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

ALISON E. BENNETT AND AIMEE
T. CLASSEN. 2020. Climate change influences mycorrhizal fungal–plant interactions, but conclusions are limited by geographical study bias. Ecology 101(4):e02978. 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 leads 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.

Flow is more Important than Temperature in Driving Patterns of Organic Matter Storage and Stoichiometry in Stream Ecosystems

James R. Junker, Wyatt F. Cross, Jonathan P. Benstead, Alexander D. Huryn, James M. Hood, Daniel Nelson, Gísli M. Gíslason & Jón S. Ólafsson. Ecosystems (2020). https://doi.org/10.1007/s10021-020-00585-6

Abstract

Understanding the connections between biological communities and elemental cycles is increasingly important given that alterations to both are occurring on a global scale. Biological control of elemental cycles is tied to patterns of biomass and the elemental stoichiometry of organisms and organic matter (OM) pools that comprise ecosystems. The structure and size of these ecosystem components are, in turn, shaped by key environmental factors that influence species composition, functional traits, and OM and element storage. In stream and river ecosystems, temperature and flow regime have a strong influence on ecosystem structure and function, yet little is known about their relative importance in driving patterns of ecosystem OM and stoichiometry. We quantified ecosystem OM pools and elemental stoichiometry in 11 Icelandic streams across a wide gradient of temperature (~ 5 to 25 °C) and flow. Across these environmental gradients, we observed two orders of magnitude variation in ecosystem OM mass, as well as relatively large variation in certain ecosystem stoichiometries (that is, C:N, C:P). We found that flow regime was more important than temperature in driving variation in OM pools and stoichiometry because of large shifts in community structure, that is, from dominance by large-bodied macrophyte and bryophyte communities to epilithic and detrital OM pools. Although temperature is known to influence mass-specific rates of metabolic and chemical processes, our study suggests that the flow disturbance regime may be the dominant control on patterns of OM storage and may thus control ecosystem fluxes by constraining ecosystem OM pool mass, organism size structure, and stoichiometric traits.

Bottom hypoxia alters the spatial distribution of pelagic intermediate consumers and their prey

Rebecca A. Dillon, Joseph D. Conroy, Kathryn J. Lang, Kevin L Pangle, and Stuart A. Ludsin. Canadian Journal of Fisheries and Aquatic Sciences. 26 November 2020. https://doi.org/10.1139/cjfas-2020-0001

Abstract

While recent research has shed insight into how bottom hypoxia affects pelagic food webs in coastal marine ecosystems and natural lakes, its effects on man-made lake (reservoir) food webs remains more incomplete. To address this gap, we conducted a study in two Midwestern USA reservoirs to examine how the spatial overlap and vertical distributions of dominant zooplanktivores (i.e., pelagic fish, the bentho-pelagic macroinvertebrate Chaoborus) and their prey vary between periods of normoxia and hypoxia. Surprisingly, we found high levels of spatial overlap between zooplankton and both intermediate consumers (pelagic fish and Chaoborus) during both normoxia and hypoxia, though the extent of spatial overlap was higher during hypoxia at night relative to day. As expected, pelagic fish and zooplankton avoided hypoxic waters, and Chaoborus moved from hypoxic waters during the day to the well-oxygenated surface waters at night. Using our findings, we discuss the potential influence of bottom hypoxia and Chaoborus on the function and structure of north-temperate reservoir food webs.

Natural selection on traits and trait plasticity in Arabidopsis thaliana varies across competitive environments

Palacio-Lopez K, King CM, Bloomberg J, Hovick SM.Scientific Reports, 09 Dec 2020, 10(1):21632
DOI: 10.1038/s41598-020-77444-w 

Abstract 

Interspecific competition reduces resource availability and can affect evolution. We quantified multivariate selection in the presence and absence of strong interspecific competition using a greenhouse experiment with 35 natural accessions of Arabidopsis thaliana. We assessed selection on nine traits representing plant phenology, growth, and architecture, as well as their plasticities. Competition reduced biomass and fitness by over 98%, and plastic responses to competition varied by genotype (significant G × E) for all traits except specific leaf area (SLA). Competitive treatments altered selection on flowering phenology and plant architecture, with significant selection on all phenology traits and most architecture traits under competition-present conditions but little indication that selection occurred in the absence of competitors. Plasticity affected fitness only in competition-present conditions, where plasticity in flowering time and early internode lengths was adaptive. The competitive environment caused changes in the trait correlation structure and surprisingly reduced phenotypic integration, which helped explain some of the observed selection patterns. Despite this overall shift in the trait correlation matrix, genotypes with delayed flowering had lower SLA (thicker, tougher leaves) regardless of the competitive environment, a pattern we have not seen previously reported in the literature. Overall, our study highlights multiple ways in which interspecific competition can alter selective regimes, contributing to our understanding of variability in selection processes over space and time.

