Seed size of co‐occurring forb species predicts rates of predispersal seed loss from insects

Abstract

Plants often face chronic seed loss from predispersal seed predation by insects.Although many studies have documented the rates of seed loss for single species in different communities, it is unclear how rates of predispersal seed predation vary among co-occurring species within the same community. If interspecific asymmetries in seed loss are great, this common interaction could have important implications for coexistence. Species traits, such as seed size or seed nitrogen and carbon, might correlate with interspecific variation in predispersal seed predation among co-occurring grassland forb species. We collected infructescences from 13 co-occurring forb species from each of four western Montana grasslands over 2 years. We quantified the magnitude of seed loss due to predispersal seed predation by insects. The average level of seed loss was 15.8%. Larger seeded species suffered significantly higher levels of predispersal seed predation than smaller seeded species, and seed size predicted seed loss more than seed nitrogen or carbon. Although large-seeded species often have greater proportional recruitment and early survival than small-seeded species, our study suggests that these advantages are partially counterbalanced by greater predispersal seed loss for larger versus smaller seeded species. Asymmetries in predispersal seed predation may importantly affect coexistence among these species.

The effect of local habitat and spatial connectivity on urban seed predation

“…Acorn infestation by moths and weevils was negatively correlated at the level of individual acorns in 2018, whereas infestation by moths and weevils was positively correlated at the acorn and the tree levels in 2020. The strong negative correlation between moths and weevils at the acorn level in 2018 indicates the avoidance of resource competition, which agrees with previous demonstrations that seed predators generally avoid infested acorns (Debouzie et al, 1996; Palmer et al, 2022). Notably, the (weakly) positive co‐occurrence at the acorn level in 2020 indicate that avoidance behavior is context specific and might have depended, for example, on the lower resource availability and higher infestation levels or shifts in relative phenology between the species.…”

“…Seed predators that feed on the same host might interact with each other through resource competition and co‐occur more or less frequently than expected by chance due to similar responses to environmental factors or tree defences (Debouzie et al, 1996; Bonal and Muñoz, 2009; Venner et al, 2011). Even though seeds can be infested simultaneously by multiple species (Desouhant et al, 2000; Espelta et al, 2009; Bonal et al, 2011), seed predators frequently avoid seeds that are already occupied by other species (Palmer et al, 2022). For example, early infestations of acorns by moths might inhibit subsequent infestation by weevils (Debouzie et al, 1996).…”

Contrasting patterns of host selection and performance of insect seed predators on three sympatric host plant species

“…The food resources available for immature stages of EPIs are highly restricted to seed nutritional content of its host plants. Previous studies have suggested a positive relationship between seed mass and EPIs body mass (e.g., Gianoli et al, 2007;Mezquida et al, 2021;Palmer et al, 2022;Souza & Fagundes, 2017). Thus, it would be reasonable to think that the insects that developed inside seeds of plants that produce larger seeds would reach greater body mass and store a higher amount of reserves in the form of fat, achieving higher reproductive success (González-Teuber et al, 2008).…”

“…Although many studies have suggested that the architectural complexity and appearance of plants (e.g., Fagundes et al, 2013; Ferreira et al, 2022; Ramírez & Traveset, 2010) and seed mass (e.g., Azcárate et al, 2010; Foffová et al, 2020; Gripenberg et al, 2019; Palmer et al, 2022; Souza & Fagundes, 2017) positively drive host plant selection and seed predation by insects, other aspects involving the plant‐EPI interaction can also affect this relationship. For example, the pattern of resource distribution in the landscape (Abdala‐Roberts et al, 2010; Rossi et al, 2011; Pardini et al, 2017; Weissflog et al, 2017; Kuchenbecker & Fagundes, 2018; Coutinho et al, 2019) and the dispersal ability of herbivores (Otway et al, 2005; Rossi et al, 2011) might also explain variation in insect attack on their host plants.…”

“…Seed size and nutritional quality vary greatly among host plants, both intra‐ and interspecifically (Moles & Westoby, 2006; Schupp, 1990; Souza et al, 2015), potentially affecting host selection by female EPIs (Madeira et al, 2013; Palmer et al, 2022; Souza & Fagundes, 2017). In general, large‐sized plants such as trees, produce larger seeds and in greater numbers than congeneric shrubs (Moles & Westoby, 2006; Souza et al, 2015).…”