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Browsing Research Data by Faculty "Science"

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    Dataset from : Browsing is a strong filter for savanna tree seedlings in their first growing season
    (ARCHIBALD ECOLOGY LAB, 2021-06-15) Archibald, Sally; Twine, Wayne; Mthabini, Craddock; Stevens, Nicola
    1: Newly germinated seedlings are vulnerable to biomass removal but usually have at least six months to grow before they are exposed to dry-season fires, a major disturbance in savannas. In contrast, plants are exposed to browsers from the time they germinate, making browsing potentially a very powerful bottleneck for establishing seedlings. 2: Here we assess the resilience of seedlings of 10 savanna tree species to top-kill during the first 6 months of growth. Newly-germinated seeds from four dominant African genera from across the rainfall gradient were planted in a common garden experiment at the Wits Rural Facility and clipped at 1 cm when they were ~2, 3, 4, and 5 months old. Survival, growth, and key plant traits were monitored for the following 2.5 years. 3: Seedlings from environments with high herbivory pressure survived top-kill at a younger age than those from low-herbivore environments, and more palatable genera had higher herbivore-tolerance. Most individuals that survived were able to recover lost biomass within 12 months, but the clipping treatment affected root mass fraction and branching patterns. 4: Synthesis: The impact of early browsing as a demographic bottleneck can be predicted by integrating information on the probability of being browsed and the probability of surviving a browse event. Establishment limitation through early-browsing is an under-recognised constraint on savanna tree species distributions. Data may be used without requesting permission after the J Ecology paper is published and in the public domain (estimated after October 2021).
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    Dataset from : The lateral semicircular canal and head posture in “ungulate” mammals: implications on diet, behavior and paleobiological reconstructions
    (2020-07-07) Benoit, Julien; Legendre, Lucas; Farke, Andrew; Neenan, James M; Mennecart, Bastien; Costeur, Loic; Merigeaud, Samuel; Manger, Paul
    For over a century, it has been assumed that the plane of the lateral semicircular canal of the inner ear is parallel to the earth horizontal when the head is at rest. This has long been used by paleontologists to reconstruct head posture in extinct species. Thought this hypothesis has been repeatedly questioned, it has never been tested on a large sample size and at a broad taxonomic scale in mammals. This study presents a comprehensive test of this hypothesis in more than a hundred “ungulate” species. Using CT scanning and manual segmentation, the orientation of the skull was reconstructed as if the lateral semicircular canal of the bony labyrinth was aligned with the earth's horizontal plane. This reconstructed cranial orientation was statistically compared to the actual head posture of the corresponding animals using a dataset of 10,000 photographs and phylogenetic regressions. A statistically significant correlation between the reconstructed cranial orientation and head posture is found, although the plane of the lateral semicircular canal significantly departs from the earth's horizontal plane. We thus caution against the use of the lateral semicircular canal as a proxy to infer the horizontal plane on dry skulls and in extinct species. Diet (browsing or grazing) and head-butting behavior are significantly correlated to the orientation of the lateral semicircular canal, but not to the actual head posture. Head posture and the orientation of the lateral semicircular canal are both strongly predetermined by phylogeny
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    Sterkfontein Member 4 fabric data
    (2022) Stratford, Dominic