Adler, P. B., HilleRislambers, J., & Levine, J. M. (2007).
A niche for neutrality.
Ecology Letters,
10(2), 95–104.
https://doi.org/10.1111/j.1461-0248.2006.00996.xEcologists now recognize that controversy over the
relative importance of niches and neutrality cannot be resolved by
analyzing species abundance patterns. Here, we use classical coexistence
theory to reframe the debate in terms of stabilizing mechanisms (niches)
and fitness equivalence (neutrality). The neutral model is a special
case where stabilizing mechanisms are absent and species have equivalent
fitness. Instead of asking whether niches or neutral processes structure
communities, we advocate determining the degree to which observed
diversity reflects strong stabilizing mechanisms overcoming large
fitness differences or weak stabilization operating on species of
similar fitness. To answer this question, we propose combining data on
per capita growth rates with models to: (i) quantify the strength of
stabilizing processes; (ii) quantify fitness inequality and compare it
with stabilization; and (iii) manipulate frequency dependence in growth
to test the consequences of stabilization and fitness equivalence for
coexistence. 2007 Blackwell Publishing Ltd/CNRS.
Buchkowski, R. W., Barel, J. M., & Jassey, V. E. J. (2022).
Cannibalism has its limits in soil food
webs.
172(January).
https://doi.org/10.1016/j.soilbio.2022.108773Cannibalism imperfectly recycles resources back to the
same species and so decreases trophic transfer efficiency in food webs.
As such, viable populations have some limit on how much of their diet
can come from cannibalism. We applied a Lotka-Volterra model to derive a
theoretical maximum for the proportion of the diet coming from
cannibalism. This proportion is set by the food conversion efficiency
for both cannibalism and alternative prey. We apply the result to
sixteen published soil food web models and find that cannibalism cannot
exceed 20% of the diet of most organisms, which includes
eating conspecifics that were already dead. However, predators can show
a strong (>80%) preference for cannibalism
because encountering conspecifics is rare. Cannibalism increased carbon
and nitrogen mineralization in fifteen soil food webs and had
non-monotonic effects in the remaining one. Our estimates map a
physiological parameter (conversion efficiency) to an ecological one
(cannibalism) to help to improve model fit and to help soil ecologists
identify taxa where cannibalism may be most important. 1.
Buisson, E., Archibald, S., Fidelis, A., & Suding, K. N. (2022).
Ancient grasslands guide ambitious goals in
grassland restoration.
Science,
377(6606),
594–598.
Grasslands, which constitute almost
40% of the terrestrial biosphere, provide habitat for a
great diversity of animals and plants and contribute to the livelihoods
of more than 1 billion people worldwide. Whereas the destruction and
degradation of grasslands can occur rapidly, recent work indicates that
complete recovery of biodiversity and essential functions occurs slowly
or not at all. Grassland restoration—interventions to speed or guide
this recovery—has received less attention than restoration of forested
ecosystems, often due to the prevailing assumption that grasslands are
recently formed habitats that can reassemble quickly. Viewing grassland
restoration as long-term assembly toward oldgrowth endpoints, with
appreciation of feedbacks and threshold shifts, will be crucial for
recognizing when and how restoration can guide recovery of this globally
important ecosystem.
Feng, Y., Schmid, B., Loreau, M., Forrester, D. I., Fei, S., Zhu, J.,
Tang, Z., Zhu, J., Hong, P., Ji, C., Shi, Y., Su, H., Xiong, X., Xiao,
J., Wang, S., & Fang, J. (2022).
Multispecies
forest plantations outyield monocultures across a broad range of
conditions.
