2009年2月23日 星期一

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

Behavioural Evology and Sociobiology, Vol. 62, No. 8, 1267-1276

Eira Ihalainen, Leena Lindström, Johanna Mappes and Sari Puolakkainen
Department of Biological and Environmental Science, FI-40014 University of Jyväskylä

Müllerian co-mimics are aposematic species that resemble each other; sharing a warning signal is thought to be mutually beneficial for the co-mimics by reducing per capita predation risk. In Batesian mimicry, edible mimics avoid predation by resembling an aposematic model species. The protection of both the model and the mimic is weakened when the mimics are abundant compared to the models. The quasi-Batesian view suggests that defended (Müllerian) co-mimics, when unequal in their defences, could also show a Batesian-like trend of increasing mortality with increasing abundance of a less defended “mimic”. We manipulated frequencies of unequally distasteful artificial co-mimics that were prey for great tits. The co-mimics had different signals (imperfect mimicry) but were equally preferred by the birds when palatable. Unexpectedly, when unpalatable, one of the signals was easier for the birds to learn to avoid. Consequently, during predator learning, the signal design of the prey strongly affected mortality of the co-mimics; there was an interaction between the signal and frequency treatments, but increasing the frequency of a less defended “mimic” did not increase co-mimic mortalities as predicted. In contrast, in a memory test that followed, the effect of signal design disappeared; if the birds had experienced high frequency of “mimics” during learning, co-mimic mortalities did subsequently increase. Since the effect of co-mimic frequencies on mortalities changed depending on the signal design of the prey and predator experience, the results suggest that mimetic relationship may be an unpredictable interplay of several factors in addition to taste and abundance.

Keywords: Aposematism - Quasi-Batesian mimicry - Predator psychology - Avoidance learning - Memory

2009年2月21日 星期六

The effect of rainforest fragmentation on species diversity and mimicry ring composition of ithomiine butterflies

The effect of rainforest fragmentation on species diversity and mimicry ring composition of ithomiine butterflies

Insect Conservation and Diversity. 2009. Vol. 2, No. 1, 23-28.
MARCIO UEHARA-PRADO (1,2) and ANDRÉ V.L. FREITAS (1)
1 Departamento de Zoologia, Instituto de Biologia, Universidade Estadual de Campinas
2 Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Estadual de Campinas

1. Subfamily Ithomiinae comprises about 370 species of Neotropical butterflies associated with humid forest habitats from Mexico to northern Argentina. Adult Ithomiinae are central models in many mimicry rings throughout their range, and are assumed to have high potential as bio-indicators. Here, we compare diversity and composition of Ithomiinae mimicry rings in continuous vs. fragmented landscapes, and evaluate values these butterflies hold for ecological assessment and monitoring of anthropogenic disturbance.

2. Sampling was carried out at four sites inside a large forest block, the Morro Grande State Reserve, and in five forest fragments in a neighbour-fragmented landscape. Butterflies were sampled with portable traps, baited with a fermented mixture of banana and sugar cane juice. Sampling was carried out during the period most favourable for the capture of ithomiine butterflies in southeastern Brazil.

3. There was no difference between landscapes in species richness and diversity index, but dominance index, and the distributions of tribes and mimicry rings between them was clearly different. The higher average light intensity in the understorey of fragments could explain in part the higher abundance of mimicry patterns typical of open sunny habitats, and concomitantly reduced abundance of clearwing mimicry patterns, typical of shaded habitats. These results confirm the potential of ithomiine assemblages as biological indicators of habitat quality.

