The strength of seeds and their destruction by granivorous insects

Abstract

The influence of seed structure and strength on their destruction by granivores is central to understanding the dynamics of granivore-plant interactions. For up to nine seed species, the effects of seed size (cm 3 ), mass (mg), density (mg/cm 3 ) and coat strength (MPa) on the damage inflicted by three post-dispersal granivores (Harpalus pensylvanicus, Anisodactylus sanctaecrucis, and Gryllus pennsylvanicus) were evaluated. Seed destruction rates by G. pennsylvanicus were statistically unrelated to the size and toughness of the seeds. Seed densities significantly affected their destruction by A. sanctaecrucis and H. pensylvanicus, as did seed size, mass, and strength in H. pensylvanicus under choice conditions. The carabid beetles destroyed more of the small, denser seeds with stronger seed coats. The results show that different granivores are able to distinguish the structural strength and physical density of seeds as well as seed size. The relative ability of granivores to detect these seed characteristics offers a way in which diverse communities of post-dispersal insect granivores can persist within a single habitat. The authors redefine how the strength of biological structures should be evaluated in ecological studies, using guidelines commonplace in the field of engineering.

Seed Detection and Discrimination by Ground Beetles (Coleoptera: Carabidae) Are Associated with Olfactory Cues

“…Ground beetles assess habitat suitability using a range of cues and, it is well known that volatile chemicals associated with the habitat can be involved [17,18]. Granivorous carabids also use tactile stimuli associated with seeds, particularly seed structural strength and physical density in seed detection [19]. Volatile compounds associated with hosts or prey items provide olfactory cues that help many invertebrates orient to food [20, 21], and perception of such olfactory cues also play an important role in detecting food patches or selecting sites for oviposition among ground beetles [14, 21, 22].…”

Postdispersal Weed Seed Predation by Crickets in a Rice Paddy Field after Irrigation Water Recedes

“…Crickets 11 and granivorous carabids such as Harpalus 12,13 inhabit the margins of rice paddy fields, including the paddy levees that surround the fields to retain water, during the summer crop-growing season because the field interiors are flooded with irrigation water. These insects, especially crickets, have a high ability to feed on seeds 3,14,24 and can contribute to biological weed control if present in large numbers 5,7,10,18 . Teleogryllus emma (Ohmachi et Matsuura), a widespread field cricket in Japan, feeds on the seeds of Lolium multiflorum Lam., a non-native grass weed that…”

Skylarks trade size and energy content in weed seeds to maximize total ingested lipid biomass

“…However, we did not control for other seed traits such as seed coat thickness or seed strength that can influence seed selection. For instance, the relative strengths of the seeds was found to be negatively correlated with seed size (Lundgren and Rosentrater, 2007), suggesting that smaller seeds require a greater force and energy to crush them. It would be interesting in further studies to take into account other morphological seed traits even though the relationship between seed traits such as size, nutrient composition, secondary compounds or digestibility is often complex and nonlinear (Gardarin et al, 2010;Blate et al, 1998;Shimada, 2001).…”