P2C2M.GMYC: An R package for assessing the utility of the Generalized Mixed Yule Coalescent model

Emanuel M. Fonseca, Drew J. Duckett, Bryan C. Carstens. Methods Ecol Evol. 2020;00:1–7. wileyonlinelibrary.com/journal/mee3

Abstract

1. In clades that contain large numbers of undescribed species, DNA barcoding
methods can serve as a first pass at identifying species limits. The General Mixed Yule Coalescent (GMYC) approach to species delimitation is accurate under certain conditions that are difficult to verify in the very clades for which the GMYC holds the greatest appeal.
2. To circumvent this challenge, we have developed an R package for assessing how well the statistical model implemented in the GMYC fits empirical data. Our approach uses either a parametric bootstrap or a posterior predictive simulation to evaluate model fit.
3. Computational requirements are modest for our package, and most analyses can be completed within minutes to an hour on a typical laptop, depending on whether a user selects a maximum likelihood or Bayesian framework.
4. Results of simulation testing indicate that our approach is effective for assessing the utility of the GMYC model and suggest that it should be included in the analytical pipeline whenever researchers apply the GMYC to clades with unknown species boundaries.

Egg parasitoids of the cassava hornworm (Erinnyis spp.) associated to cassava in the Pará State, Brazil

Aloyséia Cristina da Silva Noronha, Dimison Garcia Blanco, Valmir Antonio Costa, Ranyse Barbosa Querino, Dênmora Gomes de Araújo & Norman F. Johnson. EntomoBrasilis 13: e932 (2020). https://doi.org/10.12741/ebrasilis.v13.e932

Abstract

The aim of this study was to assess the occurrence and identify the egg-parasitoid species of the cassava hornworm (Erinnyis spp.) in cassava plants (Manihot esculenta Crantz - Euphorbiaceae), facilitating their usage in the biological control as a management strategy in the Pará State. During February to December of 2016, cassava hornworm eggs were collected in the Cassava Germplasm Bank area of the Embrapa Amazônia Oriental, located at the city of Belém, State of Pará. In the laboratory, eggs were separated in viable and parasitized and were daily observed until the hatching of the caterpillars and emergence of the parasitoids. The caterpillars were reared until reaching the adult stage and the sex determined at the pupae stage. A total of 482 eggs were collected, with a higher occurrence at March, and 244 caterpillars were obtained with sex ratio of 0.52 with 191 specimens reaching adult stage. Among these adults, 95.81% were Erinnyis ello (Linnaeus) and 4.19% Erinnyis alope (Drury). A total of 1,087 parasitoids were obtained from 131 eggs and belong to four Hymenoptera families: Platygastridae (Telenomus dilophonotae Cameron), Eulophidae (Chrysonotomyia sp. aff. serjaniae), Trichogrammatidae (Trichogramma marandobai Brun, Moraes & Soares) and Encyrtidae (Ooencyrtus sp.). The Erinnyis spp. eggs were mostly parasitized by T. dilophonotae, which was classified along with T. marandobai as constant. The occurrence of these natural enemies highlights the potential for natural biological control against Erinnyis spp.

The scales of coevolution: comparative phylogeography and genetic demography of a locally adapted venomous predator and its prey

Matthew L Holding; Michael G Sovic; Timothy J Colston; H Lisle Gibbs. 2020. Biological Journal of the Linnean Society (IF 1.961), DOI: 10.1093/biolinnean/blaa192

Abstract

Coevolutionary theory predicts that differences in the genetic demography of interacting species can influence patterns of local adaptation by affecting the potential of local populations to respond to selection. We conducted a comparative phylogeographical study of venomous rattlesnakes and their venom-resistant ground squirrel prey across California, and assessed how effective population size (Ne) estimates correspond with a previously documented pattern of rattlesnake local adaptation. Using RAD sequencing markers, we detected lineage relationships among both the rattlesnakes (Crotalus oreganus ssp.) and ground squirrels (Otospermophilus sp.) that are incongruent with previous phylogenetic hypotheses. Both rattlesnakes and squirrels share a deep divergence at the Sacramento–San Joaquin River Delta. At this broad phylogeographical scale, we found that the locally adapted rattlesnakes had higher Ne than squirrels. At the population scale, snakes also had larger Ne accompanied by larger values of several metrics of population genetic diversity. However, the specific magnitude of local adaptation of venom activity to ground squirrel venom resistance was not significantly correlated with local differences in Ne or other diversity statistics between predator and prey populations, suggesting that other factors in the geographic mosaic of coevolution contribute to the specific local-scale outcomes of this interaction. These results suggest an evolutionary mechanism that may explain some (but clearly not all) of rattlesnake local adaptation in this coevolutionary interaction – larger population sizes raise the adaptive potential of rattlesnakes compared to ground squirrels.