Science,
376(6595), 865–868.
https://doi.org/10.1126/science.abm6363Multispecies tree planting has long been applied in
forestry and landscape restoration in the hope of providing better
timber production and ecosystem services; however, a systematic
assessment of its effectiveness is lacking. We compiled a global dataset
of matched single-species and multispecies plantations to evaluate the
impact of multispecies planting on stand growth. Average tree height,
diameter at breast height, and aboveground biomass were 5.4, 6.8, and
25.5% higher, respectively, in multispecies stands compared
with single-species stands. These positive effects were mainly the
result of interspecific complementarity and were modulated by
differences in leaf morphology and leaf life span, stand age, planting
density, and temperature. Our results have implications for designing
afforestation and reforestation strategies and bridging experimental
studies of biodiversity-ecosystem functioning relationships with
real-world practices.
Huang, Y., Schuldt, A., Hönig, L., Yang, B., Liu, X., Bruelheide, H.,
Ma, K., Schmid, B., & Niklaus, P. A. (2022).
Effects of enemy exclusion on biodiversity–productivity
relationships in a subtropical forest experiment (pp. 0–3).
https://doi.org/10.1111/1365-2745.13940Interspecific niche complementarity is a key mechanism
posited to explain positive species richness–productivity relationships
in plant communities. However, the exact nature of the niche dimensions
that plant species partition remains poorly known. Species may partition
abiotic resources that limit their growth, but species may also be
specialized with respect to their set of biotic interactions with other
trophic levels, in particular with enemies including pathogens and
consumers. The lower host densities present in more species-diverse
plant communities may therefore result in smaller populations of
specialized enemies, and in a smaller associated negative feedback these
enemies exert on plant productivity. To test whether such host
density-dependent effects of enemies drive diversity–productivity
relationships in young forest stands, we experimentally manipulated leaf
fungal pathogens and insect herbivores in a large subtropical forest
biodiversity–ecosystem functioning experiment in China (BEF-China). We
found that fungicide spraying of tree canopies removed the positive
tree-species richness–productivity relationship present in untreated
control plots. The tree species that contributed the most to this effect
were the ones with the highest fungicide-induced growth increase in
monoculture. Insecticide application did not cause comparable effects.
Synthesis. Our findings suggest that tree species diversity may not only
promote productivity by interspecific resource-niche partitioning but
also by trophic niche partitioning. Most likely, partitioning occurred
with respect to enemies such as pathogenic fungi. Alternatively, similar
effects on tree growth would have occurred if fungicide had eliminated
positive effects of a higher diversity of beneficial fungi (e.g.
mycorrhizal symbionts) that may have occurred in mixed tree species
communities.
Klink, R. V., August, T., Bas, Y., Bodesheim, P., Bonn, A., &
Fossøy, F. (2022).
Trends in Ecology
& Evolution Emerging technologies revolutionise insect
ecology and monitoring.
July.
https://doi.org/10.1016/j.tree.2022.06.001
LaManna, J. A., Jones, F. A., Bell, D. M., Pabst, R. J., & Shaw, D.
C. (2022).
Tree species diversity increases with
conspecific negative density dependence across an elevation
gradient.
Ecology Letters,
25(5), 1237–1249.
https://doi.org/10.1111/ele.13996Elevational and latitudinal gradients in species
diversity may be mediated by biotic interactions that cause
density-dependent effects of conspecifics on survival or growth to
differ from effects of heterospecifics (i.e. conspecific density
dependence), but limited evidence exists to support this. We tested the
hypothesis that conspecific density dependence varies with elevation
using over 40 years of data on tree survival and growth from 23
old-growth temperate forest stands across a 1,000-m elevation gradient.
We found that conspecific-density-dependent effects on survival of
small-to-intermediate-sized focal trees were negative in lower
elevation, higher diversity forest stands typically characterised by
warmer temperatures and greater relative humidity.
Conspecific-density-dependent effects on survival were less negative in
higher elevation stands and ridges than in lower elevation stands and
valley bottoms for small-to-intermediate-sized trees, but were neutral
for larger trees across elevations. Conspecific-density-dependent
effects on growth were negative across all tree size classes and
elevations. These findings reveal fundamental differences in biotic
interactions that may contribute to relationships between species
diversity, elevation and climate.
