Climate change influences mycorrhizal fungal–plant interactions, but conclusions are limited by geographical study bias

Alison E. Bennett  Aimée T. Classen. 2020. Ecology. https://doi.org/10.1002/ecy.2978

Abstract

Climate change is altering the interactions among plants and soil organisms in ways that will alter the structure and function of ecosystems. We reviewed the literature and developed a map of studies focused on how the three most common types of mycorrhizal fungi (arbuscular mycorrhizal (AM), ectomycorrhizal (EcM), and ericoid mycorrhizal (ErM) fungi) respond to elevated atmospheric carbon dioxide concentrations (eCO2), climatic warming, and changes in the distribution of precipitation. Broadly, we ask how do mycorrhizal fungi respond to climate change, how do these responses vary by fungal type, and how do mycorrhizal traits influence plant adaptation, movement, or extinction in response to climatic change? First, we found that 92% of studies were conducted in the northern hemisphere, and plant host, ecosystem type and study location were only correlated with each other in the northern hemisphere because studies across all mycorrhizal fungal types were only common in the northern hemisphere. Second, we show that temperature and rainfall variability had more variable effects than eCO2 on mycorrhizal fungal structures, but these effects were context dependent. Third, while mycorrhizal fungal types vary in their responses to climate change, it appears that warming lead to more variable responses in ectomycorrhizal than in arbuscular mycorrhizal fungi. Finally, we discuss common traits of mycorrhizal fungi that could aid in fungal and plant adaption to climate change. We posit that mycorrhizal fungi can buffer plant hosts against extinction risk, they can facilitate or retard the dispersal success of plants moving away from poor environments, and, by buffering host plants, they can enable host plant adaptation to new climates. All of these influences are, however, context dependent a finding that reflects the complex traits of mycorrhizal fungi as a group, the diversity of plant species they associate with and the variation in ecosystems in which they reside. Overall, while we point out many gaps in our understanding of the influence of climate changes on mycorrhizal fungi, we also highlight the large number of opportunities for researching plant and mycorrhizal fungal responses to and mitigation of climate changes.

Changes in Energy Reserves and Gene Expression Elicited by Freezing and Supercooling in the Antarctic Midge, Belgica antarctica

Nicholas M. Teets, Emma G. Dalrymple, Maya H. Hillis, J. D. Gantz, Drew E. Spacht, Richard E. Lee Jr., David L. Denlinger. 2020. Insects 11(1), 18. https://doi.org/10.3390/insects11010018

Abstract

Freeze-tolerance, or the ability to survive internal ice formation, is relatively rare among insects. Larvae of the Antarctic midge Belgica antarctica are freeze-tolerant year-round, but in dry environments, the larvae can remain supercooled (i.e., unfrozen) at subzero temperatures. In previous work with summer-acclimatized larvae, we showed that freezing is considerably more stressful than remaining supercooled. Here, these findings are extended by comparing survival, tissue damage, energetic costs, and stress gene expression in larvae that have undergone an artificial winter acclimation regime and are either frozen or supercooled at −5◦C. In contrast to summer larvae, winter larvae survive at −5◦C equally well for up to 14 days, whether frozen or supercooled, and there is no tissue damage at these conditions. In subsequent experiments, we measured energy stores and stress gene expression following cold exposure at −5◦C for either 24 h or 14 days, with and without a 12 h recovery period. We observed slight energetic costs to freezing, as frozen larvae tended to have lower glycogen stores across all groups. In addition, the abundance of two heat shock protein transcripts, hsp60 and hsp90, tended to be higher in frozen larvae, indicating higher levels of protein damage following freezing. Together, these results indicate a slight cost to being frozen relative to remaining supercooled, which may have implications for the selection of hibernacula and responses to climate change.

Multi-instar descriptions of cave dwelling Erythraeidae (Trombidiformes: Parasitengona) employing an integrative approach

SAMUEL GEREMIAS DOS SANTOS COSTA, HANS KLOMPEN, LEOPOLDO FERREIRA DE OLIVEIRA BERNARDI, LUCIANA CARDOSO GONÇALVES, DANTE BATISTA RIBEIRO, ALMIR ROGÉRIO PEPATO. 2020. Zootaxa 4717, 1. http://dx.doi.org/10.11646/zootaxa.4717.1.10

Abstract

The life cycle of Parasitengona includes major morphological changes precluding an instar association based only on the morphology. This makes rearing and/or molecular data necessary to associate the heteromorphic instars. Most of the described species are known from either post larval instars or larva. Following a previous study on Palearctic Erythraeidae, in the present study the instar association was made through an integrative approach including rearing trials and molecular analysis of the cytochrome oxidase I (COI) gene with the Bayesian Generalized Mixed Yule Coalescent (bGMYC) algorithm for species delimitation. Two new cave dwelling Erythraeidae (Trombidiformes: Parasitengona) species are described Lasioerythraeus jessicae sp. nov. and Leptus sidorchukae sp. nov. including all active instars. Additionally, a complete description of the previously unknown adults of Charletonia rocciai Treat & Flechtmann, 1979 is provided with notes on the larva and deutonymph. We also demonstrate experimentally that Ch. rocciai larvae are not attached to the same individual host during the entire feeding stage. We discuss the presence of troglomorphisms in Le. sidorchukae sp. nov.; and the distribution of the species.

