Unravelling the functional and phylogenetic dimensions of novel ecosystem assemblages

Human activities are causing taxonomic rearrangements across ecosystems that often result in the emergence of novel communities (assemblies with no historical representative). It is commonly assumed that these changes in the taxonomic makeup of ecosystems also inevitably lead to changes in other aspects of biodiversity, namely functional and phylogenetic diversity. However, this assumption is not always valid, as the changes in functional and phylogenetic composition resulting from taxonomic shifts depend on the level of redundancy in the evaluated community. Therefore, we need improved theoretical frameworks to predict when we can expect coordinated or decoupled responses among these three facets of biodiversity. To advance this understanding, we discuss the conceptual and methodological issues that complicate establishing a link between taxonomic rearrangements driven by human activities and the associated functional and phylogenetic changes. Here, we show that is crucial to consider the expected changes in functional and phylogenetic composition as communities are reshaped owing to human drivers of biodiversity loss to forecast the impacts of novel assemblages on ecosystem functions and the services they provide to humanity. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

The Entangled Phenology of the Olive Tree: A Compiled Ecological Calendar of Olea Europaea L. Over the Last Three Millennia With Sicily as a Case Study

Seasonal cycles in plants and animals drive key timings of human practices in an agrosystem like the best time for harvest, planting, or pruning. Within the framework of historical phenological studies, we attempt a reconstruction of the olive (Olea europaea L.) phenology along millennia. Thanks to its extraordinary longevity, the olive tree is a living proxy from the past and embodies a still uncollected long-term memory of ecological behaviors. A cultural keystone species, olive cultivation has more and more played a crucial role for biodiversity conservation, livelihood of rural communities and their enrooted cultural identity in the whole Mediterranean. By compiling traditional phenological knowledge from historical written sources and oral traditions, and using it as historical bio-indicator of the linkage between human ecological practices and seasonal changes of plant behavior, we compiled a monthly ecological calendar of the olive tree covering the last ∼2800 years. As a case study, we chose a special place: Sicily, unique for its position in the Mediterranean, geomorphology and legacies in the form of cross-temporal accumulated eco-cultures. Such a sui generis ecological calendar provides an additional case study to explore the intertwining of plant behavior and human adaptation strategies and the interplay between cultural diversity, ecological disturbance and phenological stability. All of this, in turn, can inform action for the present and future sustainable management of these millennial trees.

Changing plant functional diversity over the last 12,000 years provides perspectives for tracking future changes in vegetation communities

Plant communities are largely reshaped by climate and the environment over millennia, providing a powerful tool for understanding their response to future climates. Using a globally applicable functional palaeocological approach, we provide a deeper understanding of fossil pollen-inferred long-term response of vegetation to past climatic disturbances based on changes in functional trait composition. Specifically, we show how and why the ecological strategies exhibited by vegetation have changed through time by linking observations of plant traits to multiple pollen records from southeast Australia to reconstruct past functional diversity (FD, the value and the range of species traits that influence ecosystem functioning). The drivers of FD changes were assessed quantitatively by comparing FD reconstructions to independent records of past climates. During the last 12,000 years, peaks in FD were associated with both dry and wet climates in southeast Australia, with shifts in leaf traits particularly pronounced under wet conditions. Continentality determined the degree of stability maintained by high FD, with the greatest seen on the mainland. We expect projected frequent drier conditions in southeast Australia over coming decades to drive changes in vegetation community functioning and productivity mirroring the functional palaeocological record, particularly in western Tasmania and western southeast mainland.