Mechanic defences and reproduction in desert trees under different habitat management

ASCHERO, V.

BASIC AND APPLIED ECOLOGY

ELSEVIER GMBH, URBAN & FISCHER VERLAG

Lugar: ALEMANIA; Año: 2014

1439-1791

Herbivory can have deleterious effects on plant reproduction by limitation of photosynthates that are either lost by consumption, used to re-growth or invested in defences. In addition, herbivores can also exert direct impact on plant reproduction by consuming flowers. Spine length can act as an inducible defence in plants, because it tends to increase with increasing herbivore pressure. I hypothesized that almost 40 years of different habitat management (cattle exclusion within a protected area vs. cattle grazing in adjacent areas) could affect inflorescence abundance, spine length and fruit production in Prosopis flexuosa trees. The study area was located in the Central Monte desert of Argentina. I estimated differences in spine length, number of inflorescences and fruit production in trees inside the Man and Biosphere Reserve of Ñacuñán and in the adjacent cattle ranches surrounding the protected area. Inflorescence abundance in the tree canopy was similar in cattle grazed and protected sites, but the presence of large herbivores was associated with limited fruit production. Spines were 37% shorter and fruit production three times higher in trees inside the reserve than in trees in cattle ranches. A negative exponential model was used to describe the relationship between reproduction and spine length in trees. The results indicate that after almost four decades of cattle exclusion, trees inside the protected area show higher reproduction and shorter spines than cattle-browsed trees in surrounding areas. The negative association between defence and reproduction may be due to competition for photosynthates. The present results could be useful and relevant in conservation because they provide evidence on how anthropogenic habitat use can affect plant phenotypes and fitness, which in turn can affect the long-term ecological and evolutionary dynamics of plant populations.