Jm. Pisani et Ra. Distel, INTERSPECIFIC AND INTRASPECIFIC VARIATIONS IN PRODUCTION OF SPINES AND PHENOLS IN PROSOPIS-CALDENIA AND PROSOPIS-FLEXUOSA, Journal of chemical ecology, 24(1), 1998, pp. 23-36
In central Argentina the leguminous tree Prosopis caldenia is more abu
ndant in sites of relatively high productivity (lowlands), whereas P.
flexuosa is more abundant in sites of relatively low productivity (slo
pes and uplands). Based upon current antiherbivore defense theory, we
predicted: (1) a higher investment in defenses in P. flexuosa than in
P. caldenia, and (2) that limitations in resources would result in an
increase of the defenses in both species. Our approach for testing the
se predictions was to estimate leaf phenol concentration and spinescen
ce in adults (field study) and seedlings (greenhouse study) of both sp
ecies growing at different levels of resource availability. In adult p
lants, the concentration of phenols was higher (P < 0.01) in P. flexuo
sa than in P. caldenia, but the opposite relationship was observed in
seedlings. The amount of biomass invested in spines was similar IP > 0
.10) in both species, whereas spine density was higher (P < 0.05) in P
. caldenia than in P. flexuosa. In both species, limitations in resour
ces did not result (P < 0.05) in increases in leaf phenol concentratio
n, amount of biomass invested in spines, spine length, or spine densit
y, except for the increase (P < 0.05)of spine density in seedlings of
P. caldenia at low water and nutrient availability. In general, our re
sults did not support current hypotheses on the production of antiherb
ivore defenses. It is argued that factors such as herbivore behavior (
e.g., habitat selection, trampling, branch breakage) and alternative s
inks for carbon (e.g., N-2 fixation, carbohydrate reserves), in additi
on to resource availability in evolutionary and ecological time, shoul
d be considered for a more complete understanding of the inter-and int
raspecific variations in the production of both physical and chemical
antiherbivore defenses.