Structural anti-herbivore defense reduction of two Patagonian spiny shrubs in response to long time exclusion of large herbivores.

GOLLUSCIO R.A; CAVAGNARO F.P.

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 142 p. 36 - 40

0140-1963

This work focuses on the structural defenses of the two dominant spiny shrub species of the Patagonianshrub-grass steppe. We compared the amount of structural defenses (spines and thorns) of Mulinumspinosum (Cav.) Pers. (Apiaceae) and Adesmia volckmannii Phil. (Fabaceae) between grazed and long termnon-grazed plots. M. spinosum showed a higher spinescence than A. volckmannii. Moreover, both speciesplants located in grazed plots showed higher spinescence than those located in non-grazed ones.Therefore, we can conclude that (1) M. spinosum has higher spinescence than A. volckmannii, probablybecause sheep prefer M. spinosum flowers than A. volckmannii leaves; and (2) both M. spinosum andA. volckmannii showed an increase of spinescence induced by herbivory. These responses may be evidences of co-evolution between these shrub species and large wild browsers that guarantee an adequatecapacity to tolerate herbivory disturbance. Such capacity would be important to maintain communityfunctioning, because shrubs provide secure sites for seed germination and, in some cases, are able to setsymbiotic interactions with N-fixing bacteria.