Combination of local selection pressures drives diversity in aposematic signals

Abstract

The diversity of aposematic signals is one of the most difficult phenomena for understanding the evolution of such signals because aposematic animals are most effectively protected when they are common. Theoretical and experimental studies predict that a combination of local selection pressures could maintain variation in aposematic signals. However, the application of this hypothesis to large-scale geographic variation in aposematic signals, other than mimicry systems, is yet to be tested empirically. I investigated geographic variation in morphological and behavioural aposematic signals of the newts, Cynops pyrrhogaster, and in predation pressures on them in populations ranging over 800 km of latitude. Field experiments demonstrated that local differences in predation pressures explain well the island-mainland variation in the aposematic colouration and behaviour of newts. Furthermore, I found a latitudinal gradient in aposematic colouration but not in behaviour, independent of predation pressures. The results suggested that islandmainland variation in aposematic signals resulting from local differences in predation pressures might also be shaped by several factors, such as temperature, body size variation, and genetic differences, and such factors might act on each aposematic trait differently.

Not Everything Is Black and White: Color and Behavioral Variation Reveal a Continuum Between Cryptic and Aposematic Strategies in a Polymorphic Poison Frog

“…This can occur by at least two mechanisms. First, if prey populations are exposed to different combinations of predators and predators differ in their susceptibility to prey toxins (Endler and Mappes ) or in the use of visual versus olfactory cues (e.g., Mochida ), then less conspicuous and/or more toxic phenotypes will be favored where toxin‐resistant, and olfactory‐oriented predators are more common. Interestingly, from South to North O. granulifera is decreasingly conspicuous and increasingly toxic (Wang ).…”

Influences of geographic differentiation in the forewing warning signal of the wood tiger moth in Alaska

“…Some of the species found to have geographically varying warning signals include Neotropical Heliconius butterflies (Brown & Benson 1974, Brower 1996, Mallet 2010, ladybird beetles (Creed 1966, Brakefield 1985, Dolenská et al 2009, Blount et al 2012, monarch butterflies (Brower 1958, Davis et al 2005, Davis et al 2012, newts (Mochida 2009, Mochida 2011, poison frogs (Daly & Myers 1967, Savage 1968, Summers et al 2003, Wang & Summers 2010, Wang 2011, Rudh et al 2011, Maan & Cummings 2012, Willink et al 2013, RichardsZawacki et al 2013, Hegna et al 2013b), velvet ants (Wilson et al 2012), alpine leaf beetles (Borer et al 2010), and bumble bees (Plowright & Owen 1980). Interestingly, some aposematic species appear to switch between aposematic and cryptic strategies across their distributions.…”

Warning Signal Efficacy: Assessing the Effects of Color, Iridescence, and Time of Day in the Field

“…). Additionally, the predator community structure may change throughout the day, and different types of predators are likely to vary in their visual capabilities and tendency to attack aposematic prey (e.g., Endler & Mappes ; Kelber & Roth ; Ratcliffe & Nydam ; Mochida ; Valkonen et al. ; Nokelainen et al.…”