abstract: Climate and environmental forcing are widely accepted to be important drivers of evolutionary and ecological change in mammal communities over geologic time scales. This paradigm has been particularly influential in studies of the eastern African late Cenozoic fossil record, in which aridification, increasing seasonality, and C4 grassland expansion are seen as having shaped the major patterns of human and faunal evolution. Despite the ubiquity of studies linking climate and environmental forcing to evolutionary and ecological shifts in the mammalian fossil record, many central components of this paradigm remain untested or poorly developed. To fill this gap, this dissertation employs biogeographical and macroecological analyses of present-day African mammal communities as a lens for understanding how abiotic change may have shaped community turnover and structure in the eastern African Plio-Pleistocene. Three dissertation papers address: 1) the role of ecological niche breadth in shaping divergent patterns of macroevolutionary turnover across clades; 2) the effect of climatic and environmental gradients on community assembly; 3) the relative influence of paleo- versus present-day climates in structuring contemporary patterns of community diversity. Results of these papers call into question many tenets of current theory, particularly: 1) that niche breadth differences (and, by extension, their influence on allopatric speciation) are important drivers of macroevolution, 2) that climate is more important than biotic interactions in community assembly, and 3) that communities today are in equilibrium with present-day climates. These findings highlight the need to critically reevaluate the role and scale-dependence of climate in mammal evolution and community ecology and to carefully consider potential time lags and disequilibrium dynamics in the fossil record. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2018

Extant monotremes have a combination of plesiomorphic and apomorphic characters that causes ambiguity about their basic anatomy and evolutionary history. The problem is compounded by the lack of extinct and extant specimens of monotremes available for study. Only five species of monotremes are currently recognized, and all are endangered. The most speciose subclade, the long-beaked echidna, Zaglossus, has few specimens archived in mammalogy collections relative to the platypus, Ornithorhynchus anatinus, and the short-beaked echidna, Tachyglossus aculeatus. As a result, researchers sample from Ornithorhynchus and Tachyglossus, excluding species of Zaglossus from analysis. An equally depauperate fossil record consisting primarily of fragmentary jaws and isolated molars over a broad temporal range (~125 Ma) has led to controversies surrounding the origin and evolution of Monotremata and its major subclades. As new fossils attributable to Monotremata have been discovered, they are placed in conflicting positions on either the crown or the stem. I used CT scans of skeletally immature and mature specimens of Zaglossus bruijni and Zaglossus bartoni, respectively, to describe the cranial osteology of Zaglossus in detail. New insights about the anatomy of Zaglossus were then utilized in a phylogenetic analysis. Zaglossus and the extinct echidna, Megalibgwilia were added to a previously published morphological character matrix, along with 42 new skeletal characters. For the first time, I illustrated the cranial anatomy of Zaglossus bruijnii and Zaglossus bartoni, and described the endocranial morphology and individual variation among the two species. I described patterns of ossification throughout ontogeny that may explain a preservation bias against echidnas. My phylogenetic analysis placed the Early Cretaceous monotremes either on the stem of Ornithorhynchidae or in the monotreme crown, supporting an Early Cretaceous divergence estimate between platypuses and echidnas. I provide the first phylogenetic definition and diagnosis of Monotremata, Ornithorhynchidae, and Tachyglossidae. Based on the distribution of characters of extant monotremes, the ancestral monotreme was likely a terrestrial, scratch-digger capable of electroreception. The ancestral population gave rise to the semi-aquatic platypuses and the large, terrestrial echidnas. Tachyglossus is the most derived of the extant echidnas; it is more appropriate to include Ornithorhynchus and Zaglossus in future phylogenetic analyses. / text

abstract: Providing an environmental context to early hominins is as important as describing the hominin fossils themselves, because evolutionary processes are tightly linked to everchanging ecosystems that vary across space and through time. An optimal understanding of ecosystems changes is critical to formulate and test hypotheses regarding human evolution and adaptation. Fortunately, the fossil record has yielded abundant remains of mammals which can be used to explore the possible causal relationships between environmental change and mammal – including hominin –evolution. Although many studies have already been conducted on this topic, most of them are framed at large spatial and temporal scales. Instead, this dissertation focuses on the evolution and paleoecology of only one group of mammals (the Suidae) in a specific geographical area (lower Awash Valley in Ethiopia) and within a constrained time frame (3.8–2.6 Ma). Three dissertation papers address: 1) changes in suid taxonomic composition in relation to Late Pliocene faunal turnover ~2.8 Ma in the Lee-Adoyta basin, Ledi-Geraru; 2) comparisons of suid diets from Hadar (~3.45–2.95 Ma) with respect to those of Kanapoi (~4.1 Ma, West Turkana, Kenya); 3) the dietary ecology of the suids from Woranso-Mille (~3.8–3.2 Ma). Results of these papers show that 1) after ~2.8 Ma there is a replacement of suid species that is coupled with low relative abundance of suids. This is compatible with more open and/or arid environments at this time; 2) suid dietary breadth was broader in Hadar than in Kanapoi, but this is mostly driven by the dietary niche space occupied by Kolpochoerus in Hadar, a suid genus absent from Kanapoi; 3) suid diets vary both temporally and geographically within the lower Awash Valley. Kolpochoerus incorporates more C4 resources (e.g., grasses) in its diet after ~3.5 Ma and in general, suids after ~3.5 Ma in Woranso-Mille had C4-enriched diets in comparison with those from nearby Hadar and Dikika. Presumably, the changes in suid communities (relative abundance and taxonomic composition) and dietary shifts observed in suids were triggered by climatic and habitat changes that also contributed to shape the behavioural and morphological evolution of early hominins. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2018