Biology subjects

Epperly, K.

Publications and source records attributed to Epperly, K..

3 recordsLinked to original sources

bioRxiv2025

Sharper, Straighter, Stiffer, Stronger: Bill shape of male Green Hermits (Phaethornis guy) confers superior biomechanical performance during stabbing simulations.

In hummingbirds, bill sexual dimorphism has been mainly related to differential use of floral resources between the sexes (i.e., intersexual resource partitioning). However, intrasexual selection has a potential role in driving hermit bill morphology. Males of Phaethornis longirostris possess weaponized bills, sharp and elongated dagger-like bill-tips, that enhance puncturing ability and territory defense during male-to-male combat at leks. In this study, we employed 3D modelling and finite element analysis to explore bill dimorphism and biomechanical stabbing performance in Phaethornis guy. We found that P. guy also exhibit a dimorphic weapon, with males displaying significantly sharper bill-tips than females. Additionally, we demonstrated a greater degree in biomechanical performance during horizontal stabbing in the straighter bills of male P. guy through a reduction in the energy expended in deformation (strain energy) and the risk of breakage (von Mises stress). Our findings indicate another example of bill-tip weapons and support the potential role of sexual selection in the evolution of hummingbird bill dimorphism.

evolutionary biology↗

bioRxiv2024

PicoCam: High-resolution 3D imaging of live animals and preserved specimens

1. The PicoCam system is a multi-camera photogrammetry rig used for generating high-resolution 3D models of animals in the field, or preserved specimens in laboratory or museum settings. The digital measurement of 3D models is increasingly useful for studying body shape. However, methods that capture sub-millimetric detail often do so at the cost of portability and versatility; this system aims to bridge this gap. 2. The PicoCam system employs 3D digital photogrammetry, a process that generates accurate, full-color, 3D models from sequences of photographs. By using six cameras and a rotating base, the system is able to capture multiple angles in rapid succession - a key advantage for both 3D-imaging live specimens and efficiently scanning museum specimens. Through the use of macro lenses and high-resolution camera sensors, this system can capture sub-millimetric detail without sacrificing portability. 3. In this study, we 3D imaged the bills of 19 species of hummingbirds using the PicoCam system and measured length, height, width, surface area, and volume of their bills. We examined eight species in the field and 11 from the Burke Museum in Seattle. We chose Hummingbird bills as a model system, as their fine-scale interspecific differences in 3D shape can have significant functional and behavioral implications, and could tell us more about how these traits predict habitat and resource use. 4. The prospect of a common 3D-imaging method for both museum and field use is compelling when documenting structures shape within and among species. The PicoCam system is also valuable for quantifying the 3D shape of fine-scale phenotypes (like hummingbird bills) that benefit from digital measurement, preservation, and improved accessibility. Lastly, the PicoCam system allows "digital 3D collection", by which the shape of biological structures in the field can be recorded and stored in a public database without the need to collect a specimen. This opens the door to studies in which multiple 3D image captures of the same individual across different time scales permit 3D shape/color comparisons (e.g., seasonal, ontogenetic changes).

evolutionary biology↗

bioRxiv2018

Dense geographic and genomic sampling reveals paraphyly and a cryptic lineage in a classic sibling species complex

Incomplete or geographically biased sampling poses significant problems for research in phylogeog-raphy, population genetics, phylogenetics, and species delimitation. Despite the power of using genome-wide genetic markers in systematics and related fields, approaches such as the multispecies coalescent remain unable to easily account for unsampled lineages. The Empidonax difficilis / E. occidentalis complex of small tyrannid flycatchers (Aves: Tyrannidae) is a classic example of a widely distributed species with limited phenotypic geographic variation that was broken into two largely cryptic (or \"sibling\") lineages following extensive study. Though the group is well-characterized north of the U.S. Mexico border, the evolutionary distinctiveness and phylogenetic relationships of southern populations remain obscure. In this paper, we use dense genomic and geographic sampling across the majority of the range of the E. difficilis / E. occidentalis complex to assess whether current taxonomy and species limits reflect underlying evolutionary patterns, or whether they are an artifact of historically biased or incomplete sampling. We find that additional samples from Mexico render the widely recognized species-level lineage E. occidentalis paraphyletic, though it retains support in the best-fit species delimitation model from clustering analyses. We further identify a highly divergent unrecognized lineage in a previously unsampled portion of the groups range, which a cline analysis suggests is more reproductively isolated than the currently recognized species E. difficilis and E. occidentalis. Our phylogeny supports a southern origin of these taxa. Our results highlight the pervasive impacts of biased geographic sampling, even in well-studied vertebrate groups like birds, and illustrate what is a common problem when attempting to define species in the face of recent divergence and reticulate evolution.

evolutionary biology↗