Predicting plastic responses is crucial to assess plant species potential to adapt to climate change, but little is known about which factors drive the biogeographical patterns of phenotypic ...plasticity in plants. Theory predicts that climatic variability would select for increased phenotypic plasticity, whereas evidence indicates that stressful conditions can limit phenotypic plasticity. Using a meta‐analytic, phylogeny‐corrected approach to global data on plant phenotypic plasticity, we tested whether latitude, climate, climatic variability and/or stressful conditions are predictors of plastic responses at a biogeographical scale. We found support for a positive association between phenotypic plasticity and climatic variability only for plasticity in allocation. Plasticity in leaf morphology, size and physiology were positively associated with mean annual temperature. We also found evidence that phenotypic plasticity in physiology is limited by cold stress. Overall, plant plastic responses to non‐climatic factors were stronger than responses to climatic factors. However, while climatic conditions were associated with plant plastic responses to climatic factors, they generally did not relate to plastic responses to other abiotic or biotic factors. Our study highlights the need to consider those factors that favour and limit phenotypic plasticity in order to improve predictive frameworks addressing plant species’ potential to adapt to climate change.
Studies on plant phenotypic plasticity have long focused on climatic variability as the main predictor, but there is a need to also consider factors that may limit phenotypic plasticity. This study found some evidence supporting the positive association between climatic variability and phenotypic plasticity in plants. More importantly, however, it also shows that phenotypic plasticity is positively associated with mean annual temperature, with some evidence of limits to phenotypic plasticity under cold conditions.
Invasive species can alter the structure and function of the communities they invade, as well as lead to biotic homogenization across their invasive range, thus affecting large-scale diversity ...patterns. The mechanisms by which invasive species can lead to biotic homogenization are poorly understood. We argue that invasive species acting as strong, deterministic, and consistent filters within and across invaded communities are likely to cause biotic homogenization at multiple spatial scales. We studied Bromus inermis Leyss. invasion into eight grasslands covering most of the grassland and parkland natural regions of Alberta (western Canada). Specifically, we tested whether B. inermis (1) has a strong impact on species richness and composition, (2) consistently alters resources (nutrients, light, and soil moisture), imposing the same ecological filter to species establishment and persistence across sites, and hence (3) whether it leads to biotic homogenization within and across sites. We recorded plant cover and resources across native-to-invaded transition areas combining space-for-time substitutions with time-series data analyses. Bromus inermis invasion was associated with rapid biotic homogenization of communities, within and among the eight grasslands. The sharp changes in species relative abundances following invasion was the initial driver of biotic homogenization, and species loss was delayed. Supporting the idea that biotic homogenization can occur when an invasive species presents a broad and consistent filter, resources modified by B. inermis invasion (particularly light and certain nutrients) were altered rather consistently within and across sites. The 50% reduction in light was likely the initial driver of biotic homogenization, and the increase in nutrient availability probably facilitates the displacement of species from the invaded areas and could lead to the establishment of self-reinforcing dynamics. Overall, our results support the idea that invaders acting as strong, deterministic, and consistent ecological filters are likely to cause biotic homogenization of the communities they invade.
Indirect facilitation among exotic species may promote their establishment on ecosystems, causing biodiversity losses. However, few experimental studies have identified the mechanisms underlying the ...indirect facilitation among exotic species. In central-northern Chile,
Mesembryanthemum crystallinum
(Aizoaceae) is an exotic halophyte that increases soil salinity, while
M. nodiflorum
is another exotic halophyte –currently less dominant– that often co-occurs with
M. crystallinum
. In this study, we evaluated the indirect facilitation of
M. nodiflorum
by
M. crystallinum
which was mediated by the suppression of salt-susceptible native competitors via increased soil salinity. We further determined the relationship between salt-tolerance traits and the outcome of competitive interactions in saline soil. We included two native Asteraceae plants co-occurring with these
Mesembryanthemum
species: the –highly probable– salt-susceptible
Helenium urmenetae
and the salt-tolerant
Amblyopappus pusillus
. We combined field co-occurrence surveys with greenhouse germination and competition experiments. The
Mesembryanthemum
species tended to co-occur, which suggests facilitation. Further, the salinity level found under
M. crystallinum
significantly decreased germination and performance of
H. urmenetae
, but not of
M. nodiflorum
and
A. pusillus
. Accordingly, when in competition, the increased salinity counteracted the negative effect of
H. urmenetae
on
M. nodiflorum
biomass, giving
M. nodiflorum
a competitive advantage. These patterns were associated with decreased specific leaf area and crassulacean acid metabolism expression in
M. nodiflorum
. In contrast,
A. pusillus
and
M. nodiflorum
maintained a neutral interaction regardless of salinity. Overall, our results suggest that
M. crystallinum
, by increasing soil salinity, may reduce the performance of salt-susceptible competitors, indirectly facilitating the establishment of
M. nodiflorum
.
