Plant Life History Research Articles

Can Functional Traits Explain Plant Coexistence? A Case Study with Tropical Lianas and Trees

Organisms are adapted to their environment through a suite of anatomical, morphological, and physiological traits. These functional traits are commonly thought to determine an organism’s tolerance to environmental conditions. However, the differences in functional traits among co-occurring species, and whether trait differences mediate competition and coexistence is still poorly understood. Here we review studies comparing functional traits in two co-occurring tropical woody plant guilds, lianas and trees, to understand whether competing plant guilds differ in functional traits and how these differences may help to explain tropical woody plant coexistence. We examined 36 separate studies that compared a total of 140 different functional traits of co-occurring lianas and trees. We conducted a meta-analysis for ten of these functional traits, those that were present in at least five studies. We found that the mean trait value between lianas and trees differed significantly in four of the ten functional traits. Lianas differed from trees mainly in functional traits related to a faster resource acquisition life history strategy. However, the lack of difference in the remaining six functional traits indicates that lianas are not restricted to the fast end of the plant life–history continuum. Differences in functional traits between lianas and trees suggest these plant guilds may coexist in tropical forests by specializing in different life–history strategies, but there is still a significant overlap in the life–history strategies between these two competing guilds.

Bringing Botany into Focus: Addressing Plant Blindness in Undergraduates Through an Immersive Botanical Experience

Abstract Undergraduate science, technology, engineering, and math students (STEM) are usually not attuned to the intricacies of plant life histories or to the dynamic role plants play in ecosystems and human society, a phenomenon termed plant blindness. Botany education has declined in the past decades, whereas career paths that need and benefit from a workforce with botanical knowledge have increased. Consequently, there is a need to reduce plant blindness among undergraduate students, regardless of their career trajectories. We provide evidence that participation in a botanical experience as part of a general biology course can positively shift undergraduates’ perception of botany, the study of plants. Students participating in the botanical experience showed significant positive shifts in their ability to connect botany to their college major and future careers. In addition, we show qualitative data indicating a new respect for plants and a new appreciation for the diversity among plants.

Life history variation in an invasive plant is associated with climate and recent colonization of a specialist herbivore.

Spatial variation in selective pressures can lead to intraspecific variation in life history, favoring some life histories and constraining others depending on the vulnerability of life stages. We examined how spatial variation in herbivory and climate influences flowering size and the occurrence of semelparity (reproducing once) versus iteroparity (reproducing multiple times) in the introduced range of an invasive plant, houndstongue (Cynoglossum officinale). Houndstongue is a short-lived, semelparous perennial in its native range. In its introduced range, we previously documented increased rates of iteroparity and a higher median threshold flowering size compared to the native range. We hypothesized that the recent introduction of a specialist biocontrol insect (a root-boring weevil, Mogulones crucifer) would decrease threshold flowering size and reduce the proportion of iteroparous plants because M. crucifer preferentially attacks large individuals and may reduce overwinter survival. We surveyed 24 sites across the northwestern United States to quantify the frequency of semelparity versus iteroparity and to estimate weevil abundance and used demographic data collected from six sites to estimate median threshold flowering size. We found that sites with greater winter precipitation and no weevils had a greater proportion of iteroparous plants. Sites with higher weevil attack had a lower median threshold flowering size. The variation in frequency of flowering and threshold flowering size that we documented in North American houndstongue populations, and the relationships between this variation and herbivory and climate, provide evidence for how selective pressures covary with the life histories of invasive plants.

