ARTICLE | doi:10.20944/preprints201902.0215.v4
Subject: Biology And Life Sciences, Insect Science Keywords: coevolution; herbivory; host-plant specialization; phylogeny; speciation
Online: 17 October 2019 (10:12:05 CEST)
During the last two decades, ecological speciation has been a major research theme in evolutionary biology. Ecological speciation occurs when reproductive isolation between populations evolves as a result of niche differentiation. Phytophagous insects represent model systems for the study of this evolutionary process. The host-plants on which these insects feed and often spend parts of their life cycle constitute ideal agents of divergent selection for these organisms. Adaptation to feeding on different host-plant species can potentially lead to ecological specialization of populations and subsequent speciation. This process is thought to have given birth to the astonishing diversity of phytophagous insects and is often put forward in macroevolutionary scenarios of insect diversification. Consequently, numerous phylogenetic studies on phytophagous insects have aimed at testing whether speciation driven by host-plant adaptation is the main pathway for the diversification of the groups under investigation. The increasing availability of comprehensive and well-resolved phylogenies and the recent developments in phylogenetic comparative methods are offering an unprecedented opportunity to test hypotheses on insect diversification at a macroevolutionary scale, in a robust phylogenetic framework. Our purpose here is to review the contribution of phylogenetic analyses to investigate the importance of plant-mediated speciation in the diversification of phytophagous insects and to present suggestions for future developments in this field.
ARTICLE | doi:10.20944/preprints202205.0312.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: Tasmania; Australia; herbivory; macropods; soil moisture; grazing; blazing
Online: 24 May 2022 (03:25:50 CEST)
Very few multi-species or ecosystem comparisons of post-fire vertebrate herbivore activity and food preference exist to inform fire-management and conservation strategies. We inferred post-fire (1-3 years) native and introduced vertebrate herbivore activity and attraction to six diverse temperate vegetation communities (grassland to rainforest) from scat counts. We hypothesised that where fire reduced herbaceous and grassy vegetation (‘fodder’), vertebrate herbivores would decline, and that post-fire preferences of native versus exotic herbivores would differ significantly. Instead, we found evidence for a ‘fire and fodder reversal phenomenon’ whereby native macropod and exotic rabbit scats were more abundant after fire in consistently ‘fodder-poor’ vegetation types (e.g wet forests) but more less abundant after fire in previously fodder-rich vegetation communities (e.g. grassland). Fodder cover predicted native macropod, wombat, and introduced deer activity and bareground cover was strongly associated with introduced herbivore activity only, with the latter indicating post-fire competition for food sources due to their abundance in high altitude open ecosystems. We therefore found environmental and vegetation predictors for each individual species/group and suggest broadscale multi-environment, multispecies observations to be informative for conservation management in potentially overlapping post-fire niches.
REVIEW | doi:10.20944/preprints202302.0134.v1
Subject: Biology And Life Sciences, Forestry Keywords: planting depth; drought; freeze injury; herbivory; mortality; survival; insects
Online: 7 February 2023 (14:01:52 CET)
Artificial regeneration is successful when high performing seedlings are transported with care to the planting site, stored for a short period in an environment without desiccation or fungal growth, and are planted in a deep hole so roots are in contact with moist soil. One of the requirements for success is the ability to avoid common planting mistakes. Due, in part, to use of container stock plus an increase in rainfall, average 1st year survival of pine seedlings (89%) in the southern United States is about 15% greater now than 45 years ago. However, when survival is less than 50% six months after planting, some landowners seek reimbursement for their loss. Some assume poor seedling quality was the cause without realizing that anaerobic soils or sudden freeze events or shallow planting holes or pruning roots, a lack of rain, or underground insects can kill pines. With a focus on pines planted in the southern United States, we list non-nursery factors that have killed seedlings in North America, Africa and Europe.
ARTICLE | doi:10.20944/preprints202112.0082.v1
Subject: Biology And Life Sciences, Animal Science, Veterinary Science And Zoology Keywords: Avian olfaction; foraging; herbivore-induced plant volatiles; defence against herbivory
Online: 6 December 2021 (15:21:49 CET)
The tri-trophic interactions between plants, insects, and insect predators and parasitoids are often mediated by chemical cues. The attraction to Herbivore-Infested Plant Volatiles (HIPVs) has been well documented for arthropod predators and parasitoids, and more recently for insectivorous birds. The attraction to plant volatiles induced by the exogenous application of methyl jasmonate (MeJA), a phytohormone typically produced in response to an attack of chewing herbivores, have provided controversial results, both in arthropod and avian predators. In this study, we aimed to examine whether potential differences in the composition of bouquets of volatiles produced by Herbivore-infested and MeJA-treated Pyrenean oak trees (Quercus pyrenaica) were related to differential avian attraction, as results from a previous study suggested. Results showed that the overall emission of volatiles produced by MeJA-treated and Herbivore-infested trees did not differ, and were higher than emissions of Control trees, although MeJA treatment showed more significant reaction and released several specific compounds in contrast to Herbivore-induced trees. These slight differences in the volatile composition may explain why avian predators were not so attracted to MeJA-treated trees as observed in a previous study in this plant-herbivore system. Unfortunately, the lack of avian visits to the experimental trees in the current study does not allow us to confirm this result and points out the need to perform more robust predator studies.
