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What do spring migrants reveal about sex and host selection in the melon aphid?

Thomas S, Boissot N, Vanlerberghe-Masutti F - BMC Evol. Biol. (2012)

Bottom Line: Moreover, an analysis of the genetic composition of these alate and apterous populations in four geographic regions suggested differences in life-history strategies, such as host choice and reproductive mode, and questioned the common assertion that A. gossypii is an anholocyclic species throughout its distribution area, including Europe.Our results clearly demonstrate that the melon plant acts as a selective filter against the reproduction of non-specialised individuals.We showed that olfactory cues are unlikely to be decisive in natura for host recognition by spring-migrant aphid populations that are not specialised on Cucurbitaceae.

View Article: PubMed Central - HTML - PubMed

Affiliation: INRA, UMR1062 CBGP, F-34988 Montferrier-sur-Lez, France.

ABSTRACT

Background: Host plants exert considerable selective pressure on aphids because the plants constitute their feeding, mating and oviposition sites. Therefore, host specialisation in aphids evolves through selection of the behavioural and chemical mechanisms of host-plant location and recognition, and through metabolic adaptation to the phloem content of the host plant. How these adaptive traits evolve in an aphid species depends on the complexity of the annual life cycle of that species. The purpose of this field study was to determine how winged spring-migrant populations contribute to the evolution and maintenance of host specialisation in Aphis gossypii through host-plant choice and acceptance. We also assessed whether host-specialised genotypes corresponded exclusively to anholocyclic lineages regardless of the environmental conditions.

Results: The spring populations of cotton-melon aphids visiting newly planted melon crops exhibited an unexpectedly high level of genetic diversity that contrasted with the very low diversity characterising the host-specialised populations of this aphid species. This study illustrated in natura host-plant-selection pressure by showing the great differences in genetic diversity between the spring-migrant populations (alate aphids) and the melon-infesting populations (the apterous offspring of the alate aphids). Moreover, an analysis of the genetic composition of these alate and apterous populations in four geographic regions suggested differences in life-history strategies, such as host choice and reproductive mode, and questioned the common assertion that A. gossypii is an anholocyclic species throughout its distribution area, including Europe.

Conclusions: Our results clearly demonstrate that the melon plant acts as a selective filter against the reproduction of non-specialised individuals. We showed that olfactory cues are unlikely to be decisive in natura for host recognition by spring-migrant aphid populations that are not specialised on Cucurbitaceae. The agroecosystem structure and history of the four studied regions may have partially shaped the genetic structure of the spring-migrant populations of A. gossypii. Cucurbitaceae-specialised genotypes corresponded exclusively to anholocyclic lineages, regardless of the environmental conditions. However, some genotypes that were genetically close to the host-specialised genotypes and some genotypes that probably originated from wild plants had never been previously sampled; both were holocylic.

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Occurrence of multilocus genotypes in the A. gossypii populations sampled in France and Lesser Antilles. The numbers of multilocus genotypes are shown in the bars and the percentages of individuals exhibiting those multilocus genotypes are shown in the axis y according to a. morphs, b. years and c. areas.
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Figure 2: Occurrence of multilocus genotypes in the A. gossypii populations sampled in France and Lesser Antilles. The numbers of multilocus genotypes are shown in the bars and the percentages of individuals exhibiting those multilocus genotypes are shown in the axis y according to a. morphs, b. years and c. areas.

Mentions: Among the 596 MLGs discriminated, 316 were observed within only the alate samples, 183 were observed within only the apterous samples and 97 were observed within both of the morphs (Figure 2a). The distribution was different for the numbers of individuals: 8% of the individuals had an MLG that was observed within only the alate samples, 6% of the individuals had an MLG that was observed within only the apterous samples and 86% of individuals had an MLG that was observed within both the alate and apterous samples. We observed 551 MLGs that were present in only one of the studied years, but more than 70% of the individuals had an MLG that was observed in two or more years (Figure 2b). We observed 571 MLGs that were present in only one of the areas, but approximately 50% of the individuals had an MLG that was observed in two or more areas (Figure 2c). None of the MLGs that were observed in the LA were observed in the other areas.


