A mast fruiting episode of the tropical tree Peltogyne purpurea (Caesalpinaceae) in the Osa Peninsula, Costa Rica

The existence of mast fruiting has not been well documented in the Neotropics. The occurrence of a mast fruiting episode in the population of the tree Peltogyne purpurea in the Osa Peninsula of Costa Rica is described. In February and March of 2000 most of the trees of this species produced a large fruit crop, compared with 1995-1999, when the number of fruit producing trees was very low or zero and those that did bear fruit, did so at a low intensity. In contrast, the fruit crop of 2000 was massive, all trees examined produced fruits and the intensity of fruiting was maximal. There is not enough information on the event for a hypothesis to be formed because the climatic or biological cues that triggered this sporadic flowering are unknown and there is no meteorological data available for this area. Populations with this mode of reproduction may experience local extinction bacause of logging operations.

Se describe un episodio de fructificación en masa en una población de Peltogyne purpurea de la Península de Osa, Costa Rica. En febrero y marzo de 2000, la mayor parte de los árboles de esta especie tuvo una gran cosecha de frutos. En los años anteriores, desde 1995, ninguno o muy pocos árboles produjeron frutos y la producción por árbol fue escasa. La cosecha del año 2000 fue masiva y todos los árboles examinados produjeron frutos abundantes. Este patrón reproductivo podría producir extinciones locales si la extracción maderera no lo toma en cuenta.

Estructura de una población del árbol Peltogyne purpurea (Cesalpinaceae) en un bosque intervenido de la Península de Osa, Costa Rica / Population structure of the tree Peltogyne purpurea (Cesalpinaceae) in an altered forest at Osa Peninsula, Costa Rica

The regeneration of the rain forest tree Peltogyne purpururea Pittier after selective logging was studied in Mogos, Osa Peninsula, Costa Rica. The distribution of all adult trees of P. purpurea according to diameter at breath height (dbh) categories revealed that the distribution of the adult trees followed a bell-shaped curve. The largest number of individuals was found in the 70 to 80 cm dbh category. We did not find any significant differences in the distribution of saplings around seed-producing trees. There were similar numbers of saplings in the four transects established around each reproductive tree following the four cardinal directions. Overall, the majority of the saplings were found in the first meters around each seed-producing tree. There was another peak in the number of saplings at the distance where the crown of the tree ended. Logging can negatively affect the regeneration of P. purpurea.

Se estudió la regeneración de una población del árbol Peltogyne purpurea Pittier después de una corta selectiva de madera en el bosque lluvioso tropical de Mogos, Península de Osa, Costa Rica. La distribución de los árboles adultos de P. purpurea según el diámetro del tallo a la altura del pecho tiene forma de campana. La categoría con la mayor cantidad de individuos correspondió a los árboles con tallos con diámetros entre 70 y 80 cm. No hubo diferencia significativa en el número de brinzales encontrados en los transectos establecidos siguiendo los cuatro puntos cardinales alrededor de los árboles reproductivos (madre). En general, la mayoría de los brinzales se encontraban en los primeros metros alrededor del árbol madre. Se observó otro pico de abundancia de brinzales a la distancia correspondiente con el final de la copa del árbol. La extracción de madera puede tener un efecto negativo en la regeneración de P. purpurea.

Leaf herbivory on three tree species in a monodominant and two other Terra firme forests on Maracá Island, Brazil

The aim of this study was to test the hypothesis that the monodominant non-pioneer Peltogyne gracilipes, typically does not suffer density-dependent herbivory (Janzen-Connell model). Two components of intraspecific variation in leaf herbivory were measured: 1) the variation between individuals in the population at the same time and 2) the temporal variation in rates of damage to each individual. The study was carried out on Maracá Island, Roraima, Brazil in three plots (50 m 50 m) in each of three forest types: Peltogyne-rich forest (PRF), Peltogyne-poor forest (PPF), and forest without Peltogyne (FWP). Two other non-pioneer species (Ecclinusa guianensis and Pradosia surinamensis) were chosen for comparison because they were fairly abundant and their seedlings could be readily identified. The values of leaf area removed by herbivores of trees and seedlings of the three study species were in the range reported for other tropical tree species (2-16%, standing damage). There were no differences within species between forests. However, there was a significant difference among species but this was not correlated with seedling density. Peltogyne seedlings showed no evidence of density-dependent herbivory as predicted by the Janzen-Connell model despite the fact that adult trees were observed to suffer a mass defoliation in April 1992. This result suggests that Peltogyne may be dominant partly due to escape from herbivory in the early stages of its life although it may suffer occasional mass defoliation as an adult.

O objetivo deste trabalho foi testar a hipótese de que Peltogyne gracilipes, espécie climax e monodominante, tipicamente não sofre herbivoria dependente da densidade (Modelo de Janzen-Connell). Dois componentes da variação intraespecífica na herbivoria foliar foram avaliados: 1) a variação entre indivíduos na população no mesmo tempo e 2) a variação temporal na taxa de danos em cada indivíduo. O estudo foi realizado na Ilha de Maracá, Roraima, Brasil em três parcelas de 50 m 50 m em cada um dos três tipos florestais (Floresta rica em Peltogyne, PRF; Floresta pobre em Peltogyne, PPF e Floresta sem Peltogyne, FWP). Duas outras espécies não pioneiras (Ecclinusa guianensis e Pradosia surinamensis) foram escolhidas para comparações por serem abundantes nas diferentes classes de tamanho e suas plântulas de fácil identificação no campo. A percentagem de área foliar removida pelos herbívoros está entre os valores reportados para outras espécies arbóreas tropicais (2-16%). Não houve diferenças dentro das espécies entre florestas. Entretanto, existiu uma diferença significativa entre espécies. As plântulas de Peltogyne não apresentaram nenhuma evidência de herbivoria dependente da densidade como previsto pelo modelo de Janzen-Connell, embora para árvores adultas tenha sido observado a ocorrência de desfolhamento em massa em abril de 1992. Este resultado sugere que Peltogyne pode ser dominante parcialmente devido ao escape da herbivoria nos estágios iniciais de sua vida embora possa sofrer ocasionais desfolhamentos quando adulta.