Aim: Functional traits mediate the interactions of species among themselves and with their environment, providing a link between diversity and ecosystem function. Crucially, the loss of biodiversity can jeopardize the functionality of ecosystems. Much focus is on predicting the impacts of current and future species loss; however, modern ecosystems have undergone biodiversity decline throughout the Late Quaternary, starting with the Pleistocene megafaunal extinctions. Thus, the fossil record offers the opportunity to investigate the long-term legacy of biodiversity erosion and how this is affecting modern ecosystems in a cumulative manner. We aimed to investigate changes in functional diversity and redundancy of a local mammal community at Hall's Cave, a site with a continuous record from 21,000 years ago to the present. Additionally, we included several common introduced species in the modern community to test whether they restore some lost ecological function.Location: Central Texas.Time period: Late Pleistocene to Present.Major taxa studied: Mammals. Methods:We used eight functional traits (mass, diet, arboreality, cursoriality, soil disturbance, group size, activity period and migration habit), which, collectively, describe the ecological role of a species and its influence on ecosystem processes, to construct a multidimensional functional space. The functional richness, range and distribution of the Hall's Cave community and the degree of functional redundancy were characterized statistically over time. Results:We found that declines in functional diversity were greater than expected given the decrease in species richness, implying that lost taxa contributed higher than average distinct ecological function. Functional distances between the remaining species increased through time, leading to reduced functional redundancy in younger communities. However, recently introduced taxa increased functional diversity to levels similar to those in the Holocene and partly restored the functional space occupied by Late Pleistocene fauna.Main conclusions: Our local-scale analysis demonstrates how prolonged biodiversity erosion not only leads to functionally depauperate communities, but, crucially, lowers ecological resilience to future disturbance.

Microscopic wear patterns on teeth, that is, dental microwear, are capable of recording observed dietary behaviour in a diversity of extant and extinct animals. However, recent work has questioned the utility of dental microwear at clarifying dietary behaviour, instead suggesting that dental microwear textures are reflective of grit consumed and not the dietary properties of ingested food. Some suggest that dental microwear cannot reflect the textural properties of vegetation consumed because phytoliths are too soft to form microwear. Koalas (Phascolarctos cinereus) are model organisms for examining dental microwear formation because they consume a specialized diet consisting almost exclusively of eucalyptus leaves, which notably lack phytoliths. Here, we assess if koala dental microwear records a diet consistent with the consumption of tough leaves – despite the absence of phytoliths in their primary food source. Dental microwear texture data of koalas are consistent with tough folivorous diets, with high anisotropy values indistinguishable from folivorous primates and grazing bovids. However, koalas have significantly higher complexity (indicative of hard object feeding) than the folivorous primate Alouatta palliata, and are indistinguishable in this variable from mixed feeding and browsing bovids. While higher complexity values in koalas may result from increased dust and/or grit on the landscape in comparison to folivores that occur in wetter environments, it may also result from the mastication of woody browse. We also determined that complexity and textural fill volume are not significantly greater in drier environments – as one would predict if grit was the major contributor to dental microwear formation. Koalas may instead be selecting softer younger leaves in drier regions where water is more limited. Collectively, microwear associated with tough object feeding can be formed in the absence of phytoliths and grit may interact with food to form microwear reflective of diet, as opposed to overprinting dietary signals.

Our review discusses the ecological consequences of the late Pleistocene extinctions on major aspects of earth systems as well as on the diet, distribution and behavior of surviving mammals. We demonstrate that the late Pleistocene loss of megafauna was pervasive and left legacies detectable within the modern atmosphere, geosphere, hydrosphere and biosphere. Moreover, the ecological roles that extinct and modern megafauna play in the earth system are not replicated by smaller-bodied animals. Our review highlights the importance of integrating a paleontological perspective into modern conservation efforts to develop a more synoptic understanding of ecosystems.

Australia has undergone significant climate change, both today and in the past. Koalas, due to their restricted diet of predominantly eucalyptus leaves and limited drinking behaviour may serve as model organisms for assessing past climate change via stable isotopes of tooth enamel. Here, we assess whether stable carbon and oxygen isotopes from tooth enamel record known climate variables, including proxies of relative aridity (e.g. mean annual precipitation, mean annual maximum temperature, and relative humidity). The results demonstrate significant negative relationships between oxygen isotope values and both relative humidity and mean annual precipitation, proxies for relative aridity. The best model for predicting enamel oxygen isotope values incorporates mean annual precipitation and modelled oxygen isotope values of local precipitation. These data and the absence of any relationship between modelled oxygen isotope precipitation values, independently, suggest that koalas do not track local precipitation values but instead record relative aridity. The lack of significant relationships between carbon isotopes and climate variables suggests that koalas may instead be tracking the density of forests and/or their location in the canopy. Collectively, these data suggest that koalas are model organisms for assessing relative aridity over time – much like kangaroos.

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