What do spring migrants reveal about sex and host selection in the melon aphid?

Thomas S, Boissot N, Vanlerberghe-Masutti F - BMC Evol. Biol. (2012)

Occurrence of multilocus genotypes in the A. gossypii populations sampled in France and Lesser Antilles. The numbers of multilocus genotypes are shown in the bars and the percentages of individuals exhibiting those multilocus genotypes are shown in the axis y according to a. morphs, b. years and c. areas.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368726&req=5

Figure 2: Occurrence of multilocus genotypes in the A. gossypii populations sampled in France and Lesser Antilles. The numbers of multilocus genotypes are shown in the bars and the percentages of individuals exhibiting those multilocus genotypes are shown in the axis y according to a. morphs, b. years and c. areas.
Mentions: Among the 596 MLGs discriminated, 316 were observed within only the alate samples, 183 were observed within only the apterous samples and 97 were observed within both of the morphs (Figure 2a). The distribution was different for the numbers of individuals: 8% of the individuals had an MLG that was observed within only the alate samples, 6% of the individuals had an MLG that was observed within only the apterous samples and 86% of individuals had an MLG that was observed within both the alate and apterous samples. We observed 551 MLGs that were present in only one of the studied years, but more than 70% of the individuals had an MLG that was observed in two or more years (Figure 2b). We observed 571 MLGs that were present in only one of the areas, but approximately 50% of the individuals had an MLG that was observed in two or more areas (Figure 2c). None of the MLGs that were observed in the LA were observed in the other areas.

Bottom Line: Moreover, an analysis of the genetic composition of these alate and apterous populations in four geographic regions suggested differences in life-history strategies, such as host choice and reproductive mode, and questioned the common assertion that A. gossypii is an anholocyclic species throughout its distribution area, including Europe.Our results clearly demonstrate that the melon plant acts as a selective filter against the reproduction of non-specialised individuals.We showed that olfactory cues are unlikely to be decisive in natura for host recognition by spring-migrant aphid populations that are not specialised on Cucurbitaceae.

View Article: PubMed Central - HTML - PubMed

Affiliation: INRA, UMR1062 CBGP, F-34988 Montferrier-sur-Lez, France.

ABSTRACT

Background: Host plants exert considerable selective pressure on aphids because the plants constitute their feeding, mating and oviposition sites. Therefore, host specialisation in aphids evolves through selection of the behavioural and chemical mechanisms of host-plant location and recognition, and through metabolic adaptation to the phloem content of the host plant. How these adaptive traits evolve in an aphid species depends on the complexity of the annual life cycle of that species. The purpose of this field study was to determine how winged spring-migrant populations contribute to the evolution and maintenance of host specialisation in Aphis gossypii through host-plant choice and acceptance. We also assessed whether host-specialised genotypes corresponded exclusively to anholocyclic lineages regardless of the environmental conditions.

Results: The spring populations of cotton-melon aphids visiting newly planted melon crops exhibited an unexpectedly high level of genetic diversity that contrasted with the very low diversity characterising the host-specialised populations of this aphid species. This study illustrated in natura host-plant-selection pressure by showing the great differences in genetic diversity between the spring-migrant populations (alate aphids) and the melon-infesting populations (the apterous offspring of the alate aphids). Moreover, an analysis of the genetic composition of these alate and apterous populations in four geographic regions suggested differences in life-history strategies, such as host choice and reproductive mode, and questioned the common assertion that A. gossypii is an anholocyclic species throughout its distribution area, including Europe.

Conclusions: Our results clearly demonstrate that the melon plant acts as a selective filter against the reproduction of non-specialised individuals. We showed that olfactory cues are unlikely to be decisive in natura for host recognition by spring-migrant aphid populations that are not specialised on Cucurbitaceae. The agroecosystem structure and history of the four studied regions may have partially shaped the genetic structure of the spring-migrant populations of A. gossypii. Cucurbitaceae-specialised genotypes corresponded exclusively to anholocyclic lineages, regardless of the environmental conditions. However, some genotypes that were genetically close to the host-specialised genotypes and some genotypes that probably originated from wild plants had never been previously sampled; both were holocylic.

Show MeSH
Related in: MedlinePlus