Phenotypic plasticity is a key mechanism by which plants respond to changing or heterogeneous conditions. Efforts to predict phenotypic plasticity across plant species have mainly focused on ...environmental variability or abiotic conditions, i.e. site characteristics. However, the considerable variation in phenotypic plasticity within sites calls for alternative approaches. Different functional groups are thought to differ in their plasticity levels. Further, traits such as leaf specific area (SLA), leaf area (LA) and maximum photosynthetic rate (Amax) reflect central aspects of plant strategies. Lower values of SLA, LA and Amax are indicative of a resource‐conservative strategy, which is thought to be associated with lower phenotypic plasticity. We used meta‐analytical data to test whether plant functional group (herbs, woody deciduous and woody evergreens) and SLA, LA and Amax are associated with phenotypic plasticity in four trait types: biomass allocation, plant size, leaf morphology and physiology. We obtained data from 168 plant species and accounted for phylogenetic relationships in all analyses. We found a positive relationship between SLA and phenotypic plasticity in biomass allocation, leaf morphology and physiology, with differences across functional groups. In contrast, there was no evidence of greater plasticity in plant size in species with higher SLA; rather the opposite was true for woody evergreens. Amax and LA showed similar, but less consistent associations with phenotypic plasticity. Our results show the potential of building predictive frameworks for phenotypic plasticity based on easily measured plant functional characteristics. Results also provide insights into plant strategies and suggest the existence of potential compromises: resource‐conservative, low‐SLA species tend to be more stress‐tolerant but may be less able to cope with variable conditions due to their generally lower phenotypic plasticity. Further studies are needed to explore the mechanisms and the potential implications of this association.
Grime's strategies (competitor, stress tolerator, ruderal; CSR) represent viable trait combinations with which species deal with environmental conditions. CSR strategies are broadly used to ...understand plant adaptation to the environment, yet their plastic responses have received little attention. A globally‐calibrated tool (StrateFy) estimates CSR strategies using specific leaf area (SLA), leaf dry matter content (LDMC) and leaf area (LA) data, but these three traits can hardly characterise whole‐plant responses to the environment individually. CSR strategies reflect tradeoffs among growth, survival and reproduction, at both leaf and whole‐plant levels, thus integrating several functions. We hypothesised that CSR strategies and the three constituent traits would show independent plasticity patterns, and that CSR strategies would be more likely to show adaptive responses, i.e. to fit expected functional responses to environmental gradients. We compared phenotypic plasticity to drought in single traits (SLA, LDMC and LA) with the integrated plasticity of the resulting CSR strategy. The study species was the invasive plant
Mesembryanthemum crystallinum
, which is distributed in arid and semiarid Chile. We found that trait plasticity was rather idiosyncratic and contrary to what would be expected from a functional adjustment to drought: LDMC did not change (expected response: increase) and SLA increased (expected response: decrease). Conversely, plastic responses of CSR strategy and LA were consistent with functionally adaptive responses to drought in all populations: S‐strategy increased, while C‐strategy and LA decreased. We advocate the use of Grime's CSR theory as an integrative approach to further our understanding of adaptive plasticity in plants.
