Pre‐dispersal seed predators and fungi differ in their effect on Luehea seemannii capsule development, seed germination, and dormancy across two Panamanian forests

Abstract

Pre‐dispersal seed predation can greatly reduce crop size affecting recruitment success. In addition, non‐fatal damage by seed predators may allow infection by fungi responsible for post‐dispersal seed losses. The objectives of this study were (1) to quantify pre‐dispersal seed predation and fungal infection in a Neotropical tree species, Luehea seemannii, that produces dehiscent fruits and wind‐dispersed seeds, and (2) to link pre‐dispersal effects on seed quality to seed survival in the soil. To examine how seed predators and fungi influence seed losses, mesh exclosures, fungicide, and the combination of both treatments were applied to separate branches in the canopy of trees in Gamboa and Parque Natural Metropolitano (PNM), Panama. To determine if treatments affect seed viability and survival in the soil, half of the seeds collected from each treatment were buried for 4 weeks in forest soils and subsequently allowed to germinate before and after the breaking of dormancy. Overall, 24 percent of developing fruit were lost to insect attack. In contrast, fungi infected only 3 percent of seeds at the pre‐dispersal stage. For seeds germinated directly after collection, fungicide significantly increased germination in the wetter site (Gamboa) but decreased germination in the drier site (PNM). The pre‐dispersal insect exclosure treatment increased the fraction of seeds that remained dormant after burial in the soil. This result suggests that exposure to insect predators may cause physical damage to seeds that results in the loss of physical dormancy but does not necessarily increase the susceptibility of seeds to pathogen attack in the soil.

High dispersal ability is related to fast life‐history strategies

“…Each of these may have different energy requirements and developmental times, which may covary with other life‐history traits, such as traits related to reproduction and growth. During these phases, plants may incur costs from predators and pathogens that reduce their ability to disperse seeds (Tewksbury & Nabhan, ; Tiansawat, Beckman, & Dalling, ). A plant's ability to deter reductions in dispersal due to predation would be related to its ability to develop and disperse fast enough to escape predation (related to growth strategies), satiate predators (related to number of seeds produced) or otherwise defend themselves.…”

Adaptation to seasonal drought in two closely related species of Neotropical Costus (Costaceae)

“…Other than artificial irrigation, we argue that seed germination of C. villosissimus may also be partially inducible by extrinsic factors such as the differences in day length, light intensity, diurnal temperature, and potentially other uncontrolled variables among the controlled trials. The germination mechanisms of hundreds of tropical tree species have been identified and categorized (Baskin & Baskin, ; Burrows, ; Sautu, Baskin, Baskin, Deago, & Condit, ), and the effects of pest pressure and light availability on seed germination and seedling survival vary among these species (Gaviria & Engelbrecht, ; Tiansawat, Beckman, & Dalling, ). However, the germination mechanisms of tropical herbaceous plants are relatively unexplored (but see Horvitz & Schemske, ; Baskin & Baskin, ) despite their physiological differences from the neighboring trees.…”

Fruits, frugivores, and the evolution of phytochemical diversity

“…Fruits, in particular, are highly nutritious resources and face complex and highly variable selection pressures from different consumers over time. As they develop on the parent plant, they must defend against complex communities of antagonistic herbivores, seed predators, and pathogens (Andersen 1988, Kolb et al 2007, Tiansawat et al 2017). Once mature, animal‐dispersed fruits must attract mutualists that will effectively disperse their seeds away from the parent plant (Howe and Smallwood 1982, Schupp et al 2010, Ruxton et al 2014).…”