Proceedings of the Royal Society B: Biological Sciences
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Adaptive value of a predatory mouth-form in a dimorphic nematode

Vahan Serobyan

Vahan Serobyan

Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstraße 37, 72076 Tübingen, Germany

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Erik J. Ragsdale

Erik J. Ragsdale

Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstraße 37, 72076 Tübingen, Germany

Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA

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Ralf J. Sommer

Ralf J. Sommer

Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstraße 37, 72076 Tübingen, Germany

[email protected]

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Published:https://doi.org/10.1098/rspb.2014.1334

    Polyphenisms can be adaptations to environments that are heterogeneous in space and time, but to persist they require conditional-specific advantages. The nematode Pristionchus pacificus is a facultative predator that displays an evolutionarily conserved polyphenism of its mouthparts. During development, P. pacificus irreversibly executes either a eurystomatous (Eu) or stenostomatous (St) mouth-form, which differ in the shape and number of movable teeth. The Eu form, which has an additional tooth, is more complex than the St form and is thus more highly derived relative to species lacking teeth. Here, we investigate a putative fitness trade-off for the alternative feeding-structures of P. pacificus. We show that the complex Eu form confers a greater ability to kill prey. When adults were provided with a prey diet, Eu nematodes exhibited greater fitness than St nematodes by several measures, including longevity, offspring survival and fecundity when followed by bacterial feeding. However, the two mouth-forms had similar fecundity when fed ad libitum on bacteria, a condition that would confer benefit on the more rapidly developing St form. Thus, the two forms show conditional fitness advantages in different environments. This study provides, to our knowledge, the first functional context for dimorphism in a model for the genetics of plasticity.

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