Abstracts (first author)

Poster 

Snake head shape mimicry: implications to the conservation of the endangered mimic

Author(s): Valkonen JK, Nokelainen O, Galarza J, Mappes J

Summary:

Most research on the adaptive significance of warning signals has focused on the colouration and patterns of prey animals. However, behaviour, odour and body shape can also have signal functions and thereby reduce predators’ willingness to attack defended prey. For example, European vipers all have a distinctive triangular head shape and they are all venomous. Several non-venomous snakes are known to flatten their heads (head triangulation) when disturbed. Also many Lepidopteran larvae enhance their resemblance to tree vipers by concealing their heads and inflating their thorax or abdomen to express a false, sometimes triangular-shaped head. Even though anecdotal evidence of significance of snake head mimicry is dated back to the Henry Bates (1862), the role of body shape recognition is rarely experimentally investigated. Here we present data from field experiments and show that the triangular head shape can be recognized and avoided by predators. We also discuss the significance of this finding on population dynamics of snakes and its application their conservation. The smooth snake (Coronella austriaca) is non-venomous endangered species. By head triangulation it mimics vipers (Vipera sp.) which are not always protected by law. Because vipers are heavily killed by humans, it is possible that this asymmetric conservation program will be flawed because deceptive mimicry only works if the relative density and frequency of model species is higher than mimics. Based on the experimental evidence, we suggest that vipers should be protected at least in the locations where they co-exist with endangered mimic species.



Abstracts (coauthor)

Summary:

Polymorphic warning signals are puzzling since positive frequency-dependent selection should promote monomorphic warning coloration. We studied predation pressure in the aposematic moth Parasemia plantaginis by using artificial prey resembling white and yellow male colour morphs in five separate populations. We tested if predation was influenced by: 1) natural frequencies of colour morphs; 2) number of interspecific Lepidopterans sharing similar coloration, and; 3) predator community composition. Predation on yellows was lower than whites’ regardless of their local frequency. The number of white interspecifics increased the attack risk of whites and decreased it on yellows, whereas yellow interpecifics lowered predation on both morphs. Interestingly, predation pressure was dependent on predator community composition: Yellows suffered less attacks when Paridae were abundant, whereas whites suffered less attacks when Prunellidae were abundant. Our results suggest spatial heterogeneity in prey and predator community composition can generate geographic mosaic selection facilitating the evolution of polymorphic warning signals.

Summary:

Flavobacterium columnare is a gram-negative bacterial pathogen that causes columnaris disease in freshwater aquaculture. Columnaris outbreaks occur at fish farms during summer months and may cause mortality up to 100 %. Virulence of environmental isolates of F. columnare has been found to be lower than those isolated during disease outbreaks at fish farms. In order to understand factors selecting for the higher virulence at fish farms, we studied if the bacterial dose, exposure time (transient or continuous), or nutrients have an effect on the virulence of F. columnare. Three F. columnare strains were used in two separate experiments: a non-virulent strain B398 isolated from the lake and two virulent strains from disease outbreaks (B185 and B67). In the first experiment zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss) fingerlings were individually infected with bath immersion (transient challenge) with 9 different doses of bacterial strains B185, B398, and a mixture of these strains. In the second experiment the bacteria (strains B185, B398 and B67) were added in three doses directly into aquaria (continuous challenge) where zebrafish and rainbow trout were maintained. Longevity of fish was monitored for five days in both experiments, and the infection verified by bacterial culture from gills.
We found bacterial dose to have a positive effect on mortality of both fish species. Increase in nutrients had a significantly positive effect on columnaris infection and fish mortality. The non-virulent strain was able to infect the fish when introduced in continuous exposure, but not in transient challenge. Our results suggest that the continuous exposure to bacteria at fish farms combined with a high nutrient level can promote virulence also in environmental non-virulent bacteria. In addition, the zebrafish can be used as a functional model host to study F. columnare virulence and infection dynamics in the laboratory.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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