Seeds of the threatened dry rainforest tree Cadellia pentastylis (Surianaceae) are non-dormant

Cadellia pentastylis (Surianaceae) is an Australian endemic threatened rainforest tree. Irregular flowering and fruiting events coupled with high rates of infertility and insect predation has meant that seed testing has not been possible for this species. Seeds were opportunistically collected from a wild population in early 2021, which allowed for the first germination tests to be conducted. In this study, the presence of physical dormancy was examined by performing an imbibition test using scarified and non-scarified seeds. We also investigated whether a 5-min heat shock treatment at temperatures ranging from 60 to 120°C improved germination success. The presence of physiological dormancy was also examined by recording germination success following a gibberellic acid or smoke-water pre-treatment. Both scarified and non-scarified seeds readily imbibed water over a 72-h period, and several seeds had germinated in both treatments after 48 h. Final germination proportion and t50 following a heat shock, gibberellic acid or smoke-water pre-treatment did not significantly differ from the controls. We conclude that C. pentastylis seeds are non-dormant. Although a palisade cell layer has been reported in the endocarp, our results suggest that this layer may not be sufficiently formed to restrict germination. We recommend that seeds are collected from populations following dispersal and propagated shortly after or stored as conservation collections in ex situ Seedbanks.

The role of Epichloë grass endophytes during pasture renewal

The literature on the importance of Epichloë grass endophytes during pasture renewal is reviewed. Perennial ryegrass endophyte strains such as AR1, NEA2, and Standard Endophyte (SE) as well as tall fescue and meadow fescue endophytes, significantly increase seedling survival at establishment under insect pressure, for example from adult Argentine stem weevil, grass grub, and African black beetle. However, in endophyte-infected ryegrass, insect-derived plant damage increases 10–43 days after sowing despite the presence of endophyte. Insecticidal seed treatments can mitigate the vulnerability to insect predation during this time.

Assessment and Models of Insect Damage to Cones and Seeds of Pinus strobiformis in the Sierra Madre Occidental, Mexico

Insect damage to cones and seeds has a strong impact on the regeneration of conifer forest ecosystems, with broader implications for ecological and economic services. Lack of control of insect populations can lead to important economic and environmental losses. Pinus strobiformis is the most widespread of the white pines in Mexico and is widely distributed throughout the mountains of northern Mexico. Relatively few studies have examined insect damage to the cones and seeds of these pines, especially in Mexico. In this study, we therefore analyzed insect damage to cones and seeds of P. strobiformis in Mexico by using X-ray and stereomicroscopic analysis. The specific objectives of the study were (a) to characterize insect damage by measuring external and internal cone traits, (b) to assess the health of seeds and cones of P. strobiformis in the Sierra Madre Occidental, Mexico, and (c) to estimate the relative importance of the effects of different environmental variables on cone and seed damage caused by insects. We found that 80% of P. strobiformis seeds and 100% of the tree populations studied had damage caused by insects. Most seeds were affected by Leptoglossus occidentalis, Tetyra bipunctata, Megastigmus albifrons, and the Lepidoptera complex (which includes Apolychrosis synchysis, Cydia latisigna, Eucosma bobana, and Dioryctria abietivorella). The cones of all tree populations were affected by some type of insect damage, with Lepidoptera causing most of the damage (72%), followed by Conophthorus ponderosae (15%), the hemipteran L. occidentalis (7%), and the wasp M. albifrons (6%). The proportion of incomplete seeds in P. strobiformis at the tree level, cone damage by M. albifrons and seed damage in L. occidentalis were associated with various climate and soil variables and with crown dieback. Thus, cone and seed insect damage can be severe and potentially impact seed production in P. strobiformis and the reforestation potential of the species. The study findings will enable managers to better identify insects that cause damage to cone and seeds. In addition, identification of factors associated with damage may be useful for predicting the levels of insect predation on seeds and cones.

Cone characteristics and insect predation levels vary across years in mast seeding white spruce

Populations of many tree species exhibit synchronous and highly temporally variable seed crops across years. This is called mast seeding, and there are two predominant hypotheses for this pattern of reproduction, pollination efficiency and seed-predator satiation. Mast seeding studies typically involve records of population-level reproduction, with less information on the characteristics of reproductive structures. Here, we use data across six years (2012-2017), spanning a range of population-level cone conditions, to characterize i) white spruce (Picea glauca) cone lengths and seeds per cone, and ii) levels of seed predation. We quantified population-level cone production and collected 1,399 cones from a total of 38 trees in the Huron Mountains, Michigan, USA. Linear mixed models showed that mean and minimum cone lengths varied significantly across years; both being longest during the greatest cone production year. Larger cones had more seeds and the slopes of the relationships as well as the intercepts varied significantly across years. Generalized linear mixed models and AIC model selection showed that cones with insect predation damage was greatest when population-level reproduction was the lowest, with a mean proportion of cones damaged 0.82 in that year. Our findings show that white spruce cone characteristics and losses to insect seed predation vary temporally, and follow expectations based on mast seeding hypotheses.

