American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Transformational mimicry in a myrmecomorphic spider”

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Stano Pekár, Yun-Yun Tsai, and Radek Michalko (Aug 2020)

Leptorchestes berolinensis is an ant-mimicking spider with all stages being accurate mimics

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Ant-like spider changes its appearance to gain protection from predators

An adult female of <i>Leptorchestes berolinenis</i>.<br />(Credit: Ondřej Michálek)
An adult female of Leptorchestes berolinenis.
(Credit: Ondřej Michálek)

There are few species of spiders that look alike ants during their entire lives. Such spiders cannot imitate the same ant species because spiders grow in size but ant imagoes do not. A hundred years ago naturalists observed, for the first time, that ant-like spiders change their shape and coloration as they grow in size and thus imitate different ant species – small ant species when they are juvenile and large ant species when they are adult. The phenomenon has been dubbed transformational mimicry. Strangely, it has not been tested whether these successive mimetic appearances are similarly protected from predators. Researchers from the Masaryk University in Czechia tested the hypotheses of transformational mimicry in the ant-mimicking jumping spider Leptorchestes berolinensis. The research was conducted in a meadow area with old oak tree trunks which are inhabited by ants and the ant-mimicking spiders. The researchers quantified the mimetic resemblance of different ontogenetic stages to potential ant models. They measured movement, body shape, body size, and coloration. Analysis revealed spider adults to possess more accurate resemblance to ants than juveniles. Adults were similar to smaller morphs of Camponotus or Lasius ants, whereas juveniles were more similar to Lasius and Colobopsis ants. Then the scientists tested whether co-occurring natural predators – mantises and Pisaura spiders – were deceived by juvenile and adult mimics after having experience with ant models. These predators never captured any ant or mimic. The researchers conclude that Leptorchestes berolinensis is a mimic of ants undergoing transformational mimicry, with all stages being similarly protected from predators. This study shows that even less accurate resemblance to ants is sufficient to protect ant-mimicking spiders from predators.


Abstract

Species that are Batesian mimics during post-embryonic development shift between mimetic models as they grow in size. However, it has not yet been tested whether these successive mimetic phenotypes are similarly protected from predators. Early instar phenotypes could represent an inaccurate phenotype or an accurate phenotype because of selection from different predators. Here, we tested the hypotheses of transformational Batesian mimicry in the ant-mimicking jumping spider Leptochestes berolinensis. We quantified the mimetic accuracy of different ontogenetic stages to potential ant models by using an multi-trait approach. We measured movement, body profile, body size, and coloration. Analysis revealed adults to be more accurate mimics than juveniles. Adults were similar to smaller morphs of Camponotus or Lasius ants, whereas juveniles were more similar to Lasius and Colobopsis ants. We tested whether predators, mantises and Pisaura spiders, were deceived by mimics after having experience with ant models. These predators never captured any ant or a mimic, but always captured the non-myrmecomorphic spider. We conclude that Leptorchestes berolinensis is a Batesian mimic of ants undergoing transformational mimicry with all stages being accurate mimics.