Indigenous impacts on north Australian savanna fire regimes over the Holocene

Fire is an essential component of tropical savannas, driving key ecological feedbacks and functions. Indigenous manipulation of fire has been practiced for tens of millennia in Australian savannas, and there is a renewed interest in understanding the effects of anthropogenic burning on savanna systems. However, separating the impacts of natural and human fire regimes on millennial timescales remains difficult. Here we show using palynological and isotope geochemical proxy records from a rare permanent water body in Northern Australia that vegetation, climate, and fire dynamics were intimately linked over the early to mid-Holocene. As the El Niño/Southern Oscillation (ENSO) intensified during the late Holocene, a decoupling occurred between fire intensity and frequency, landscape vegetation, and the source of vegetation burnt. We infer from this decoupling, that indigenous fire management began or intensified at around 3 cal kyr BP, possibly as a response to ENSO related climate variability. Indigenous fire management reduced fire intensity and targeted understory tropical grasses, enabling woody thickening to continue in a drying climate.

Multi-morph eco-evolutionary dynamics in structured populations

Our understanding of the evolution of quantitative traits in nature is still limited by the challenge of including realistic trait distributions in the context of frequency-dependent selection and ecological feedbacks. We develop a theoretical framework to analyse the dynamics of populations composed of several morphs and structured into distinct classes (e.g. age, size, habitats, infection status, species...). Our approach extends to class-structured populations a recently introduced "oligomorphic approximation" which bridges the gap between adaptive dynamics and quantitative genetics approaches and allows for the joint description of the dynamics of ecological variables and of the moments of multimodal trait distributions. We also introduce a new approximation to simplify the eco-evolutionary dynamics using reproductive values. This effectively extends Lande's univariate theorem not only to frequency- and density-dependent selection but also to multimodal trait distributions. We illustrate the effectiveness of this approach by applying it to the important conceptual case of two-habitat migration-selection models. In particular, we use our approach to predict the equilibrium trait distributions in a local adaptation model with asymmetric migration and habitat-specific mutational variance. We discuss the theoretical and practical implications of our results and sketch perspectives for future work.

Positive Social-Ecological Feedbacks in Community-Based Conservation

Marine area-based conservation measures including no-take zones (areas with no fishing allowed) are often designed through lengthy processes that aim to optimize for ecological and social objectives. Their (semi) permanence generates high stakes in what seems like a one-shot game. In this paper, we theoretically and empirically explore a model of short-term area-based conservation that prioritizes adaptive co-management: temporary areas closed to fishing, designed by the fishers they affect, approved by the government, and adapted every 5 years. In this model, no-take zones are adapted through learning and trust-building between fishers and government fisheries scientists. We use integrated social-ecological theory and a case study of a network of such fisheries closures (“fishing refugia”) in northwest Mexico to hypothesize a feedback loop between trust, design, and ecological outcomes. We argue that, with temporary and adaptive area-based management, social and ecological outcomes can be mutually reinforcing as long as initial designs are ecologically “good enough” and supported in the social-ecological context. This type of adaptive management also has the potential to adapt to climate change and other social-ecological changes. This feedback loop also predicts the dangerous possibility that low trust among stakeholders may lead to poor design, lack of ecological benefits, eroding confidence in the tool’s capacity, shrinking size, and even lower likelihood of social-ecological benefits. In our case, however, this did not occur, despite poor ecological design of some areas, likely due to buffering by social network effects and alternative benefits. We discuss both the potential and the danger of temporary area-based conservation measures as a learning tool for adaptive co-management and commoning.

Habitat shapes diversity of gut microbiomes in a wild population of blue tits (Cyanistes caeruleus)

Microbiome constitutes and important axis of individual variation, affecting physiology and body condition via a number of pathways. Consequently, microbiome may be involved in ecological feedbacks, manifesting themselves as associations between microbiome characteristics and ecological factors experienced by individuals. In this study we report on the diversity and habitat dependence of microbiomes in a wild population of blue tits (Cyanistes caeruleus). Our results indicate, that birds nesting in different habitats (full-grown deciduous forest vs. open forest hay meadows) have microbiomes of different composition and microbial diversity, with birds nesting in dens forests having higher diversity of microbial species.

Probabilistic patterns of inundation and biogeomorphic changes due to sea-level rise along the northeastern U.S. Atlantic coast

Context Coastal landscapes evolve in response to sea-level rise (SLR) through a variety of geologic processes and ecological feedbacks. When the SLR rate surpasses the rate at which these processes build elevation and drive lateral migration, inundation is likely. Objectives To examine the role of land cover diversity and composition in landscape response to SLR across the northeastern United States. Methods Using an existing probabilistic framework, we quantify the probability of inundation, a measure of vulnerability, under different SLR scenarios on the coastal landscape. Resistant areas—wherein a dynamic response is anticipated—are defined as unlikely (p < 0.33) to inundate. Results are assessed regionally for different land cover types and at 26 sites representing varying levels of land cover diversity. Results Modeling results suggest that by the 2050s, 44% of low-lying, habitable land in the region is unlikely to inundate, further declining to 36% by the 2080s. In addition to a decrease in SLR resistance with time, these results show an increasing uncertainty that the coastal landscape will continue to evolve in response to SLR as it has in the past. We also find that resistance to SLR is correlated with land cover composition, wherein sites containing land cover types adaptable to SLR impacts show greater potential to undergo biogeomorphic state shifts rather than inundating with time. Conclusions Our findings support other studies that have highlighted the importance of ecological composition and diversity in stabilizing the physical landscape and suggest that flexible planning strategies, such as adaptive management, are particularly well suited for SLR preparation in diverse coastal settings.

