Medio Ambiente y Seguridad
Cats developed spots and stripes to lure rodents. A multidisciplinary framework for understanding the functions of the colour pattern on cats.
Author(s): Benavides Hernández, L, Benavides, O
To date the precise function of spots and stripes pattern on feline´s fur remains a mystery. Predators use lures in the type and range of signals used by their prey to sense his environment in feeding activities and possible in other intra- and inter- species communication. The type of signals can be acoustic, visual, chemical, mechanical or other used by the prey. In our work we argue that predation by luring is a driving force to the formation of skin color patterns and behavior of cats. We propose a computational visual comparative model to demonstrate the function of the color pattern on feline’s fur. We hypothesized that felines have developed a selective signaling, meaning that a signal pattern is intended to be detected by a specific receiver, but it would pass undetected for non-convenient receivers.
Centre for Marine Biology
Contrasting shape, color plasticity and habitat use indicate morph-specific roles in a marine shrimp
Author(s): Duarte, RC, Flores, AAV
Color and shape polymorphisms are important traits of species, allowing a more generalist strategy and a better use of resources. An efficient occupation of space may lead to very abundant populations, triggering density‐dependent processes and alternative mating systems. Hippolyte obliquimanus is a small gonochoristic shrimp species, and supposedly a generalist algal dweller in shallow waters. Yet, populations comprise two main morphotypes, homogeneous shrimps of variable color (H) and transparent individuals with disruptive stripes or bands (D). H color patterns tend to inhabit macroalgal substrates of matching background, while D individuals are evenly distributed between habitats. Unlike D shrimps, H morphs are capable of color change within a few days, but camouflage efficiency is habitat‐dependent. Pink (P) animals collected in the red algal Galaxaura turned cryptic when supplied the brown weed Sargassum, but color change of greenish‐brown (GB) shrimps from Sargassum did not fully conceal in Galaxaura. Homogeneous GB and disruptive morphs select Sargassum, while no preference was detected for homogeneous P individuals. Crypsis efficiency and habitat selection explain the much higher shrimp density in Sargassum compared to Galaxaura. The overall population sex‐ratio did not depart from the 1 : 1 ratio, but D individuals were mostly males and H shrimps chiefly females. These main morphs also differ in shape; D shrimps are more streamlined and H ones stouter, further suggesting enhanced mobility and substrate fidelity, respectively. Morph‐specific functional roles would promote lower density and stable population dynamics at mixed algal beds, but higher density and a more fluctuating trend in monospecific Sargassum stands.
Department of Zoology
Mimicry evolution: it's in the eye of the beholder
Author(s): Kazemi, B, Leimar, O, Gamberale-Stille, G
During mimicry evolution the perceived mimic-model similarity increases and the evolutionary direction could be strongly influenced by predators judgement of similarity. Mimicry evolution is thus more likely to commence in traits that predators use prior to others to categorise prey. If they use such feature-based categorisation, a similarity with the model in such a feature should lead to increased survival. I tested the idea by studying if birds attend to specific features of prey appearance when they learn to discriminate and generalise between them. I used wild Blue Tits as predators and tested the colour, pattern and shape dimension of artificial prey. The birds first learned to avoid a specific model prey appearance and then performed a generalisation test with new mimics that shared one dimension with the model. I found that colour mimics were strongly avoided whereas pattern and shape mimics were attacked. This shows that the birds primarily attended to a single feature, colour, and thus generalised between models and colour mimics. In a separate experiment I found that the birds learned the colour dimension significantly quicker than pattern and shape, showing that colour is a significantly more salient trait to them in terms of learning and categorisation.
The cichlid and reef fish visual system as a model for speciation processes
Author(s): Stieb, SM, Marshall, J, Salzburger, W
Freshwater cichlid and marine reef fish species represent spectacular products of adaptive radiations. Their amazing color diversities and well-adapted visual systems make them ideal candidates for a comparative study of molecular mechanisms involved in speciation based on the visual system. These will help to identify external factors and environmental conditions that shape color morphs and visual sensitivities. The major aims of this study are to compare (1) the coloration, (2) the molecular basis of the diversity of visual pigments, (3) visual pigment expression patterns, (4) transmission properties of the ocular media and (5) photic properties of habitats between cichlids and reef fish. Up to now, we sampled a representative set of shallow-water labrids (Labridae), damselfish (Pomacentridae) and cichlids (Cichlidae) in definite light habitats and studied their visual sensitivities composed of opsin gene variations and opsin gene expression patterns. Spectrophotometry was used to define the different light environments. To determine the molecular basis of visual pigments, we sequenced opsin genes using DNA and next generating sequencing. To quantify the relative amount of opsin gene expression we performed real time quantitative PCR.
Dept. of Biosciences
Warning signals and handicap theory
Author(s): Holen, ØH, Svennungsen, TO
Aposematism has often been seen as a dynamical, transient phenomenon that can be destabilised by the appearance of undefended cheater prey (mimics). Recent theoretical work has made it clear that warning signals can also be evolutionarily stable and honest. Signalling theory predicts that an honest signalling system can contain a limited number of cheats without being destabilised as long as the system remains 'honest on average'. Somewhat analogous to this, a game theoretical analysis of three different mechanisms for honest warning signalling predicted an overall positive relationship between conspicuousness and defence across prey, given that signals were honest on average. Here we extend this analysis further and identify mechanisms for honest warning signalling that do not give rise to a positive relation between conspicuousness and defence. Some complicating factors include tradeoffs between warning signals and life-history traits, and non-monotonic relations between prey aversion and toxicity that may arise when predators can taste-reject prey.