A putatively extinct higher taxon of Spirotrichea (Ciliophora) from the Lower Cretaceous of Brazil

Fossil microeukaryotes are key elements for understanding ancient ecosystems at microscopic level and improving the knowledge on the diversification of microbial life as a whole. We describe Palaeohypothrix bahiensis gen. et sp. nov., an exceptionally well-preserved Lower Cretaceous (Berriasian–Barremian; 145–125 Mya) amber-entrapped microeukaryote, identified as a spirotrich ciliate. The preservation of structures interpreted as the nuclear apparatus and remains of the ciliature revealed a novel ground plan, not found in modern Spirotrichea, thus representing a putatively extinct higher taxon lineage, viz. the Palaeohypotricha nov. tax. Based on cladistic analysis, the new taxon is hypothesized as phylogenetically related to the Protohypotrichia.

Fossil fern rhizomes as a model system for exploring epiphyte community structure across geologic time: evidence from Patagonia

Background In extant ecosystems, complex networks of ecological interactions between organisms can be readily studied. In contrast, understanding of such interactions in ecosystems of the geologic past is incomplete. Specifically, in past terrestrial ecosystems we know comparatively little about plant biotic interactions besides saprotrophy, herbivory, mycorrhizal associations, and oviposition. Due to taphonomic biases, epiphyte communities are particularly rare in the plant-fossil record, despite their prominence in modern ecosystems. Accordingly, little is known about how terrestrial epiphyte communities have changed across geologic time. Here, we describe a tiny in situ fossil epiphyte community that sheds light on plant-animal and plant-plant interactions more than 50 million years ago. Methods A single silicified Todea (Osmundaceae) rhizome from a new locality of the early Eocene (ca. 52 Ma) Tufolitas Laguna del Hunco (Patagonia, Argentina) was studied in serial thin sections using light microscopy. The community of organisms colonizing the tissues of the rhizome was characterized by identifying the organisms and mapping and quantifying their distribution. A 200 × 200 µm grid was superimposed onto the rhizome cross section, and the colonizers present at each node of the grid were tallied. Results Preserved in situ, this community offers a rare window onto aspects of ancient ecosystems usually lost to time and taphonomic processes. The community is surprisingly diverse and includes the first fossilized leafy liverworts in South America, also marking the only fossil record of leafy bryophyte epiphytes outside of amber deposits; as well as several types of fungal hyphae and spores; microsclerotia with possible affinities in several ascomycete families; and evidence for oribatid mites. Discussion The community associated with the Patagonian rhizome enriches our understanding of terrestrial epiphyte communities in the distant past and adds to a growing body of literature on osmundaceous rhizomes as important hosts for component communities in ancient ecosystems, just as they are today. Because osmundaceous rhizomes represent an ecological niche that has remained virtually unchanged over time and space and are abundant in the fossil record, they provide a paleoecological model system that could be used to explore epiphyte community structure through time.

Early hominins evolved within non-analog ecosystems

Present-day African ecosystems serve as referential models for conceptualizing the environmental context of early hominin evolution, but the degree to which modern ecosystems are representative of those in the past is unclear. A growing body of evidence from eastern Africa’s rich and well-dated late Cenozoic fossil record documents communities of large-bodied mammalian herbivores with ecological structures differing dramatically from those of the present day, implying that modern communities may not be suitable analogs for the ancient ecosystems of hominin evolution. To determine when and why the ecological structure of eastern Africa’s herbivore faunas came to resemble those of the present, here we analyze functional trait changes in a comprehensive dataset of 305 modern and fossil herbivore communities spanning the last ∼7 Myr. We show that nearly all communities prior to ∼700 ka were functionally non-analog, largely due to a greater richness of non-ruminants and megaherbivores (species >1,000 kg). The emergence of functionally modern communities precedes that of taxonomically modern communities by 100,000s of years, and can be attributed to the combined influence of Plio-Pleistocene C4 grassland expansion and pulses of aridity after ∼1 Ma. Given the disproportionate ecological impacts of large-bodied herbivores on factors such as vegetation structure, hydrology, and fire regimes, it follows that the vast majority of early hominin evolution transpired in the context of ecosystems that functioned unlike any today. Identifying how past ecosystems differed compositionally and functionally from those today is key to conceptualizing ancient African environments and testing ecological hypotheses of hominin evolution.

