Plant networks are more connected by invasive brome and native shrub facilitation in Central California drylands.

Dominant vegetation in many ecosystems is an integral component of structure and habitat. In many drylands, native shrubs function as foundation species that benefit other plants and animals. However, invasive exotic plant species can comprise a significant proportion of the vegetation. In Central California drylands, the facilitative shrub Ephedra californica and the invasive Bromus rubens are widely dispersed and common. Using comprehensive survey data structured by shrub and open gaps for the region, we compared network structure with and without this native shrub canopy and with and without the invasive brome. The presence of the invasive brome profoundly shifted the network measure of centrality in the microsites structured by a shrub canopy (centrality scores increased from 4.3 under shrubs without brome to 6.3, i.e. a relative increase of 42%). This strongly suggests that plant species such as brome can undermine the positive and stabilizing effects of native foundation plant species provided by shrubs in drylands by changing the frequency that the remaining species connect to one another. The net proportion of positive and negative associations was consistent across all microsites (approximately 50% with a total of 14% non-random co-occurrences on average) suggesting that these plant-plant networks are rewired but not more negative. Maintaining resilience in biodiversity thus needs to capitalize on protecting native shrubs whilst also controlling invasive grass species particularly when associated with shrubs.

A realized facilitation cascade mediated by biological soil crusts in a sagebrush steppe community.

Biological soil crusts can have strong effects on vascular plant communities which have been inferred from short-term germination and early establishment responses. However, biocrusts are often assumed to function as an "organizing principle" in communities because their effects can "cascade" to interactions among crust-associated plant species. We conducted surveys and experiments to explore these cascades and found that biocrusts were positively associated with large patches (> 10 m diameter) of a dominant shrub Artemisia tridentata. At the smaller scale of individual shrubs and the open matrices between shrubs, biocrusts were negatively associated with Artemisia. Juveniles of Artemisia were found only in biocrusts in intershrub spaces and never under shrubs or in soil without biocrusts. In two-year field experiments, biocrusts increased the growth of Festuca and the photosynthetic rates of Artemisia. Festuca planted under Artemisia were also at least twice as large as those planted in open sites without crusts or where Artemisia were removed. Thus, biocrusts can facilitate vascular plants over long time periods and can contribute to a "realized" cascade with nested negative and positive interactions for a range of species, but unusual among documented cascades in that it includes only autotrophs.

Teach different: The CREATE pedagogy for ecology and evolution.

Globally, teaching has changed and innovated profoundly in the last 3 years. With novel and more seamless opportunities to use technology and more actively teach visually online or in-person and to engage in inclusive dialogue within and between groups, we can teach very differently now. An innovation proposed a number of years ago and revisited anew in a recent and novel application to ecology and evolution course offerings, and the CREATE pedagogy or Consider, Read, Elucidate the hypothesis or purpose, Analyze and interpret data or evidence, and Think of the next Experiment is an inspiring framework for unique student work and teaching. CREATE proposes that students engage in active reading through specific exercises that are both creative and heavily anchored in critical thinking when working with publications. Here, the palette of CREATE exercises is expanded further for ecology and evolution and affirms that this approach to student engagement with literature can be highly effective in many courses. Furthermore, the application of this pedagogy dramatically influences and likely enhances how one teaches in a lecture setting as an educator making the content in all modalities more engaging and active.

Foundation plant species provide resilience and microclimatic heterogeneity in drylands.

Climate change profoundly influences plants and animals in all ecosystems including drylands such as semi-arid and arid scrublands and grasslands. At the peak of an extended megadrought in the Southwestern USA, the microclimatic refuges provided by foundation plant species and through associated vegetation were examined. Shrubs and open interstitial spaces without a canopy but with annual plants were instrumented in 2016 and the wet season of 2017 in the central drylands of California. In both years and all seasons tested, vegetation significantly mediated fine-scale near-surface air temperature and relative soil moisture content-defined here as microclimate. The foundation species with other vegetation provided the most significant thermal refuge potential capacity for other plants and animals, but there was variation by growing season. Soil moisture content was frequently increased by the direct canopy effects of shrubs. This evidence suggests that the climate many plants and animals experience, even during an extended megadrought, is mediated by the local plants in highly impacted drylands with anthropogenic disturbance and significant water-induced challenges. Foundation species such as shrubs in drylands function as a potent starting point in examining the ecological relevance of climate at scales germane to many species locally. An ecological framework for climate resilience using shrubs will improve conservation and restoration planning in drylands.

The EICA is dead? Long live the EICA!

An important hypothesis for how plants respond to introduction to new ranges is the evolution of increased competitive ability (EICA). EICA predicts that biogeographical release from natural enemies initiates a trade-off in which exotic species in non-native ranges become larger and more competitive, but invest less in consumer defences, relative to populations in native ranges. This trade-off is exceptionally complex because detecting concomitant biogeographical shifts in competitive ability and consumer defence depends upon which traits are targeted, how competition is measured, the defence chemicals quantified, whether defence chemicals do more than defend, whether 'herbivory' is artificial or natural, and where consumers fall on the generalist-specialist spectrum. Previous meta-analyses have successfully identified patterns but have yet to fully disentangle this complexity. We used meta-analysis to reevaluate traditional metrics used to test EICA theory and then expanded on these metrics by partitioning competitive effect and competitive tolerance measures and testing Leaf-Specific Mass in detail as a response trait. Unlike previous syntheses, our meta-analyses detected evidence consistent with the classic trade-off inherent to EICA. Plants from non-native ranges imposed greater competitive effects than plants from native ranges and were less quantitatively defended than plants from native ranges. Our results for defence were not based on complex leaf chemistry, but instead were estimated from tannins, toughness traits and primarily Leaf-Specific Mass. Species specificity occurred but did not influence the general patterns. As for all evidence for EICA-like trade-offs, we do not know if the biogeographical differences we found were caused by trade-offs per se, but they are consistent with predictions derived from the overarching hypothesis. Underestimating physical leaf structure may have contributed to two decades of tepid perspectives on the trade-offs fundamental to EICA.

