-resolution remotely sensed data, hold great promise for offering a more mechanistic framework for assessing the appropriate grain(s) for population monitoring and management and enable more reliable estimates of abundances and species' distributions.
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Affiliation(s)
- Katherine Mertes
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
- Conservation Ecology Center, Smithsonian Conservation Biology Institute, 1500 Remount Road, Front Royal, Virginia, 22630, USA
| | - Marta A Jarzyna
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
- Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, Ohio, 43210, USA
| | - Walter Jetz
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511, USA
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, SL5 7PY, Ascot, Berks, United Kingdom
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3
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Noonan MJ, Fleming CH, Tucker MA, Kays R, Harrison A, Crofoot MC, Abrahms B, Alberts SC, Ali AH, Altmann J, Antunes PC, Attias N, Belant JL, Beyer DE, Bidner LR, Blaum N, Boone RB, Caillaud D, de Paula RC, de la Torre JA, Dekker J, DePerno CS, Farhadinia M, Fennessy J, Fichtel C, Fischer C, Ford A, Goheen JR, Havmøller RW, Hirsch BT, Hurtado C, Isbell LA, Janssen R, Jeltsch F, Kaczensky P, Kaneko Y, Kappeler P, Katna A, Kauffman M, Koch F, Kulkarni A, LaPoint S, Leimgruber P, Macdonald DW, Markham AC, McMahon L, Mertes K, Moorman CE, Morato RG, Moßbrucker AM, Mourão G, O'Connor D, Oliveira‐Santos LGR, Pastorini J, Patterson BD, Rachlow J, Ranglack DH, Reid N, Scantlebury DM, Scott DM, Selva N, Sergiel A, Songer M, Songsasen N, Stabach JA, Stacy‐Dawes J, Swingen MB, Thompson JJ, Ullmann W, Vanak AT, Thaker M, Wilson JW, Yamazaki K, Yarnell RW, Zieba F, Zwijacz‐Kozica T, Fagan WF, Mueller T, Calabrese JM. Effects of body size on estimation of mammalian area requirements. Conserv Biol 2020; 34:1017-1028. [PMID: 32362060 PMCID: PMC7496598 DOI: 10.1111/cobi.13495] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 11/27/2019] [Accepted: 12/24/2019] [Indexed: 06/08/2023]
Abstract
Accurately quantifying species' area requirements is a prerequisite for effective area-based conservation. This typically involves collecting tracking data on species of interest and then conducting home-range analyses. Problematically, autocorrelation in tracking data can result in space needs being severely underestimated. Based on the previous work, we hypothesized the magnitude of underestimation varies with body mass, a relationship that could have serious conservation implications. To evaluate this hypothesis for terrestrial mammals, we estimated home-range areas with global positioning system (GPS) locations from 757 individuals across 61 globally distributed mammalian species with body masses ranging from 0.4 to 4000 kg. We then applied block cross-validation to quantify bias in empirical home-range estimates. Area requirements of mammals <10 kg were underestimated by a mean approximately15%, and species weighing approximately100 kg were underestimated by approximately50% on average. Thus, we found area estimation was subject to autocorrelation-induced bias that was worse for large species. Combined with the fact that extinction risk increases as body mass increases, the allometric scaling of bias we observed suggests the most threatened species are also likely to be those with the least accurate home-range estimates. As a correction, we tested whether data thinning or autocorrelation-informed home-range estimation minimized the scaling effect of autocorrelation on area estimates. Data thinning required an approximately93% data loss to achieve statistical independence with 95% confidence and was, therefore, not a viable solution. In contrast, autocorrelation-informed home-range estimation resulted in consistently accurate estimates irrespective of mass. When relating body mass to home range size, we detected that correcting for autocorrelation resulted in a scaling exponent significantly >1, meaning the scaling of the relationship changed substantially at the upper end of the mass spectrum.
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Affiliation(s)
- Michael J. Noonan
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
- Department of BiologyUniversity of MarylandCollege ParkMD20742U.S.A.
| | - Christen H. Fleming
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
- Department of BiologyUniversity of MarylandCollege ParkMD20742U.S.A.
| | - Marlee A. Tucker
- Senckenberg Biodiversity and Climate Research CentreSenckenberg Gesellschaft für NaturforschungSenckenberganlage 25Frankfurt (Main)60325Germany
- Department of Biological SciencesGoethe UniversityMax‐von‐Laue‐Straße 9Frankfurt (Main)60438Germany
- Department of Environmental ScienceInstitute for Wetland and Water ResearchRadboud UniversityP.O. Box 9010NijmegenGLNL‐6500The Netherlands
| | - Roland Kays
- North Carolina Museum of Natural SciencesBiodiversity LabRaleighNC27601U.S.A.