Optimal resource allocation and prolonged dormancy strategies in herbaceous plants

Abstract Understanding the fitness consequences of different life histories is critical for explaining their diversity and for predicting effects of changing environmental conditions. However, current theory on plant life histories relies on phenomenological, rather than mechanistic, models of resource production. We combined a well‐supported mechanistic model of ontogenetic growth that incorporates differences in the size‐dependent scaling of gross resource production and maintenance costs with a dynamic optimization model to predict schedules of reproduction and prolonged dormancy (plants staying below ground for ≥1 growing season) that maximize lifetime offspring production. Our model makes three novel predictions: First, maintenance costs strongly influence the conditions under which a monocarpic or polycarpic life history evolves and how resources should be allocated to reproduction by polycarpic plants. Second, in contrast to previous theory, our model allows plants to compensate for low survival conditions by allocating a larger proportion of resources to storage and thereby improving overwinter survival. Incorporating this ecological mechanism in the model is critically important because without it our model never predicts significant investment into storage, which is inconsistent with empirical observations. Third, our model predicts that prolonged dormancy may evolve solely in response to resource allocation trade‐offs. Significance. Our findings reveal that maintenance costs and the effects of resource allocation on survival are primary determinants of the fitness consequences of different life history strategies, yet previous theory on plant life history evolution has largely ignored these factors. Our findings also validate recent arguments that prolonged dormancy may be an optimal response to costs of sprouting. These findings have broad implications for understanding patterns of plant life history variation and predicting plant responses to changing environments.

Effects of light availability and seed size on germination and initial growth of two congeneric species of Fabaceae

Background and Aims: Environmental factors can interact with plant life history to determinate the reproductive strategies of adult plants and seedling recruitment. We expect that widely distributed tree species produce heavier seed and with greater variation in seed size than shrubs of restricted geographic distribution. We also predict that widely distributed tree species should be capable to germinate and develop under variable range of light conditions, while sun-adapted shrubs should germinate and develop better under high light intensity. We used as models two congeneric species of Fabaceae. Copaifera langsdorffii is a widely distributed arboreal species and C oblongifolia is a shrub with restricted distribution. Methods: Seeds were collected from two plant species in a Cerrado vegetation area, northern Minas Gerais, Brazil. The effects of light available on seed germination and seedling development was conducted in a germination chamber with controlled photoperiod, temperature and light intensity.Key results: The widely distributed tree (C. langsdorffii) had greater seed mass than the shrub (C. oblongifolia). Seeds of C. langsdorffii germinated faster under available high light, while the shrub C. oblongifolia seeds required less time to germinate under available low light and darkness. Under high light intensity, germination percentage of C. langsdorffii and C. oblongifolia seeds did not vary. However, seeds of the shrub showed a higher germination percentage under low light intensity and darkness. In general, seed mass showed a negative relationship with germination percentage, but this relationship varied in function of species and the availability of light. Copaifera langsdorffii seedlings had larger shoots and roots than C. oblongifolia. In contrast, the root:shoot ratio was higher in shrub than in tree species.Conclusions: Our results have important implications for understanding the patterns of distribution of two Copaifera species and explain the ability of C. oblongifolia to colonize disturbed areas.

Plant traits and vegetation data from climate warming experiments along an 1100\u2009m elevation gradient in Gongga Mountains, China

Functional trait data enhance climate change research by linking climate change, biodiversity response, and ecosystem functioning, and by enabling comparison between systems sharing few taxa. Across four sites along a 3000–4130 m a.s.l. gradient spanning 5.3 °C in growing season temperature in Mt. Gongga, Sichuan, China, we collected plant functional trait and vegetation data from control plots, open top chambers (OTCs), and reciprocally transplanted vegetation turfs. Over five years, we recorded vascular plant composition in 140 experimental treatment and control plots. We collected trait data associated with plant resource use, growth, and life history strategies (leaf area, leaf thickness, specific leaf area, leaf dry matter content, leaf C, N and P content and C and N isotopes) from local populations and from experimental treatments. The database consists of 6,671 plant records and 36,743 trait measurements (increasing the trait data coverage of the regional flora by 500%) covering 11 traits and 193 plant taxa (ca. 50% of which have no previous published trait data) across 37 families.

Amphicarpic plants: definition, ecology, geographic distribution, systematics, life history, evolution and use in agriculture.

