Temporal relationship between genetic and warning signal variation in the aposematic wood tiger moth (Parasemia plantaginis)

Abstract

Many plants and animals advertise unpalatability through warning signals in the form of colour and shape. Variation in warning signals within local populations is not expected because they are subject to directional selection. However, mounting evidence of warning signal variation within local populations suggests that other selective forces may be acting. Moreover, different selective pressures may act on the individual components of a warning signal. At present, we have a limited understanding about how multiple selection processes operate simultaneously on warning signal components, and even less about their temporal and spatial dynamics. Here, we examined temporal variation of several wing warning signal components (colour, UV-reflectance, signal size and pattern) of two co-occurring colour morphs of the aposematic wood tiger moth (Parasemia plantaginis). Sampling was carried out in four geographical regions over three consecutive years. We also evaluated each morph's temporal genetic structure by analysing mitochondrial sequence data and nuclear microsatellite markers. Our results revealed temporal differences between the morphs for most signal components measured. Moreover, variation occurred differently in the fore- and hindwings. We found no differences in the genetic structure between the morphs within years and regions, suggesting single local populations. However, local genetic structure fluctuated temporally. Negative correlations were found between variation produced by neutrally evolving genetic markers and those of the different signal components, indicating a non-neutral evolution for most warning signal components. Taken together, our results suggest that differential selection on warning signal components and fluctuating population structure can be one explanation for the maintenance of warning signal variation in this aposematic species.

Colour polymorphism torn apart by opposing positive frequency‐dependent selection, yet maintained in space

“…White coloration might be a more effective warning signal in these circumstances because they have much higher luminance values compared to the yellow morph (Galarza et al . ).…”

“…; Galarza et al . ). Adaptive coloration also varies spatially as well as temporally in our system, and viability strongly favours one morph over the other via predation, immunocompetence response to disease (Nokelainen, Lindstedt & Mappes ) and potentially other pressures.…”

An aposematic colour‐polymorphic moth seen through the eyes of conspecifics and predators – Sensitivity and colour discrimination in a tiger moth

“…Thus, additional selective or genetic factors are usually involved. In A. plantaginis , where yellow males, on average, have an advantage against predators while white males tend to have a mating advantage, gene flow and variable selection by predators seem to offer an explanation for polymorphism (Galarza, Nokelainen, Ashrafi, Hegna, & Mappes, ; Nokelainen et al., ). Our results on A. plantaginis vision confirm that male selection for female coloration is unlikely, but a female may use chromatic cues for mate choice once a male has approached her, favouring the UV‐reflecting white males.…”

No evidence of quantitative signal honesty across species of aposematic burnet moths (Lepidoptera: Zygaenidae)

“…With only 2 years of data, it is difficult to explain the observed patterns of between‐year variation, but environmental conditions, linked to variation in weather across years (see Supporting Information Data S7), are likely to impact investment in coloration and chemical defences in burnet moths. Variation in coloration in tiger moths (Erebidae) has been linked to fluctuations in local ecological conditions (Galarza, Nokelainen, Ashrafi, Hegna, & Mappes, ), and in particular temperature (Goulson & Owen, ; Lindstedt, Lindström, & Mappes, ). Climate may also indirectly affect resource allocation to signals and defences in aposematic species, via effects on their host plants.…”