Disarmed trees gain in reproduction

ASCHERO, V; N. CHACOFF & S. MARTÍN

Bariloche, Argentina

Congreso; VI Southern Connection Congress; 2010

UNIV. NAC. DEL COMAHUE-INTA-CONICET

&amp;amp;amp;lt;!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --&amp;amp;amp;gt; Spine length can act as an inducible defense in plants, because spine length tends to increase with increasing herbivore pressure. Thus, the lower investment in spine production in herbivore-free plants could mean more resources available for reproduction. We hypothesized that 37 years of large herbivore exclusion at a reserve had an effect in the relaxation of mechanic defenses and consequently in tree reproduction. We expect the length of spines would be shorter and the fruit production higher in trees inside the reserve than trees in cattle ranches. Our study area was located in and around Nacuñán Reserve, in the Central Monte Desert of Argentina. We measured spine length in new branches and the total number of fruits per tree in 15 P. flexuosa individuals at 3 pairs of sites inside and outside the reserve. Spines were shorter (ANOVA: F=12.8 , p<0.05) and fruit production was higher (Poisson generalized linear model: z=21.1 , p<0.001) in trees inside the reserve than in trees in cattle ranches.We described the decrease in fruit production with spine length with a negative exponential model fitted by a negative binomial generalized linear model: fruits=376e-0.0097*spine length (mm) . Our study suggests that P. flexuosa trees under almost four decades of large herbivore exclusion are less spiny and have greater fruit production than their cattle browsed neighbors.