Divergence in communication systems should influence the likelihood that individuals from different lineages interbreed, and consequently shape the direction and rate of hybridization. Here, we studied the role of chemical communication in hybridization, and its contribution to asymmetric and sexually selected introgression between two lineages of the common wall lizard (Podarcis muralis). Males of the two lineages differed in the chemical composition of their femoral secretions. Chemical profiles provided information regarding male secondary sexual characters, but the associations were variable and inconsistent between lineages. In experimental contact zones, chemical composition was weakly associated with male reproductive success, and did not predict the likelihood of hybridization. Consistent with these results, introgression of chemical profiles in a natural hybrid zone resembled that of neutral nuclear genetic markers overall, but one compound in particular (tocopherol methyl ether) matched closely the introgression of visual sexual characters. These results imply that associations among male chemical profiles, sexual characters, and reproductive success largely reflect transient and environmentally driven effects, and that genetic divergence in chemical composition is largely neutral. We therefore suggest that femoral secretions in wall lizards primarily provide information about residency and individual identity rather than function as sexual signals.
Bibliographical noteFunding Information:
We thank B. Halliwell, J. Barrett, S. Michaelides, N. Zajac, N. Feiner, and L. Kidd for assistance in the field and with experiments, and M. Zuffi, R. Sacchi and F. Aubret for logistical support. We are grateful to W. Yang and B. Reid for assistance with the cline analysis. We also thank D. Stuart-Fox, M. S. Webster and two anonymous reviewers for their helpful comments on earlier versions of this manuscript. Project funding was kindly provided by the Royal Society of London, the British Ecological Society, the National Geographic Society (all to TU) and the Holsworth Wildlife Research Endowment (HEAM). TU was supported by a Royal Society University Research Fellowship and a Wallenberg Academy Fellowship and HEAM by a University of Tasmania Graduate Research Scholarship. All experiments carried out as part of this research comply with U.K. laws and the work was approved by the University of Oxford’s Local Ethical Review Process and the U.K. Home Office (PPL: 30/2560). Fieldwork was carried out under permits from Direction Régionale de l’Environnement, de l’Aménagement et du Logement (nos. 2010/DDEA/SEPR/175, 2010–11, 11/2012, No 2010-DDEA-SE-105, 29/2012, 11/DDTM/657-SERN-NB, and SE-2010-24), Ministero dell’Ambiente e della Tutela del Territorio del Mare—DG Protezione della Natura e del Mare (prot. PNM-2012-2738, prot. 0011511/PNM, prot. PNM-2012-3878, ISRA prot. 14392, 2764/PNM) and Societas Her-petologica Italica (prot. ISPRA 9139 T/-A31).
© 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.
Copyright 2017 Elsevier B.V., All rights reserved.
- Femoral pores
- hybrid zone