This study investigated adaptive parental effects in the annual grass Avena barbata. The results showed: 1) Offspring of parents grown in dry conditions performed better than those from wet parents, regardless of the offspring environment. 2) Functional traits like seed nitrogen content and seed weight underpinned these adaptive parental effects. 3) Seeds were heavier when parents grew in dry vs. wet conditions, indicating parental effects can influence offspring phenotypes through traits.

1. Functional traits underlie adaptive parental effects in
the annual grass Avena barbata
Rachel M. Germain*, Christina M. Caruso, and Hafiz Maherali
Department of Integrative Biology, University of Guelph
Background Drought-induced parental effects are adaptive Results
Adaptive parental effects are increasingly recognized as •Offspring performed 6% better when originating from
effective and widespread strategies for preparing dry- over wet-grown parents (F1,145 = 9.48, P =
offspring for survival in predictable environments.
7 0.002), with no interaction with the offspring
However, understanding how adaptive parental effects environment (F1,145 = 2.59, P = 0.109 ; Fig. 1)
Biomass at 186 days (g)
6
evolve has been limited by the small number of
experimental tests of when parental effects are •Seed nitrogen content was correlated with
adaptive and of which functional traits underlie this
5 Parent germination success (F1,20 = 4.92, P = 0.038), but the
adaptation. If parental effects are adaptive rather than 4 environment strength of this relationship was stronger when
just a passive consequence of resource offspring originated from parents grown in wet
limitation, specific functional traits likely underlie their
Dry environments (F1,20 = 7.16, P = 0.015 ; Fig. 2A)
3
expression. Furthermore, functional traits that allow Wet
adaptation in offspring environments that match that 2 •Seed weight was correlated with radicle length (F1,20 =
of their parents may also incur fitness costs in 5.23, P = 0.034), but the strength of this relationship
alternative environments, leading to adaptive 1 was stronger when offspring originated from parents
matching1 as is observed in many species. grown in wet environments (F1,20 = 4.71, P = 0.043; Fig.
0 2B)
Here, we ask:
Dry Wet
(i) What is the adaptive value of parental effects?
Offspring environment
Maladaptive Adaptively matched Adaptive
12
Parent
12 12 Figure 1: Offspring performed better when originating from parents grown in dry (dark green) compared to
10
environment 10 10 wet (light green) environments, regardless of the offspring environment
Dry
Biomass
8 8 8
Wet
6 6 6
4
2
4
2
4
2
Seed traits underlie adaptive parental effects in A. barbata
0 0 0
Dry Wet Dry Wet Dry Wet Figure 3: Seeds were 53% heavier when originating from parents
Offspring environment 1.0 5 grown in dry (right) compared to wet (left) environments
(ii) Do functional traits underlie parental effect A B
Germination success
4
Radicle length (cm)
expression? 0.8
Conclusions
0.6 3 •Parental effects were adaptive, but without tradeoffs
Greenhouse experiment
that lead to adaptive matching3
•Seeds of plants grown in wet and dry environments 0.4 2
during a previous drought experiment2 were reciprocally •Environmental similarity across generations may not
transplanted into wet and dry offspring environments be critical for the evolution of parental effects as
0.2 1 previously thought
•We measured two functional traits, seed nitrogen
content and seed weight, as mechanisms for parental 0.0 0 •Adaptive parental effects can evolve through direct
effects on germination success and radicle length selection on seed weight and seed nitrogen content
2 3 4 5 6 7 0 25 50 75 100
•To test for adaptation, we measured aboveground % Seed nitrogen content Seed weight (mg) Literature Cited
1. Sultan, Barton, and Wilczek. 2009. Ecology 90: 1831-1839.
biomass as a fitness estimate as plants senesced 2. Sherrard and Maherali. 2006. Evolution 60: 2478-2489.
Figure 2: Influence of (A) % seed nitrogen content on germination success and (B) seed weight on radicle length
of offspring originating from parents grown in wet (light green) and dry (dark green) environments. 3. Hereford. 2009. American Naturalist 173: 579-588.