A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the

A single origin of Batesian mimicry among hybridizing populations of admiral butterflies (Limenitis arthemis) rejects an evolutionary reversion to the ancestral phenotype

Wesley K. Savage and Sean P. Mullen
Department of Biological Sciences, Lehigh University

Batesian mimicry is a fundamental example of adaptive phenotypic evolution driven by strong natural selection. Given the potentially dramatic impacts of selection on individual fitness, it is important to understand the conditions under which mimicry is maintained versus lost. Although much empirical and theoretical work has been devoted to the maintenance of Batesian mimicry, there are no conclusive examples of its loss in natural populations. Recently, it has been proposed that non-mimetic populations of the polytypic Limenitis arthemis species complex represent an evolutionary loss of Batesian mimicry, and a reversion to the ancestral phenotype. Here, we evaluate this conclusion using segregating amplified fragment length polymorphism markers to investigate the history and fate of mimicry among forms of the L. arthemis complex and closely related Nearctic Limenitis species. In contrast to the previous finding, our results support a single origin of mimicry within the L. arthemis complex and the retention of the ancestral white-banded form in non-mimetic populations. Our finding is based on a genome-wide sampling approach to phylogeny reconstruction that highlights the challenges associated with inferring the evolutionary relationships among recently diverged species or populations (i.e. incomplete lineage sorting, introgressive hybridization and/or selection).

Keywords: wing pattern evolution, mimicry, amplified fragment length polymorphism, Limenitis phylogeny, gene flow

Concealed by conspicuousness: distractive prey markings and backgrounds

Concealed by conspicuousness: distractive prey markings and backgrounds

Proceedings of Royal Society B (2009) vol. 276, no. 1663, 1905-1910
Marina Dimitrova(1), Nina Stobbe(2), H. Martin Schaefer(2) and Sami Merilaita(1)

(1)Department of Zoology, Stockholm University
(2)Department of Evolutionary Biology and Animal Ecology, Faculty of Biology, University of Freiburg Hauptstrasse 1

High-contrast markings, called distractive or dazzle markings, have been suggested to draw and hold the attention of a viewer, thus hindering detection or recognition of revealing prey characteristics, such as the body outline. We tested this hypothesis in a predation experiment with blue tits (Cyanistes caeruleus) and artificial prey. We also tested whether this idea can be extrapolated to the background appearance and whether high-contrast markings in the background would improve prey concealment. We compared search times for a high-contrast range prey (HC-P) and a low-contrast range prey (LC-P) in a high-contrast range background (HC-B) and a low-contrast range background (LC-B). The HC-P was more difficult to detect in both backgrounds, although it did not match the LC-B. Also, both prey types were more difficult to find in the HC-B than in the LC-B, in spite of the mismatch of the LC-P. In addition, the HC-P was more difficult to detect, in both backgrounds, when compared with a generalist prey, not mismatching either background. Thus, we conclude that distractive prey pattern markings and selection of microhabitats with distractive features may provide an effective way to improve camouflage. Importantly, high-contrast markings, both as part of the prey coloration and in the background, can indeed increase prey concealment.

keywords: crypsis, predation, dazzle, disruptive coloration, camouflage, background matching

Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos

Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos

Proceedings of the royal society series B, vol. 276, no. 1662, 1565-1673
photo from Nature 433, 211-212

Karen L Cheney(1), Charlotta Skogh(2), Nathan S Hart(2) and N. Justin Marshall(2)

(1)School of Integrative Biology, The University of Queensland St Lucia
(2)School of Biomedical Sciences, The University of Queensland St Lucia

Animals change their body coloration for a variety of purposes including communication, thermoregulation and crypsis. The cues that trigger adaptive colour change are often unclear, and the role of colour vision remains largely untested. Here, we investigated the bluestriped fangblenny (Plagiotremus rhinorhynchos), an aggressive mimic that changes its body coloration to impersonate a variety of coral reef fishes. In this field, we determined the fish species that the fangblenny associated with and measured the spectral reflectance of mimics and their models. We measured the spectral absorbance characteristics of the retinal photoreceptor visual pigments in the bluestriped fangblenny using microspectrophotometry and found it to have rod photoreceptors (λmax 498 nm), single cones (449 nm) and double cones (561 nm principal member; 520 nm accessory member). Using theoretical vision models, fangblennies could discriminate between the colours they adopted and the colours of the fish they associated with. Potential signal receivers (Abudefduf abdominalis and Ctenochaetus strigosus) perceived colours of most mimics to closely resemble fishes they associated with. However, fishes with ultraviolet-sensitive visual pigments were better at discriminating between mimics and models. Therefore, colour vision could be used by fangblennies when initiating colour change enabling them to accurately resemble fishes they associate with and to avoid detection by signal receivers.

Keywords: facultative mimicry, microspectrophotometry, colour vision, colour change, spectral reflectance, coral reef fish