Liu, Y., Speißer, B., Knop, E., & Kleunen, M. van. (2022).
The Matthew effect: Common species become more common and
rare ones become more rare in response to artificial light at
night.
Global Change Biology,
28(11),
3674–3682.
https://doi.org/10.1111/gcb.16126Artificial light at night (ALAN) has been and still is
rapidly spreading and has become an important component of global
change. Although numerous studies have tested its potential biological
and ecological impacts on animals, very few studies have tested whether
it affects alien and native plants differently. Furthermore, common
plant species, and particularly common alien species, are often found to
benefit more from additional resources than rare native and rare alien
species. Whether this is also the case with regard to increasing light
due to ALAN is still unknown. Here, we tested how ALAN affected the
performance of common and rare alien and native plant species in Germany
directly, and indirectly via flying insects. We grew five common alien,
six rare alien, five common native, and four rare native plant species
under four combinations of two ALAN (no ALAN vs. ALAN) and two
insect-exclusion (no exclusion vs. exclusion) treatments, and compared
their biomass production. We found that common plant species,
irrespective of their origin, produced significantly more biomass than
rare species and that this was particularly true under ALAN.
Furthermore, alien species tended to show a slightly stronger positive
response to ALAN than native species did (p =.079). Our study shows that
common plant species benefited more from ALAN than rare ones. This might
lead to competitive exclusion of rare species, which could have
cascading impacts on other trophic levels and thus have important
community-wide consequences when ALAN becomes more widespread. In
addition, the slightly more positive response of alien species indicates
that ALAN might increase the risk of alien plant invasions.
Palmer, M. W. (1994).
Variation in species
richness: towards a unification of hypotheses.
Folia
Geobotanica Et Phytotaxonomica,
29(4), 511–530.
The question, "why do areas vary in species richness’
has been important throughout the history of ecology. It is difficult to
answer definitively because we have so many (at least 120) plausible
hypotheses. This abundance of hypotheses has led to a number of attempts
to classify them. Unfortunately, richness hypotheses often defy such
categorization. Instead of placing species richness hypotheses into
categories, I suggest an alternative approach: to treat species richness
hypotheses as violations of the assuml~ions of Gause’s
Competitive Exclusion Principle. This is a very similar approach to the
pedagogy of population genetics: evolution occurs if and only if at
least one assumption of the Hardy-Weinberg principle is violated. The
classification of hypotheses advocated here treats interspecific
competition as a central organizing concept in community theory.
However, it does not treat competition as an organizing concept in
communities: indeed, the relaxation or disruption of competition is
considered to be the status quo in the majority of conmmnities
Pastore, A. I., Barabás, G., Bimler, M. D., Mayfield, M. M., &
Miller, T. E. (2021).
The evolution of niche
overlap and competitive differences.
Nature Ecology and
Evolution,
5(3), 330–337.
https://doi.org/10.1038/s41559-020-01383-yCompetition can result in evolutionary changes to
coexistence between competitors but there are no theoretical models that
predict how the components of coexistence change during this
eco-evolutionary process. Here we study the evolution of the coexistence
components, niche overlap and competitive differences, in a two-species
eco-evolutionary model based on consumer–resource interactions and
quantitative genetic inheritance. Species evolve along a one-dimensional
trait axis that allows for changes in both niche position and species
intrinsic growth rates. There are three main results. First, the breadth
of the environment has a strong effect on the dynamics, with broader
environments leading to reduced niche overlap and enhanced coexistence.
Second, coexistence often involves a reduction in niche overlap while
competitive differences stay relatively constant or vice versa; in
general changes in competitive differences maintain coexistence only
when niche overlap remains constant. Large simultaneous changes in niche
overlap and competitive difference often result in one of the species
being excluded. Third, provided that the species evolve to a state where
they coexist, the final niche overlap and competitive difference values
are independent of the system’s initial state, although they do depend
on the model’s parameters. The model suggests that evolution is often a
destructive force for coexistence due to evolutionary changes in
competitive differences, a finding that expands the paradox of diversity
maintenance.
