10.5061/DRYAD.QFTTDZ0D5
David, Aaron
0000-0002-0802-7799
University of Miami
Thapa-Magar, Khum
Colorado State University
Afkhami, Michelle
University of Miami
Searcy, Christopher
University of Miami
Menges, Eric
Archbold Biological Station
Data from: Do plant-microbe interactions support the Stress Gradient
Hypothesis?
Dryad
dataset
2020
University of Miami
https://ror.org/02dgjyy92
Provost Award
2021-04-14T00:00:00Z
2020-09-02T00:00:00Z
en
https://doi.org/10.1086/704684
https://doi.org/10.1002/ecy.2153
https://doi.org/10.1002/ecy.3081
101466 bytes
4
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
The Stress Gradient Hypothesis (SGH), which predicts increasing ratios of
facilitative:competitive interactions with increasing stress, has long
been a guiding framework for conceptualizing plant-plant interactions.
Recently, there has been a growing recognition of the roles of microbes in
mitigating or exacerbating environmental stress for their plant hosts. As
such, we might predict based on the SGH that beneficial microbial effects
on plant performance should be positively associated with stress. We
hypothesized that support for the SGH would also vary depending on the
host plant’s habitat specialization such that species that specialize in
high stress habitats and thus likely coevolved with the resident microbes
would exhibit stronger support for the SGH than non-specialist plant
species. We further hypothesized that support for the SGH would vary with
germination frequency, since boosting germination of low-frequency
germinators is one effective means by which microbes can benefit plant
species performance. Here, we explore whether plant-microbial interactions
support the SGH, using 12 plant species native to the Florida rosemary
scrub. We conducted factorial experiments that manipulated the presence of
microbes in nine soils collected along an elevational stress gradient, and
recorded germination frequency and biomass. Microbes increased the
germination frequency of four species, all of which had relatively low
germination rates. Furthermore, we found support for the SGH in nearly
half of the species examined, with soil microbes facilitating germination
with increasing stress for five of the 12 species tested, and none of the
species exhibiting the opposite trend. Support for the SGH was not
predicted by either the plant hosts’ habitat specialization or germination
frequency. In contrast to germination, biomass results showed little
support for the SGH, with four of 12 species refuting and one species
supporting SGH predictions. Taken together, our study documents that
interactions between the soil microbial community and plant species along
a stress gradient can support the SGH, but emphasizes that these effects
are life history stage-dependent. This work also identifies a common
mechanism (germination facilitation) by which microbes can benefit plant
species in stressful habitats.
Data from germination and plant growth experiments in which 12 plant
species (specialists: Lechea cernua, Polygonella robusta, P. basiramia,
Eryngium cuneifolium, Hypericum cumulicola, Liatris ohlingerae;
non-specialists: Chamaecrista fasciculata, Pityopsis graminifolia, Liatris
tenuifolia, Balduina angustifolia, Chapmannia floridana, Lechea
deckerti) were grown in Live or Sterilized soil collected from 9 different
patches of Florida rosemary scrub. We manipulated the presence of soil
microbes following David et al. (2019) American Naturalist. Briefly, we
inoculated pots (15% soil volume) with Live (unmanipulated,
microbially-active) or Sterilized (autoclaved, microbially-sterile) soils,
with the remainder of the soil consisting of sterilized soil from the same
rosemary scrub patch as the inoculum. All pots (66 mL; Ray Leach
Cone-tainer, Stuewe & Sons, Tangent, OR, USA) and sterilized soils
were autoclaved at 121°C twice prior to use. For eight species, seeds were
sown directly into pots. For logistical reasons, we conducted separate
germination experiments for the remaining four species in soil-filled
Petri plates using the same 15% soil inoculum. In order to examine later
life history stages of these four species, seedlings were either
transplanted into Cone-tainers directly from the germination study plates
(E. cuneifolium) or germinated from additional seeds on Petri plates with
moistened filter paper (L. ohlinerae, L. tenuifoila, C. floridana). Seeds
were allowed to germinate under ambient light conditions in the
laboratory. Once the germination rate plateaued, pots were placed under
fluorescent grow lights (16:8 light:dark conditions), though we continued
to monitor for new germinants. At this stage, we thinned germinants as
necessary to prevent overcrowding. We harvested each species before plants
outgrew their pots, and dried and weighed above- and belowground biomass.