- Fisheries, Wildlife, and Conservation Biology Program, College of Natural Resources Campus Box 8001North Carolina State UniversityRaleighNC27695U.S.A.
| | - Autumn‐Lynn Harrison
- Migratory Bird CenterSmithsonian Conservation Biology InstituteWashingtonD.C.20013U.S.A.
| | - Margaret C. Crofoot
- Department of AnthropologyUniversity of California, DavisDavisCA95616U.S.A.
- Smithsonian Tropical Research InstituteBalboa Ancon0843‐03092Republic of Panama
| | - Briana Abrahms
- Environmental Research DivisionNOAA Southwest Fisheries Science CenterMontereyCA93940U.S.A.
| | - Susan C. Alberts
- Departments of Biology and Evolutionary AnthropologyDuke UniversityDurhamNC27708U.S.A.
| | | | - Jeanne Altmann
- Department of Ecology and EvolutionPrinceton University106A Guyot HallPrincetonNJ08544U.S.A.
| | - Pamela Castro Antunes
- Department of EcologyFederal University of Mato Grosso do SulCampo GrandeMS79070–900Brazil
| | - Nina Attias
- Programa de Pós‐Graduaçao em Biologia Animal, Universidade Federal do Mato Grosso do SulCidade UniversitáriaAv. Costa e SilvaCampo GrandeMato Grosso do Sul79070‐900Brazil
| | - Jerrold L. Belant
- Camp Fire Program in Wildlife Conservation, State University of New YorkCollege of Environmental Science and ForestrySyracuseNY13210U.S.A.
| | - Dean E. Beyer
- Michigan Department of Natural Resources1990 U.S. 41 SouthMarquetteMI49855U.S.A.
| | - Laura R. Bidner
- Department of AnthropologyUniversity of California, DavisDavisCA95616U.S.A.
- Mpala Research CentreNanyuki555–104000Kenya
| | - Niels Blaum
- University of Potsdam, Plant Ecology and Nature ConservationAm Mühlenberg 3Potsdam14476Germany
| | - Randall B. Boone
- Natural Resource Ecology LaboratoryColorado State UniversityFort CollinsCO80523U.S.A.
- Department of Ecosystem Science and SustainabilityColorado State UniversityFort CollinsCO80523U.S.A.
| | - Damien Caillaud
- Department of AnthropologyUniversity of California, DavisDavisCA95616U.S.A.
| | - Rogerio Cunha de Paula
- National Research Center for Carnivores ConservationChico Mendes Institute for the Conservation of BiodiversityEstrada Municipal Hisaichi Takebayashi 8600AtibaiaSP12952‐011Brazil
| | - J. Antonio de la Torre
- Instituto de Ecología, Universidad Nacional Autónoma de Mexico and CONACyTCiudad UniversitariaMexicoD.F.04318Mexico
| | - Jasja Dekker
- Jasja Dekker DierecologieEnkhuizenstraat 26ArnhemWZ6843The Netherlands
| | - Christopher S. DePerno
- Fisheries, Wildlife, and Conservation Biology Program, College of Natural Resources Campus Box 8001North Carolina State UniversityRaleighNC27695U.S.A.
| | - Mohammad Farhadinia
- Wildlife Conservation Research Unit, Department of ZoologyUniversity of OxfordTubney House, OxfordshireOxfordOX13 5QLU.K.
- Future4Leopards FoundationTehranIran
| | | | - Claudia Fichtel
- German Primate CenterBehavioral Ecology & Sociobiology UnitKellnerweg 4Göttingen37077Germany
| | - Christina Fischer
- Restoration Ecology, Department of Ecology and Ecosystem ManagementTechnische Universität MünchenEmil‐Ramann‐Straße 6Freising85354Germany
| | - Adam Ford
- The Irving K. Barber School of Arts and Sciences, Unit 2: BiologyThe University of British ColumbiaOkanagan Campus, SCI 109, 1177 Research RoadKelownaBCV1V 1V7Canada
| | - Jacob R. Goheen
- Department of Zoology and PhysiologyUniversity of WyomingLaramieWY82071U.S.A.
| | | | - Ben T. Hirsch
- Zoology and Ecology, College of Science and EngineeringJames Cook UniversityTownsvilleQLD4811Australia
| | - Cindy Hurtado
- Museo de Historia NaturalUniversidad Nacional Mayor de San MarcosLima15072Peru
- Department of Forest Resources ManagementThe University of British ColumbiaVancouverBCV6T 1Z4Canada
| | - Lynne A. Isbell
- Department of AnthropologyUniversity of California, DavisDavisCA95616U.S.A.