2H/1H variation in microbial lipids is controlled by NADPH metabolism

The hydrogen-isotopic compositions (2H/1H ratios) of lipids in microbial heterotrophs are known to vary enormously, by at least 40% (400‰) relative. This is particularly surprising, given that most C-bound H in their lipids appear to derive from the growth medium water, rather than from organic substrates, implying that the isotopic fractionation between lipids and water is itself highly variable. Changes in the lipid/water fractionation are also strongly correlated with the type of energy metabolism operating in the host. Because lipids are well preserved in the geologic record, there is thus significant potential for using lipid 2H/1H ratios to decipher the metabolism of uncultured microorganisms in both modern and ancient ecosystems. But despite over a decade of research, the precise mechanisms underlying this isotopic variability remain unclear. Differences in the kinetic isotope effects (KIEs) accompanying NADP+ reduction by dehydrogenases and transhydrogenases have been hypothesized as a plausible mechanism. However, this relationship has been difficult to prove because multiple oxidoreductases affect the NADPH pool simultaneously. Here, we cultured five diverse aerobic heterotrophs, plus five Escherichia coli mutants, and used metabolic flux analysis to show that 2H/1H fractionations are highly correlated with fluxes through NADP+-reducing and NADPH-balancing reactions. Mass-balance calculations indicate that the full range of 2H/1H variability in the investigated organisms can be quantitatively explained by varying fluxes, i.e., with constant KIEs for each involved oxidoreductase across all species. This proves that lipid 2H/1H ratios of heterotrophic microbes are quantitatively related to central metabolism and provides a foundation for interpreting 2H/1H ratios of environmental lipids and sedimentary hydrocarbons.

Ediacaran scavenging as a prelude to predation

Predation is one of the most fundamental ecological and evolutionary drivers in modern and ancient ecosystems. Here, we report the discovery of evidence of the oldest scavenging of shallowly buried bodies of iconic soft-bodied members of the Ediacara Biota by cryptic seafloor mat-burrowing animals that produced the furrow and levee trace fossil, Helminthoidichnites isp. These mat-burrowers were probably omnivorous, stem-group bilaterians that largely grazed on microbial mats but when following mats under thin sands, they actively scavenged buried Dickinsonia, Aspidella, Funisia and other elements of the Ediacara Biota. These traces of opportunistic scavengers of dead animals from the Ediacaran of South Australia represent a fundamental ecological innovation and a possible pathway to the evolution of macrophagous predation in the Cambrian. While the Ediacaran oceans may have had oxygen levels too low to support typical large predators, the Helminthoidichnites maker lived in and grazed on microbial mats, which may have provided a localized source of oxygen.

Coprolites reveal ecological interactions lost with the extinction of New Zealand birds

Over the past 50,000 y, biotic extinctions and declines have left a legacy of vacant niches and broken ecological interactions across global terrestrial ecosystems. Reconstructing the natural, unmodified ecosystems that preceded these events relies on high-resolution analyses of paleoecological deposits. Coprolites are a source of uniquely detailed information about trophic interactions and the behaviors, gut parasite communities, and microbiotas of prehistoric animal species. Such insights are critical for understanding the legacy effects of extinctions on ecosystems, and can help guide contemporary conservation and ecosystem restoration efforts. Here we use high-throughput sequencing (HTS) of ancient eukaryotic DNA from coprolites to reconstruct aspects of the biology and ecology of four species of extinct moa and the critically endangered kakapo parrot from New Zealand (NZ). Importantly, we provide evidence that moa and prehistoric kakapo consumed ectomycorrhizal fungi, suggesting these birds played a role in dispersing fungi that are key to NZ’s natural forest ecosystems. We also provide the first DNA-based evidence that moa frequently supplemented their broad diets with ferns and mosses. Finally, we also find parasite taxa that provide insight into moa behavior, and present data supporting the hypothesis of coextinction between moa and several parasite species. Our study demonstrates that HTS sequencing of coprolites provides a powerful tool for resolving key aspects of ancient ecosystems and may rapidly provide information not obtainable by conventional paleoecological techniques, such as fossil analyses.

