Population dynamics of Euterpe edulis along a short altitudinal gradient

Background/Question/Methods

Range limits are related with the reduction of performance, like a decrease of seedling recruitment and low survival. But some studies verify that the range limits can arise due to dispersal limitation. Euterpe edulis is considered a keystone species in the Atlantic Forest hotspot. This species occur from sea level up to 1400m of elevation in the National Park of Serra dos Órgãos, Rio de Janeiro, Brazil, with a reduction of the density at its upper altitudinal limit. To determine if the reduction of density of this species at its upper altitudinal limits is related to a decrease in performance we analyzed the population dynamics of two populations of E. edulis along a short altitudinal gradient in the National Park of Serra dos Órgãos, Rio de Janeiro, Brazil. We verify if at the elevational limit of E. edulis (low density) the population growth rate (λ) and vital rates are lower than the population located at lower elevation (high density). We constructed summary projection matrices for this species for each transition years.

Results/Conclusions

Population growth rates of the two populations of Euterpe edulis along an altitudinal gradient determined by the matrix population model were not different from unity (λ=1) in the first transition years. The mortality was not different between the two populations for all ontogenetic stages during the first two years of the study. On the other hand, on the second transition years we observed a lower fecundity (nº new seedlings/nºadults) in the population at the upper elevational limit. Thus, a lower fecundity was the only vital rate that decrease at the upper elevational limit of this species. Other process can be involved in the creation of the elevational limit of E. edulis, like dispersal limitation. Another factor can be that extreme conditions that exceed the tolerance of E. edulis may occur in few years, so it is necessary a longer period of study to observe a decrease of performance at its elevational limit.