- Mpala Research CentreNanyuki555–104000Kenya
| | - René Janssen
- Bionet NatuuronderzoekValderstraat 39Stein6171ELThe Netherlands
| | - Florian Jeltsch
- University of Potsdam, Plant Ecology and Nature ConservationAm Mühlenberg 3Potsdam14476Germany
| | - Petra Kaczensky
- Norwegian Institute for Nature Research — NINASluppenTrondheimNO‐7485Norway
- Research Institute of Wildlife Ecology, University of Veterinary MedicineSavoyenstraße 1ViennaA‐1160Austria
| | - Yayoi Kaneko
- Tokyo University of Agriculture and TechnologyTokyo183–8509Japan
| | - Peter Kappeler
- German Primate CenterBehavioral Ecology & Sociobiology UnitKellnerweg 4Göttingen37077Germany
| | - Anjan Katna
- Ashoka Trust for Research in Ecology and the Environment (ATREE)BangaloreKarnataka560064India
- Manipal Academy of Higher EducationManipalKarnataka576104India
| | - Matthew Kauffman
- U.S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and PhysiologyUniversity of WyomingLaramieWY82071U.S.A.
| | - Flavia Koch
- German Primate CenterBehavioral Ecology & Sociobiology UnitKellnerweg 4Göttingen37077Germany
| | - Abhijeet Kulkarni
- Ashoka Trust for Research in Ecology and the Environment (ATREE)BangaloreKarnataka560064India
| | - Scott LaPoint
- Max Planck Institute for OrnithologyVogelwarte RadolfzellAm Obstberg 1RadolfzellD‐78315Germany
- Black Rock Forest65 Reservoir RoadCornwallNY12518U.S.A.
| | - Peter Leimgruber
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
| | - David W. Macdonald
- Wildlife Conservation Research Unit, Department of ZoologyUniversity of OxfordTubney House, OxfordshireOxfordOX13 5QLU.K.
| | | | - Laura McMahon
- Office of Applied ScienceDepartment of Natural ResourcesRhinelanderWI54501U.S.A.
| | - Katherine Mertes
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
| | - Christopher E. Moorman
- Fisheries, Wildlife, and Conservation Biology Program, College of Natural Resources Campus Box 8001North Carolina State UniversityRaleighNC27695U.S.A.
| | - Ronaldo G. Morato
- National Research Center for Carnivores ConservationChico Mendes Institute for the Conservation of BiodiversityEstrada Municipal Hisaichi Takebayashi 8600AtibaiaSP12952‐011Brazil
- Institute for the Conservation of Neotropical Carnivores – Pró‐CarnívorosAtibaiaSao Paulo12945‐010Brazil
| | | | - Guilherme Mourão
- Embrapa PantanalRua 21 de setembro 1880Corumb´aMS79320–900Brazil
| | - David O'Connor
- Department of Biological SciencesGoethe UniversityMax‐von‐Laue‐Straße 9Frankfurt (Main)60438Germany
- San Diego Zoo Institute of Conservation Research15600 San Pasqual Valley RoadEscondidoCA92027U.S.A.
- National Geographic Partners1145 17th Street NWWashingtonD.C.20036U.S.A.
| | | | - Jennifer Pastorini
- Centre for Conservation and Research26/7 C2 Road, KodigahawewaJulpallamaTissamaharama82600Sri Lanka
- Anthropologisches InstitutUniversität ZürichWinterthurerstrasse 190Zurich8057Switzerland
| | - Bruce D. Patterson
- Integrative Research CenterField Museum of Natural HistoryChicagoIL60605U.S.A.
| | - Janet Rachlow
- Department of Fish and Wildlife SciencesUniversity of Idaho875 Perimeter Drive MS 1136MoscowID83844‐1136U.S.A.
| | - Dustin H. Ranglack
- Department of BiologyUniversity of Nebraska at KearneyKearneyNE68849U.S.A.
| | - Neil Reid
- Institute for Global Food Security (IGFS), School of Biological SciencesQueen's University BelfastBelfastBT9 5DLU.K.
| | - David M. Scantlebury
- School of Biological SciencesQueen's University Belfast19 Chlorine GardensBelfastNorthern IrelandBT9 5DLU.K.
| | - Dawn M. Scott
- School of Life SciencesKeele UniversityKeeleStaffordshireST5 5BGU.K.
