Caracterización química de arbustos patagónicos con diferente preferencia por los herbívoros.

CAVAGNARO, F; GOLLUSCIO, RA; D.F. WASSNER; RAVETTA, D.A.

ECOLOGÍA AUSTRAL

ASOCIACIÓN ARGENTINA DE ECOLOGÍA

Lugar: Buenos Aires; Año: 2003 vol. 13 p. 215 - 222

0327-5477

<!-- /* Font Definitions */ @font-face {font-family:Arial; panose-1:2 11 6 4 2 2 2 2 2 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:-536859905 -1073711037 9 0 511 0;} @font-face {font-family:Arial; panose-1:2 11 6 4 2 2 2 2 2 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:-536859905 -1073711037 9 0 511 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; mso-bidi-font-size:10.0pt; font-family:Arial; mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-AR;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page WordSection1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.WordSection1 {page:WordSection1;} --> In SW  Chubut (Patagonia, Argentina), shrubs provide safe sites for  the recruitment of almost all the species of the community. As different shrubs species are subjected to different sheep grazing pressures, the knowledge of their response mechanisms to grazing is crucial to the designing of sustainable systems of grazing management for  these ecosystems. This work tested two hypotheses related to the adaptive and plastic responses to grazing for the three dominant shrubs of this community (Adesmia campestris, Mulinum spinosum and Senecio filaginoides). We studied the chemical composition of the leaves of these shrubs under two contrasting sheep grazing pressures. We carried out a chemical screening to sequentially extract three groups of different polarity carbon based secondary metabolites (CBSM): oil, phenols and hydrocarbon compounds. We found that  (1) the less preferred species (S. filaginoides) contained higher levels of the three fractions of  CBSM than the other  two species (adaptive response), and (2) only in S. filaginoides the CBSM content, in particular those of oil and hydrocarbon fractions, increased with grazing. The absence of plastic responses in  the other two species could be explained by the presence of structural defenses (thorns). Key words:  Secondary metabolites, Grazing, Adesmia campestris, Mulinum spinosum, Senecio filaginoides