The role of herbivorous insects and pathogens in the regeneration dynamics of Guazuma ulmifolia in Panama

By

Solé, Raphaële
Gripenberg, Sofia
Lewis, Owen T.
Markesteijn, Lars
Barrios, Héctor
Ratz, Tom
Ctvrtecka, Richard
Butterill, Philip T.
Segar, Simon t.
Metz, Mark A.
Dahl, Chris
Rivera, Marleny
Viquez, Karina
Ferguson, Wessley
Guevara, Maikol
Basset, Yves

Type

Article

Date of Publication

2019-2-6

Original Publication

Subterranean Biology

Volume

32

Pages

81--101

Subjects

Anobiidae , fungal pathogen , negative density-dependence , rainforest , seed predation

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia, Bulgaria Pensoft Publishers

Identifiers

DOI: https://doi.org/10.3897/natureconservation.32.30108

 

Abstract

A significant proportion of the mortality of rainforest trees occurs during early life stages (seeds and seedlings), but mortality agents are often elusive. Our study investigated the role of herbivorous insects and pathogens in the early regeneration dynamics of Guazumaulmifolia (Malvaceae), an important tree species in agroforestry in Central America. We reared pre-dispersal insect seed predators from G.ulmifolia seeds in Panama. We also carried out an experiment, controlling insects and pathogens using insecticide and/or fungicide treatments, as well as seed density, and compared survivorship of G.ulmifolia seeds and seedlings among treatments and relative to untreated control plots. We observed (1) high pre-dispersal attack (92%) of the fruits of G.ulmifolia, mostly by anobiine and bruchine beetles; (2) negligible post-dispersal attack of isolated seeds by insects and pathogens; (3) slow growth and high mortality (> 95%) of seedlings after 14 weeks; (4) low insect damage on seedlings; and (5) a strong positive correlation between seedling mortality and rainfall. We conclude that for G.ulmifolia at our study site the pre-dispersal seed stage is by far the most sensitive stage to insects and that their influence on seedling mortality appears to be slight as compared to that of inclement weather. Thus, the regeneration of this important tree species may depend on effective primary dispersal of seeds by vertebrates (before most of the seed crop is lost to insects), conditioned by suitable conditions in which the seedlings can grow.