| | - Nuria Selva
- Institute of Nature ConservationPolish Academy of SciencesMickiewicza 33Krakow31–120Poland
| | - Agnieszka Sergiel
- Institute of Nature ConservationPolish Academy of SciencesMickiewicza 33Krakow31–120Poland
| | - Melissa Songer
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
| | - Nucharin Songsasen
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
| | - Jared A. Stabach
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
| | - Jenna Stacy‐Dawes
- San Diego Zoo Institute of Conservation Research15600 San Pasqual Valley RoadEscondidoCA92027U.S.A.
| | - Morgan B. Swingen
- Fisheries, Wildlife, and Conservation Biology Program, College of Natural Resources Campus Box 8001North Carolina State UniversityRaleighNC27695U.S.A.
- 1854 Treaty Authority4428 Haines RoadDuluthMN55811U.S.A.
| | - Jeffrey J. Thompson
- Asociación Guyra Paraguay – CONACYTParque Ecológico Asunción VerdeAsuncion1101Paraguay
- Instituto SaiteCoronel Felix Cabrera 166Asuncion1101Paraguay
| | - Wiebke Ullmann
- University of Potsdam, Plant Ecology and Nature ConservationAm Mühlenberg 3Potsdam14476Germany
| | - Abi Tamim Vanak
- Ashoka Trust for Research in Ecology and the Environment (ATREE)BangaloreKarnataka560064India
- Wellcome Trust/DBT India AllianceHyderabad500034India
- School of Life SciencesUniversity of KwaZulu‐NatalWestvilleDurban4041South Africa
| | - Maria Thaker
- Centre for Ecological SciencesIndian Institute of ScienceBangalore560012India
| | - John W. Wilson
- Department of Zoology & EntomologyUniversity of PretoriaPretoria0002South Africa
| | - Koji Yamazaki
- Ibaraki Nature MuseumZoological Laboratory700 OsakiBando‐cityIbaraki306–0622Japan
- Forest Ecology LaboratoryDepartment of Forest ScienceTokyo University of Agriculture1‐1‐1 SakuragaokaSetagaya‐KuTokyo156–8502Japan
| | - Richard W. Yarnell
- School of Animal, Rural and Environmental SciencesNottingham Trent UniversityBrackenhurst CampusSouthwellNG25 0QFU.K.
| | - Filip Zieba
- Tatra National ParkKúznice 1Zakopane34–500Poland
| | | | - William F. Fagan
- Department of BiologyUniversity of MarylandCollege ParkMD20742U.S.A.
| | - Thomas Mueller
- Senckenberg Biodiversity and Climate Research CentreSenckenberg Gesellschaft für NaturforschungSenckenberganlage 25Frankfurt (Main)60325Germany
- Department of Biological SciencesGoethe UniversityMax‐von‐Laue‐Straße 9Frankfurt (Main)60438Germany
| | - Justin M. Calabrese
- Smithsonian Conservation Biology InstituteNational Zoological Park1500 Remount RoadFront RoyalVA22630U.S.A.
- Department of BiologyUniversity of MarylandCollege ParkMD20742U.S.A.
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5
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Abstract
Several cyclic and alicyclic C11 hydrocarbons have been shown to act as gamete releasing and/or attracting pheromones during sexual reproduction of brown algae (Phaeophyceae). The same compounds are also found in the essential oils of various plants, of which the occurrence of the cycloheptadiene-pheromone ectocarpene in Senecio isatideus (Compositae) is noteworthy. Administration of [3H]dodeca-3,6,9-trienoic acid to cuttings of this plant leads to incorporation of radioactivity into ectocarpene. Double-bond-deuterated nona-3,6-dienoic acid is converted to fucoserratene, the pheromone of several Fucales, which is certainly not present among the hydrocarbons of Senecio. This proves that the pool of medium-chain, multiply unsaturated fatty acids includes precursors of all types of highly unsaturated hydrocarbons. Appropriately labelled (deuterium markers) fatty acid homologues were synthesized and applied to Senecio plantlets to unravel the mechanistic aspects. The results strongly suggest radical initiation of the pheromone biosynthesis by abstraction of a single hydrogen from a 1,4-pentadienyl segment of the fatty acid followed by oxidation to the corresponding cation. This causes fragmentation of the reactive intermediate into an olefine and carbon dioxide by neighbouring-group participation of the flanking double bonds. A tentative biosynthetic scheme is deduced from the experimental results which also sets the stereochemistry of the algal pheromones into a uniform mechanistic concept.
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