Rixen, C., Wipf, S., Rumpf, S. B., Giejsztowt, J., Millen, J., Morgan,
J. W., Nicotra, A. B., Venn, S., Zong, S., Dickinson, K. J. M.,
Freschet, G. T., Kurzböck, C., Li, J., Pan, H., Pfund, B., Quaglia, E.,
Su, X., Wang, W., Wang, X., … Deslippe, J. R. (2022).
Intraspecific trait variation in alpine plants relates to
their elevational distribution.
Journal of Ecology,
110(4), 860–875.
https://doi.org/10.1111/1365-2745.13848Climate warming is shifting the distributions of
mountain plant species to higher elevations. Cold-adapted plant species
are under increasing pressure from novel competitors that are
encroaching from lower elevations. Plant capacity to adjust to these
pressures may be measurable as variation in trait values within a
species. In particular, the strength and patterns of intraspecific trait
variation along abiotic and biotic gradients can inform us whether and
how species can adjust their anatomy and morphology to persist in a
changing environment. Here, we tested whether species specialized to
high elevations or with narrow elevational ranges show more conservative
(i.e. less variable) trait responses across their elevational
distribution, or in response to neighbours, than species from lower
elevations or with wider elevational ranges. We did so by studying
intraspecific trait variation of 66 species along 40 elevational
gradients in four countries in both hemispheres. As an indication of
potential neighbour interactions that could drive trait variation, we
also analysed plant species’ height ratio, its height relative to its
nearest neighbour. Variation in alpine plant trait values over elevation
differed depending on a species’ median elevation and the breadth of its
elevational range, with species with lower median elevations and larger
elevational range sizes showing greater trait variation, i.e. a steeper
slope in trait values, over their elevational distributions. These
effects were evidenced by significant interactions between species’
elevation and their elevational preference or range for several traits:
vegetative height, generative height, specific leaf area and patch area.
The height ratio of focal alpine species and their neighbours decreased
in the lower part of their distribution because neighbours became
relatively taller at lower elevations. In contrast, species with lower
elevational optima maintained a similar height ratio with neighbours
throughout their range. Synthesis. We provide evidence that species from
lower elevations and those with larger range sizes show greater
intraspecific trait variation, which may indicate a greater ability to
respond to environmental changes. Also, larger trait variation of
species from lower elevations may indicate stronger competitive ability
of upslope shifting species, posing one further threat to species from
higher ranges.
Semchenko, M., Barry, K. E., Vries, F. T. de, Mommer, L., Moora, M.,
& Maciá-Vicente, J. G. (2022).
Deciphering
the role of specialist and generalist plant–microbial interactions as
drivers of plant–soil feedback (Vol. 234, pp. 1929–1944).
https://doi.org/10.1111/nph.18118Feedback between plants and soil microbial communities
can be a powerful driver of vegetation dynamics. Plants elicit changes
in the soil microbiome that either promote or suppress conspecifics at
the same location, thereby regulating population density-dependence and
species co-existence. Such effects are often attributed to the
accumulation of host-specific antagonistic or beneficial microbiota in
the rhizosphere. However, the identity and host-specificity of the
microbial taxa involved are rarely empirically assessed. Here we review
the evidence for host-specificity in plant-associated microbes and
propose that specific plant–soil feedbacks can also be driven by
generalists. We outline the potential mechanisms by which generalist
microbial pathogens, mutualists and decomposers can generate
differential effects on plant hosts and synthesize existing evidence to
predict these effects as a function of plant investments into defence,
microbial mutualists and dispersal. Importantly, the capacity of
generalist microbiota to drive plant–soil feedbacks depends not only on
the traits of individual plants but also on the phylogenetic and
functional diversity of plant communities. Identifying factors that
promote specialization or generalism in plant–microbial interactions and
thereby modulate the impact of microbiota on plant performance will
advance our understanding of the mechanisms underlying plant–soil
feedback and the ways it contributes to plant co-existence.
