Biomedical subjects

H Martin Schaefer

Publications and source records attributed to H Martin Schaefer.

3 recordsLinked to original sources

PubMed2006

Disruptive coloration provides camouflage independent of background matching.

Natural selection shapes the evolution of anti-predator defences, such as camouflage. It is currently contentious whether crypsis and disruptive coloration are alternative mechanisms of camouflage or whether they are interrelated anti-predator defences. Disruptively coloured prey is characterized by highly contrasting patterns to conceal the body shape, whereas cryptic prey minimizes the contrasts to background. Determining bird predation of artificial moths, we found that moths which were dissimilar from the background but sported disruptive patterns on the edge of their wings survived better in heterogeneous habitats than did moths with the same patterns inside of the wings and better than cryptic moths. Despite lower contrasts to background, crypsis did not provide fitness benefits over disruptive coloration on the body outline. We conclude that disruptive coloration on the edge camouflages its bearer independent of background matching. We suggest that this result is explainable because disruptive coloration is effective by exploiting predators' cognitive mechanisms of prey recognition and not their sensory mechanisms of signal detection. Relative to disruptive patterns on the body outline, disruptive markings on the body interior are less effective. Camouflage owing to disruptive coloration on the body interior is background-specific and is as effective as crypsis in heterogeneous habitats. Hence, we hypothesize that two proximate mechanisms explain the diversity of visual anti-predator defences. First, disruptive coloration on the body outline provides camouflage independent of the background. Second, background matching and disruptive coloration on the body interior provide camouflage, but their protection is background-specific.

Animals↗

PubMed2006

Plants on red alert: do insects pay attention?

Two recent hypotheses have proposed that non-green plant colouration evolved as a defence against herbivores, either as protective colouration promoting handicap signals indicating plant fitness or by undermining their crypsis. The handicap hypothesis posits a co-evolutionary process between plants and herbivores, whereas the anti-crypsis hypothesis suggests that an arms race between insects and plants is the evolutionary mechanism. Both explanations assume that insects are the evolutionary origin causing plants' colouration. Here, we propose a different hypothesis, termed the "Defence Indication hypothesis". This idea focuses on the multiple protective functions of anthocyanins and carotenoids as pigments, and suggests that plant colouration evolved primarily in response to various stressors. Because pigments and defensive compounds share a common biosynthesis, the production of pigments also provides elevated defensive strengths against herbivores, a process termed priming. In effect, the Defence Indication hypothesis predicts that pleiotropic effects of the pigments and, more generally, plants' shared defence responses, explain why insects might react to plant colouration.

Animals↗

PubMed2004

Red leaves, insects and coevolution: a red herring?

W.D. (Bill) Hamilton proposed that coevolution between plants and herbivorous insects explains the bright autumnal colouration of leaves. Accordingly, plants invest in bright signals to reduce their herbivore load, whereas insects use these bright signals to identify less-defended hosts more efficiently. Archetti and Brown have recently revisited this theory by explaining its basic predictions and providing new research perspectives. Their work presents an important basis to our understanding of non-green leaf colouration, provided that alternative adaptive explanations on the photoprotective and antioxidant role of leaf pigments, or their possible function in crypsis to herbivores are incorporated into future research.

Journal Article↗