Enhanced Ecologies and Ecosystem Engineering

Anthropological and archaeological representations of Aboriginal Australians as hunter-gatherers adapting to the natural availability of food resources are simplistic and inconsistent with ethnographic records of active, strategic, and sociopolitically meaningful resource enhancement. Scholarship over the past four decades has documented plant and animal food resource enhancement by Aboriginal Australians that blur socioeconomic boundaries with agricultural societies of New Guinea. Enhancements were achieved by using intimate knowledge of local ecological processes to modify ecosystems through a range of strategies such as landscape burning, animal translocation, protected rearing, shelter creation, and restocking. These strategies were embedded within broader sociocultural and sociopolitical domains that were often accompanied by ritual. Such engineered food enhancement practices reveal that many documented and modelled associations between environment and behaviour are in fact correlations between behaviour and the products of behaviour. The uneven distribution of animal resource enhancement practices across Australia indicates considerable regional diversity and supports existing views that many enhancements are related to regionally specific and historically contingent developments in social complexity.

Natural selection on a carbon cycling trait drives ecosystem engineering by Sphagnum (peat moss)

Sphagnum peat mosses have an extraordinary impact on the global carbon cycle as they control long-term carbon sequestration in boreal peatland ecosystems. Sphagnum species engineer peatlands, which harbour roughly a quarter of all terrestrial carbon, through peat accumulation by constructing their own niche that allows them to outcompete other plants. Interspecific variation in peat production, largely resulting from differences in tissue decomposability, is hypothesized to drive niche differentiation along microhabitat gradients thereby alleviating competitive pressure. However, little empirical evidence exists for the role of selection in the creation and maintenance of such gradients. In order to document how niche construction and differentiation evolved in Sphagnum , we quantified decomposability for 54 species under natural conditions and used phylogenetic comparative methods to model the evolution of this carbon cycling trait. We show that decomposability tracks the phylogenetic diversification of peat mosses, that natural selection favours different levels of decomposability corresponding to optimum niche and that divergence in this trait occurred early in the evolution of the genus prior to the divergence of most extant species. Our results demonstrate the evolution of ecosystem engineering via natural selection on an extended phenotype, of a fundamental ecosystem process, and one of the Earth's largest soil carbon pools.

Using the Goldilocks Principle to model coral ecosystem engineering

The occurrence and proliferation of reef-forming corals is of vast importance in terms of the biodiversity they support and the ecosystem services they provide. The complex three-dimensional structures engineered by corals are comprised of both live and dead coral, and the function, growth and stability of these systems will depend on the ratio of both. To model how the ratio of live : dead coral may change, the ‘Goldilocks Principle’ can be used, where organisms will only flourish if conditions are ‘just right’. With data from particle imaging velocimetry and numerical smooth particle hydrodynamic modelling with two simple rules, we demonstrate how this principle can be applied to a model reef system, and how corals are effectively optimizing their own local flow requirements through habitat engineering. Building on advances here, these approaches can be used in conjunction with numerical modelling to investigate the growth and mortality of biodiversity supporting framework in present-day and future coral reef structures.