Biology subjects

Hlusko, L. J.

Publications and source records attributed to Hlusko, L. J..

3 recordsLinked to original sources

bioRxiv2023

Uncovering the mosaic evolution of carnivoran skeletal systems

The diversity of vertebrate skeletons is often attributed to adaptations to distinct ecological factors such as diet, locomotion, and sensory environment. Although the adaptive evolution of skull, appendicular skeleton, and vertebral column is well studied in vertebrates, comprehensive investigations of all skeletal components simultaneously are rarely performed. Consequently, we know little of how modes of evolution differ among skeletal components. Here, we tested if ecological and phylogenetic effects led to distinct modes of evolution among the cranial, appendicular, and vertebral regions in extant carnivoran skeletons. Using multivariate evolutionary models, we found mosaic evolution in which only the mandible, hindlimb, and posterior (i.e., last thoracic and lumbar) vertebrae showed evidence of adaptation towards ecological regimes whereas the remaining skeletal components reflect clade-specific evolutionary shifts. We hypothesize that the decoupled evolution of individual skeletal components may have led to the origination of distinct adaptive zones and morphologies among extant carnivoran families that reflect phylogenetic hierarchies. Overall, our work highlights the importance of examining multiple skeletal components simultaneously in ecomorphological analyses. Ongoing work integrating the fossil and paleoenvironmental record will further clarify deep-time drivers that govern carnivoran diversity we see today and reveal the complexity of evolutionary processes in multicomponent systems.

evolutionary biology↗

bioRxiv2023

Severe enamel defects in wild Japanese macaques

Plane-form enamel hypoplasia (PFEH) is a severe dental defect in which large areas of the crown are devoid of enamel. This condition is rare in humans and rarer in wild primates. The etiology of PFEH has been linked to exposure to severe disease, malnutrition, environmental toxins, and other systemic conditions. Similar defects have also been associated with genetic conditions such as amelogenesis imperfecta. In this study, we examined the prevalence of all types of enamel hypoplasia in several populations of wild Japanese macaques (Macaca fuscata) with the aim of providing context for the severe defects found in macaques from Yakushima Island. We found that macaques from other islands and from the mainland of Japan have low prevalence of the more common types of enamel hypoplasia and none exhibit PFEH. In contrast, 10 of the 21 individuals (48%) from Yakushima Island displayed uniform and significant PFEH, with all 10 living in two adjacent locations in the south of the island. All permanent teeth were affected to varying degrees except for first molars, and the mineral content of the remaining enamel in teeth with PFEH is normal (i.e., no hypo- or hyper mineralization). Given that the affected individuals have smaller first molars compared to non-affected macaques, and that they all underwent dental development during a period of substantial human-related habitat change, we conclude that the PFEH likely resulted from environmental stress. Extreme weather events on the island may also have influenced the formation of these defects. Additionally, it is plausible that a documented recent population bottleneck could have heightened the susceptibility of these macaques to PFEH. Further research on living primate populations is needed to better understand the causes of PFEH in wild primates and to evaluate whether such features can be used to assess the impact of human-related disturbance.

ecology↗

bioRxiv2023

OH 89: A newly described ~1.8-million-year-old hominid clavicle from Olduvai Gorge

ObjectivesHere, we describe the morphology and geologic context of OH 89, a [~]1.8million-year-old partial hominid clavicle from Olduvai (Oldupai) Gorge, Tanzania. We compare the morphology and clavicular curvature of OH 89 to modern humans, extant apes, and a sample of other hominid fossil clavicles. Materials and MethodsComparative samples include 25 modern human clavicles, 30 Gorilla, 31 Pan, 7 Papio, and five hominid clavicles. Length regression on midshaft size using the extant comparative samples is used to estimate the total length of OH 89. A set of 9 linear measurements are taken from each individual. We also describe a new methodology for measuring clavicular curvature using measurements of sternal and acromial curvature, from which an overall curvature measurement is calculated. A principal component analysis (PCA) and a t-distributed stochastic neighbor embedding (tSNE) analysis are used to compare the morphology of OH 89 with the extant and fossil comparative samples. ResultsOur new method of measuring clavicular curvature successfully separates the different genera of the extant clavicles. The length estimate and sternal and acromial curve measurements for OH 89 falls within the larger male humans. The PCA shows OH 89 and most of the fossil hominids falling between the modern human and Pan groups, while the t-SNE suggests that OH 89, KSD-VP-1/1, KNM-ER 1808, and OH 48 are more similar to each other than to any of the other groups. This analysis also plots KNM-WT 15000 with the modern humans and Krapina 158 with the Pan individuals. DiscussionThe OH 89 clavicle derives from an individual of unknown hominid species with a shoulder breadth similar to that of a large human male. The curvature of OH 89 is relatively human-like relative to its length. Our new methodology for measuring clavicular curvature, combined with the utilization of t-SNE analyses and comparison of t-SNE results to PCA results, provides greater separation of genera than previously used methods, and wider use of t-SNE may be useful in paleoanthropological work.

evolutionary biology↗