The Role of Host Demographic Storage in the Ecological Dynamics of Heritable Symbionts

Heritable symbioses are widespread and ecologically important. Many host organisms have complex life cycles that include diverse opportunities for symbionts to affect their host and be lost during development. Yet, existing theory takes a simplified view of host demography. Here, we generalize symbiosis theory to understand how demographic “storage” in the form of dormant or prereproductive life stages can modify symbiosis dynamics. Using grass-endophyte symbioses as context, we developed models to contrast the role of the seed bank (a storage stage) against the reproductive stage in symbiont persistence and prevalence. We find that the seed bank is as important as or more important than the reproductive stage in driving symbiont dynamics, as long as passage through the seed bank is obligate. Flexible entry to the seed bank substantially weakens its influence on symbiont persistence but can modify prevalence in counterintuitive ways. Our models identify a role for legacy effects, where hosts that lose symbionts retain their demographic influence. The retention of benefits via legacy effects can reduce symbiont prevalence and even cause prevalence to decline with increasing benefits to hosts because symbiont-free hosts carry those benefits. Our results resolve connections between individual-level host-symbiont interactions and population-level patterns, providing guidance for empirical studies

Culturable Root Endophyte Communities are Shaped by Both Warming and Plant Host Identity in the Rocky Mountains, USA

Understanding the biogeographic patterns of root-associated fungi and their sensitivity to temperature may improve predictions of future changes in terrestrial biodiversity and associated ecosystem processes, but data are currently limited. Anticipating change will require combining observational data, which predict how climatic factors limit current species distributions, with direct manipulations of climate, which can isolate responses to specific climate variables. Root endophytes are common symbionts of plants, particularly in arctic and alpine environments, yet their responses to climate warming are not resolved. Here, we directly cultured endophytic fungi from roots collected along altitudinal gradients in replicated mountain watersheds and from a 27 y field warming experiment in the Rocky Mountains, USA, to improve understanding of climate impacts on fungal root endophytes. Fungal taxa that were common at high elevations declined most under climate warming, whereas low elevation dominants responded neutrally or increased with experimental warming. Altitudinal gradients in fungal communities were strongly specific to the plant host species. Specifically, Poa species had 25–60% greater fungal isolate abundance and 25–38% greater fungal diversity at high elevations than at low elevation sites. In contrast, Festuca thurberi had 64% lower fungal diversity on roots at high elevation than at low elevation. Our results help to improve understanding of the potential for climate change to alter plant-fungal interactions in mountain ecosystems

Exile Vol. XLII No. 1

40th Year Title Page by Sakura Yamamoto \u2797 i Epigraph by Ezra Pound ii Table of Contents iii / Untitled (artwork) by Gretchen Hambly \u2796 iv Breughel Again, Brussels by Adrienne Fair \u2796 1 for play with whitman by alex e blazer \u2797 4 Saeta Sunday by Carl Boon \u2796 5 An Abbreviated Life by Mike Westmoreland 6 Anthem of Governor\u27s Bay by Jamey Hein \u2796 7-10 Time is everywhere, yet nowhere (artwork) by Susanne Ducker \u2796 11 Crosses by Liz Bolyard \u2796 12 Raccoons at the Cats\u27 Food by Jennifer Rudgers \u2796 13-14 Father Federico by Trish Klei \u2797 15 Dream Poem I by Colin Bossen \u2798 16 Virgin Mary in Kentucky by Amy Ard \u2796 17 the jig is up by alex e blazer \u2797 18-20 Visiting Uncle Ernie by Liz Bolyard \u2796 21-22 A Capuchin Monk by Linda Fuller-Smith 23 Sunday, October 15, 1995 by Carl Boon \u2796 24 Old Man and the Marriage Party by Trish Klei \u2797 25 Untitled (artwork) by Gretchen Hambly \u2796 26 Cowboy Up by J. Murdoch Be Matheson \u2796 27-34 Fragments by Colin Bossen \u2798 35 meditation (artwork) by alex e blazer \u2797 36 Palazzo Rezzonico by Linda Fuller-Smith 37 A Poem About The Photographic Imprint I Would Leave If A Nuclear Bomb Hit Nearby As I Took Out The Trash One Night by Trish Klei \u2797 38 The Crazies I\u27ve Called by Julie Johnston \u2796 39-46 Contributors\u27 Notes 47-48 Editorial Board 49 Editorial decisions are shared equally among the Editorial Board. -49 Cover art by alex emmons -4

