Plant density can increase invertebrate postdispersal seed predation in an experimental grassland community

Abstract

Janzen–Connell effects are negative effects on the survival of a plant's progeny at high conspecific densities or close to its conspecifics. Although the role of Janzen–Connell effects on the maintenance of plant diversity was frequently studied, only few studies targeted Janzen–Connell effects via postdispersal seed predation in temperate grassland systems. We examined effects of conspecific density (abundance of conspecific adult plants) on postdispersal seed predation by invertebrates of three grassland species (Centaurea jacea, Geranium pratense, and Knautia arvensis) in experimental plant communities. Additionally, we examined the impact of plant species richness and different seed predator communities on total and relative seed predation (= seed predation of one plant species relative to others). We offered seeds in an exclusion experiment, where treatments allowed access for (1) arthropods and slugs, (2) arthropods only, (3) small arthropods only, and (4) slugs only. Treatments were placed in plots covering a gradient of abundance of conspecific adults at different levels of plant species richness (1, 2, 3, 4, 8 species). Two of the plant species (C. jacea and K. arvensis) experienced higher rates of seed predation and relative predation with increasing abundance of conspecific adults. For C. jacea, this effect was mitigated with increasing plant species richness. Differences in seed predator communities shifted seed predation between the plant species and changed the magnitude of seed predation of one plant species relative to the others. We exemplify density‐dependent increase in seed predation via invertebrates in grassland communities shaping both the total magnitude of species‐specific seed predation and seed predation of one species relative to others. Further differences in seed predator groups shift the magnitude of seed predation between different plant species. This highlights the importance of invertebrate seed predation to structure grasslands via density‐dependent effects and differing preferences of consumer groups.

Factors that influence the level of weed seed predation: A review

“…), but differences in seed predator groups shift the magnitude of seed predation between different plant species (Dudenhoffer et al . ). For example, Honek et al .…”

“…Weed seed predators are classified into two groups: those which feed immature and mature seeds before shed from the parent plant are called predispersal predators, and those which feed after shed on the soil surface are called postdispersal predators. Both vertebrates (e.g., birds and rodents) and invertebrates (e.g., ground beetles, ants, crickets, and slugs) feed on weed seeds (Brust & House 1988;Cardina et al 1996;Zhang et al 1997;Cromar et al 1999), but differences in seed predator groups shift the magnitude of seed predation between different plant species (Dudenhoffer et al 2016). For example, Honek et al (2017) reported that invertebrate predation is an important factor of weed and seedling mortality of shining orache (Atriplex sagittata Borkh.)…”

Inter-Individual Nectar Chemistry Changes of Field Scabious, Knautia arvensis

“…Order of displayed amino acids reflects the order of appearance in the chromatogram. 5 Total AA (amino acids) are the mean sum of all single amino acids ± SD (standard deviation) in mg per mL, followed by individual amino acids. Total C (carbohydrates) are the mean sum of the three main carbohydrates (fructose, glucose, sucrose) in mg/mL ± SD (standard deviation).…”

“…Plants are important bottom up partners of multitrophic interactions [1][2][3]. Interactions between plants and animals further drive important ecosystem functions and processes, such as herbivory, pollination or seed dispersal [1,[4][5][6], because plants provide a habitat and resources for many animals [7,8]. These interactions in turn depend on the composition and diversity of the surrounding plant community [1].…”

Overcoming challenges on using native seeds for restoration of megadiverse resource‐poor environments: a reply to Madsen et al.

“…The use of mulch (Nyamai et al ) and chemical repellants (Brakes & Smith ) has been reported to protect the seeds, and late‐season seeding and drill seeding may effectively reduce the impacts of granivory on seedling establishment (Gurney et al ). Additionally, selection of species based on least preferred seed traits (Suazo et al ) and appropriate abundance of seeds in seeding mixtures can also increase on‐site retention of heavily predated seeds (Beard et al ; Dudenhoffer et al ).…”