Global impacts of exotic eucalypt plantations on wildlife

The establishment of exotic tree plantations poses a pervasive threat to wildlife across the globe. Among the most important tree species used for forestry purposes worldwide are members of the genus Eucalyptus, which have now been established in at least 107 countries outside of their native range. When introduced into non-native areas, eucalypt plantations are associated with myriad novel challenges for native fauna, and have often been associated with reductions in the biodiversity of local communities. However, similar to other anthropogenic habitats, eucalypt plantations can also create novel opportunities for species that can allow them to survive and thrive in these novel environments. In this review, we use eucalypt plantations as a case study for understanding the ecological and evolutionary responses of wildlife to anthropogenic habitat loss and change. We begin by summarising the main avenues of research addressing the study of wildlife responses at the individual, community, and ecosystem levels, and highlight critical research gaps. We also consider the characteristics of different types of eucalypt plantations and how such attributes are linked with the ability of animals to respond appropriately to the establishment of plantations, and summarise important considerations for the conservation of animal communities in these human-altered habitats.

Environmental colour pattern variation in Mediterranean Podarcis

BACKGROUND

Lizards of the genus Podarcis are widespread in the Mediterranean region, including islands and island archipelagos. These small-bodied lizards have a predominantly protective green-brown colouration. However, some populations display unusual patterns, in which the colouration is predominantly blue or uniformly black. This study explores the factors that influence this chromatic variation, whether environmental (climate and island conditions) or evolutionary (phylogenetic trait conservatism). The colouration of 1400 individuals (27 species) was analysed in the CIELAB colour space.

RESULTS

Pagel's λ indicated that colouration is weakly conserved within phylogenetic lineages. Although the island surface plays a key role in the chromatic variability of these lacertids, geographic isolation and climate hold less influence. The colouration of some small island populations tends to be uniform and dark, possibly due to intense intraspecific competition and lower predatory pressure.

CONCLUSIONS

This study highlights the importance of island populations in understanding the processes that favour the emergence of extreme phenotypes in small ectothermic vertebrates.

Pattern variation is linked to anti-predator coloration in butterfly larvae

Prey animals typically try to avoid being detected and/or advertise to would-be predators that they should be avoided. Both anti-predator strategies primarily rely on colour to succeed, but the specific patterning used is also important. While the role of patterning in camouflage is relatively clear, the design features of aposematic patterns are less well understood. Here, we use a comparative approach to investigate how pattern use varies across a phylogeny of 268 species of cryptic and aposematic butterfly larvae, which also vary in social behaviour. We find that longitudinal stripes are used more frequently by cryptic larvae, and that patterns putatively linked to crypsis are more likely to be used by solitary larvae. By contrast, aposematic larvae are more likely to use horizontal bands and spots, but we find no differences in the use of individual pattern elements between solitary and gregarious aposematic species. However, solitary aposematic larvae are more likely to display multiple pattern elements, whereas those with no pattern are more likely to be gregarious. Our study advances our understanding of how pattern variation, coloration and social behaviour covary across lepidopteran larvae, and highlights new questions about how patterning affects larval detectability and predator responses to aposematic prey.

Poison frog social behaviour under global change: potential impacts and future challenges

The current and cascading effects of global change challenges the interactions both between animal individuals (i.e. social and sexual behaviour) and the environment they inhabit. Amphibians are an ecologically diverse class with a wide range of social and sexual behaviours, making them a compelling model to understand the potential adaptations of animals faced with the effects of human-induced rapid environmental changes (HIREC). Poison frogs (Dendrobatoidea) are a particularly interesting system, as they display diverse social behaviours that are shaped by conspecific and environmental interactions, thus offering a tractable system to investigate how closely related species may respond to the impacts of HIREC. Here, we discuss the potential impacts of global change on poison frog behaviour, and the future challenges this group may face in response to such change. We pay special attention to parental care and territoriality, which are emblematic of this clade, and consider how different species may flexibly respond and adapt to increasingly frequent and diverse anthropogenic stress. More specifically, we hypothesise that some parents may increase care (i.e. clutch attendance and distance travelled for tadpole transport) in HIREC scenarios and that species with more generalist oviposition and tadpole deposition behaviours may fare more positively than their less flexible counterparts; we predict that the latter may either face increased competition for resources limited by HIREC or will be forced to adapt and expand their natural preferences. Likewise, we hypothesise that human-driven habitat alteration will disrupt the acoustic and visual communication systems due to increased noise pollution and/or changes in the surrounding light environment. We highlight the need for more empirical research combining behavioural ecology and conservation to better predict species’ vulnerability to global change and efficiently focus conservation efforts.

