Variation in the Responses of Spotted Alfalfa Aphids, Therioaphis maculata Buckton (Homoptera: Aphididae) and Pea Aphids, Acythosiphon pisum Harris (Homoptera: Aphididae) to Drought Conditions in Alfalfa (Medicago sativa L., Fabaceae)

Forbes, Andrew E.; Harvey, Chad T.; Tilmon, Kelley J.

doi:10.2317/0412.06.1

Cited by 7 publications

(6 citation statements)

References 2 publications

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“…We successfully generated a priori qualitative predictions about the effects that reduced precipitation would have on our system by synthesizing available information on these species. This was possible because of previous work asking basic questions about the effects of precipitation on these two aphid species (Forbes et al 2005) as well as the general ecology of the community (Snyder and Ives 2003, Harmon et al 2009). Thus, predicting the net effect of climate change on communities will likely benefit from basic research into the functioning of ecological systems.…”

Section: Discussionmentioning

confidence: 99%

“…Pea aphids (Acyrthosiphon pisum) and spotted aphids (Therioaphis maculata) are two common pests in the alfalfa (lucerne, Medicago sativa) fields of Wisconsin, USA, yet they are affected by drought differently. Previous work showed that pea aphid population growth rates are strongly tied to alfalfa water content, reaching high densities in healthy alfalfa but suffering lower growth rates when alfalfa is water stressed (Forbes et al 2005). In contrast, spotted aphids are insensitive across a wide range of alfalfa moisture levels and are seemingly unaffected by precipitation.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, spotted aphids are insensitive across a wide range of alfalfa moisture levels and are seemingly unaffected by precipitation. Competition between pea aphid and spotted aphids is weak (Forbes et al 2005), but because they share a suite of natural enemies, predators could mediate interactions between these two aphids. One of the most common predators of pea and spotted aphids is the multicolored Asian ladybeetle (Harmonia axyridis).…”

Section: Introductionmentioning

confidence: 99%

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Species interactions and a chain of indirect effects driven by reduced precipitation

Barton

Ives

2014

Ecology

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Climate change can affect species directly and indirectly by altering interactions between species within communities. These indirect effects can ramify through a community and affect many species, including some that may not have been directly affected by the perturbation. Identifying these chains of indirect effects is difficult, and most studies only follow indirect effects across two or three species. Here, we use a factorial field experiment to demonstrate that precipitation affects spotted aphids through a complex chain of indirect interactions that are mediated by other herbivores and a generalist predator. We experimentally simulated drought, which reduced water content in alfalfa plants. While water stress in alfalfa had no direct effect on spotted aphids, it lowered the population growth rate of pea aphids, another common alfalfa pest. Because ladybeetle predators were attracted to high pea aphid densities, predator densities were lower in drought treatments. Consequently, spotted aphid densities were released from top-down control (apparent competition) in drought treatments and reached densities three times higher than spotted aphids in ambient treatments with high pea aphid densities. Thus, drought affected spotted aphids in the interaction chain: drought --> alfalfa --> pea aphids --> predators --> spotted aphids. This result illustrates the lengthy path that indirect effects of climate change may take through a community, as well as the importance of community-level experiments in determining the net effect of climate change.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Species interactions and a chain of indirect effects driven by reduced precipitation

Barton

Ives

2014

Ecology

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“…Finally, temperature could increase drought stress in plants which could in turn affects alate production. Pea aphid population growth is reduced under drought-stress conditions (Forbes et al 2005, Barton & Ives 2014). Therefore, if drought-reduced plant quality at higher temperatures were important, the expected relationship between temperature and alate production would be positive, rather than the observed negative relationship.…”

Section: Discussionmentioning

confidence: 99%

Identifying environmental factors affecting the production of pea aphid dispersal morphs in field populations

