Rare plants are common where you find them

Broad patterns in distribution and abundance can elucidate processes of evolution. A positive association between local abundance and the size of the geographic range has been demonstrated for closely related species across many taxa. This pattern is usually explained by assuming that species with smaller ranges are ecologically inferior (e.g., poor competitors or dispersers). Many areas of high endemism support local species that have evolved recently. The distribution of these neoendemics may reflect historical processes not accounted for by ecological, equilibrium hypotheses. We asked whether such traditional macroecological hypotheses also applied to the local abundance of seven narrowly endemic species and ecologically similar widespread congeners in the northern Rocky Mountains. For each of the 14 species, we estimated abundance of five randomly chosen populations by counting plants in 10 randomly located plots. The association between range size and local abundance was not positive. Instead, all seven narrow endemics were more abundant than their widespread congeners. Ecological specialization or differences in dispersal ability are not likely explanations for our results. We believe the local abundance of narrowly endemic species may be a sign of recent speciation. Most or all of our narrowly distributed species have probably not yet had time to spread to their full potential. Furthermore, theory predicts that speciation is more likely to occur in locally abundant populations. Our results suggest that strictly ecological mechanisms cannot explain abundance and distribution in regions with high neoendemism

Disappearing Plants: Why They Hide and How They Return

Prolonged dormancy is a life-history stage in which mature plants fail to resprout for one or more growing seasons and instead remain alive belowground. Prolonged dormancy is relatively common, but the proximate causes and consequences of this intriguing strategy have remained elusive. In this study we tested whether stored resources are associated with remaining belowground, and investigated the resource costs of remaining belowground during the growing season. We measured stored resources at the beginning and end of the growing season in Astragalus scaphoides, an herbaceous perennial in southwest Montana, USA. At the beginning of the growing season, dormant plants had lower concentrations of stored mobile carbon (nonstructural carbohydrates, NSC) than did emergent plants. Surprisingly, during the growing season, dormant plants gained as much NSC as photosynthetically active plants, an increase most likely due to remobilization of structural carbon. Thus, low levels of stored NSC were associated with remaining belowground, and remobilization of structural carbon may allow for dormant plants to emerge in later seasons. The dynamics of NSC in relation to dormancy highlights the ability of plants to change their own resource status somewhat independently of resource assimilation, as well as the importance of considering stored resources in understanding plant responses to the environment

Using statistics to design and estimate vital rates in matrix population models for a perennial herb

Matrix population models are widely used to assess population status and to inform management decisions. Despite existing theories for building such models, model construction is often partially based on expert opinion. So far, model structure has received relatively little attention, although it may affect estimates of population dynamics. Here, we assessed the consequences of two published matrix structures (a 4 × 4 matrix based on expert opinion and a 10 × 10 matrix based on statistical modeling) for estimates of vital rates and stochastic population dynamics of the long‐lived herb Astragalus scaphoides. We explored the ways in which choice of model structure alters the accuracy (i.e., mean) and precision (i.e., variance) of predicted population dynamics. We found that model structure had a negligible effect on the accuracy and precision of vital rates and stochastic stage distribution. However, the 10 × 10 matrix produced lower estimates of stochastic population growth rates than the 4 × 4 matrix, and more accurately predicted the observed trends in population abundance for three out of four study populations. Moreover, estimates of realized variation in population growth rate due to fluctuations in population stage structure over time were occasionally sensitive to matrix structure, suggesting differential roles of transient dynamics. Our study indicates that statistical modeling for choosing categories in matrix models might be preferable over expert opinion to accurately predict population trends and can provide a more objective way for model construction when the biological knowledge of the species is limited.</p

Time-lagged effects of weather on plant demography: drought and Astragalus scaphoides

Temperature and precipitation determine the conditions where plant species can occur. Despite their significance, to date, surprisingly few demographic field studies have considered the effects of abiotic drivers. This is problematic because anticipating the effect of global climate change on plant population viability requires understanding how weather variables affect population dynamics. One possible reason for omitting the effect of weather variables in demographic studies is the difficulty in detecting tight associations between vital rates and environmental drivers. In this paper, we applied Functional Linear Models (FLMs) to long‐term demographic data of the perennial wildflower, Astragalus scaphoides, and explored sensitivity of the results to reduced amounts of data. We compared models of the effect of average temperature, total precipitation, or an integrated measure of drought intensity (standardized precipitation evapotranspiration index, SPEI), on plant vital rates. We found that transitions to flowering and recruitment in year t were highest if winter/spring of year t was wet (positive effect of SPEI). Counterintuitively, if the preceding spring of year t − 1 was wet, flowering probabilities were decreased (negative effect of SPEI). Survival of vegetative plants from t − 1 to t was also negatively affected by wet weather in the spring of year t − 1 and, for large plants, even wet weather in the spring of t − 2 had a negative effect. We assessed the integrated effect of all vital rates on life history performance by fitting FLMs to the asymptotic growth rate, log(). Log() was highest if dry conditions in year t − 1 were followed by wet conditions in the year t. Overall, the positive effects of wet years exceeded their negative effects, suggesting that increasing frequency of drought conditions would reduce population viability of A. scaphoides. The drought signal weakened when reducing the number of monitoring years. Substituting space for time did not recover the weather signal, probably because the weather variables varied little between sites. We detected the SPEI signal when the analysis included data from two sites monitored over 20 yr (2 × 20 observations), but not when analyzing data from four sites monitored over 10 yr (4 × 10 observations). </p

The Knotted Protein UCH-L1 Exhibits Partially Unfolded Forms under Native Conditions that Share Common Structural Features with Its Kinetic Folding Intermediates.

