Abstract
Background and aims – Plants display a variety of resistance and tolerance responses to herbivory. Compensation, or changes in growth, allocation, and/or physiology, after damage is one way that plants tolerate herbivory, but geographic patterns in intraspecific plant compensatory responses are understudied. We aimed to study geographic variation in tolerance to herbivory to help explain geographic patterns in the distribution of resistance traits and the relationship between tolerance and resistance traits in common milkweed, Asclepias syriaca . Material and methods – We grew milkweed from 14 different populations in the greenhouse, mechanically applied 25% leaf damage to an experimental group, and compared the control and experimental groups to measure compensatory responses in final biomass, root:shoot ratios, stem investment, and relative growth rate. We compared compensatory responses across populations grouped by latitude and by temperature. Key results – Compared to controls, milkweed plants that were damaged lost mass and expressed reduced root:shoot ratios. However, the effect of damage on total mass, stem investment, and relative growth rate varied among genetic families. In regional contrasts, plants from colder climates grew larger and invested less in stems and roots than plants from warmer climates under control conditions, but they were less able to compensate for damage in terms of biomass. Plants from cold regions also showed a tendency to reduce growth rate and stem investment after damage; whereas, plants from warmer climates tended to increase their growth rate and stem investment in response to damage. Conclusion – While plants from high latitudes and colder climates were less able to compensate for damage than those from lower latitudes, we are not confident that these differences are caused by geographic differences in growth rate, or that they explain differences in resistance to herbivory. Instead, we suspect that differences in the phenology of development in plants from regions with different climates affect the impact of damage and the potential for compensatory growth. Milkweed plants from colder regions with short growing seasons grew larger during our measurement period, while those from regions with longer growing seasons invested more in stems and roots, traits which may have facilitated greater long-term growth, as well as the greater compensatory ability observed in our study. Future studies should explicitly manipulate the timing of damage applied to plants from different regions to test the relationship between phenology and compensation.
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Claims 9
Claim · model-written summary
Damaged milkweed plants lost mass compared with undamaged controls.
Verbatim
t0“common milkweed”
e0“Compared to controls, milkweed plants that were damaged lost mass and expressed reduced root:shoot ratios”
Claim · model-written summary
Damaged milkweed plants had reduced root:shoot ratios compared with controls.
Verbatim
t0“common milkweed”
e0“Compared to controls, milkweed plants that were damaged lost mass and expressed reduced root:shoot ratios”
Claim · model-written summary
The effect of damage on total mass, stem investment and relative growth rate varied among genetic families of common milkweed.
- Taxon
- common milkweedt0
- Material
- genetic familiese0
- Treatment
- damagee0
- Outcome
- total mass, stem investment, and relative growth ratee0
Not reportedComparatorDirection
Verbatim
t0“common milkweed”
e0“the effect of damage on total mass, stem investment, and relative growth rate varied among genetic families”
Claim · model-written summary
Under control conditions, plants from colder climates grew larger than plants from warmer climates.
Verbatim
t0“common milkweed”
e0“plants from colder climates grew larger and invested less in stems and roots than plants from warmer climates under control conditions”
Claim · model-written summary
Under control conditions, plants from colder climates invested less in stems and roots than plants from warmer climates.
Verbatim
t0“common milkweed”
e0“plants from colder climates grew larger and invested less in stems and roots than plants from warmer climates under control conditions”
Claim · model-written summary
Plants from colder climates were less able to compensate for damage in terms of biomass than plants from warmer climates.
Verbatim
t0“common milkweed”
e0“but they were less able to compensate for damage in terms of biomass”
Claim · model-written summary
Plants from cold regions tended to reduce growth rate and stem investment after damage.
- Taxon
- common milkweedt0
- Material
- Plants from cold regionse0
- Treatment
- damagee0
- Outcome
- growth rate and stem investmente0
- Direction
- reducee0
Not reportedComparator
Verbatim
t0“common milkweed”
e0“Plants from cold regions also showed a tendency to reduce growth rate and stem investment after damage”
Claim · model-written summary
Plants from warmer climates tended to increase their growth rate and stem investment in response to damage.
- Taxon
- common milkweedt0
- Material
- plants from warmer climatese0
- Treatment
- damagee0
- Outcome
- growth rate and stem investmente0
- Direction
- increasee0
Not reportedComparator
Verbatim
t0“common milkweed”
e0“plants from warmer climates tended to increase their growth rate and stem investment in response to damage”
Claim · model-written summary
The authors suspect that differences in developmental phenology among plants from different climates affect the impact of damage and the potential for compensatory growth.
Verbatim
t0“common milkweed”
e0“we suspect that differences in the phenology of development in plants from regions with different climates affect the impact of damage and the potential for compensatory growth”