Literature Cited:

1. Riginos, C., M.S. Herschel, and J. Schmitt. 2007. Am. J. Bot. 94(12): 1984-1991

2. Sultan, S.E., K. Barton, and A.M. Wilczek. 2009. Ecology 90(7): 1831-1839

3. Sultan, S.E. 1996. Ecology 77(6): 1791-1807

4. Weiner, J., S. Martinez, H. Muller-Scharer, P. Stoll, and B. Schmid. 1997. J. Ecol. 85(2): 133-142

5. Jakobsson, A. & Eriksson, O 2000.. Oikos 88: 494-502.

Background

Experiment Conclusions

Results

In plants, ‘maternal effects’ refer to the effect of the maternal

environment on offspring phenotype. For example, some

studies have shown that parents in good environments produce

larger, healthier seeds.

Despite clear examples of maternal effects in some species,

there has been no systematic study of their importance for a

broad suite of species1,2. In addition, the type of maternal effect

can differ – species have shown differences in terms of the

quality and quantity of offspring, but the potential trade-off in

these responses has not been tested.

In our study, we examined the generality of maternal effects for

Mediterranean annual plants found in California. This large

group of species commonly faces drought conditions, with

highly variable rainfall from one year to the next. Our goal was

to test the generality of maternal effects among these species,

using ecologically relevant conditions. In this study, we asked:

1) Are drought induced maternal effects still prevalent at

the community level?

2) Does phylogeny and area of origin (native to California

or Spain) account for any variation in maternal effects?

Drought-induced maternal effects vary across species

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C. Seed mass vs. number (negative values indicate a trade-off)

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B. Number of seeds per plant

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A. Seed mass

Figure 2: a) t-values for mass per seed testing null hypothesis μDry – μWet = 0, b) t-values for total number of seeds per plant testing

null hypothesis μDry – μWet = 0, c) t-values testing null hypothesis that the linear relationship between seed mass and number is equal

to zero. All tests showed significant species x environment interactions, indicating different responses among species.

* Significant P-value with 0.05 significance level

Native species

Non-Native species

Pe

rform

ance

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dry

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ents

(t-

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lues)

Maternal effects to drought were negligible for 58% of the

species, with five and seven species responding significantly

through seed mass and seed number, respectively (Fig. 2)

Seed mass varied in direction. However, seed number was

mainly increased in wet compared to dry environments.

Phylogeny and area of origin does not appear to play a

significant role in species’ drought responses, except for some

grouping of significant seed mass effects in the Poales order.

Many species had one favourable environment (seed mass or

seed number effect with a positive or no relationship between the

two). However, for those species that do show a trade-off, it is

unclear if gain in seed size offsets loss in seed number, and vice

versa, in response to the environment.

Despite many studies showing the importance of maternal

effects on specific species, these effects are not consistent in

magnitude or direction within a community4.

Maternal effects are expressed at several nodes across a

diverse phylogeny, suggesting that their expression is not

constrained by recent evolutionary relationships. Similarly,

maternal effects do not seem to be related to the geographical

origin of the plant.

The importance of different types of effects (seed size and

seed number) and their trade-offs remains an important area of

research5. Our ongoing study is designed to address these

questions.

ROP project supervisors Rachel Germain and

Dr. Benjamin Gilbert.

Learn more about the Gilbert Lab at :

http://labs.eeb.utoronto.ca/gilbert/people.htm

ACKNOWLEDGMENTS

Ecological community: 29 species from Mediterranean climates

native to California or Spain comprising taxonomic orders

Asterales, Lamiales, Fabales, Caryophyllales, Ranunculales and

Poales

Maternal plants were grown in dry (5.8 % soil moisture) or wet

(11.1% soil moisture) greenhouse conditions, which are known to

be important to Mediterranean species3. Seeds were counted and

weighed, and a subset were planted to examine seedling

performance (Fig. 1).

We used generalized linear models to examine the effect of

maternal environment on seed size, seed number and any

potential trade-off.

Figure 1: Growing plants and processing seeds.

Hvulg Vmyur Pcamp

Figure 3: Seed morphology of three species used in this experiment.