Testing the paradox of enrichment along a land use gradient in a multitrophic aboveground and belowground community

In the light of ongoing land use changes, it is important to understand how multitrophic communities perform at different land use intensities. The paradox of enrichment predicts that fertilization leads to destabilization and extinction of predator-prey systems. We tested this prediction for a land use intensity gradient from natural to highly fertilized agricultural ecosystems. We included multiple aboveground and belowground trophic levels and land use-dependent searching efficiencies of insects. To overcome logistic constraints of field experiments, we used a successfully validated simulation model to investigate plant responses to removal of herbivores and their enemies. Consistent with our predictions, instability measured by herbivore-induced plant mortality increased with increasing land use intensity. Simultaneously, the balance between herbivores and natural enemies turned increasingly towards herbivore dominance and natural enemy failure. Under natural conditions, there were more frequently significant effects of belowground herbivores and their natural enemies on plant performance, whereas there were more aboveground effects in agroecosystems. This result was partly due to the “boom-bust” behavior of the shoot herbivore population. Plant responses to herbivore or natural enemy removal were much more abrupt than the imposed smooth land use intensity gradient. This may be due to the presence of multiple trophic levels aboveground and belowground. Our model suggests that destabilization and extinction are more likely to occur in agroecosystems than in natural communities, but the shape of the relationship is nonlinear under the influence of multiple trophic interactions.

Exile Vol. XXXIX No. 1

Title Page by Ellen Gurley \u2793 i Epigraph by Ezra Poind ii Table of Contents iii-iv Remaining a Soldier by Kristin Kruse \u2793 1-2 Vietnam War Memorial by Brooke MacKaye 3 We both ride in back by Chris Macaluso \u2793 4 Artwork by Jamie Oliver \u2794 5 Liberal Dirge #1 by Charis Brummitt \u2796 6-7 Artwork (anonymous) 7 Two ex-lovers and a dirty glass door by Chris Macaluso \u2793 8 The Salt of the Air by Kristen Padden \u2793 9-12 Artwork (anonymous) 13 Artwork by Ellen Gurley \u2793 14 Sun-Child by Jen Rudgers \u2796 15 Crazy Horse by Kevin Nix \u2794 16 The Fall of the Western Field by Rich Croft \u2793 17 In the Closet by Beth Widmaier \u2795 18 Winter Strawberries by Katy Rudder \u2793 19 Still Life (anonymous) 19 For This and Much Beyond This Poem by Matt Wanat \u2795 20-21 Artwork by Peggy Ryan \u2793 22 The Cycle Repeats: Apathy by Ishak Kang \u2793 23 The Judge by Ellen Gurley \u2793 24 Pear Colored by Erin Dempsey \u2793 25-26 4-Square by Trey Dunham \u2794 27 Artwork by Jamie Oliver \u2794 28 Ink & Heroine by Rich Croft \u2793 29 Figments by Craig Bowers \u2793 30-31 Malfi Coast (anonymous) 31 Suzanne (anonymous) 32 Hey Stella by Carey Chistie \u2795 33 Turning Leaves by Erin Lott \u2796 34-35 Reclining Nude (anonymous) 35 Blazon by Matt Wanat \u2795 36-37 Artwork by Holly Aikens \u2793 38 Awake by A. Fair \u2796 39 Dell the Barber by Kevin Nix \u2795 40 Artwork by Holly Aikens \u2793 40 Tree House by Katy Rudder \u2793 41-46 Jailbait by Ellison J. Stind \u2795 47 Mother by Charis Brummitt \u2796 48-49 Artwork by Bess Hammer \u2795 49 Private Origami by Trey Dunham \u2794 50 Among the Tendrils of Sleep by J. Trevett Allen \u2795 51 Poet of the Unforgiven by Carey Christie \u2795 52 Stuntman Steve by Andrew Zobay \u2793 53 sculpture by Lily Streett \u2794 53 Wonderings of an Adopted Son by Andy Heckert \u2793 54-55 Artwork by Holly Aikens \u2793 55 Odd Binge by C. N. Polumbus \u2793 56-57 Artwork by Holly Aikens \u2793 57 Artwork by Peggy Ryan \u2793; untitled by Jennifer Wendell \u2794 (superimposed) 58 Shadows of Pearl by Travis Brady \u2793 59-60 October/Rt. 161 by Annette Gallagher 61 Artwork by Jamie Oliver \u2794 61 The Influx by Craig Bowers \u2793 62 Artwork by Michael Norpell \u2794 63 editorial board 64 Editorial decision is shared equally among the Editorial Board. -64 Cover: Jamie Oliver -64 NOTE: With the exeption of Malfi Coast , all artwork listed as anonymous in the published table of contents appears to be signed by Ellen Gurley. 37th Yea

Do Herbivores Eavesdrop on Ant Chemical Communication to Avoid Predation?

