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Are all forms of defence lost on islands? Persistence of a defensive mutualism in six island colonists from New Zealand.

ABSTRACT: The loss of defence hypothesis posits that island colonizers experience a release from predation on the mainland and subsequently lose their defensive adaptations. However, while support for the hypothesis from direct defensive traits is abundant, far less is known about indirect defensive traits. Leaf domatia are cave-like structures produced on the underside of leaves that facilitate an indirect defensive interaction with predaceous and microbivorous mites. I tested the loss of defence hypothesis in six domatia-bearing taxa inhabiting New Zealand and its offshore islands. No support for the loss of defence hypothesis was found. Changes in domatia investment were instead associated with changes in leaf size-a trait that has been repeatedly observed to undergo rapid evolution on islands. Overall results suggest that not all types of defence are lost on islands.

SUBMITTER: Biddick M

PROVIDER: S-EPMC10114016 | biostudies-literature | 2023 Apr

REPOSITORIES: biostudies-literature

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Are all forms of defence lost on islands? Persistence of a defensive mutualism in six island colonists from New Zealand.

Biddick M M

Biology letters 20230419 4

The loss of defence hypothesis posits that island colonizers experience a release from predation on the mainland and subsequently lose their defensive adaptations. However, while support for the hypothesis from direct defensive traits is abundant, far less is known about indirect defensive traits. Leaf domatia are cave-like structures produced on the underside of leaves that facilitate an indirect defensive interaction with predaceous and microbivorous mites. I tested the loss of defence hypothe ...[more]

PMID: 37073525

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Project description:Insects and other animals commonly form symbioses with heritable bacteria, which can exert large influences on host biology and ecology. The pea aphid, Acyrthosiphon pisum, is a model for studying effects of infection with heritable facultative symbionts (HFS), and each of its seven common HFS species has been reported to provide resistance to biotic or abiotic stresses. However, one common HFS, called X-type, rarely occurs as a single infection in field populations and instead typically superinfects individual aphids with Hamiltonella defensa, another HFS that protects aphids against attack by parasitic wasps. Using experimental aphid lines comprised of all possible infection combinations in a uniform aphid genotype, we investigated whether the most common strain of X-type provides any of the established benefits associated with aphid HFS as a single infection or superinfection with H. defensa We found that X-type does not confer protection to any tested threats, including parasitoid wasps, fungal pathogens, or thermal stress. Instead, component fitness assays identified large costs associated with X-type infection, costs which were ameliorated in superinfected aphids. Together these findings suggest that X-type exploits the aphid/H. defensa mutualism and is maintained primarily as a superinfection by "hitchhiking" via the mutualistic benefits provided by another HFS. Exploitative symbionts potentially restrict the functions and distributions of mutualistic symbioses with effects that extend to other community members.IMPORTANCE Maternally transmitted bacterial symbionts are widespread and can have major impacts on the biology of arthropods, including insects of medical and agricultural importance. Given that host fitness and symbiont fitness are tightly linked, inherited symbionts can spread within host populations by providing beneficial services. Many insects, however, are frequently infected with multiple heritable symbiont species, providing potential alternative routes of symbiont maintenance. Here we show that a common pea aphid symbiont called X-type likely employs an exploitative strategy of hitchhiking off the benefits of a protective symbiont, Hamiltonella Infection with X-type provides none of the benefits conferred by other aphid symbionts and instead results in large fitness costs, costs lessened by superinfection with Hamiltonella These findings are corroborated by natural infections in field populations, where X-type is mostly found superinfecting aphids with Hamiltonella Exploitative symbionts may be common in hosts with communities of heritable symbionts and serve to hasten the breakdown of mutualisms.

Dataset Information

Are all forms of defence lost on islands? Persistence of a defensive mutualism in six island colonists from New Zealand.

Publications

Are all forms of defence lost on islands? Persistence of a defensive mutualism in six island colonists from New Zealand.

Similar Datasets

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