Kelp forests provide habitat and resources to diverse organisms and provide valuable ecosystem services. However, marine deforestation due to wild kelp harvesting, among other drivers, is being ...observed worldwide. Studies assessing kelp removal effects often focus on the effects on kelp populations, although deforestation also impacts the organisms that interact directly or indirectly with kelp, including herbivores and algal assemblages. Using a meta-analytical approach, we estimated the magnitude and direction of kelp removal effects on kelp, invertebrate herbivores, and understory algae. We also tested if responses varied among functional groups of understory algae and whether results were influenced by the subtidal or intertidal distribution of the removed kelp species and the time elapsed since kelp removal. We observed a substantial decrease in kelp abundance, remaining for up to 4 years following kelp removal, with a larger decrease in subtidal kelp but no recovery observed in intertidal kelp over time. Invertebrate herbivore abundance showed no significant change over time. Understory algae abundance responded positively, although this effect tended to slightly decline over time following subtidal kelp removal. Canopy-, turf-forming and foliose algae were the most benefited, which raises concern about their potential to outcompete kelp. The early succession patterns and cascading effects within kelp forests illustrated here highlight the need for long-term studies to elucidate the long-lasting effects of kelp fisheries, which are scarce at present. There is also a need to consider kelp forests’ role in providing habitat and resources to improve predictive frameworks allowing kelp forest conservation and sustainable fisheries.
•Wild kelp harvesting triggers bottom-up effects in kelp forests communities.•First meta-analyses to quantify community effects of kelp removal over time.•Opposite trends of kelp recovery following intertidal and subtidal kelp removal.•Changing effects on understory algae abundance were observed over time.•Multi-trophic and long-term effects of kelp removal need to be further studied.
Many pathways of invasion have been posited, but ecologists lack an experimental framework to identify which mechanisms are dominant in a given invasion scenario. Plant–soil feedbacks (PSFs) are one ...such mechanism that tend to initially facilitate, but over time attenuate, invasive species' impacts on plant diversity and ecosystem function. PSFs are typically measured under greenhouse conditions and are often assumed to have significant effects under field conditions that change over time. However, direct tests of PSFs effects in natural settings and their change over time are rare. Here we compare the role of PSFs with the effects of biomass in limiting the dominance of an invasive species and impacts on resident species diversity. We characterized the effects of the invader Bromus inermis (Leyss.) on native plant communities over time and measured changes in its conspecific PSFs and vegetative growth to understand their integrated effects on community diversity. To do so, we combined data from a 6‐year field study documenting the rate and impacts of invasion with a short‐term greenhouse experiment quantifying PSF as a function of time since invasion in the field. We found that the nature and strength of B. inermis PSFs did not change over time and were not mediated by soil microbial communities. Though PSFs impacted B. inermis reproduction, they did not sufficiently limit vegetative growth to diminish the negative impacts of B. inermis biomass on native species. B. inermis experienced the full strength of its negative PSFs immediately upon invasion, but they were ineffective at reducing B. inermis vigor to facilitate the recovery of the native plant community. We recommend that conservation efforts focus on limiting B. inermis vegetative growth to facilitate community recovery.
We investigated the role of plant–soil feedbacks (PSFs) and biomass in limiting the dominance of the invasive species Bromus inermis. We found that though PSFs affected B. inermis reproduction, they did not reduce its vegetative growth or its negative effects on native species diversity over time. We suggest conservation efforts should prioritize controlling B. inermis vegetative growth to aid native community recovery.
Aridity is increasing in many regions of the world, but microclimatic conditions may buffer plant communities from the direct effects of decreased precipitation, creating habitat islands. However, ...reduced precipitation can also impact these communities indirectly by decreasing the suitability of the surrounding habitat, thus limiting incoming propagules and increasing the chances of population decline and species loss. We test whether decreased precipitation results in loss of species and functional diversity within habitat islands, evaluating in particular whether declines in species diversity and abundance are less likely to result in loss of functional diversity if species/individual loss is stochastic (i.e. independent of species/individual traits) and communities/populations are functionally redundant.
