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Lack of evolution in a leaf beetle that lives on two contrasting host plants.

Gould K, Wilson P - Ecol Evol (2015)

Bottom Line: Males did not prefer to mate with females from E. trichocalyx.Females from E. crassifolium did prefer males from E. trichocalyx over males from E. crassifolium, but did not lay more eggs as a result of these matings.We conclude that the beetle populations we studied have not differentiated based on their host plants and may not have even adapted to the better host.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology California State University Northridge California 91330-8303.

ABSTRACT
The interactions between plant-eating insects and their hosts have shaped both the insects and the plants, driving evolution of plant defenses and insect specialization. The leaf beetle Trirhabda eriodictyonis (Chrysomelidae) lives on two shrubs with differing defenses: Eriodictyon crassifolium has hairy leaves, whereas E. trichocalyx has resinous leaves. We tested whether these beetles have differentiated onto the two host plants, and if not, whether the beetles prefer the better host plant and prefer mates who are from that host plant. In feeding tests, adult beetles strongly preferred eating E. trichocalyx regardless of which host they came from. In addition, females laid more eggs if they ate E. trichocalyx than E. crassifolium. So, E. trichocalyx is generally the better host. However, beetle mate preference was not in line with food choice. Males did not prefer to mate with females from E. trichocalyx. Females from E. crassifolium did prefer males from E. trichocalyx over males from E. crassifolium, but did not lay more eggs as a result of these matings. We conclude that the beetle populations we studied have not differentiated based on their host plants and may not have even adapted to the better host. Although to humans these host plant defenses differ dramatically, signs that they have caused evolution in the beetles are lacking. The case of T. eriodictyonis stands counter to many other studies that have seen the differentiation of ecotypes and/or adaptive coordination of an herbivore's life cycle based on host plant differences.

No MeSH data available.


Trirhabda eriodictyonis mating. (A) Male initiating mating. (B) Pair successfully mating. (C) Female rejecting male with upturned tip of abdomen, preventing the male from inserting his aedeagus. Drawings by Cindy Hichcock.
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ece31658-fig-0001: Trirhabda eriodictyonis mating. (A) Male initiating mating. (B) Pair successfully mating. (C) Female rejecting male with upturned tip of abdomen, preventing the male from inserting his aedeagus. Drawings by Cindy Hichcock.

Mentions: Both males and females mate with multiple partners. Mating in T. eriodictyonis is prefaced by no obvious courtship. In the laboratory, the male approaches the female and mounts, grasping the edges of her elytra with his tarsi (Fig. 1A). He strokes her head and pronotum with his antennae while extending his aedeagus. If the female accepts him, she allows him to insert his aedeagus through a notch at the end of her abdomen (Fig. 1B). Once his aedeagus is inserted, the couple stops moving and remains still for 10 min on average before the female starts twisting her body quickly side to side in what appears to be an attempt to dislodge the male. She will continue this “waggle” behavior until he removes his aedeagus and dismounts, on average after 9 more minutes.


Lack of evolution in a leaf beetle that lives on two contrasting host plants.

Gould K, Wilson P - Ecol Evol (2015)

Trirhabda eriodictyonis mating. (A) Male initiating mating. (B) Pair successfully mating. (C) Female rejecting male with upturned tip of abdomen, preventing the male from inserting his aedeagus. Drawings by Cindy Hichcock.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4588663&req=5

ece31658-fig-0001: Trirhabda eriodictyonis mating. (A) Male initiating mating. (B) Pair successfully mating. (C) Female rejecting male with upturned tip of abdomen, preventing the male from inserting his aedeagus. Drawings by Cindy Hichcock.
Mentions: Both males and females mate with multiple partners. Mating in T. eriodictyonis is prefaced by no obvious courtship. In the laboratory, the male approaches the female and mounts, grasping the edges of her elytra with his tarsi (Fig. 1A). He strokes her head and pronotum with his antennae while extending his aedeagus. If the female accepts him, she allows him to insert his aedeagus through a notch at the end of her abdomen (Fig. 1B). Once his aedeagus is inserted, the couple stops moving and remains still for 10 min on average before the female starts twisting her body quickly side to side in what appears to be an attempt to dislodge the male. She will continue this “waggle” behavior until he removes his aedeagus and dismounts, on average after 9 more minutes.

Bottom Line: Males did not prefer to mate with females from E. trichocalyx.Females from E. crassifolium did prefer males from E. trichocalyx over males from E. crassifolium, but did not lay more eggs as a result of these matings.We conclude that the beetle populations we studied have not differentiated based on their host plants and may not have even adapted to the better host.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology California State University Northridge California 91330-8303.

ABSTRACT
The interactions between plant-eating insects and their hosts have shaped both the insects and the plants, driving evolution of plant defenses and insect specialization. The leaf beetle Trirhabda eriodictyonis (Chrysomelidae) lives on two shrubs with differing defenses: Eriodictyon crassifolium has hairy leaves, whereas E. trichocalyx has resinous leaves. We tested whether these beetles have differentiated onto the two host plants, and if not, whether the beetles prefer the better host plant and prefer mates who are from that host plant. In feeding tests, adult beetles strongly preferred eating E. trichocalyx regardless of which host they came from. In addition, females laid more eggs if they ate E. trichocalyx than E. crassifolium. So, E. trichocalyx is generally the better host. However, beetle mate preference was not in line with food choice. Males did not prefer to mate with females from E. trichocalyx. Females from E. crassifolium did prefer males from E. trichocalyx over males from E. crassifolium, but did not lay more eggs as a result of these matings. We conclude that the beetle populations we studied have not differentiated based on their host plants and may not have even adapted to the better host. Although to humans these host plant defenses differ dramatically, signs that they have caused evolution in the beetles are lacking. The case of T. eriodictyonis stands counter to many other studies that have seen the differentiation of ecotypes and/or adaptive coordination of an herbivore's life cycle based on host plant differences.

No MeSH data available.