COSORE: A community database for continuous soil respiration and other soil‐atmosphere greenhouse gas flux data

Bond‐Lamberty, Ben ; Christianson, Danielle S. ; Malhotra, Avni ; Pennington, Stephanie C. ; Sihi, Debjani ; AghaKouchak, Amir ; Anjileli, Hassan ; Altaf Arain, M. ; Armesto, Juan J. ; Ashraf, Samaneh ; Ataka, Mioko ; Baldocchi, Dennis ; Andrew Black, Thomas ; Buchmann, Nina ; Carbone, Mariah S. ; Chang, Shih‐Chieh ; Crill, Patrick ; Curtis, Peter S. ; Davidson, Eric A. ; Desai, Ankur R. ; Drake, John E. ; El‐Madany, Tarek S. ; Gavazzi, Michael ; Görres, Carolyn‐Monika ; Gough, Christopher M. ; Goulden, Michael ; Gregg, Jillian ; Gutiérrez del Arroyo, Omar ; He, Jin‐Sheng ; Hirano, Takashi ; Hopple, Anya ; Hughes, Holly ; Järveoja, Järvi ; Jassal, Rachhpal ; Jian, Jinshi ; Kan, Haiming ; Kaye, Jason ; Kominami, Yuji ; Liang, Naishen ; Lipson, David ; Macdonald, Catriona A. ; Maseyk, Kadmiel ; Mathes, Kayla ; Mauritz, Marguerite ; Mayes, Melanie A. ; McNulty, Steve ; Miao, Guofang ; Migliavacca, Mirco ; Miller, Scott ; Miniat, Chelcy F. ; Nietz, Jennifer G. ; Nilsson, Mats B. ; Noormets, Asko ; Norouzi, Hamidreza ; O’Connell, Christine S. ; Osborne, Bruce ; Oyonarte, Cecilio ; Pang, Zhuo ; Peichl, Matthias ; Pendall, Elise ; Perez‐Quezada, Jorge F. ; Phillips, Claire L. ; Phillips, Richard P. ; Raich, James W. ; Renchon, Alexandre A. ; Ruehr, Nadine K. ; Sánchez‐Cañete, Enrique P. ; Saunders, Matthew ; Savage, Kathleen E. ; Schrumpf, Marion ; Scott, Russell L. ; Seibt, Ulli ; Silver, Whendee L. ; Sun, Wu ; Szutu, Daphne ; Takagi, Kentaro ; Takagi, Masahiro ; Teramoto, Munemasa ; Tjoelker, Mark G. ; Trumbore, Susan ; Ueyama, Masahito ; Vargas, Rodrigo ; Varner, Ruth K. ; Verfaillie, Joseph ; Vogel, Christoph ; Wang, Jinsong ; Winston, Greg ; Wood, Tana E. ; Wu, Juying ; Wutzler, Thomas ; Zeng, Jiye ; Zha, Tianshan ; Zhang, Quan ; Zou, Junliang. 2020. Global Change Biology. Volume 26, Issue 12. https://doi.org/10.1111/gcb.15353

Abstract

Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand how soil greenhouse gas (GHG) emissions and uptake will respond to ongoing climate change. In particular, the soil‐to‐atmosphere CO2 flux, commonly though imprecisely termed soil respiration (RS), is one of the largest carbon fluxes in the Earth system. An increasing number of high‐frequency RS measurements (typically, from an automated system with hourly sampling) have been made over the last two decades; an increasing number of methane measurements are being made with such systems as well. Such high frequency data are an invaluable resource for understanding GHG fluxes, but lack a central database or repository. Here we describe the lightweight, open‐source COSORE (COntinuous SOil REspiration) database and software, that focuses on automated, continuous and long‐term GHG flux datasets, and is intended to serve as a community resource for earth sciences, climate change syntheses and model evaluation. Contributed datasets are mapped to a single, consistent standard, with metadata on contributors, geographic location, measurement conditions and ancillary data. The design emphasizes the importance of reproducibility, scientific transparency and open access to data. While being oriented towards continuously measured RS, the database design accommodates other soil‐atmosphere measurements (e.g. ecosystem respiration, chamber‐measured net ecosystem exchange, methane fluxes) as well as experimental treatments (heterotrophic only, etc.). We give brief examples of the types of analyses possible using this new community resource and describe its accompanying R software package.