ABSTRACTAlthough most plants produce all of their fruits (seeds) aboveground, amphicarpic species produce fruits (seeds) both above‐ and belowground. Our primary aims were to determine the number of reported amphicarpic species and their taxonomic, geographic, life form and phylogenetic distribution, to evaluate differences in the life history of plants derived from aerial and subterranean seeds, to discuss the ecological and evolutionary significance of amphicarpy, to explore the use of amphicarpic plants in agriculture, and to suggest future research directions for studies on amphicarpy. Amphicarpy occurs in at least 67 herbaceous species (31 in Fabaceae) in 39 genera and 13 families of angiosperms distributed in various geographical regions of the world and in various habitats. Seeds from aerial and subterranean fruits differ in size/mass, degree of dormancy, dispersal and ability to form a persistent seed bank, with aerial seeds generally being smaller, more dormant and more likely to be dispersed and to form a seed bank than subterranean seeds. In addition, plants produced by aerial and subterranean seeds may differ in survival and growth, competitive ability and biomass allocation to reproduction. Amphicarpic plants may exhibit a high degree of plasticity during reproduction. Subterranean fruits are usually formed earlier than aerial ones, and plants may produce only subterranean propagules under stressful environmental conditions. Differences in the life histories of plants from aerial and subterranean seeds may be an adaptive bet‐hedging strategy.

Reaching similar goals by different means – Differences in life-history strategies of clonal and non-clonal plants

Clonality is a largely underexplored plant life-history trait with possibly profound effects on plant demography. Clonal growth constitutes an alternative reproductive pathway, which should provide clonal species with an advantage over non-clonal ones under disturbance regimes unfavourable to regeneration from seeds.We investigated how clonal and non-clonal species differ in their life histories (other than clonality) and how this relates to disturbance regimes where the studied species occur. Further, we focused on the contribution of clonality to fluctuations in the populations of species and the importance of clonality for the life cycle of a species in relation to its other life-history characteristics. We achieved this through phylogenetically informed analyses of the matrix population models available from the COMPADRE database coupled with information on species clonality from the CLO-PLA database.The phylogenetic principal component analysis revealed that plant life-history characteristics could be aligned along two gradients. The gradient of generation time and individual turnover in populations was more important and corresponded to the frequency of habitat disturbance. Clonal species on average had populations with lower overall rates of individual turnover and disturbance frequencies. The second gradient was correlated with disturbance severity and plant ability to regenerate after the loss of biomass. The importance of clonal growth for the life cycle of a clonal species increased with more severe disturbance events. The fluctuation of population growth rates depended on the life-history characteristics of a species but not on clonality. The net effect of clonal growth on the fluctuations of the populations of a species was positive.In general, clonality seems to provide an important alternative for adjusting plant life history to the disturbance regime and other site conditions allowing a plant to circumvent its morphological or developmental constraints. Clonal growth turned out to be mainly a mechanism that enables population expansion under favourable conditions rather than a mechanism that buffers the effects of adverse conditions.

Silica entry and accumulation in standing trees in a hot‐spring environment: cellular pathways, rapid pace and fossilization potential

AbstractSilicification is the most important process of fossilization resulting in the preservation of internal tissues in plants, thereby providing essential information on the anatomy, life history, and evolution of land plants. However, fundamental knowledge of silica uptake, precipitation, and contribution to in situ plant fossilization is limited. To identify the cellular pathway of aqueous silica and subsequent fluid–wood interaction processes, we investigated upright standing young trees of lodgepole pine (Pinus contorta) in the hot‐spring environment of Cistern Spring, Yellowstone National Park, USA. Our multi‐method analytical approach using x‐ray diffraction, Raman spectroscopy, scanning electron microscopy, and electron probe microanalyses shows that the surficial and internally co‐precipitated silica–halite–gypsum assemblage traces the flow of silica‐rich fluid and documents fluid retention after short‐term hot‐spring water immersion and evaporation. Element distribution maps reveal systematic 2D and 3D differences between silica quantities deposited in earlywood and latewood. The distribution of inorganic impurities in cell walls traces the anatomical structure of the wood and indicates rapid migration of homogeneous fluid into the waterlogged organic substrate. Our results show that the preferential pathway of silica‐rich fluid into the above‐ground wood was through the decorticated periphery which took place during a short‐term flooding, ranging from days to weeks, of hot‐spring fluid. In conclusion, the fluid retention capability in cellular pore space controls the in situ silicification process. The silicification of trees in growth position is a rapid process in which the in vivo transport of silica‐rich fluid upward through the secondary xylem plays an insignificant role.