The human ubiquitin C-terminal hydrolase, UCH-L1, is an abundant neuronal deubiquitinase that is associated with Parkinson's disease. It contains a complex Gordian knot topology formed by the polypeptide chain alone. Using a combination of fluorescence-based kinetic measurements, we show that UCH-L1 has two distinct kinetic folding intermediates that are transiently populated on parallel pathways between the denatured and native states. NMR hydrogen-deuterium exchange (HDX) experiments indicate the presence of partially unfolded forms (PUFs) of UCH-L1 under native conditions. HDX measurements as a function of urea concentration were used to establish the structure of the PUFs and pulse-labelled HDX NMR was used to show that the PUFs and the folding intermediates are likely the same species. In both cases, a similar stable core encompassing most of the central β-sheet is highly structured and α-helix 3, which is partially formed, packs against it. In contrast to the stable β-sheet core, the peripheral α-helices display significant local fluctuations leading to rapid exchange. The results also suggest that the main difference between the two kinetic intermediates is structure and packing of α-helices 3 and 7 and the degree of structure in β-strand 5. Together, the fluorescence and NMR results establish that UCH-L1 neither folds through a continuum of pathways nor by a single discrete pathway. Its folding is complex, the β-sheet core forms early and is present in both intermediate states, and the rate-limiting step which is likely to involve the threading of the chain to form the 52-knot occurs late on the folding pathway.This work was supported by the National Science Council (99-2911-I-007-034 and 104-2113-M-001-016), National Tsing Hua University and Academia Sinica, Taiwan. S.-T.D.H. was supported by a Career Development Award (CDA- 00025/2010-C) from the International Human Frontier Science Program. The NMR spectra were obtained at the NMR facility of the Department of Chemistry, University of Cambridge and at the Core Facility for Protein Structural Analysis, supported by the National Core Facility Program for Biotechnology, Taiwan.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.jmb.2016.04.00

Does masting scale with plant size? High reproductive variability and low synchrony in small and unproductive individuals

Background and Aims In a range of plant species, the distribution of individual mean fecundity is skewed and dominated by a few highly fecund individuals. Larger plants produce greater seed crops, but the exact nature of the relationship between size and reproductive patterns is poorly understood. This is especially clear in plants that reproduce by exhibiting synchronized quasi-periodic variation in fruit production, a process called masting. Methods We investigated covariation of plant size and fecundity with individual-plant-level masting patterns and seed predation in 12 mast-seeding species: Pinus pinea, Astragalus scaphoides, Sorbus aucuparia, Quercus ilex, Q. humilis, Q. rubra, Q. alba, Q. montana, Chionochloa pallens, C. macra, Celmisia lyallii and Phormium tenax. Key Results Fecundity was non-linearly related to masting patterns. Small and unproductive plants frequently failed to produce any seeds, which elevated their annual variation and decreased synchrony. Above a low fecundity threshold, plants had similar variability and synchrony, regardless of their size and productivity. Conclusions Our study shows that within-species variation in masting patterns is correlated with variation in fecundity, which in turn is related to plant size. Low synchrony of low-fertility plants shows that the failure years were idiosyncratic to each small plant, which in turn implies that the small plants fail to reproduce because of plant-specific factors (e.g. internal resource limits). Thus, the behaviour of these sub-producers is apparently the result of trade-offs in resource allocation and environmental limits with which the small plants cannot cope. Plant size and especially fecundity and propensity for mast failure years play a major role in determining the variability and synchrony of reproduction in plants

Does masting scale with plant size? High reproductive variability and low synchrony in small and unproductive individuals

Centro de Investigación Forestal (CIFOR)In a range of plant species, the distribution of individual mean fecundity is skewed and dominated by a few highly fecund individuals. Larger plants produce greater seed crops, but the exact nature of the relationship between size and reproductive patterns is poorly understood. This is especially clear in plants that reproduce by exhibiting synchronized quasi-periodic variation in fruit production, a process called masting.The study was supported by the Polish National Science Centre (2017/24/C/NZ8/00151), the Polish State Committee for Scientific Research (6 P04G 045 21, 3 P04G 111 25), the Polish Ministry of Science and Higher Education (N304 362938), the US National Science Foundation (DEB 165511, DEB-02-40963, DEB-05-15756, DEB-10-20889, DBI-9978807, DEB-0642594, DEB-1556707), the Wilkes University Fenner Endowment, USDA/NIFA grant 2017-03807, the Hatch Act (225165) through the USDA National Institute of Food and Agriculture, PROPINEA (CC-16-095, AGL-2017-83828-C2), FORASSEMBLY (CGL2015-70558-P), BEEMED (SGR913) and a Marsden Fund grant (UOC1401).Peer reviewed9 Pág