Which Seed Properties Determine the Preferences of Carabid Beetle Seed Predators?

Abstract

Ground beetles are important invertebrate seed predators in temperate agro-ecosystems. However, there is a lack of information regarding which seed properties are important to carabids when they select seeds for consumption. Therefore, seed properties, such as size, shape, morphological defence, and chemical composition, were measured, and in addition to seed taxonomy and ecology, these data were used to explain carabid preferences. Carabid preferences were assessed using a multi-choice experiment with 28 species of weed seeds presented to 37 species of Carabidae. Multiple regression on distance matrices (MRM) was used to determine the importance of particular sets of seed properties for carabids. The analysis was conducted for the full set of carabids (37 species) as well as for subsets of species belonging to the tribes of Harpalini or Zabrini. For the complete set of species, seed dimensions, seed mass, taxonomy, plant strategy, and seed coat properties significantly explained carabid preferences (proportion of explained variance, R2 = 0.465). The model for Harpalini fit the data comparably well (R2 = 0.477), and seed dimensions, seed mass and seed coat properties were significant. In comparison to that for Harpalini, the model for Zabrini had much lower explanatory power (R2 = 0.248), and the properties that significantly affected the preferences were seed dimensions, seed mass, taxonomy, plant strategy, and seed coat properties. This result suggests that the seed traits that carabids respond to may be specific to taxonomic and likely relate to the degree of specialisation for seeds. This study contributes to understanding the mechanisms that determine the preferences of carabid beetles for seeds.

The biology of seed discrimination and its role in shaping the foraging ecology of carabids: A review

“…Similarly, for seeds of multiple weed species, the physical characteristics of the seed were more crucial for avoiding predation by carabid predators than was seed chemistry (Foffova et al, 2020). We suggest that given the evidence to date, seed chemistry per se is unlikely to be the only driver of seed selection decisions in carabid weed seed predators.…”

“…Weed seeds are imbedded in an intricate matrix of environmental variables that could influence the foraging decisions of carabid predators in unpredictable ways (De Heij & Willenborg, 2020 ; Sarabi, 2019 ). Under such conditions, there will be certain cases where predicting the suitable seed type based on chemical cues alone fails to explain the observed seed selection responses of carabid weed seed predators (Foffova et al., 2020 ). That is, there will be certain cases where other impactful ecological factors might interfere and sway weed seed preferences in certain directions (De Heij & Willenborg, 2020 ).…”

“…et al (2012);Foffova et al (2020);Saska et al (2020) Note: +, indicates a positive effect; −, indicates a negative effect; 0, indicates no documented effect. a Net effects depend on the seed-predator mass-ratio scaling relationship.…”

Environmental conditions and seed traits affect seed dispersal patterns in a slug–legume model system

“…whether ingested seeds are digested (seed predation) or excreted intact (endozoochory). Seed traits that are known to affect their palatability to granivores are seed size, seed coat hardness, seed density and nutritional quality (Kulkarni et al 2015, Clause et al 2017, Hana et al 2020. In general, the size of preferred seeds correlates positively with the animal's size, as has been shown for carabids (Honek et al 2007, Kulkarni et al 2015, slugs (Türke and Weisser 2013), some ant species (Arnan et al 2010) and millipedes (Koprdová et al 2010).…”

“…The extent of many invertebrate-seed interactions is often species-specific for both invertebrate and/or seed species (whether and how many seeds are ingested initially) (Honek et al 2007, Eisenhauer et al 2009, Clause et al 2011, Hana et al 2020). However, this species-specificity can also be linked to animal and seed traits that affect not only the initial interaction of seed ingestion but also the outcome of seed fate, i.e.…”