Tabular strategies for metadata in ecology, evolution, and the environmental sciences.

Data support knowledge development and theory advances in ecology and evolution. We are increasingly reusing data within our teams and projects and through the global, openly archived datasets of others. Metadata can be challenging to write and interpret, but it is always crucial for reuse. The value metadata cannot be overstated-even as a relatively independent research object because it describes the work that has been done in a structured format. We advance a new perspective and classify methods for metadata curation and development with tables. Tables with templates can be effectively used to capture all components of an experiment or project in a single, easy-to-read file familiar to most scientists. If coupled with the R programming language, metadata from tables can then be rapidly and reproducibly converted to publication formats including extensible markup language files suitable for data repositories. Tables can also be used to summarize existing metadata and store metadata across many datasets. A case study is provided and the added benefits of tables for metadata, a priori, are developed to ensure a more streamlined publishing process for many data repositories used in ecology, evolution, and the environmental sciences. In ecology and evolution, researchers are often highly tabular thinkers from experimental data collection in the lab and/or field, and representations of metadata as a table will provide novel research and reuse insights.

Alpine cushion plants inhibit the loss of phylogenetic diversity in severe environments.

Biotic interactions can shape phylogenetic community structure (PCS). However, we do not know how the asymmetric effects of foundation species on communities extend to effects on PCS. We assessed PCS of alpine plant communities around the world, both within cushion plant foundation species and adjacent open ground, and compared the effects of foundation species and climate on alpha (within-microsite), beta (between open and cushion) and gamma (open and cushion combined) PCS. In the open, alpha PCS shifted from highly related to distantly related with increasing potential productivity. However, we found no relationship between gamma PCS and climate, due to divergence in phylogenetic composition between cushion and open sub-communities in severe environments, as demonstrated by increasing phylo-beta diversity. Thus, foundation species functioned as micro-refugia by facilitating less stress-tolerant lineages in severe environments, erasing a global productivity - phylogenetic diversity relationship that would go undetected without accounting for this important biotic interaction.

A test of the reserve meristem hypothesis using Verbascum thapsus (Scrophulariaceae).

The reserve meristem hypothesis predicts that latent meristems may act as a bet-hedging strategy given high-cost, predictable herbivory. Under this hypothesis, damage to a plant should elicit greater branching. This prediction was tested in Verbascum thapsus with three experiments manipulating the intensity and type of damage to reproductive tissue. In the first experiment, seed set was prevented in the treatment group by stigma excision and lanolin application to 80% of the flowers of each plant. In the second experiment, a minimum of two mating pairs of weevils were added to treated plants prior to the onset of flowering. In the third experiment, all fruits were sliced lengthwise twice. All three treatments significantly reduced seed set. In the first two experiments, treated plants significantly increased degree of branching (branch number and total branch length). This supports the reserve meristem hypothesis as an explanation for greater branching in larger plants of V. thapsus. Interestingly, the fruit destruction experiment failed to elicit a branching response, which suggests that the timing of damage is important.

Fitness consequences of branching in Verbascum thapsus (Scrophulariaceae).

The reserve meristem hypothesis proposes that strong apical dominance suppresses lateral meristems and branches to escape from predictable damage (herbivory). This hypothesis was tested for Verbascum thapsus and its seed predator the weevil Gynmnetron tetrum by two mensurative experiments. The following predictions were made under this hypothesis: the proportion of individuals branched within a population will increase with increased damage, the main stalk of branched plants will be more damaged, and branching increases net seed production. Fifty populations of V. thapsus were extensively surveyed, and one pair of similar-sized individuals (branched vs. unbranched) were selected from each population to determine damage patterns and measure seed production. Two of the predictions of the reserve meristem hypothesis were clearly supported. The proportion of fruits damaged on the main stalk of branched plants was significantly greater than unbranched plants, and branched plants produced significantly more seeds. Hence, the reserve meristem hypothesis is supported as an adaptive interpretation of apical dominance in this species. This study is a potential example of overcompensation following granivory in the field.

Pollination in Verbascum thapsus (Scrophulariaceae): the advantage of being tall.

According to the "effective pollination" hypothesis, tall stature resulting from strong apical dominance attracts greater pollinator visitation, thus allowing larger pollen loads and/or greater outcrossing rates, which in turn produces more vigorous offspring with greater genotypic variability and/or less inbreeding depression. Components of this hypothesis were tested in Verbascum thapsus, which commonly grows unbranched to over 2 m tall with strong apical dominance suppressing all axillary meristems. A natural population survey indicated that plants with visiting pollinators were significantly taller than their nearest neighboring individuals not possessing a visiting pollinator. Plants in natural populations with excluded pollinators produced seeds via a delayed selfing mechanism. However, delayed selfing under pollinator exclusion resulted in only 75% of the seed set obtained with natural pollinators. Under natural pollination, emasculated flowers experienced a 50% reduction in pollen deposition by the time of flower closure but only a 5% reduction in seed set relative to intact flowers. Hence, taller plants attracted more pollinators and maximum seed set could not be achieved without pollinators. Comparison of seed set and seed mass in plants that were artificially selfed and artificially crossed (in both the greenhouse and in natural populations) indicated that plants were fully self-compatible with no evidence of early-acting inbreeding depression. However, this does not exclude the possibility that inbreeding depression is manifested in later life stages. The results suggest that V. thapsus has a mixed mating system with potential for reproductive assurance and various levels of outcrossing depending on variables affecting pollinator availability (e.g., population size).