Germination and allometry of the native palm tree Euterpe edulis compared to the introduced E. oleracea and their hybrids in Atlantic rainforest

Abstract

Palms are distinctive plants of tropics and have peculiar allometric relations. Understanding such relations is useful in the case of introduced species because their ability to establish and invade must be clarified in terms of their responses in the new site. Our purpose was to assess the survival and invasive capacity of an introduced palm species in the Atlantic rainforest, Euterpe oleracea Mart., compared to the native Euterpe edulis Mart. and to the hybrids produced between the two species. Considering this, we compared the allometry in different ontogenetic stages, the germination rates, and aspects of the initial development. The ontogenetic stages proposed for both Euterpe illustrated the growth patterns described for palm trees. E. oleracea and hybrids adjusted to the geometric similarity allometric model, while E. edulis presented a slope greater than would be expected considering this model, indicating a greater height for a given diameter. E. oleracea showed the same amount of pulp per fruit as E. edulis and a similar initial development of seedlings. The main differences observed were a lower germination rate and a faster height gain of E. oleracea seedlings. We conclude that E. oleracea, which is similar to E. edulis in aspects of allometry, development, seed and seedling morphology, may be an important competitor of this native palm tree in the Atlantic Forest.Keywords: palms, hybridization, growth model, species introduction. Germinação e alometria de Euterpe edulis comparadas à palmeira introduzida Euterpe oleracea e seus híbridos na floresta Atlântica ResumoPalmeiras são plantas características dos trópicos que apresentam relações alométricas peculiares. Compreender tais padrões pode ser útil no caso de espécies introduzidas, uma vez que sua habilidade de estabelecimento e invasão deve ser esclarecida em relação as suas respostas à nova localidade. Nosso propósito foi compreender a sobrevivência e a capacidade de invasão de uma palmeira introduzida na floresta Atlântica, Euterpe oleracea Mart. (açaizeiro) comparada à palmeira nativa Euterpe edulis Mart. (juçara), também considerando seus híbridos. Para isso comparamos suas relações alométricas em estádios ontogenéticos, sua germinação e seu desenvolvimento inicial. Os estádios ontogenéticos propostos para ambas as Euterpe ilustraram os padrões de crescimento esperados para palmeiras. E. oleracea e híbridos apresentaram-se sob o modelo alométrico de similaridade geométrica e E. edulis apresentou inclinação maior do que este modelo. E. oleracea produziu a mesma quantidade de polpa por fruto que E. edulis. As principais diferenças observadas foram menor taxa de germinação e maior velocidade de crescimento em altura para as plântulas de E. oleracea. Em conclusão, nossos resultados indicam que E. oleracea, sendo similar a E. edulis em termos de alometria, desenvolvimento e morfologia de sementes e plântulas, pode ser um importante competidor para a espécies nativa na Floresta Atlântica.Palavras-chave: palmeiras, hibridização, modelo de cres...

The risks of introduction of the Amazonian palm Euterpe oleracea in the Atlantic rainforest

“…At the same region of our site of introduction, E. edulis populations usually have higher densities and negative exponential distribution of stages (Silva Matos and Bovi, 2002). E. edulis also shows high fruit production patterns (von Allmen et al, 2004;Silva Matos and Watkinson, 1998) and germination rates (Leite et al, 2012;Tiberio et al, 2012), and also keeps seedling banks instead of seed banks. So it is always expected to find high abundance of seedlings, specially after fruit production period.…”

“…Considering that these species can spontaneously produce viable hybrid seeds (Tiberio et al, 2012) and that hybrids may reach the reproductive stage (Bovi et al, 1987), the introduction of E. oleracea increases the vulnerability of the native species. The cross pollination between congener species may decrease the number of viable seeds of the native species consequently dropping the number of seedlings (Traveset and Richardson, 2006) and, finally, the total population density.…”

“…We sampled seedlings in randomly located sub-plots (2×2m) within each 100 m 2 plot. We identified the hybrids based on leaves shape and leaflets spacing (Tiberio et al, 2012). No individuals of E. oleracea were to be found at control site.…”

“…No individuals of E. oleracea were to be found at control site. Individuals from each population were then divided into five ontogenetic life stages according to their morphology: seedling, juvenile I, juvenile II, immature, reproductive adult (Tiberio et al, 2012). Besides height and diameter, we also observed leaf and leaflet shape and signs of reproduction such as presence of inflorescences, infrutescences or its scars on the stems (previous reproduction).…”

“…This species was once considered the solution for the vulnerability of E. edulis to harvesting. These congeneric palms are able to produce E. edulis x E. oleracea hybrids under experimental management (Tiberio et al, 2012;Campos et al, 1991;Bovi et al, 1987) and these hybrids are also used in palm heart crops. However, neither the ecology of E. oleracea in this new area nor E. edulis responses in sites where the exotic palm was introduced are known.…”