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Adams SA, Gurajapu A, Qiang A, Gerbaulet M, Schulz S, Tsutsui ND, Ramirez SR, Gillespie RG. Chemical species recognition in an adaptive radiation of Hawaiian Tetragnatha spiders (Araneae: Tetragnathidae). Proc Biol Sci 2024; 291:20232340. [PMID: 38593845 PMCID: PMC11003775 DOI: 10.1098/rspb.2023.2340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 03/05/2024] [Indexed: 04/11/2024] Open
Abstract
Studies of adaptive radiations have played a central role in our understanding of reproductive isolation. Yet the focus has been on human-biased visual and auditory signals, leaving gaps in our knowledge of other modalities. To date, studies on chemical signals in adaptive radiations have focused on systems with multimodal signalling, making it difficult to isolate the role chemicals play in reproductive isolation. In this study we examine the use of chemical signals in the species recognition and adaptive radiation of Hawaiian Tetragnatha spiders by focusing on entire communities of co-occurring species, and conducting behavioural assays in conjunction with chemical analysis of their silks using gas chromatography-mass spectrometry. Male spiders significantly preferred the silk extracts of conspecific mates over those of sympatric heterospecifics. The compounds found in the silk extracts, long chain alkyl methyl ethers, were remarkably species-specific in the combination and quantity. The differences in the profile were greatest between co-occurring species and between closely related sibling species. Lastly, there were significant differences in the chemical profile between two populations of a particular species. These findings provide key insights into the role chemical signals play in the attainment and maintenance of reproductive barriers between closely related co-occurring species.
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Affiliation(s)
- Seira A. Adams
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, #3114, Berkeley, CA 94720, USA
- Center for Population Biology, University of California, 2320 Storer Hall, Davis, CA 95616, USA
- Department of Evolution and Ecology, University of California, 2320 Storer Hall, Davis, CA 95616, USA
| | - Anjali Gurajapu
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, #3114, Berkeley, CA 94720, USA
| | - Albert Qiang
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, #3114, Berkeley, CA 94720, USA
| | - Moritz Gerbaulet
- Institute of Organic Chemistry, Technische Universität Braunschweig, Hagenring 30, Braunschweig 38106, Germany
| | - Stefan Schulz
- Institute of Organic Chemistry, Technische Universität Braunschweig, Hagenring 30, Braunschweig 38106, Germany
| | - Neil D. Tsutsui
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, #3114, Berkeley, CA 94720, USA
| | - Santiago R. Ramirez
- Center for Population Biology, University of California, 2320 Storer Hall, Davis, CA 95616, USA
- Department of Evolution and Ecology, University of California, 2320 Storer Hall, Davis, CA 95616, USA
| | - Rosemary G. Gillespie
- Department of Environmental Science, Policy, and Management, University of California, 130 Mulford Hall, #3114, Berkeley, CA 94720, USA
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Redjdal A, Sahnoune M, Moali A, De Biseau JC. High Divergence of Cuticular Hydrocarbons and Hybridization Success in Two Allopatric Seven-Spot Ladybugs. J Chem Ecol 2023; 49:103-115. [PMID: 36749496 DOI: 10.1007/s10886-023-01406-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 01/14/2023] [Accepted: 01/18/2023] [Indexed: 02/08/2023]
Abstract
The seven-spotted ladybug is a widespread species in the Palearctic, and also acclimated in the Nearctic. It has been classified into different species on the basis of certain morphological characteristics, the geographical origin, and the genitalia structure of both sexes. The morphotypes of North Africa and the Canary Islands are separated, under the name of Coccinella algerica Kovář, 1977, from the rest of the Palearctic and Nearctic populations of Coccinella septempunctata Linnaeus, 1758. In this study, we investigated, on one hand, whether potential reproductive barriers have been established during evolution between the geographically isolated North African and the European seven-spotted ladybugs by performing reciprocal crosses. On the other hand, we assessed their cuticular hydrocarbon (CHC) divergence by GC-MS. The 33 CHCs indentified are with a skeleton of 23 to 32 carbon atoms. These CHCs are linear alkanes (24.9 ± 3.6%) and methyl-branched alkanes (75.1 ± 3.6%) including monomethylalkanes (48.8 ± 2.4%), dimethylalkanes (24.6 ± 4.0%) and trimethylalkanes (2.0 ± 1.0%). Although all the CHC compounds identified are present in the two seven-spotted ladybugs and their F1 and F2 hybrids, their profiles diverged significantly. However, these chemical divergences have not altered the sexual communication to cause reproductive isolation. The two ladybugs interbreed and leave viable and fertile offspring, with even a heterosis effect on reproductive performances, without phenotypic degradation after the F1 generation. So, these chemical differences are just an intraspecific variability in response to heterogeneous environments. The two types of ladybugs can be considered as two different races of the same species with reduced genetic divergence.
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Affiliation(s)
- Ahcene Redjdal
- Faculté Des Sciences de La Nature Et de La Vie, Laboratoire d'Ecologie Et Environnement, Université de Bejaia, 06000, Bejaia, Algérie.
| | - Mohamed Sahnoune
- Faculté Des Sciences de La Nature Et de La Vie, Laboratoire d'Ecologie Et Environnement, Université de Bejaia, 06000, Bejaia, Algérie
| | - Aïssa Moali
- Faculté Des Sciences de La Nature Et de La Vie, Laboratoire d'Ecologie Et Environnement, Université de Bejaia, 06000, Bejaia, Algérie
| | - Jean-Christophe De Biseau
- UR. Evolution Biologique Et Ecologie, Faculté Des Sciences, Université Libre de Bruxelles, Campus du Solbosch - CP 160/12, Avenue F.D. Roosevelt, 50, 1050, Brussels, Belgium
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