A phylogenomic approach reveals a low somatic mutation rate in a long-lived plant.

Somatic mutations can have important effects on the life history, ecology, and evolution of plants, but the rate at which they accumulate is poorly understood and difficult to measure directly. Here, we develop a method to measure somatic mutations in individual plants and use it to estimate the somatic mutation rate in a large, long-lived, phenotypically mosaic Eucalyptus melliodora tree. Despite being 100 times larger than Arabidopsis, this tree has a per-generation mutation rate only ten times greater, which suggests that this species may have evolved mechanisms to reduce the mutation rate per unit of growth. This adds to a growing body of evidence that illuminates the correlated evolutionary shifts in mutation rate and life history in plants.

Functional Trait Variation Among and Within Species and Plant Functional Types in Mountainous Mediterranean Forests.

Plant structural and biochemical traits are frequently used to characterise the life history of plants. Although some common patterns of trait covariation have been identified, recent studies suggest these patterns of covariation may differ with growing location and/or plant functional type (PFT). Mediterranean forest tree/shrub species are often divided into three PFTs based on their leaf habit and form, being classified as either needleleaf evergreen (Ne), broadleaf evergreen (Be), or broadleaf deciduous (Bd). Working across 61 mountainous Mediterranean forest sites of contrasting climate and soil type, we sampled and analysed 626 individuals in order to evaluate differences in key foliage trait covariation as modulated by growing conditions both within and between the Ne, Be, and Bd functional types. We found significant differences between PFTs for most traits. When considered across PFTs and by ignoring intraspecific variation, three independent functional dimensions supporting the Leaf-Height-Seed framework were identified. Some traits illustrated a common scaling relationship across and within PFTs, but others scaled differently when considered across PFTs or even within PFTs. For most traits much of the observed variation was attributable to PFT identity and not to growing location, although for some traits there was a strong environmental component and considerable intraspecific and residual variation. Nevertheless, environmental conditions as related to water availability during the dry season and to a smaller extend to soil nutrient status and soil texture, clearly influenced trait values. When compared across species, about half of the trait-environment relationships were species-specific. Our study highlights the importance of the ecological scale within which trait covariation is considered and suggests that at regional to local scales, common trait-by-trait scaling relationships should be treated with caution. PFT definitions by themselves can potentially be an important predictor variable when inferring one trait from another. These findings have important implications for local scale dynamic vegetation models.

Hanging in there: Aloe lettyae populations in Critically Endangered grassland fragments

This is the first study documenting the distribution and population biology of the Endangered Aloe lettyae, an endemic to the highly threatened Woodbush Granite Grassland (WGG) in Limpopo Province, South Africa. We documented 19 A. lettyae populations and calculated the total area of occupied habitat at 17.5 ha within its extent of occurrence of 123 km2. Most populations were clustered on the south western side of the WGG, with all known localities less than 40 km apart in this severely fragmented vegetation type. Population size varied from 10 to 6547 plants, with ∼10,800 individuals estimated in total. Plant size and life history stage demographics were determined in seven of the 19 currently known A. lettyae populations, including two large populations, as well as a high- and a low-lying population, and constituted a representative sample of the entire geographical range of the species. For plant size, four metrics (number of leaves, number of leaf layers, height and diameter of the leaf rosette) were recorded for each sampled A. lettyae plant, and the presence of an inflorescence indicated its reproductive status. By means of the classification tree technique CHAID (Chi-square Automatic Interaction Detection), we determined that of the four plant size metrics, the ‘number of leaves’ predicts A. lettyae’s life history stages and fecundity most accurately, and revealed significant differences in the life history stage structure of the seven surveyed populations. Five populations occurring in relatively undisturbed WGG fragments, including the two large populations, comprised high proportions of adult individuals (77–89%), while only few A. lettyae juveniles were found (3–14%). By contrast, the relatively high percentage of juveniles (25–58%) and low percentage of adults (32–63%) observed in two small populations found in a degraded WGG fragment and in non-natural habitat respectively, appeared atypical. The percentage of subadults varied little across the surveyed populations (8–13%). In slow-growing, long-lived species such as A. lettyae, the dominance of adult individuals with a high probability of survival may be considered as indicative of stable populations. This study provides baseline A. lettyae population data for long-term demographic monitoring which will aid management and conservation of the range restricted, Endangered A. lettyae.

