Ecological Strategies Begin at Germination: Traits, Plasticity, and Survival in the First Four Days of Plant Life

We commonly use trait variation to characterize plant function within and among species and understand how vegetation responds to the environment. Seedling emergence is an especially vulnerable window affecting population and community dynamics, yet trait‐based frameworks often bypass this earliest stage of plant life. Here we assess whether traits vary in ecologically‐meaningful ways when seedlings are just days old. How do shared evolutionary history and environmental conditions shape trait expression, and can traits explain which seedlings endure drought?. We measured seedling traits in the first four days of life for 16 annual plant species under two water treatments, exploring trait tradeoffs, species‐level plasticity, and the ability of traits to predict duration of survival under drought. Nearly half of traits showed the imprint of evolutionary history (i.e., significant phylogenetic signal), often reflecting differences between grasses and forbs, two groups separated by a deep evolutionary split. Water availability altered trait expression in most cases, though species‐level plastic responses also reflected evolutionary history. On average, new seedlings exhibited substantial trait variation structured as multiple tradeoffs like those found in mature plants. Some species invested in thick roots and shoots while others invested in more efficient tissues. Separately, some invested in tougher roots and others in deeper roots. We also observed tradeoffs related to growth rates (fast or slow) and biomass allocation (above or belowground). Drought survival time was correlated most strongly with seed mass, root construction and allocation traits, and phylogeny (grasses versus forbs). Synthesis. Our results show that seed and seedling trait variation among annual species is substantial, and that a few attributes could capture major dimensions of ecological strategies during emergence. With seedling survival times ranging two‐fold among annuals (from 7.5 to 14.5 days), these strategies could mitigate recruitment responses to more frequent or longer dry spells. Multivariate trait and plasticity strategies should be further explored in studies designed to assess trait‐fitness linkages during recruitment

Origins and Consequences of Serpentine Endemism in the California Flora

Habitat specialization plays an important role in the creation and loss of biodiversity over ecological and evolutionary time scales. In California, serpentine soils have a distinctive flora, with 246 serpentine habitat specialists (i.e., endemics). Using molecular phylogenies for 23 genera containing 784 taxa and 51 endemics, we infer few transitions out of the endemic state, which is shown by an analysis of transition rates to simply reflect the low frequency of endemics (i.e., reversal rates were high). The finding of high reversal rates, but a low number of reversals, is consistent with the widely hypothesized trade-off between serpentine tolerance and competitive ability, under which serpentine endemics are physiologically capable of growing in less-stressful habitats but competitors lead to their extirpation. Endemism is also characterized by a decrease in speciation and extinction rates and a decrease in the overall diversification rate. We also find that tolerators (species with nonserpentine and serpentine populations) undergo speciation in serpentine habitats to give rise to new serpentine endemics but are several times more likely to lose serpentine populations to produce serpentine-intolerant taxa. Finally, endemics were younger on average than nonendemics, but this alone does not explain their low diversification

Physiological Correlates of Volunteering

We review research on physiological correlates of volunteering, a neglected but promising research field. Some of these correlates seem to be causal factors influencing volunteering. Volunteers tend to have better physical health, both self-reported and expert-assessed, better mental health, and perform better on cognitive tasks. Research thus far has rarely examined neurological, neurochemical, hormonal, and genetic correlates of volunteering to any significant extent, especially controlling for other factors as potential confounds. Evolutionary theory and behavioral genetic research suggest the importance of such physiological factors in humans. Basically, many aspects of social relationships and social activities have effects on health (e.g., Newman and Roberts 2013; Uchino 2004), as the widely used biopsychosocial (BPS) model suggests (Institute of Medicine 2001). Studies of formal volunteering (FV), charitable giving, and altruistic behavior suggest that physiological characteristics are related to volunteering, including specific genes (such as oxytocin receptor [OXTR] genes, Arginine vasopressin receptor [AVPR] genes, dopamine D4 receptor [DRD4] genes, and 5-HTTLPR). We recommend that future research on physiological factors be extended to non-Western populations, focusing specifically on volunteering, and differentiating between different forms and types of volunteering and civic participation

Extreme drought impacts have been underestimated in grasslands and shrublands globally

Climate change is increasing the frequency and severity of short-term (~1 y) drought events-the most common duration of drought-globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function-aboveground net primary production (ANPP)-was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought

Data from: Historical and ecological controls on phylogenetic diversity in Californian plant communities

