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When competitive traits are costly, negative frequency dependence can maintain genetic variance. Most theoretical studies examining this problem assume binary polymorphisms, yet most trait variation in wild populations is continuous. We propose that continuous trait variation can result from continuous variation in resource quality and that, specifically, the shape of the resource distribution determines trait maintenance. We used an individual-based model to test which conditions favour the stable maintenance of variation and which cause temporal fluctuations in trait values. This approach, inspired by contrasting outcomes of previous studies regarding variance and fluctuations in trait values, clearly showed a decisive role played by the shape of resource distributions. Under extreme conditions, e.g. the absence of resource variation or with very scarce resources for weak competitors, traits evolved to a single non-competitive or highly competitive strategy, respectively. Most other distributions led to strong temporal fluctuations on trait values or the maintenance of stable, standing variation. Our results thus explain the contradicting outcomes of previous theoretical studies and, at the same time, provide hypotheses to explain the maintenance of genetic variation and individual differences. We suggest ways to empirically test the proposed effects of resource variation on trait maintenance. [ABSTRACT FROM AUTHOR]

Keywords: antipredator defences; aposematism; camouflage; chemical defence; intraspecific predation; multimodal signals; ontogenetic change; predator cognition; synergy; trade-offs EN antipredator defences aposematism camouflage chemical defence intraspecific predation multimodal signals ontogenetic change predator cognition synergy trade-offs 961 966 6 07/18/23 20230701 NES 230701 I 'My object ... is to stimulate observation i I in a subject which will amply repay investigation, from the scientific value of the results, and the never-failing interest and charm of the inquiry.' i Edward Bagnall Poulton, [42], page vii INTRODUCTION To avoid predation, animals have evolved a wide array of antipredator defences that include visual, acoustic, chemical, mechanical, and behavioural traits (Ruxton et al., [50]). While most studies of anti-predator defences have been focused on their effect on heterospecific predators, threats from conspecifics can pose a serious danger to individuals, thus natural selection is likely to select for defences that reduce the chance of intraspecific predation. Likewise, predator communities dominated by foraging specialists may select for different types and combinations of antipredator defences than communities dominated by generalist predators (Kikuchi et al., [26]; Pekár et al., [36]). Theme 4: Phylogenetic comparisons and community ecology The evolution of antipredator defences cannot be understood without applying a broader comparative approach and considering the defences of a particular prey species in the context of prey and predator communities. [Extracted from the article]

Batesian mimics are harmless prey species that resemble dangerous ones (models), and thus receive protection from predators. How such adaptive resemblances evolve is a classical problem in evolutionary biology. Mimicry is typically thought to be difficult to evolve, especially if the model and mimic produce the convergent phenotype through different proximate mechanisms. However, mimicry may evolve more readily if mimic and model share similar pathways for producing the convergent phenotype. In such cases, these pathways can be co-opted in ancestral mimic populations to produce high-fidelity mimicry without the need for major evolutionary innovations. Here, we show that a Batesian mimic, the scarlet kingsnake Lampropeltis elapsoides, produces its coloration using the same physiological mechanisms as does its model, the eastern coral snake Micrurus fulvius. Therefore, precise color mimicry may have been able to evolve easily in this system. Generally, we know relatively little about the proximate mechanisms underlying mimicry [Current Zoology 58 (4): 658–667, 2012].

One hundred and fifty years ago, the English naturalist Henry Walter Bates (1) discovered a phenomenon that he regarded as 'a most powerful proof of the theory of natural selection'. [...]

Explaining variation in the abundance of species remains a challenge in ecology. We sought to explain variation in abundance of Neotropical forest birds using a dataset of population densities of 596 species. We tested a priori hypotheses for the roles of species traits, environmental factors, and species interactions. Specifically, we focused on four factors: 1) body mass (trait), 2) habitat type (environmental factor), 3) net primary productivity (NPP; environmental factor) and 4) species richness of competitors (species interaction). Body size explained much variation in density, although only when analyzed at higher taxonomic levels. Habitat type was a strong predictor of density. The relationship between density and productivity was weak. Densities were related negatively to the species richness of heterospecifics. This trend was particularly strong within closely related groups. Our results show that the influence of energetic factors such as body size and productivity depends on phylogeny, and that they act through indirect relations with other variables; alternative ecological factors such as habitat structure and species interactions play a more direct and stronger role in determining abundance than previously thought. [ABSTRACT FROM AUTHOR]

The article reports on an analysis of hoverflies suggesting the persistence of imperfect imitation in the face of natural selection. It argues that the mimicry in which some species evolve to resemble another species in order to avoid predation is imprecise. It also mentions English naturalist Henry Walter Bates who discovered the Batesian mimicry, which is a spectacular type of adaptation.

Novel behaviours are the raw material of cultural evolution, yet we do not have a clear picture of when they are likely to arise. I use a state-dependent model to examine how individual age and energy reserves interact with the abundance of known and novel prey to promote dietary innovation (incorporating a new food item into the diet). I measure innovativeness as persistence in attempting to capture novel prey. I find a trend towards greater persistence among younger individuals. Decreased abundance of known prey and increased abundance of novel prey also favour persistence. However, many exceptions to these trends occur. These exceptions are critical because they may explain inconsistencies among studies of animal innovation. Care must be taken in experiments to control for multiple factors relevant to an animal's energy budget and foraging opportunities. We may learn more about innovation in experimental contexts by (i) manipulating the abundance of novel and familiar food resources, (ii) directly measuring animal age and condition, and-where possible-(iii) fitting nonlinear models to innovative behaviour. Results indicate that selection for persistence may also favour neophilia.

Mimicry is common in interspecies interactions, yet conditions maintaining Batesian mimicry have been primarily tested in predator-prey interactions. In pollination mutualisms, floral mimetic signals thought to dupe animals into pollinating unrewarding flowers are widespread (greater than 32 plant families). Yet whether animals learn to both correctly identify floral models and reject floral mimics and whether these responses are frequency-dependent is not well understood. We tested how learning affected the effectiveness and frequency-dependence of imperfect Batesian mimicry among flowers using the generalist bumblebee, Bombus impatiens , visiting Begonia odorata , a plant species exhibiting intersexual floral mimicry. Unrewarding female flowers are mimics of pollen-rewarding male flowers (models), though mimicry to the human eye is imperfect. Flower-naive bees exhibited a perceptual bias for mimics over models, but rapidly learned to avoid mimics. Surprisingly, altering the frequency of models and mimics only marginally shaped responses by naive bees and by bees experienced with the distribution and frequency of models and mimics. Our results provide evidence both of exploitation by the plant of signal detection trade-offs in bees and of resistance by the bees, via learning, to this exploitation. Critically, we provide experimental evidence that imperfect Batesian mimicry can be adaptive and, in contrast with expectations of signal detection theory, functions largely independently of the model and mimic frequency. This article is part of the theme issue 'Signal detection theory in recognition systems: from evolving models to experimental tests'.