Do unprofitable prey evolve traits that profitable prey find difficult to exploit?

Prey that are unprofitable to attack (for example, those containing noxious chemicals) are often conspicuously patterned and move in a slower and more predictable manner than species lacking these defences. Contemporary theories suggest these traits have evolved as warning signals because they can facilitate both associative and discriminative avoidance learning in predators. However, it is unclear why these particular traits and not others have tended to evolve in unprofitable prey. Here we show using a signal detection model that unprofitable prey will evolve conspicuous colours and patterns partly because these characteristics cannot readily evolve in profitable prey without close mimicry. The stability of this signal is maintained through the costs of dishonesty in profitable prey. Indeed, unprofitable prey will sometimes evolve a conspicuous form to reduce mimetic parasitism, even in the unlikely event that this form can be more closely mimicked. This is one of the first mathematical models of the evolution of warning signals to allow for the possibility of mimicry, yet our analyses suggest it may offer a general explanation as to why warning signals take the form that they do. Warning signals and mimicry may therefore be more closely related than is currently supposed

The evolution of multi-component mimicry

The relative sizes of phenotypic mutations contributing to evolutionary change has long been the subject of debate. We describe how mimicry research can shed light on this debate, and frame mimicry studies within the general context of macromutationism and micromutationism, and punctuated versus gradual evolution. Balogh and Leimar [Müllerian mimicry: an examination of Fisher's theory of gradual evolutionary change. Proc. Roy. Soc. Lond. B Biol. Sci. 272, 2269–2275] have recently used a model to readdress the question of whether or not mimicry evolves gradually along a single dimension. We extend their approach, and present the first model to consider the effect of predator generalization along multiple components on the evolution of mimicry. We find that the gradual evolution of mimicry becomes increasingly less likely as the number of signal components increases, unless predators generalize widely over all components. However, we show that the contemporary two-step hypothesis (punctuated evolution followed by gradual refinement) can explain the evolution of Müllerian mimicry under all tested conditions. Thus, although the gradual evolution of mimicry is possible, the two-step hypothesis appears more generally applicable

Faecal residues of veterinary parasiticides: Non-target effects in the pasture environment

Residues of veterinary parasiticides in dung of treated livestock have nontarget effects on dung-breeding insects and dung degradation. Here, we review the nature and extent of these effects, examine the potential risks associated with different classes of chemicals, and describe how greater awareness of these nontarget effects has resulted in regulatory changes in the registration of veterinary products

Use of coupled oscillator models to understand synchrony and travelling waves in populations of the field vole Microtus agrestis in northern England

1. Earlier studies have reported that field vole Microtus agrestis populations in Kielder Forest, UK, exhibit typical 3–4‐year cyclical dynamics, and that the observed spatiotemporal patterns are consistent with a travelling wave in vole abundance moving along an axis south‐west–north‐east at approximately 19 km year–1. One property of this wave is that nearby populations fluctuate more synchronously than distant ones, with correlations falling lower than the average for the sampling area beyond approximately 13 km. 2. In this paper we present a series of models that investigate the possibility that both the observed degree of synchrony and the travelling wave can be explained as a simple consequence of linking a series of otherwise independently oscillating populations. Our ‘coupled oscillator’ models consider a series of populations, distributed either in a linear array or in a two‐dimensional regular matrix. Local population fluctuations, each with a 3–4‐year period, were generated using either a Ricker equation or a set of discrete‐time Lotka–Volterra equations. Movement among populations was simulated either by a fixed proportion of each population moving locally to their nearest neighbour populations, or the same proportion being distributed via a continuous geometric function (more distant populations receiving less). 3. For a variety of different ways of generating cycles and a number of different movement rules, local exchange between oscillating populations tended to generate synchrony domains that extended over a large number of populations. When the rates of exchange between local populations were relatively low, then permanent travelling waves emerged, especially after an initial invasion phase. There was a non‐linear relationship between the amount of dispersal and the domain of synchrony that this movement generated. Furthermore, the observed spatiotemporal patterns that emerged following an initial invasion phase were found to be highly dependent on the extreme distances reached by rare dispersers. 4. As populations of voles are predominantly distributed in grassland patches created by clear‐cutting of forest stands, we estimated the mean patch diameter and mean interpatch distance using a geographical information system (GIS) of the forest. Our simplified models suggest that if as much as 5–10% of each vole population dispersed a mean of 178 m between clear‐cuts per generation, then this would generate a synchrony domain and speed of wave in the region of 6–24 km (per year), which is reasonably consistent with the observed synchrony domain and speed. Much less dispersal would be capable of generating this scale of domain if some individuals occasionally moved beyond the nearest‐neighbour patch. 5. While we still do not know what causes the local oscillations, our models question the need to invoke additional factors to explain large‐scale synchrony and travelling waves beyond small‐scale dispersal and local density‐dependent feedback. Our work also suggests that the higher degrees of synchrony observed in Fennoscandian habitats compared with Kielder may be due in part to the relative ease of movement of voles in these former habitats. As our work confirms that the rates of exchange among local populations will have a strong influence on synchrony, then we anticipate that the spatiotemporal distribution of clear‐cuts will also have an important influence on the dynamics of predators of voles

Application of molecular techniques to non-lethal tissue samples of endangered butterfly populations (Parnassiuss apollo L.) in Norway for conservation management

Tissue from the wing tips of the endangered Apollo butterfly (Parnassius apollo L.) were collected at the end of a breeding season from two sites in Norway: Bandak and Gjendetunga/Bukkelægret about 250 km apart. We investigated the suitability of such non-lethal samples as a source of DNA for studying these populations. Universal mitochondrial DNA (mtDNA) primers were used to amplify DNA from the wing tip extractions. Primers spanning the 12s rRNA region produced 0.35 kb fragments that proved to be invariable in the selected samples when tested for restriction length polymorphisms (RFLPs). These sequences had high homology with analogous mtDNA from other insect sources, e.g. lepidoptera [Spodoptera litura (Fabricius)], and served to authenticate the DNA. Random amplified polymorphic DNA (RAPDs) technology was then used to screen for genetic variability. Of several primers tested, Primer-01 (Operon Kit F) produced a profile that differentiated the population with 88% (P<0.001) efficiency based on multivariate logistic regression analysis of banding profiles. RAPDs were also adapted to develop different molecular marker approaches to screen the samples quickly and cheaply. This work indicates that reliable ‘molecular tags’ can be designed to track demographic populations to study their distribution without endangering the butterfly and highlights the suitability of these markers for use in future population studies

Secondary chemicals protect mould from fungivory

The vast repertoire of toxic fungal secondary metabolites has long been assumed to have an evolved protective role against fungivory. It still remains elusive, however, whether fungi contain these compounds as an anti-predator adaptation. We demonstrate that loss of secondary metabolites in the soil mould Aspergillus nidulans causes, under the attack of the fungivorous springtail Folsomia candida, a disadvantage to the fungus. Springtails exhibited a distinct preference for feeding on a mutant deleted for LaeA, a global regulator of Aspergillus secondary metabolites. Consumption of the mutant yielded a reproductive advantage to the arthropod but detrimental effects on fungal biomass compared with a wild-type fungus capable of producing the entire arsenal of secondary metabolites. Our results demonstrate that fungal secondary metabolites shape food choice behaviour, can affect population dynamics of fungivores, and suggest that fungivores may provide a selective force favouring secondary metabolites synthesis in fungi