Lomas communities are discrete plant communities embedded in the Atacama Desert, maintained by the microclimatic conditions created by fog. We recorded species and functional diversity in six Lomas communities along a 500 km long precipitation gradient in northern Chile. Functional traits were measured in 20 individuals per species, in those species that accounted for approx. 75 % of the abundance at each site. We calculated functional diversity and functional redundancy of the community, and intraspecific functional variation.
Decreased precipitation was associated with lower species diversity and lower species abundances. However, no traits or functional strategies increased or decreased consistently with precipitation, suggesting stochastic species/individual loss. Species with stress-tolerant strategies were predominant in all sites. Although species diversity decreased with decreasing precipitation, functional diversity remained unchanged. Lower functional redundancy in the drier sites suggests that mainly functionally redundant species were lost. Likewise, intraspecific functional variation was similar among communities, despite the lower species abundance in drier sites.
Decreased precipitation can impact habitat island communities indirectly by decreasing the suitability of the surrounding habitat. Our results support the idea that a stochastic loss of species/individuals from functionally redundant communities and populations does not result in loss of functional diversity.
Livestock production is an important activity in drylands. However, lack of adequate regulation of ranching activities can lead to the degradation of plant communities, which in turn can impact ...ecosystem functioning. In the arid ecosystems of north‐central Chile, unregulated goat grazing is widespread. Because the vegetation has a relatively short evolutionary history of grazing, it is expected to be highly susceptible to this activity. In this study, we evaluated the effects of goat grazing on plant taxonomic, functional, and phylogenetic community structure by comparing 39‐year‐old grazing exclusion plots and unprotected plots in an arid shrubland in north‐central Chile. By integrating analyses of the impact of goat grazing on functional and phylogenetic diversity and dispersion, we studied the mechanisms behind goat impact and the potential consequences. Loss of functional and/or phylogenetic diversity can result in important losses in ecosystem function. As a measure of functional diversity, we recorded plant growth form, life span, and life form. We also reconstructed a phylogeny of all plant species found at the study site and determined the phylogenetic structure of the plant community in ungrazed and grazed areas. We found that goat grazing affected diversity and community composition, leading to taxonomic, functional, and phylogenetic biotic homogenization and causing overall community impoverishment. Goats acted as a habitat filter, increasing functional convergence and promoting the establishment of exotics plants, which can lead to further losses of biodiversity, decreased ecosystem function and overall lower ecosystem stability. Our results indicate that sustainable management strategies are necessary to prevent the further degradation of these ecosystems.
High-elevation ecosystems are traditionally viewed as environments in which predominantly autogamous breeding systems should be selected because of the limited pollinator availability. Chaetanthera ...renifolia (Asteraceae) is an endemic monocarpic triennial herb restricted to a narrow altitudinal range within the high Andes of central Chile (3300-3500 m a.s.l.), just below the vegetation limit. This species displays one of the larger capitulum within the genus. Under the reproductive assurance hypothesis, and considering its short longevity (monocarpic triennial), an autogamous breeding system and low levels of pollen limitation would be predicted for C. renifolia. In contrast, considering its large floral size, a xenogamous breeding system, and significant levels of pollen limitation could be expected. In addition, the increased pollination probability hypothesis predicts prolonged stigma longevity for high alpine plants. We tested these alternative predictions by performing experimental crossings in the field to establish the breeding system and to measure the magnitude of pollen limitation in two populations of C. renifolia. In addition, we measured the stigma longevity in unpollinated and open pollinated capitula, and pollinator visitation rates in the field. We found low levels of self-compatibility and significant levels of pollen limitation in C. renifolia. Pollinator visitation rates were moderate (0.047-0.079 visits per capitulum per 30 min). Although pollinator visitation rate significantly differed between populations, they were not translated into differences in achene output. Finally, C. renifolia stigma longevity of unpollinated plants was extremely long and significantly higher than that of open pollinated plants (26.3±2.8 days vs. 10.1±2.2, respectively), which gives support to the increased pollination probability hypothesis for high-elevation flowering plants. Our results add to a growing number of studies that show that xenogamous breeding systems and mechanisms to increase pollination opportunities can be selected in high-elevation ecosystems.
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