Life History Variation as a Model for Understanding Trade-Offs in Plant-Environment Interactions.

All plants must allocate limited resources to survival, growth, and reproduction. In natural species, allocation strategies reflect trade-offs between survivorship risk and subsequent fitness benefits and are therefore central to a species' ecology. Artificial selection on allocation has generated high-yielding crops that often invest the bare minimum in defense or longevity. Ecological, genetic, and evolutionary analyses of plant life history - particularly with respect to longevity and resource allocation along an axis from annual to perennial species - provides a framework to evaluate trade-offs in plant-environment interactions in natural and managed systems. Recent efforts to develop new model plant systems for research and to increase agricultural resilience and efficiency by developing herbaceous perennial crops motivates our critical assessment of traditional assumptionsregarding differences between annual and perennial plant species. Here, we review our present understanding of the genetic basis of physiological, developmental, and anatomical differences in wild and crop species and reach two broad conclusions. First, that perenniality and annuality should be considered syndromes comprised of many interacting traits, and that elucidating the genetic basis of these traits is required to assess models of evolution and to develop successful breeding strategies. Modern phenomic and biotechnology tools will facilitate these enquiries. Second, many classic assumptions about the difference between the two syndromes are supported by limited evidence. Throughout this Review, we highlight key knowledge gaps in the proximate and ultimate mechanisms driving life history variation, and suggest empirical approaches to parameterize trade-offs and to make progress in this critical area of direct relevance to ecology and plant performance in a changing world.

Unique bacterial assembly, composition, and interactions in a parasitic plant and its host.

How plant-associated microbiota are shaped by, and potentially contribute to, the unique ecology and heterotrophic life history of parasitic plants is relatively unknown. Here, we investigate the leaf and root bacterial communities of the root holoparasite Orobanche hederae and its host Hedera spp. from natural populations. Root bacteria inhabiting Orobanche were less diverse, had fewer co-associations, and displayed increased compositional similarity to leaf bacteria relative to Hedera. Overall, Orobanche bacteria exhibited significant congruency with Hedera root bacteria across sites, but not the surrounding soil. Infection had localized and systemic effects on Hedera bacteria, which included effects on the abundance of individual taxa and root network properties. Collectively, our results indicate that the parasitic plant microbiome is derived but distinct from the host plant microbiota, exhibits increased homogenization between shoot and root tissues, and displays far fewer co-associations among individual bacterial members. Host plant infection is accompanied by modest changes of associated microbiota at both local and systemic scales compared with uninfected individuals. Our results are a first step towards extending the growing insight into the assembly and function of the plant microbiome to include the ecologically unique but often overlooked guild of heterotrophic plants.

Fire can promote germination, recruitment and seed bank accumulation of the threatened annual grass Arthraxon hispidus

Disturbance plays an important role in plant life history strategies and has been documented as both enhancing and threatening populations of the vulnerable grass Arthraxon hispidus (Thunb.) Makino (hairy jointgrass) on the NSW north coast. Mechanical disturbance (slashing) is often used in A. hispidus conservation management, but many Australian plants are adapted to fire-based disturbance regimes. In this study we undertook a field burning experiment, along with soil seed bank sampling and germination trials, to explore how fire influences A. hispidus population dynamics in terms of plant recruitment and seed bank fluctuations. We found that winter burning strongly promoted A. hispidus spring germination without entirely depleting the residual seedbank. Although drought affected our field study population, burning also led to increased adult cover and substantial seed bank replenishment the following autumn. Exposure to a smoke treatment almost doubled the germination rate of A. hispidus seeds in nursery trials. Our study suggests that appropriate burning regimes can help to maintain this species in the landscape, by both structural and chemical mechanisms, by enhancing plant recruitment and facilitating seed bank accumulation. However, some A. hispidus plants also successfully germinated, established, and reproduced in unburnt plots during our study, suggesting that populations of this species can persist without disturbance in some habitats, such as native wetland communities. We found that A. hispidus has a multi-year seed longevity and a persistent seed bank, providing the species a degree of resilience in the event of unpredictable disturbance regimes and climatic anomalies.

