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Tectonic processes drive the evolution of basins through local and regional changes in topographic relief, which have long-term effects on mammalian richness and distribution. Mammals respond to the resulting changes in landscape and climate through evolution, shifts in geographic range, and by altering their community composition. Here, we evaluate the relationship between tectonic episodes and the diversification history of fossil mammals in the Miocene Dove Spring Formation (12.5-8.5 Ma) of southern California, USA. This formation contains a rich fossil record of mammals and other vertebrates as well as structural and sedimentological evidence for tectonic episodes of basin extension, rotation, and translation. We used several methods to compare the fossil record to the tectonic history of the Dove Spring Formation. We updated the formation's geochronology to incorporate current radiometric dating standards and measured additional stratigraphic sections to refine the temporal resolution of large mammal (>1 kg) fossil localities to 200-kyr (or shorter) intervals. Observed species richness over time follows the same trend as the number of localities and specimens, suggesting that richness reflects sampling intensity. Estimates of stratigraphic ranges with 80% confidence intervals were used to conduct per capita diversification analysis and a likelihood approach to changes in faunal composition from one time interval to the next. While edge effects influence time bins at the beginning and end of the study interval, we found changes in diversification rates and faunal composition that are not solely linked to preservation. Several rare species appear at 10.5 Ma and persist through the top of the formation despite variable preservation rates. Changes in faunal composition at 12.1 Ma and 10.5 Ma are not associated with elevated preservation rates, which indicates that some faunal changes are not primarily driven by sampling effort. The lower portion of the formation is characterized by high origination rates and long residence times. The upper portion has high per capita extinction rates that increased in magnitude as basin rotation and translation progressed from 10.5 Ma. The greatest change in faunal composition coincided with basin rotation and translation that interrupted a long-running extensional period. Tectonics played key roles in the diversity of mammals by determining fossil productivity and shaping the landscapes that they inhabited. [ABSTRACT FROM AUTHOR]

Isotopic analyses of mammalian tooth enamel from a well-defined, laterally extensive 150 k.y. interval (9.15-9.30 Ma) reveal an ecological gradient in vegetation on the late Miocene sub-Himalayan alluvial plain. Two contemporaneous river systems deposited the sediments of this interval, with a mountain-sourced system (herein, Blue-gray) to the southwest interfingering with a foothill-sourced system (Buff) to the northeast. Fossil mammal teeth collected from a 32 km transect across this fluvial gradient are significantly more depleted in [sup.13]C from northeastern localities than from southwestern localities. This trend occurs in equids, giraffids, suids, sivapithecine hominoids, and anthracotheres. We propose that the Buff fluvial system provided more equably moist substrate conditions and supported more closed-canopy vegetation than the Blue-gray fluvial system. Herbivores living along the paleovegetation gradient thus acquired different carbon isotopic signatures during the period of tooth enamel formation, resulting from higher [delta][.sup.13]C values in the forage supported by the Blue-gray fluvial system compared with forage associated with the Buff system. The data also imply that many Siwalik mammalian herbivores displayed marked fidelity in juvenile home ranges and habitats.

The mammalian family Bovidae has been widely studied in ecomorphological research, with important applications to paleoecological and paleohabitat reconstructions. Most studies of bovid craniomandibular features in relation to diet have used linear measurements. In this study, we conduct landmark-based geometric-morphometric analyses to evaluate whether different dietary groups can be distinguished by mandibular morphology. Our analysis includes data for 100 species of extant bovids, covering all bovid tribes and 2 dietary classifications. For the first classification with 3 feeding categories, we found that browsers (including frugivores), mixed feeders, and grazers are moderately well separated using mandibular shape. A finer dietary classification (frugivore, browser, browser–grazer intermediate, generalist, variable grazer, and obligate grazer) proved to be more useful for differentiating dietary extremes (frugivores and obligate grazers) but performed equally or less well for other groups. Notably, frugivorous bovids, which belong in tribe Cephalophini, have a distinct mandibular shape that is readily distinguished from all other dietary groups, yielding a 100% correct classification rate from jackknife cross-validation. The main differences in mandibular shape found among dietary groups are related to the functional needs of species during forage prehension and mastication. Compared with browsers, both frugivores and grazers have mandibles that are adapted for higher biomechanical demand of chewing. Additionally, frugivore mandibles are adapted for selective cropping. Our results call for more work on the feeding ecology and functional morphology of frugivores and offer an approach for reconstructing the diet of extinct bovids. [ABSTRACT FROM AUTHOR]

Abstract Modern, industrial agriculture has undermined biological diversity at all levels--genetic diversity, viability of populations and species, as well as ecosystems and their services. Agriculture is the primary cause of [...]

The author describes her backpacking trip with friends through the Beartooth Mountains of Montana. Contentions with terrain and weather, how photographs relate to memory, and familiarity through many visits are discussed.