| Title: | Testing the hypothesis of loss of defenses on islands across a wide latitudinal gradient of Periploca laevigata populations |
| Author(s): | Monroy P; Garcia-Verdugo C; |
| Address: | "Departamento de Biodiversidad Molecular y Banco de ADN, Jardin Botanico Canario 'Viera y Clavijo' - Unidad Asociada CSIC, Cabildo de Gran Canaria, Camino del Palmeral 15 de Tafira Alta, 35017, Las Palmas de Gran Canaria, Spain. Institut Mediterrani d'Estudis Avancats (CSIC-UIB), C/Miquel Marques 21, 07190, Esporles, Balearic Islands, Spain" |
| ISSN/ISBN: | 1537-2197 (Electronic) 0002-9122 (Linking) |
| Abstract: | "PREMISE OF THE STUDY: We tested a hypothesis that predicts loss of chemical defenses on island plant populations (LCDIH) as an evolutionary response to limited herbivore pressures. METHODS: Using a common garden approach, we grew 16 populations (N = 286 seedlings) of Periploca laevigata, a Mediterranean shrub for which previous studies suggested that animal browsing elicits defensive responses mediated by tannins. Our experimental setting represented a wide latitudinal gradient (37-15 degrees N) encompassing three island systems, virtually free of large herbivores, and three mainland areas. Putative chemical defenses were estimated from tannin-protein precipitation assays, and inducible responses in growth and chemical traits were assessed between seasons and by subjecting plants to a pruning treatment. KEY RESULTS: We failed to find support for the LCDIH, since island populations (Canary Islands, Cape Verde) had increasingly higher constitutive levels of tannins at lower latitudes. Seasonality, but not experimental pruning, induced variation in levels of tannins in a consistent pattern across populations. Thus, net differences in leaf tannin concentration remained similar among geographical areas regardless of the factor considered, with latitude being the best explanatory factor for this trait over seasonal growth patterns. CONCLUSIONS: Geographical variation in total tannin pools appears to be mediated by factors other than herbivore pressure in P. laevigata. We hypothesize that abiotic correlates of latitude not considered in our study have promoted high constitutive levels of leaf tannins across Macaronesian populations, which ultimately may explain the pattern of seasonal variation and latitudinal increase from Mediterranean to subtropical Cape Verde populations" |
| Keywords: | Apocynaceae/genetics/growth & development/*metabolism Atlantic Islands *Biological Evolution *Islands Mediterranean Region Phenotype Secondary Metabolism/*genetics Tannins/*metabolism Apocynaceae UV exposure chemical defense common garden experiment growt; |
| Notes: | "MedlineMonroy, Pedro Garcia-Verdugo, Carlos eng ENCLAVES MAC/3/C141/PCT-MAC/International Fundacion Canaria Amurga-Maspalomas/International JCI-2012-15220/Juan de la Cierva/International Comparative Study Research Support, Non-U.S. Gov't 2019/02/12 Am J Bot. 2019 Feb; 106(2):303-312. doi: 10.1002/ajb2.1232. Epub 2019 Feb 11" |