ARTICLE | doi:10.20944/preprints202308.1907.v1
Subject: Biology And Life Sciences, Ecology, Evolution, Behavior And Systematics Keywords: latex; ruminants; stomach pH; monogastric; herbivory; deterrent; antifeedant; evolution; digestive system
Online: 29 August 2023 (04:01:18 CEST)
In the struggle for survival, all organisms have evolved adaptations for protection from predation. Angiosperms are among the most abundant producers on the planet, but they are trapped in a precarious symbiosis with animals for pollination and fruit dispersal, while also having to deter herbivory. About 10% of all angiosperms produce the deterrent latex from ubiquitous isoprene precursors. Latex is an aqueous suspension of rubber particles and other compounds which works as an antifeedant by clogging chewing mouthparts and by coagulating into a solid in stomach acid. A survey of stomach pHs from various animals supports the hypothesis that foregut-fermenting ruminants have evolved the capacity to evade latex coagulation due to the presence of anterior digestive chambers with near-neutral to alkaline pH before it enters the acidic abomasum. Hindgut-fermenting animals lack this adaptation and have to eat forage which is low in latex, such as grasses. The latex-adaptive foregut browsers vs. latex-maladapted hindgut grazer hypothesis has implications for both livestock and zoo animals which may be provided with forage that is not optimal for their gut health. Further, ruminants and herbivorous tadpoles are at risk for damage by popular bioinsecticides such as Bt which are activated by alkaline gut pH.
ARTICLE | doi:10.20944/preprints202307.1728.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: Mammalian herbivory; Vegetation dynamics; Ground cover vegetation; Invasive Plants; Hell’s Gate National Park
Online: 25 July 2023 (13:12:44 CEST)
The status of vegetation and the impacts of mammalian herbivores on rangelands are complex, and such studies in Kenya are scanty. We investigated the dynamics of ground cover vegetation in Hell’s Gate National Park in relation to mammalian herbivory. Removal of palatable vegetation is postulated to enhance the development of invasive plant species. We investigated the influence of mammalian herbivores on vegetation diversity and dynamics in this rangeland. Three sampling blocks approximately 3 Km apart measuring 100 m x 50 m were established, each divided into three belt-transects (100 m x 10 m), and separated by a 10 m buffer zone. 2 m by 2 m quadrats at 20 m intervals were established in each transect. We measured composition the richness of plant and mammal species, and herbivory levels four times for six months (September 2018 to February 2019). Plant cover (P< 0.001) and species diversity (P< 0.001) differed significantly among sampling blocks and between seasons (P< 0.001). Non-metric multidimensional scaling of plant species and herbivores showed co-occurrence of Zebras with Sida tenuicarpa and giraffes with Solanum incunum. We conclude that the removal of preferred plants through herbivory may be giving an edge to invasive species in the park.
ARTICLE | doi:10.20944/preprints201907.0023.v1
Subject: Biology And Life Sciences, Ecology, Evolution, Behavior And Systematics Keywords: plant defense; herbivory; mechanical wounding; oral secretions; induced volatiles; SpitWorm; MecWorm; Phaseolus lunatus; Spodoptera littoralis; volatile organic compounds
Online: 1 July 2019 (16:08:11 CEST)
Induction of jasmonate-mediated plant defense against insect herbivory is initiated by a combination of both, mechanical wounding and chemical factors. In order to study both effects independently on plant defense induction, SpitWorm, a computer-controlled device which mimics the damage pattern of feeding insect larvae on leaves and, in addition, can apply oral secretions (OS) or other solutions to the ‘biting site’ during ‘feeding’, was developed and evaluated. The amount of OS left by a Spodoptera littoralis larva during feeding on Phaseolus lunatus (lima bean) leaves was estimated by combining larval foregut volume, biting rate, and quantification of a fluorescent dye injected into the larvae’s foregut prior to feeding. For providing OS amounts by SpitWorm equivalent to larval feeding, dilution and delivery rate were optimized. The effectiveness of SpitWorm was tested by comparing volatile organic compounds (VOC) emissions of P. lunatus leaves treated with either SpitWorm, MecWorm or S. littoralis larvae. Identification and quantification of emitted VOCs revealed that SpitWorm induced a volatile bouquet that is qualitatively and quantitatively similar to herbivory. Additionally, RT-qPCR of four jasmonic acid responsive genes showed that SpitWorm, in contrast to MecWorm, induces the same regulation pattern as insect feeding. Thus, SpitWorm mimics insect herbivory almost identical to real larvae feeding.
ARTICLE | doi:10.20944/preprints202310.1881.v1
Subject: Biology And Life Sciences, Ecology, Evolution, Behavior And Systematics Keywords: latex; ruminants; monogastric; herbivory; deterrent; antifeedant; evolution; digestive system; alkaline gut pH; foregut; hindgut; B.thuringiensis toxin; Bt; bioinsecticide; polygastric; rubber
Online: 30 October 2023 (10:20:10 CET)
About 10% of angiosperms, an estimated 20,000 species, produce latex from ubiquitous isoprene precursors. Latex, an aqueous suspension of rubber particles and other compounds, functions as an antifeedant and herbivory deterrent. Here, I propose that the solubility of latex in neutral to alkaline pH supports the hypothesis that foregut-fermenting herbivores such as ruminants, kangaroos, sloths, insect larvae and tadpoles have evolved to adapt to the ingestion of latex with the evolution of alkaline anterior digestive chamber(s). However, they consequently become susceptible to the action of Bacillus thuringiensis (Bt) -endotoxin and related bioinsecticides which are activated in alkaline environments. By contrast, hindgut-fermenting herbivores such as horses and rabbits have acidic anterior digestive chambers in which latex coagulates and may cause gut blockage, but in which Bt is not activated. The latex-adapted foregut herbivore vs. latex-maladapted hindgut herbivore hypothesis developed in this paper has implications for foregut-fermenting husbanded livestock and zoo animals which may be provided with latex-containing forage that is detrimental to their gut health. Further, ruminants and herbivorous tadpoles with alkaline anterior chambers are at risk for damage by the supposedly “environmentally-friendly” Bt bioinsecticide which is widely disseminated, or engineered into crops which may enter animal feed streams.