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1. Diurnal patterns of productivity of arbuscular mycorrhizal fungi revealed with the Soil Ecosystem Observatory

   https://doi.org/10.1111/nph.12393  

   Hernandez, Rebecca R. ; Allen, Michael F. ( July 2013 , New Phytologist)

   Arbuscular mycorrhizal (AM) fungi are the most abundant plant symbiont and a major pathway of carbon sequestration in soils. However, their basic biology, including their activity throughout a 24‐h day : night cycle, remains unknown.

   We employed thein situSoil Ecosystem Observatory to quantify the rates of diurnal growth, dieback and net productivity of extra‐radicalAMfungi.AMfungal hyphae showed significantly different rates of growth and dieback over a period of 24 h and paralleled the circadian‐driven photosynthetic oscillations observed in plants.

   The greatest rates (and incidences) of growth and dieback occurred between noon and 18:00 h. Growth and dieback events often occurred simultaneously and were tightly coupled with soil temperature and moisture, suggesting a rapid acclimation of the external phase ofAMfungi to the immediate environment.

   Changes in the environmental conditions and variability of the mycorrhizosphere may alter the diurnal patterns of productivity ofAMfungi, thereby modifying soil carbon sequestration, nutrient cycling and host plant success.

    

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2. Legacy effects of tree mortality mediated by ectomycorrhizal fungal communities

   https://doi.org/10.1111/nph.15993  

   Mueller, Rebecca C. ; Scudder, Crescent M. ; Whitham, Thomas G. ; Gehring, Catherine A. ( July 2019 , New Phytologist)

   Successive droughts have resulted in extensive tree mortality in the southwestern United States. Recovery of these areas is dependent on the survival and recruitment of young trees. For trees that rely on ectomycorrhizal fungi (EMF) for survival and growth, changes in soil fungal communities following tree mortality could negatively affect seedling establishment.

   We used tree‐focused and stand‐scale measurements to examine the impact of pinyon pine mortality on the performance of surviving juvenile trees and the potential for mutualism limitation of seedling establishment via alteredEMFcommunities.

   Mature pinyon mortality did not affect the survival of juvenile pinyons, but increased their growth. At both tree and stand scales, high pinyon mortality had no effect on the abundance ofEMFinocula, but led to alteredEMFcommunity composition including increased abundance ofGeoporaand reduced abundance ofTuber. Seedling biomass was strongly positively associated withTuberabundance, suggesting that reductions in this genus with pinyon mortality could have negative consequences for establishing seedlings.

   These findings suggest that whereas mature pinyon mortality led to competitive release for established juvenile pinyons, changes inEMFcommunity composition with mortality could limit successful seedling establishment and growth in high‐mortality sites.

    

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3. Spatial variation in phylogenetic diversity of communities of Atlantic Forest harvestmen (Opiliones, Arachnida)

   https://doi.org/10.1111/icad.12356  

   Nogueira, André do Amaral ; Bragagnolo, Cibele ; DaSilva, Márcio Bernardino ; Carvalho, Leonardo Sousa ; Benedetti, Alípio Rezende ; Pinto‐da‐Rocha, Ricardo ; Basset, ed., Yves ; Buddle, ed., Chris ( June 2019 , Insect Conservation and Diversity)

   The study of diversity has become increasingly sophisticated, including the use of measures of phylogenetic diversity.

   We calculate the spatial variation in species richness, taxonomic beta diversity, and alpha and beta phylogenetic diversity (PDαandPDβ, respectively) of Atlantic Forest harvestman communities using a data set containing 556 species from 68 sites, distributed in 12 Brazilian states.

   We compare the congruence of phylogenetic and taxonomic diversity patterns, and also comparePDαwith null model expectations, to check for phylogenetic clustering or overdispersion in communities.

   Species richness andPDαare correlated, peaking in southern and south‐eastern coastal sites and decreasing towards the interior and towards the north‐east.PDαin north‐eastern sites was higher than expected, while a clustered phylogenetic pattern characterised most other sites.

   Communities in the southern and south‐eastern regions were dominated by species from the large family Gonyleptidae, presenting a high richness and a lowPDα. As the dominance of Gonyleptidae decreased towards the north, where local communities have fewer species, but a higherPDα, they contain representatives of other families. The beta diversity was more sensitive to the compositional changes involving closely related Gonyleptidae species, whilePDβis more influenced by deeper phylogenetic compositional changes, between more distant lineages.