We addressed the classic question of whether community diversity is determined from the bottom up by the breadth and partitioning of niche space or from the top down by historical and evolutionary forces. Specifically, we contrasted local and regional explanations for the diversity of Californian plant communities using phylogenetic and functional analyses. Our communities were sets of four field plots that sampled alpha (within-plot) and beta (among-plot) sources of variation in diversity. We sampled 93 such communities nested within 78 larger regions for which regional species pools could be independently estimated, spanning the California Floristic Province. We measured phylogenetic and functional diversity within plots and between plots on neighboring soils and slopes. We also measured the phylogenetic diversity of regional species pools and analyzed them in terms of biogeographic groups. We found no evidence linking the phylogenetic diversity of communities to within-plot functional diversity or among-plot beta diversity. Instead, we found that the phylogenetic diversity of communities depends on that of regional species pools. In turn, phylogenetically diverse pools were those with high proportions of species of northern biogeographic affinity, which have relatively mesic distributions and traits. This supports what we call the climatic refuge hypothesis rather than the biogeographic crossroads hypothesis

dryad

drya

Data from: Soil microbial community variation correlates most strongly with plant species identity, followed by soil chemistry, spatial location and plant genus

Soil ecologists have debated the relative importance of dispersal limitation and ecological factors in determining the structure of soil microbial communities. Recent evidence suggests that "everything is not everywhere", and that microbial communities are influenced by both dispersal limitation and ecological factors. However, we still do not understand the relative explanatory power of spatial and ecological factors, including plant species identity and even plant relatedness, for different fractions of the soil microbial community (i.e. bacterial and fungal communities). To ask whether factors such as plant species, soil chemistry, spatial location, and plant relatedness influence rhizosphere community composition, we examined field-collected rhizosphere soil of seven congener pairs that occur at Bodega Bay Marine Reserve, CA, USA. We characterized differences in bacterial and fungal communities using Terminal-Restriction Fragment Length Polymorphism. Plant species identity was the single best statistical predictor of both bacterial and fungal community composition in the root zone. Soil microbial community structure was also correlated with soil chemistry. The third best predictor of bacterial and fungal communities was spatial location, confirming that everything is not everywhere. Variation in microbial community composition was also related to combinations of spatial location, soil chemistry, and plant relatedness, suggesting that these factors do not act independently. Plant relatedness explained less of the variation than plant species, soil chemistry, or spatial location. Despite some congeners occupying different habitats and being spatially distant, rhizosphere fungal communities of plant congeners were more similar than expected by chance. Bacterial communities from the same samples were only weakly similar between plant congeners. Thus, plant relatedness might influence soil fungal, more than soil bacterial, community composition

Soil microbial community variation correlates most strongly with plant species identity, followed by soil chemistry, spatial location and plant genus.

Soil ecologists have debated the relative importance of dispersal limitation and ecological factors in determining the structure of soil microbial communities. Recent evidence suggests that 'everything is not everywhere', and that microbial communities are influenced by both dispersal limitation and ecological factors. However, we still do not understand the relative explanatory power of spatial and ecological factors, including plant species identity and even plant relatedness, for different fractions of the soil microbial community (i.e. bacterial and fungal communities). To ask whether factors such as plant species, soil chemistry, spatial location and plant relatedness influence rhizosphere community composition, we examined field-collected rhizosphere soil of seven congener pairs that occur at Bodega Bay Marine Reserve, CA, USA. We characterized differences in bacterial and fungal communities using terminal-restriction fragment length polymorphism. Plant species identity was the single best statistical predictor of both bacterial and fungal community composition in the root zone. Soil microbial community structure was also correlated with soil chemistry. The third best predictor of bacterial and fungal communities was spatial location, confirming that everything is not everywhere. Variation in microbial community composition was also related to combinations of spatial location, soil chemistry and plant relatedness, suggesting that these factors do not act independently. Plant relatedness explained less of the variation than plant species, soil chemistry, or spatial location. Despite some congeners occupying different habitats and being spatially distant, rhizosphere fungal communities of plant congeners were more similar than expected by chance. Bacterial communities from the same samples were only weakly similar between plant congeners. Thus, plant relatedness might influence soil fungal, more than soil bacterial, community composition

Trifolium greenhouse competition data

csv file of plant growth data for Trifolium fucatum and Trifolium macraei in greenhouse competition experimen