Cross‐scale drivers of plant trait distributions in a fragmented forest landscape

During community assembly, plant functional traits are under selective pressure from processes operating at multiple spatial scales. However, in fragmented landscapes, there is little understanding of the relative importance of local‐, patch‐ and landscape‐scale processes in shaping trait distributions. Here, we investigate cross‐scale influences of landscape change on traits that dictate plant life history strategies in re‐assembling plant communities in a fragmented landscape in eastern China. Using forest dynamics plots (FDPs) on 29 land‐bridge islands in which all woody plants have been georeferenced and identified to species, we characterized and derived two composite measures of trait variation, representing variation across the leaf economics spectrum and plant size. We then tested for trait shifts in response to local‐, patch‐ and landscape‐scale factors, and their potential cross‐scale interactions. We found substantial community‐wide trait changes along local‐scale gradients (i.e. forest edge to interior): more acquisitive leaf economic traits and larger sized species occurred at edges, with a significant increase in trait means and trait range. Moreover, there were significant cross‐scale interaction effects of patch and landscape variables on local‐scale edge effects. Altered spatial arrangement of habitat in the surrounding landscape (i.e. declining habitat amount and increasing patch density), as well as decreasing area at the patch level, exacerbated edge effects on traits distributions. We suggest that synergistic interactions of landscape‐ and patch‐scale processes, such as dispersal limitation, on local‐scale environmental filtering at edges, together shape the spatial distributions of plant life history strategies in fragmented plant communities.

Correlates of hybridization in plants.

Hybridization is a biological phenomenon increasingly recognized as an important evolutionary process in both plants and animals, as it is linked to speciation, radiation, extinction, range expansion and invasion, and allows for increased trait diversity in agricultural and horticultural systems. Estimates of hybridization frequency vary across taxonomic groups, but causes of this variation are unknown. Here, we ask on a global scale whether hybridization is linked to any of 11 traits related to plant life history, reproduction, genetic predisposition, and environment or opportunity. Given that hybridization is not evenly distributed across the plant tree of life, we use phylogenetic generalized least squares regression models and phylogenetic path analysis to detect statistical associations between hybridization and plant traits at both the family and genus levels. We find that perenniality and woodiness are each weakly associated with an increased frequency of hybridization in univariate analyses, but path analysis suggests that the direct linkage is between perenniality and increased hybridization (with woodiness having only an indirect relationship with hybridization via perenniality). Weak associations between higher rates of hybridization and higher outcrossing rates, abiotic pollination syndromes, vegetative reproductive modes, larger genomes, and less variable genome sizes are detectable in some cases but not others. We argue that correlational evidence at the global scale, such as that presented here, provides a robust framework for forming hypotheses to examine and test drivers of hybridization at a more mechanistic level.