   Phylogenetic diversity may be of special importance to assess the conservation value of distantly related lineages. These species‐poor groups are less likely to influence taxonomic‐based diversity analyses, but their importance for conservation arises from their phylogenetic distinctiveness, captured byPDαandPDβmeasures.

    

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4. Molecular and electrophysiological characterization of anion transport in Arabidopsis thaliana pollen reveals regulatory roles for pH , Ca 2+ and GABA

   https://doi.org/10.1111/nph.15863  

   Domingos, Patrícia ; Dias, Pedro N. ; Tavares, Bárbara ; Portes, Maria Teresa ; Wudick, Michael M. ; Konrad, Kai R. ; Gilliham, Matthew ; Bicho, Ana ; Feijó, José A. ( May 2019 , New Phytologist)

   We investigated the molecular basis and physiological implications of anion transport during pollen tube (PT) growth inArabidopsis thaliana(Col‐0).

   Patch‐clamp whole‐cell configuration analysis of pollen grain protoplasts revealed three subpopulations of anionic currents differentially regulated by cytoplasmic calcium ([Ca²⁺]_cyt). We investigated the pollen‐expressed proteinsAtSLAH3,AtALMT12,AtTMEM16 andAtCCCas the putative anion transporters responsible for these currents.

   AtCCC‐GFPwas observed at the shank andAtSLAH3‐GFPat the tip and shank of thePTplasma membrane. Both are likely to carry the majority of anion current at negative potentials, as extracellular anionic fluxes measured at the tip ofPTs with an anion vibrating probe were significantly lower inslah3^−/−andccc^−/−mutants, but unaffected inalmt12^−/−andtmem16^−/−. We further characterised the effect ofpHandGABAby patch clamp. Strong regulation by extracellularpHwas observed in the wild‐type, but not intmem16^−/−. Our results are compatible withAtTMEM16 functioning as an anion/H⁺cotransporter and therefore, as a putativepHsensor.GABApresence: (1) inhibited the overall currents, an effect that is abrogated in thealmt12^−/−and (2) reduced the current inAtALMT12 transfectedCOS‐7 cells, strongly suggesting the direct interaction ofGABAwithAtALMT12.

   Our data show thatAtSLAH3 andAtCCCactivity is sufficient to explain the major component of extracellular anion fluxes, and unveils a possible regulatory system linkingPTgrowth modulation bypH,GABA, and [Ca²⁺]_cytthrough anionic transporters.

    

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5. Reduced aboveground tree growth associated with higher arbuscular mycorrhizal fungal diversity in tropical forest restoration

   https://doi.org/10.1002/ece3.2487  

   Holste, Ellen K. ; Holl, Karen D. ; Zahawi, Rakan A. ; Kobe, Richard K. ( September 2016 , Ecology and Evolution)

   Establishing diverse mycorrhizal fungal communities is considered important for forest recovery, yet mycorrhizae may have complex effects on tree growth depending on the composition of fungal species present. In an effort to understand the role of mycorrhizal fungi community in forest restoration in southern Costa Rica, we sampled the arbuscular mycorrhizal fungal (AMF) community across eight sites that were planted with the same species (Inga edulis, Erythrina poeppigiana, Terminalia amazonia,andVochysia guatemalensis) but varied twofold to fourfold in overall tree growth rates. TheAMFcommunity was measured in multiple ways: as percent colonization of host tree roots, byDNAisolation of the fungal species associated with the roots, and through spore density, volume, and identity in both the wet and dry seasons. Consistent with prior tropical restoration research, the majority of fungal species belonged to the genusGlomusand genusAcaulospora, accounting for more than half of the species and relative abundance found on trees roots and over 95% of spore density across all sites. GreaterAMFdiversity correlated with lower soil organic matter, carbon, and nitrogen concentrations and longer durations of prior pasture use across sites. Contrary to previous literature findings,AMFspecies diversity and spore densities were inversely related to tree growth, which may have arisen from trees facultatively increasing their associations withAMFin lower soil fertility sites. Changes toAMFcommunity composition also may have led to variation in disturbance susceptibility, host tree nutrient acquisition, and tree growth. These results highlight the potential importance of fungal–tree–soil interactions in forest recovery and suggest that fungal community dynamics could have important implications for tree growth in disturbed soils.

    

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