Strong effects of predator chemical cues on prey are common in aquatic and marine ecosystems, but are thought to be rare in terrestrial systems and specifically for arthropods. For ants, herbivores are hypothesized to eavesdrop on ant chemical communication and thereby avoid predation or confrontation. Here I tested the effect of ant chemical cues on herbivore choice and herbivory. Using Margaridisa sp. flea beetles and leaves from the host tree (Conostegia xalapensis), I performed paired-leaf choice feeding experiments. Coating leaves with crushed ant liquids (Azteca instabilis), exposing leaves to ant patrolling prior to choice tests (A. instabilis and Camponotus textor) and comparing leaves from trees with and without A. instabilis nests resulted in more herbivores and herbivory on control (no ant-treatment) relative to ant-treatment leaves. In contrast to A. instabilis and C. textor, leaves previously patrolled by Solenopsis geminata had no difference in beetle number and damage compared to control leaves. Altering the time A. instabilis patrolled treatment leaves prior to choice tests (0-, 5-, 30-, 90-, 180-min.) revealed treatment effects were only statistically significant after 90- and 180-min. of prior leaf exposure. This study suggests, for two ecologically important and taxonomically diverse genera (Azteca and Camponotus), ant chemical cues have important effects on herbivores and that these effects may be widespread across the ant family. It suggests that the effect of chemical cues on herbivores may only appear after substantial previous ant activity has occurred on plant tissues. Furthermore, it supports the hypothesis that herbivores use ant chemical communication to avoid predation or confrontation with ants

Endophyte Microbiome Diversity in Micropropagated Atriplex canescens and Atriplex torreyi var griffithsii

Microbial diversity associated with micropropagated Atriplex species was assessed using microscopy, isolate culturing, and sequencing. Light, electron, and confocal microscopy revealed microbial cells in aseptically regenerated leaves and roots. Clone libraries and tag-encoded FLX amplicon pyrosequencing (TEFAP) analysis amplified sequences from callus homologous to diverse fungal and bacterial taxa. Culturing isolated some seed borne endophyte taxa which could be readily propagated apart from the host. Microbial cells were observed within biofilm-like residues associated with plant cell surfaces and intercellular spaces. Various universal primers amplified both plant and microbial sequences, with different primers revealing different patterns of fungal diversity. Bacterial and fungal TEFAP followed by alignment with sequences from curated databases revealed 7 bacterial and 17 ascomycete taxa in A. canescens, and 5 bacterial taxa in A. torreyi. Additional diversity was observed among isolates and clone libraries. Micropropagated Atriplex retains a complex, intimately associated microbiome which includes diverse strains well poised to interact in manners that influence host physiology. Microbiome analysis was facilitated by high throughput sequencing methods, but primer biases continue to limit recovery of diverse sequences from even moderately complex communities

Bioavailability of Macro and Micronutrients Across Global Topsoils: Main Drivers and Global Change Impacts

Understanding the chemical composition of our planet\u27s crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro- and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome-dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling-atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world

Climate Change Alters Seedling Emergence and Establishment in an Old-Field Ecosystem

Background: Ecological succession drives large-scale changes in ecosystem composition over time, but the mechanisms whereby climatic change might alter succession remain unresolved. Here, we asked if the effects of atmospheric and climatic change would alter tree seedling emergence and establishment in an old-field ecosystem, recognizing that small shifts in rates of seedling emergence and establishment of different species may have long-term repercussions on the transition of fields to forests in the future. Methodology/Principal Findings: We introduced seeds from three early successional tree species into constructed old-field plant communities that had been subjected for 4 years to altered temperature, precipitation, and atmospheric CO 2 regimes in an experimental facility. Our experiment revealed that different combinations of atmospheric CO2 concentration, air temperature, and soil moisture altered seedling emergence and establishment. Treatments directly and indirectly affected soil moisture, which was the best predictor of seedling establishment, though treatment effects differed among species. Conclusions: The observed impacts, coupled with variations in the timing of seed arrival, are demonstrated as predictors o