Biology subjects

Powers, A. K.

Publications and source records attributed to Powers, A. K..

3 recordsLinked to original sources

bioRxiv2022

Genetic mapping of craniofacial traits in the Mexican tetra reveals loci associated with bite differences between cave and surface fish

The Mexican tetra, Astyanax mexicanus, includes interfertile surface-dwelling and cave-dwelling morphs, enabling powerful studies aimed at uncovering genes involved in the evolution of cave-associated traits. Compared to surface fish, cavefish harbor several extreme traits within their skull, such as a protruding lower jaw, a wider gape, and an increase in tooth number. These features are highly variable between individual cavefish and even across different cavefish populations. To investigate these traits, we created a novel feeding behavior assay wherein bite impressions could be obtained. We determined that fish with an underbite leave larger bite impressions with an increase in the number of tooth marks. Capitalizing on the ability to produce hybrids from surface and cavefish crosses, we investigated genes underlying these segregating orofacial traits by performing Quantitative Trait Loci (QTL) analysis with F2 hybrids. We discovered significant QTL for bite (underbite vs. overbite) that mapped to a single region of the Astyanax genome. This work highlights cavefish as a valuable genetic model for orofacial patterning and will provide insight into the genetic regulators of jaw and tooth development.

evolutionary biology↗

bioRxiv2022

Geometric morphometric analysis reveals cranial shape divergence and asymmetry in extinct and extant species of big cats (Carnivora: Felidae)

Felidae, a family of the order Carnivora, includes extinct and extant species of cats spread across a wide ecological and geographical landscape. Cats are well-suited for predation due to various physical and behavioral characteristics, such as optimized limb length, skull shape, as well as enhanced hearing and vision. Morphological changes across Felidae species, particularly changes in skull shape, are likely explained by differences in predatory and feeding behaviors. Toward that end, cranial shape was analyzed across six different extant and extinct Felidae species using two-dimensional geometric morphometrics. From the lateral cranial view, we discovered that the cheetah (Acinonyx jubatus) and the North American Sabretooth (Smilodon) had the most significant shape divergence, specifically at the frontal bone and post orbital regions of the skull. Specifically, we found that the Sabretooth had a significantly shorter coronoid process compared to other Felids. We also observed a significant difference in post orbital shape in the cheetah dorsal cranium. Interestingly, we found that both the cheetah and the extinct North American Lion demonstrate significant shape asymmetry in the postorbital region from a ventral view of the skull. Shape divergence and asymmetry in select Felid skulls may arise from decreased genetic diversity. Taken together, we reasoned that morphological changes in skull shape likely evolved to support differences in predatory behavior across Felidae.

evolutionary biology↗

bioRxiv2019

A geographical cline in craniofacial morphology across populations of Mesoamerican lake-dwelling fishes

The complex geological history and tropical climate of Mesoamerica create a rich source of biodiversity from which we can study evolutionary processes. Here, we discuss highly divergent forms of lake-dwelling fishes distributed across southern Mexico and Central America, originally recognized as members of different genera (Astyanax and Bramocharax). Recent phylogenetic studies suggest these morphotypes group within the same genus and readily hybridize. Despite genetic similarities, Bramocharax morphs exhibit stark differences in cranial shape and dentition. We investigated the evolution of several cranial traits that vary across morphs collected from four lakes in Mexico and Nicaragua and discovered an ecomorphological cline from the northern to southern lakes. Northern populations of sympatric morphs exhibit similar cranial shape and tooth morphology. Southern populations of Bramocharax, however, have more maxillary teeth, larger unicuspid teeth, an elongated snout and a streamlined cranium compared to Astyanax. The divergence of craniofacial morphology in southern lakes likely evolved in response to environmental pressures. We discuss the ecological differences across the four lake systems in terms of geological history and trophic dynamics. In summary, our study suggests that Bramocharax are likely locally-adapted members derived from Astyanax lineages, highlighting the complex evolutionary history of the Astyanax genus.

evolutionary biology↗