Fossil fern rhizomes as a model system for biotic interactions across geologic time: Evidence from Patagonia

Background. A wealth of data on the networks of ecological interactions present in the modern biota can be readily obtained, due to the ease of unlimited access to the living organisms that form these networks. In contrast, understanding of such interactions in ecosystems of the geologic past is incomplete. Specifically, in terrestrial ecosystems we know comparatively little about plant biotic interactions besides herbivory, oviposition, galling. Here we describe a tiny in situ fossil community which sheds light on concurrent plant-plant, plant-fungal, and plant-animal interactions. Methods. A single silicified osmundaceous rhizome from a new locality of the early Eocene (ca. 52 Ma) Tufolitas Laguna del Hunco was studied in serial thin sections using light microscopy. The community of organisms colonizing the tissues of the rhizome was characterized by identifying the organisms, as well as mapping and quantifying their distribution. For this, a 200 x 200 µm grid was superimposed onto the rhizome cross section and the colonizers present at each node of the grid were tallied. Results. Preserved in situ, this community offers a rare window onto aspects of ancient ecosystems usually lost to time and taphonomic processes. The community is surprisingly diverse and includes the first fossilized leafy liverworts in South America, also marking the only fossil record of leafy bryophyte epiphytes; several types of fungal hyphae and spores; microsclerotia with probable affinities in several ascomycete families; and oribatid mite coprolites. Discussion. The community associated with the Patagonian rhizome enriches our understanding of plant biotic interactions in the distant past and adds to a growing body of literature, which indicates that osmundaceous rhizomes were important hosts for component communities in ancient ecosystems, just as they are today. Because osmundaceous rhizomes represent an ecological niche that has remained unchanged over time and space, and are abundant in the fossil record, they provide a good paleoecological model system that could be used for exploring plant biotic interactions across geologic time.

Fossil fern rhizomes as a model system for biotic interactions across geologic time: Evidence from Patagonia

Background. A wealth of data on the networks of ecological interactions present in the modern biota can be readily obtained, due to the ease of unlimited access to the living organisms that form these networks. In contrast, understanding of such interactions in ecosystems of the geologic past is incomplete. Specifically, in terrestrial ecosystems we know comparatively little about plant biotic interactions besides herbivory, oviposition, galling. Here we describe a tiny in situ fossil community which sheds light on concurrent plant-plant, plant-fungal, and plant-animal interactions. Methods. A single silicified osmundaceous rhizome from a new locality of the early Eocene (ca. 52 Ma) Tufolitas Laguna del Hunco was studied in serial thin sections using light microscopy. The community of organisms colonizing the tissues of the rhizome was characterized by identifying the organisms, as well as mapping and quantifying their distribution. For this, a 200 x 200 µm grid was superimposed onto the rhizome cross section and the colonizers present at each node of the grid were tallied. Results. Preserved in situ, this community offers a rare window onto aspects of ancient ecosystems usually lost to time and taphonomic processes. The community is surprisingly diverse and includes the first fossilized leafy liverworts in South America, also marking the only fossil record of leafy bryophyte epiphytes; several types of fungal hyphae and spores; microsclerotia with probable affinities in several ascomycete families; and oribatid mite coprolites. Discussion. The community associated with the Patagonian rhizome enriches our understanding of plant biotic interactions in the distant past and adds to a growing body of literature, which indicates that osmundaceous rhizomes were important hosts for component communities in ancient ecosystems, just as they are today. Because osmundaceous rhizomes represent an ecological niche that has remained unchanged over time and space, and are abundant in the fossil record, they provide a good paleoecological model system that could be used for exploring plant biotic interactions across geologic time.

Zooarchaeology and the Reconstruction of Ancient Human-Animal Relationships in the Arctic

Permafrost-preserved faunal assemblages from Arctic archaeological sites provide a high-resolution record of animal exploitation, ancient ecosystems, and climate. This chapter provides a review of what more than 90 years of archaeofaunal research has revealed about human-animal relationships in the Arctic and Aleutian Subarctic. Taking an alternate approach, the overview focuses on the evidence for the procurement, butchery, storage, and consumption of specific northern vertebrate and molluscan taxa, beginning from the earliest archaeological traces and tracking exploitation strategies geographically through time and space. Additionally, related paleoecological research, methodological advancements, and studies which address the social and ideational correlates of animal exploitation and consumption are reviewed.