Brief exposure to a diverse range of environmental stress enhances stress tolerance in the polyextremophilic Antarctic midge, Belgica antarctica

J. D. Gantz, B. N. Philip, N. M. Teets, Y. Kawarasaki, L. J. Potts, D. E. Spacht, J. B. Benoit, D. L. Denlinger, R. E Lee. 2020. bioRxiv. doi: https://doi.org/10.1101/2020.01.01.887414

Abstract

Insects use rapid acclimation to enhance their tolerance of abiotic stresses within minutes to hours. These responses are critical adaptations for insects and other small ectotherms to tolerate drastic changes in temperature, hydration, or other factors that can fluctuate precipitously with ambient conditions or as a result of behavior. Rapid cold-hardening, where insects use brief exposure to modest chilling as a cue to enhance their cold tolerance, is the most thoroughly-studied of these responses and relatively little is known about rapid acclimation that is either triggered by or enhances tolerance of other abiotic stresses. Here, we used larvae of the Antarctic midge, Belgica antarctica, a polar extremophile that routinely experiences numerous stresses in nature, to investigate how 2 h exposure to modest environmental stresses affect stress tolerance in insects. Brief pretreatment by various stresses, including hyperosmotic challenge, hypoosmotic challenge, acidity, basicity, and UV irradiation enhanced stress tolerance in B. antarctica larvae relative to untreated controls. These results indicate that numerous environmental cues can trigger rapid acclimation in insects and that these responses can enhance tolerance of multiple stresses.

Identifying model violations under the multispecies coalescent model using P2C2M.SNAPP

Drew J. Duckett, Tara A. Pelletier, Bryan C. Carstens. 2020. PeerJ 8:e8271 https://doi.org/10.7717/peerj.8271

Abstract

Phylogenetic estimation under the multispecies coalescent model (MSCM) assumes all incongruence among loci is caused by incomplete lineage sorting. Therefore, applying the MSCM to datasets that contain incongruence that is caused by other processes, such as gene flow, can lead to biased phylogeny estimates. To identify possible bias when using the MSCM, we present P2C2M.SNAPP. P2C2M.SNAPP is an R package that identifies model violations using posterior predictive simulation. P2C2M.SNAPP uses the posterior distribution of species trees output by the software package SNAPP to simulate posterior predictive datasets under the MSCM, and then uses summary statistics to compare either the empirical data or the posterior distribution to the posterior predictive distribution to identify model violations. In simulation testing, P2C2M.SNAPP correctly classified up to 83% of datasets (depending on the summary statistic used) as to whether or not they violated the MSCM model. P2C2M.SNAPP represents a user-friendly way for researchers to perform posterior predictive model checks when using the popular SNAPP phylogenetic estimation program. It is freely available as an R package, along with additional program details and tutorials.

Effects of agricultural and tillage practices on isotopic signatures and fluxes of organic and inorganic carbon in headwater streams

Scott A. Kelsey, Andréa G. Grottoli, James E. Bauer, Klaus Lorenz, Rattan Lal, Yohei Matsui & Teresa M. Huey-Sanders. 2020. Aquatic Sciences 82, 23. https://doi.org/10.1007/s00027-019-0691-7

Abstract

The amounts and characteristics of carbon (C) transported by streams and rivers are strongly connected to attributes of their associated watersheds. However, the factors controlling how different land uses influence the sources and inputs of organic and inorganic C to headwater streams are not fully understood. In order to assess how land use practices specifically influence headwater stream C, the concentrations and isotopic (natural δ13C and ∆14C) signatures of dissolved inorganic C (DIC), dissolved organic C (DOC), and particulate organic C (POC) were measured between October 2008 and August 2009 in streams of six small watersheds of differing land use. Bayesian mixing models were used to estimate contributions of potential C sources to stream DIC, DOC, and POC pools. Mixing model results indicate that sources of C to streams in tilled and non-tilled corn watersheds were dominated by C4 plant biomass and soil organic C. In all other watershed types stream C was dominated by C3 plant biomass. In addition, δ13C and Δ14C values of forested stream C were unique from values in the corn, pasture, and large mixed use watersheds, and showed greater contributions from modern-aged C3 biomass. Relative to other watershed types, tilled corn agriculture showed the greatest effect on both the sources and amounts of stream C. In the tilled corn watersheds, total C (DIC + DOC + POC) fluxes were 314% higher than in the non-tilled corn watershed and 39–76% higher than in all other watersheds. Thus, land use and agricultural practices can serve as strong controls over the sources and fluxes of organic and inorganic C to streams.

The biology of Megalolaelaps colossus (Acari: Dermanyssina)

Orlando Cómbita-Heredia, Edwin Javier Quintero-Gutiérrez, Nicole Romero-García & Hans Klompen. 2020. Experimental and Applied Acarology. https://doi.org/10.1007/s10493-019-00462-5 

Abstract

Aspects of life history and host interactions of Megalolaelaps colossus were studied in a laboratory environment. These mites appear to require a host for survival, but hosts do not survive very long in a laboratory setting, leading to a modified rearing protocol relying on regular host replacement. Specific data on phenology and incidence are reported. Direct observations on feeding, mating, transmission, and interaction with other mites could not be obtained, but indirect observations allow some hypotheses in each of these areas.

The first Nearctic record of the genus Neocheiridium (Pseudoscorpiones: Cheiridiidae), with description of Neocheiridium gullahorum sp. n. 

Kaarel Sammet , Olavi Kurina , Hans Klompen. 2020. Biodiversity Data Journal 8: e48278. https://doi.org/10.3897/BDJ.8.e48278

Abstract

The genus Neocheiridium Beier, 1932 currently contains seven Neotropical (including Caribbean) and two Afrotropical species, with no Nearctic records. An undescribed species of Neocheiridium from South Carolina was discovered in the Ohio State University Acarology Collection and is described as Neocheiridium gullahorum, n. sp. (based on specimens of both sexes). A key to known world species of Neocheiridium is proposed.