Sensitivity of dryland plant allometry to climate

Abstract Patterns of plant biomass partitioning are fundamental to estimates of primary productivity and ecosystem process rates. Allometric relationships between above‐ground plant biomass and non‐destructive measures of plant size, such as cover, volume or stem density are widely used in plant ecology. Such size‐biomass allometry is often assumed to be invariant for a given plant species, plant functional group or ecosystem type. Allometric adjustment may be an important component of the short‐ or long‐term response of plants to abiotic conditions. We used 18 years of size‐biomass data describing of 85 plant species to investigate the sensitivity of allometry to precipitation, temperature or drought across two seasons and four ecosystems in central New Mexico, USA. Size‐biomass allometry varied with climate in 65%–70% of plant species. Closely related plant species had similar sensitivities of allometry to natural spatiotemporal variation in precipitation, temperature or drought. Annuals were less sensitive than perennials, and forbs were less sensitive than grasses or shrubs. However, the differences associated with plant life history or functional group were not independent of plant evolutionary history, as supported by the application of phylogenetically independent contrasts. Our results demonstrate that many plant species adjust patterns in the partitioning of above‐ground biomass under different climates and highlight the importance of long‐term data for understanding functional differences among plant species. A free Plain Language Summary can be found within the Supporting Information of this article.

Microhabitats can be recruitment refuges and sinks

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 626:15-27 (2019) - DOI: https://doi.org/10.3354/meps13070 Microhabitats can be recruitment refuges and sinks Paul E. Carnell1,2,*, Michael A. Sams3, Michael J. Keough1 1School of BioSciences, The University of Melbourne, VIC 3010, Australia 2Deakin University, Geelong, Australia. School of Life and Environmental Sciences, Centre for Integrative Ecology, (Burwood Campus), 221 Burwood Highway, Burwood, VIC 3125, Australia 3Environment Protection Authority, Ernest Jones Drive, Macleod, VIC 3085, Australia *Corresponding author: paul.carnell@deakin.edu.au ABSTRACT: Recruitment is an important demographic bottleneck in the life history of many plant and animal species. Microhabitats provided by surfaces or plants or animals can reduce mortality during this critical life-history period. We investigated how microhabitats influence post-settlement processes on a range of ascidians, bryozoans and barnacles. We compared post-settlement mortality and growth on surfaces that were flat or were covered by artificial barnacle mimics or live adult barnacle microhabitats. We also tested whether the effects of surface type changed under different levels of environmental stress by manipulating the orientation of treatments. Orientation had the strongest influence on survival, growth and recruitment, with individuals on downwards-facing surfaces performing the best and those on upwards-facing surfaces with significantly higher mortality. The bryozoan Watersipora subatra had higher survival in microhabitats, but was not influenced by surface orientation. In contrast, barnacles showed increased mortality in microhabitats on upwards-facing panels, but were not affected by other orientations. The presence of adult barnacles caused decreased growth of barnacle recruits, but had no effect on the bryozoan. In comparison, the ascidians (Botryllus sclosseri and Diplosoma listerianum) were mostly not influenced by microhabitats. The high rates of sedimentation on upwards-facing surfaces provide the most plausible answer for the strong influences of surface orientation on survival and growth. While microhabitats can act as refuges for some species, the same microhabitat type can lead to higher mortality in other species. The response of each species to microhabitats ultimately depends on the source of mortality at each site. KEY WORDS: Post-settlement mortality · Habitat characteristics · Settlement · Environmental variability · Ascidian · Bryozoan · Barnacle Full text in pdf format PreviousNextCite this article as: Carnell PE, Sams MA, Keough MJ (2019) Microhabitats can be recruitment refuges and sinks. Mar Ecol Prog Ser 626:15-27. https://doi.org/10.3354/meps13070 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 626. Online publication date: September 12, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Root-associated microorganisms reprogram plant life history along the growth-stress resistance tradeoff.

Growth-defense tradeoffs are a major constraint on plant evolution. While the genetics of resource allocation is well established, the regulatory role of plant-associated microorganisms is still unclear. Here, we demonstrate that plant-associated microorganisms can reposition the plant phenotype along the same growth-defense tradeoff that determines phenotypic effects of plant mutations. We grew plants with microorganisms altering ethylene balance, a key hormone regulating plant investment into growth and stress tolerance. Microbial ethylene reduction had a similar effect to mutations disrupting ethylene signaling: both increased plant growth but at the cost of a strong stress hypersensitivity. We conclude that microbial impact on phenotype can offset the effects of mutations and that apparent plant growth promotion has strong pleiotropic effects. This study confirms that plant life history should be addressed as a joint product of plant genotype and its associated microbiota.