Bidirectional interactions between host social behaviour and parasites arise through ecological and evolutionary processes

An animal's social behaviour both influences and changes in response to its parasites. Here we consider these bidirectional links between host social behaviours and parasite infection, both those that occur from ecological vs evolutionary processes. First, we review how social behaviours of individuals and groups influence ecological patterns of parasite transmission. We then discuss how parasite infection, in turn, can alter host social interactions by changing the behaviour of both infected and uninfected individuals. Together, these ecological feedbacks between social behaviour and parasite infection can result in important epidemiological consequences. Next, we consider the ways in which host social behaviours evolve in response to parasites, highlighting constraints that arise from the need for hosts to maintain benefits of sociality while minimizing fitness costs of parasites. Finally, we consider how host social behaviours shape the population genetic structure of parasites and the evolution of key parasite traits, such as virulence. Overall, these bidirectional relationships between host social behaviours and parasites are an important yet often underappreciated component of population-level disease dynamics and host–parasite coevolution.

A statistical evaluation of the origin of cypress domes in Florida

Two competing explanations exist for the origin of one type of karstic landform found in Florida called the cypress dome. One explanation relies on complex ecological feedbacks stemming from nutrient cycling suggesting biota contribute more significantly to processes of landscape evolution in Florida than anywhere else in the world. The second explanation is that the landforms are sinkholes that completely preclude the biological explanation while fitting more parsimoniously with the surrounding geological narrative. This work puts forward geostatistical analyses and a model linking the landforms to sinkholes, thus bolstering the geological explanation for origin of the landform. Satellite imagery of sinkholes occurring in limestone from locations spanning the planet was analyzed. Measurements of globally distributed limestone sinkhole surface areas are best characterized by an exponential distribution indicating sinkhole formation is robust to starting conditions (i.e., climate, tectonics). This observation is supported by an analysis of sinkhole geometry and geospatial dispersion. This demonstrates the geospatial parameters space for globally distributed groups of sinkholes forming in limestone are statistically indistinguishable despite sinkhole formation in different climates, tectonic regimes, and at different times. Employing this observation as a tool, sinkholes are directly compared to the cypress domes in Florida and are found to be statistically indistinguishable. From the striking similarity in spatial parameter spaces in conjunction with the geologic history of the area, it is interpreted that these landforms originate through geologic, not biologic, processes.

A statistical evaluation of the origin of cypress domes in Florida

© 2020 Elsevier B.V. Two competing explanations exist for the origin of one type of karstic landform found in Florida called the cypress dome. One explanation relies on complex ecological feedbacks stemming from nutrient cycling suggesting biota contribute more significantly to processes of landscape evolution in Florida than anywhere else in the world. The second explanation is that the landforms are sinkholes that completely preclude the biological explanation while fitting more parsimoniously with the surrounding geological narrative. This work puts forward geostatistical analyses and a model linking the landforms to sinkholes, thus bolstering the geological explanation for origin of the landform. Satellite imagery of sinkholes occurring in limestone from locations spanning the planet was analyzed. Measurements of globally distributed limestone sinkhole surface areas are best characterized by an exponential distribution indicating sinkhole formation is robust to starting conditions (i.e., climate, tectonics). This observation is supported by an analysis of sinkhole geometry and geospatial dispersion. This demonstrates the geospatial parameters space for globally distributed groups of sinkholes forming in limestone are statistically indistinguishable despite sinkhole formation in different climates, tectonic regimes, and at different times. Employing this observation as a tool, sinkholes are directly compared to the cypress domes in Florida and are found to be statistically indistinguishable. From the striking similarity in spatial parameter spaces in conjunction with the geologic history of the area, it is interpreted that these landforms originate through geologic, not biologic, processes.

A statistical evaluation of the origin of cypress domes in Florida

Two competing explanations exist for the origin of one type of karstic landform found in Florida called the cypress dome. One explanation relies on complex ecological feedbacks stemming from nutrient cycling suggesting biota contribute more significantly to processes of landscape evolution in Florida than anywhere else in the world. The second explanation is that the landforms are sinkholes that completely preclude the biological explanation while fitting more parsimoniously with the surrounding geological narrative. This work puts forward geostatistical analyses and a model linking the landforms to sinkholes, thus bolstering the geological explanation for origin of the landform. Satellite imagery of sinkholes occurring in limestone from locations spanning the planet was analyzed. Measurements of globally distributed limestone sinkhole surface areas are best characterized by an exponential distribution indicating sinkhole formation is robust to starting conditions (i.e., climate, tectonics). This observation is supported by an analysis of sinkhole geometry and geospatial dispersion. This demonstrates the geospatial parameters space for globally distributed groups of sinkholes forming in limestone are statistically indistinguishable despite sinkhole formation in different climates, tectonic regimes, and at different times. Employing this observation as a tool, sinkholes are directly compared to the cypress domes in Florida and are found to be statistically indistinguishable. From the striking similarity in spatial parameter spaces in conjunction with the geologic history of the area, it is interpreted that these landforms originate through geologic, not biologic, processes.