Bosch

Ives

2023

Preprint

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1. Many species of insects show phenotypically plastic dispersal traits in response to suboptimal environmental conditions. These polyphenetic traits can have large impacts on the population dynamics of the dispersing insects. Therefore, it is important to understand what environmental factors affect the development of dispersal traits and how these factors affect population dynamics via immigration/emigration. 2. Pea aphids (Acyrthosiphon pisum) exhibit a polyphenetic wing dimorphism in which individuals are either winged (alate) or not (apterous). The production of alate offspring is determined by environmental cues experienced by the mother. Environmental factors associated with these cues have been intensively studied, with crowding, host plant quality, natural enemies, and fungal infection being shown to affect the production of pea aphid alates under controlled laboratory conditions. Nonetheless, environmental factors affecting alate production have rarely been studied in field populations of pea aphids. 3. Using data from a three-year study of alate production in 5-9 alfalfa (lucerne) fields, we examined the effects of (i) pea aphid abundance, (ii) host plant maturity, (iii) temperature, (iv) predator and herbivore abundance, (v) parasitism, and (vi) entomopathic fungal incidence. In twice-weekly samples taken over the growing season, alate production ranged from 0 to 83% of the nymphal population. 4. Pea aphid abundance, temperature, and alfalfa maturity together explained 67% of the variation in alate production. The other factors we investigated explained little variation. These results suggest there is a limited number of key environmental factors that consistently predict changes in alate production in field populations, while many factors identified in lab studies may be unimportant. Our results highlight the value of investigating factors affecting the expression of plastic traits in insect species at a broad spatiotemporal scale and under natural conditions.

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“…Sustained water stress in plants tends to affect aphids negatively (Huberty and Denno, 2004 ). A. pisum densities, in particular, have been closely linked to lucerne water content, with populations suffering lower growth rates when lucerne is drought stressed (Forbes et al, 2005 ). In the current study, drought negatively impacted aphids, although amino acid concentrations generally increased in plants under drought compared with those under ambient precipitation.…”

Section: Discussionmentioning

confidence: 99%

Above–Belowground Herbivore Interactions in Mixed Plant Communities Are Influenced by Altered Precipitation Patterns

et al. 2016

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Root- and shoot-feeding herbivores have the capacity to influence one another by modifying the chemistry of the shared host plant. This can alter rates of nutrient mineralization and uptake by neighboring plants and influence plant–plant competition, particularly in mixtures combining grasses and legumes. Root herbivory-induced exudation of nitrogen (N) from legume roots, for example, may increase N acquisition by co-occurring grasses, with knock-on effects on grassland community composition. Little is known about how climate change may affect these interactions, but an important and timely question is how will grass–legume mixtures respond in a future with an increasing reliance on legume N mineralization in terrestrial ecosystems. Using a model grass–legume mixture, this study investigated how simultaneous attack on lucerne (Medicago sativa) by belowground weevils (Sitona discoideus) and aboveground aphids (Acyrthosiphon pisum) affected a neighboring grass (Phalaris aquatica) when subjected to drought, ambient, and elevated precipitation. Feeding on rhizobial nodules by weevil larvae enhanced soil water retention under ambient and elevated precipitation, but only when aphids were absent. While drought decreased nodulation and root N content in lucerne, grass root and shoot chemistry were unaffected by changes in precipitation. However, plant communities containing weevils but not aphids showed increased grass height and N concentrations, most likely associated with the transfer of N from weevil-attacked lucerne plants containing more nodules and higher root N concentrations compared with insect-free plants. Drought decreased aphid abundance by 54% but increased total and some specific amino acid concentrations (glycine, lysine, methionine, tyrosine, cysteine, histidine, arginine, aspartate, and glutamate), suggesting that aphid declines were being driven by other facets of drought (e.g., reduced phloem hydraulics). The presence of weevil larvae belowground decreased aphid numbers by 30%, likely associated with a significant reduction in proline in weevil-treated lucerne plants. This study demonstrates how predicted changes to precipitation patterns and indirect interactions between herbivores can alter the outcome of competition between N-fixing legumes and non-N-fixing grasses, with important implications for plant community structure and productivity.

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Variation in the Responses of Spotted Alfalfa Aphids, Therioaphis maculata Buckton (Homoptera: Aphididae) and Pea Aphids, Acythosiphon pisum Harris (Homoptera: Aphididae) to Drought Conditions in Alfalfa (Medicago sativa L., Fabaceae)

Cited by 7 publications

References 2 publications

Species interactions and a chain of indirect effects driven by reduced precipitation

Species interactions and a chain of indirect effects driven by reduced precipitation

Identifying environmental factors affecting the production of pea aphid dispersal morphs in field populations

Above–Belowground Herbivore Interactions in Mixed Plant Communities Are Influenced by Altered Precipitation Patterns

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