Willems, F. M., Scheepens, J. F., & Bossdorf, O. (2022).
Forest wildflowers bloom earlier as Europe warms: lessons
from herbaria and spatial modelling.
New Phytologist,
235(1), 52–65.
https://doi.org/10.1111/nph.18124Today plants often flower earlier due to climate
warming. Herbarium specimens are excellent witnesses of such long-term
changes. However, the magnitude of phenological shifts may vary
geographically, and the data are often clustered. Therefore, large-scale
analyses of herbarium data are prone to pseudoreplication and
geographical biases. We studied over 6000 herbarium specimens of 20
spring-flowering forest understory herbs from Europe to understand how
their phenology had changed during the last century. We estimated
phenology trends with or without taking spatial autocorrelation into
account. On average plants now flowered over 6 d earlier than at the
beginning of the last century. These changes were strongly associated
with warmer spring temperatures. Flowering time advanced 3.6 d per 1°C
warming. Spatial modelling showed that, in some parts of Europe, plants
flowered earlier or later than expected. Without accounting for this,
the estimates of phenological shifts were biased and model fits were
poor. Our study indicates that forest wildflowers in Europe strongly
advanced their phenology in response to climate change. However, these
phenological shifts differ geographically. This shows that it is crucial
to combine the analysis of herbarium data with spatial modelling when
testing for long-term phenology trends across large spatial
scales.
Xi, N., Chen, D., Bahn, M., Wu, H., Chu, C., Cadotte, M. W., &
Bloor, J. M. G. (2022).
Drought soil legacy alters
drivers of plant diversity-productivity relationships in oldfield
systems.
Science Advances,
8(18), 1–11.
https://doi.org/10.1126/sciadv.abn3368Ecosystem functions are threatened by both recurrent
droughts and declines in biodiversity at a global scale, but the drought
dependency of diversity-productivity relationships remains poorly
understood. Here, we use a two-phase mesocosm experiment with simulated
drought and model oldfield communities (360 experimental mesocosms/plant
communities) to examine drought-induced changes in soil microbial
communities along a plant species richness gradient and to assess
interactions between past drought (soil legacies) and subsequent drought
on plant diversity-productivity relationships. We show that (i) drought
decreases bacterial and fungal richness and modifies relationships
between plant species richness and microbial groups; (ii) drought soil
legacy increases net biodiversity effects, but responses of net
biodiversity effects to plant species richness are unaffected; and (iii)
linkages between plant species richness and complementarity/selection
effects vary depending on past and subsequent drought. These results
provide mechanistic insight into biodiversity-productivity relationships
in a changing environment, with implications for the stability of
ecosystem function under climate change.
Yang, X., Gómez-Aparicio, L., Lortie, C. J., Verdú, M., Cavieres, L. A.,
Huang, Z., Gao, R., Liu, R., Zhao, Y., & Cornelissen, J. H. C.
(2022).
Net plant interactions are highly variable
and weakly dependent on climate at the global scale.
Ecology
Letters,
25(6), 1580–1593.
https://doi.org/10.1111/ele.14010Although plant–plant interactions (i.e. competition
and facilitation) have long been recognised as key drivers of plant
community composition and dynamics, their global patterns and
relationships with climate have remained unclear. Here, we assembled a
global database of 10,502 pairs of empirical data from the literature to
address the patterns of and climatic effects on the net outcome of plant
interactions in natural communities. We found that plant interactions
varied among plant performance indicators, interaction types and biomes,
yet competition occurred more frequently than facilitation in plant
communities worldwide. Unexpectedly, plant interactions showed weak
latitudinal pattern and were weakly related to climate. Our study
provides a global comprehensive overview of plant interactions,
highlighting competition as a fundamental mechanism structuring plant
communities worldwide. We suggest that further investigations should
focus more on local factors (e.g. microclimate, soil and disturbance)
than on macroclimate to identify key environmental determinants of
interactions in plant communities.