Smaller and Isolated Grassland Fragments Are Exposed to Stronger Seed and Insect Predation in Habitat Edges

Habitat fragmentation threatens terrestrial arthropod biodiversity, and thereby also leads to alterations of ecosystem functioning and stability. Predation on insects and seeds by arthropods are two very important ecological functions because of their community-structuring effects. We addressed the effect of fragment connectivity, fragment size, and edge effect on insect and seed predation of arthropods. We studied 60 natural fragments of two grassland ecosystems in the same region (Hungarian Great Plain), 30 forest-steppes, and 30 burial mounds (kurgans). The size of fragments were in the range of 0.16–6.88 ha for forest-steppe and 0.01–0.44 ha for kurgan. We used 2400 sentinel arthropod preys (dummy caterpillars) and 4800 seeds in trays for the measurements. Attack marks on dummy caterpillars were used for predator identification and calculation of insect predation rates. In the case of seeds, predation rates were calculated as the number of missing or damaged seeds per total number of exposed seeds. Increasing connectivity played a role only in generally small kurgans, with a negative effect on insect and seed predation rates in the edges. In contrast, fragment size moderated edge effects on insect and seed predation rates in generally large forest-steppes. The difference between edges and centres was more pronounced in small than in large fragments. Our study emphasizes the important role of landscape and fragment-scale factors interacting with edge effect in shaping ecosystem functions in natural grassland fragments of modified landscapes. Managing functional landscapes to optimize the assessment of ecosystem functions and services needs a multispatial scale approach.

The lateral periaqueductal gray and its role in controlling predatory hunting and social defense.

Evasion from imminent threats and prey attack are opposite behavioral choices critical to survival. The lateral periaqueductal gray (LPAG) is a key player in these behaviors, it responds to social threats and prey hunting while also driving predatory attacks and active defense. Our results revealed that distinct neuronal populations in the LPAG drive prey hunting and evasion from social threats. We show that the LPAG provides a putative glutamatergic projection to the lateral hypothalamic area (LHA). LPAG > LHA pathway optogenetic inhibition impaired insect predation but did not alter escape/attack ratio during social defeat. The results suggest that the LPAG control over evasion to a social attack may be regarded as a stereotyped response depending probably on descending projections. Conversely, the LPAG control over predatory behavior involves an ascending pathway to the LHA that likely influences LHAGABA neurons driving predatory hunting and may provide an emotional drive for appetitive rewards.

The lateral periaqeductal gray and its role in controlling the opposite behavioral choices of predatory hunting and social defense

Evasion from imminent threats and prey attack are opposite behavioral choices critical to survival. Curiously, the lateral periaqueductal gray (LPAG) has been implicated in driving both responses. The LPAG responds to social threats and prey hunting while also drives predatory attacks and active defense. However, the LPAG neural mechanisms mediating these behaviors remain poorly defined. Here, we investigate how the LPAG mediates the choices of predatory hunting and evasion from a social threat. Pharmacogenetic inhibition in Fos DD-Cre mice of neurons responsive specifically to insect predation (IP) or social defeat (SD) revealed that distinct neuronal populations in the LPAG drive the prey hunting and evasion from social threats. We show that the LPAG provides massive glutamatergic projection to the lateral hypothalamic area (LHA). Optogenetic inhibition of the LPAG-LHA pathway impaired IP but did not alter escape/attack ratio during SD. We also found that pharmacogenetic inhibition of LHAGABA neurons impaired IP, but did not change evasion during SD. The results suggest that the LPAG control over evasion to a social attack may be regarded as a stereotyped response depending probably on glutamatergic descending projections. On the other hand, the LPAG control over predatory behavior involves an ascending glutamatergic pathway to the LHA that likely influences LHAGABA neurons driving predatory attack and prey consumption. The LPAG-LHA path supposedly provides an emotional drive for prey hunting and, of relevance, may conceivably have more widespread control on the motivational drive to seek other appetitive rewards.

Effect of cover crops in olive groves on Cicadomorpha communities

Aim of study: To identify the environmental variables that affect the Cicadomorpha communities and the role played by cover crops in olive groves by comparing olive orchards with cover crop to those with bare ground.Area of study: Córdoba, Spain.Material and methods: Two study plots, one with cover crop and the other with bare ground, were delimited in three areas of olives orchards. Three passive samplings (May, June and July) were performed in each study plot to estimate the abundance and the species richness of potential Cicadomorphas vectors of Xylella fastidiosa. In each sampling, eight yellow sticky traps (22 × 35 cm) were randomly distributed in each study plot (n = 144 traps).Main results: The Cicadomorpha communities were mainly affected by landscape variables (such as the total surface and the distance to remnants of natural vegetation) and environmental variables (such as the temperature, moisture or ETo), whereas cover crops played a secondary role in the abundance of the Cicadomorpha.Research highlights: The results of the study suggest that Cicadomorpha richness and abundance depend on the structural complexity provided by cover crops (positive effect) and live hedges (negative effect), which may be owing to the higher food abundance and shelter when cover crops are present, whereas higher insect predation may occur close to hedges, probably owing to insectivorous song birds.

Elicitor and Receptor Molecules: Orchestrators of Plant Defense and Immunity

Pathogen-associated molecular patterns (PAMPs), microbe-associated molecular patterns (MAMPs), herbivore-associated molecular patterns (HAMPs), and damage-associated molecular patterns (DAMPs) are molecules produced by microorganisms and insects in the event of infection, microbial priming, and insect predation. These molecules are then recognized by receptor molecules on or within the plant, which activates the defense signaling pathways, resulting in plant’s ability to overcome pathogenic invasion, induce systemic resistance, and protect against insect predation and damage. These small molecular motifs are conserved in all organisms. Fungi, bacteria, and insects have their own specific molecular patterns that induce defenses in plants. Most of the molecular patterns are either present as part of the pathogen’s structure or exudates (in bacteria and fungi), or insect saliva and honeydew. Since biotic stresses such as pathogens and insects can impair crop yield and production, understanding the interaction between these organisms and the host via the elicitor–receptor interaction is essential to equip us with the knowledge necessary to design durable resistance in plants. In addition, it is also important to look into the role played by beneficial microbes and synthetic elicitors in activating plants’ defense and protection against disease and predation. This review addresses receptors, elicitors, and the receptor–elicitor interactions where these components in fungi, bacteria, and insects will be elaborated, giving special emphasis to the molecules, responses, and mechanisms at play, variations between organisms where applicable, and applications and prospects.