In the shadows: wildlife behaviour in tree plantations

Destruction of natural habitats for tree plantations is a major threat to wildlife. These novel environments elicit behavioural changes that can either be detrimental or beneficial to survival and reproduction, with population - and community - level consequences. However, compared with well-documented changes following other forms of habitat modification, we know little about wildlife behavioural responses to tree plantations, and even less about their associated fitness costs. Here, we highlight critical knowledge gaps in understanding the ecological and evolutionary consequences of behavioural shifts caused by tree plantations and discuss how wildlife responses to plantations could be critical in determining which species persist in these highly modified environments.

Continuous Variation in an Aposematic Pattern Affects Background Contrast, but Is Not Associated With Differences in Microhabitat Use

Variation in aposematic signals was once predicted to be rare, yet in recent years it has become increasingly well documented. Despite increases in the frequency with which polytypism and polymorphism have been suggested to occur, population-wide variance is rarely quantified. We comprehensively sampled a subpopulation of the poison frog Oophaga sylvatica, a species which is polytypic across its distribution and also shows considerable within-population polymorphism. On one hand, color pattern polymorphism could be the result of multifarious selection acting to balance different signaling functions and leading to the evolution of discrete sub-morphs which occupy different fitness peaks. Alternatively, variance could simply be due to relaxed selection, where variation would be predicted to be continuous. We used visual modeling of conspecific and heterospecific observers to quantify the extent of within population phenotypic variation and assess whether this variation produced distinct signals. We found that, despite considerable color pattern variation, variance could not be partitioned into distinct groups, but rather all viewers would be likely to perceive variation as continuous. Similarly, we found no evidence that frog color pattern contrast was either enhanced or diminished in the frogs’ chosen microhabitats compared to alternative patches in which conspecifics were observed. Within population phenotypic variance therefore does not seem to be indicative of strong selection toward multiple signaling strategies, but rather pattern divergence has likely arisen due to weak purifying selection, or neutral processes, on a signal that is highly salient to both conspecifics and predators.

Habitat disturbance alters color contrast and the detectability of cryptic and aposematic frogs

Animals use color both to conceal and signal their presence, with patterns that match the background, disrupt shape recognition, or highlight features important for communication. The forms that these color patterns take are responses to the visual systems that observe them and the environments within which they are viewed. Increasingly, however, these environments are being affected by human activity. We studied how pattern characteristics and habitat change may affect the detectability of three frog color patterns from the Bocas del Toro archipelago in Panama: Beige-Striped Brown Allobates talamancae and two spotted morphs of Oophaga pumilio, Black-Spotted Green and Black-Spotted Red. To assess detectability, we used visual modeling of conspecifics and potential predators, along with a computer-based detection experiment with human participants. Although we found no evidence for disruptive camouflage, we did find clear evidence that A. talamancae stripes are inherently more cryptic than O. pumilio spots regardless of color. We found no evidence that color pattern polytypism in O. pumilio is related to differences in the forest floor between natural sites. We did, however, find strong evidence that human disturbance affects the visual environment and modifies absolute and rank order frog detectability. Human-induced environmental change reduces the effectiveness of camouflage in A. talamancae, reduces detectability of Black-Spotted Green O. pumilio, and increases chromatic contrast, but not detectability, in Black-Spotted Red O. pumilio. Insofar as predators may learn about prey defenses and make foraging decisions based on relative prey availability and suitability, such changes may have wider implications for predator–prey dynamics.