Keywords: Atlantic rainforest • biological indicators • conservation • Ithomiinae

Octopus mimicking its follower reef fish

Octopus mimicking its follower reef fish

Journal of Natural History. 2009. Vol. 43. No. 3 & 4. 185-190.
J. P. Krajewski (ab), R. M. Bonaldo (ac), C. Sazima(d), I. Sazima(e)
(a) School of Marine and Tropical Biology, James Cook University
(b) Departamento de Zoologia e Ps-Graduao em Ecologia, Universidade Estadual de Campinas
(c) Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University
(d) Departamento de Parasitologia, Universidade Estadual de Campinas, Campinas
(e) Museu de Zoologia, Universidade Estadual de Campinas, Campinas

We describe a possible example of social mimicry between Octopus insularis and the small grouper Cephalopholis fulva, which frequently associate during foraging at Fernando de Noronha Archipelago, Brazil. The octopus, when swimming backwards, jet-propelled, becomes similar in colour and shape to accompanying C. fulva individuals and is therefore less conspicuous within the fish group. We regard this as an instance of social mimicry, a form of protection against visually-oriented predators in which different species similar in shape and colour mingle for the advantage of grouping. Even when swimming backwards alone, O. insularis may become similar to foraging C. fulva individuals, another putatively protective behaviour. We suggest that the feeding association commonly found between O. insularis and C. fulva minimized the evolutionary costs for the origin of mimicking by the octopus.

Keywords: social mimicry; Octopus insularis; Cephalopholis fulva; foraging association; Fernando de Noronha Archipelago

2009年2月20日 星期五

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?

Behavioral Ecology (2009)
Karen L. Cheney(a) and N. Justin Marshall(b)

(a) School of Integrative Biology (b) School of Biomedical Sciences, The University of Queensland,

Batesian and aggressive mimics are considered to be under selective pressure to resemble their models, whereas signal receivers are under selection to discriminate between mimics and models. However, the perceptual ability of signal receivers to discriminate between mimics and models is rarely studied. Here we examined 15 model–mimic coral reef fish pairs using nonsubjective methods to judge the accuracy of mimics in terms of color and luminance. We then investigated the potential ability of fish with various visual systems to discriminate between model and mimic colors using theoretical vision models. We found the majority of mimics closely resembled models in terms of color and luminance from a nonsubjective perspective. However, fish that have potentially trichromatic (3 distinct cone photoreceptors) visual systems with ultraviolet sensitivity had a much better capacity to discriminate between models and mimics compared with fish with midrange sensitivity or dichromatic (2 cone photoreceptors) fish. The spectral reflectance of color patches reflected by models and mimics became more similar with an increase in depth, indicating that signal receivers may be more likely to distinguish mimics from models in habitats located closer to the surface. There was no such change in luminance contrast with depth. The selection pressure on mimics to accurately resemble their model is therefore predicted to vary depending on the visual system of the signal receiver and the light environment.

Key words: aggressive mimicry, animal signaling, Batesian, color vision, signal accuracy.

2009年2月1日 星期日

Identity of Euploea orontobates Fruhstorfer, 1910 (Lepidoptera: Nymphalidae), a milkweed butterfly from Thailand and Vietnam


Identity of Euploea orontobates Fruhstorfer, 1910 (Lepidoptera: Nymphalidae), a milkweed butterfly from Thailand and Vietnam

Zootaxa (2009) Vol. 1991, 43-50

A.L. MONASTYRSKII(1) & R.I. VANE-WRIGHT(2) 1Vietnam-Russia Research Tropical Centre 2Department of Entomology, the Natural History Museum, Cromwell Road, London SW7 5BD, UK; & Durrell Institute of Conservation and Ecology, University of Kent

Euploea orontobates Fruhstorfer, 1910, described from south-eastern Thailand (Si Racha district), is demonstrated to be a senior synonym of Euploea conbuom Saito & Inayoshi, 2006, from southern Central Vietnam. The relationships and biogeography of this rare butterfly are discussed, and presented together with comments on the principal mimicry complex among the Euploea species of Indochina.

Keywords: Danainae, Euploea orontobates, Euploea conbuom, synonymy, relationships, Thailand, Vietnam, Sundaland, endemism, biogeography