Biology subjects

Garzon-Agudelo, F.

Publications and source records attributed to Garzon-Agudelo, F..

4 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

Convergent mechanisms, divergent strategies: a comparison of nectar intake between a generalist and a specialized bat species

Nectar-feeding bats exhibit a range of specialized adaptations that allow them to efficiently extract nectar from flowers. These adaptations include diverse tongue morphological traits and feeding strategies that reflect varying degrees of specialization for nectarivory. While the feeding mechanisms of highly specialized nectar-feeding bats are well-studied, little is known about the feeding behaviors of non-specialized species like Phyllostomus discolor. This study compares the nectar extraction behaviors of P. discolor and the specialized Anoura geoffroyi, examining morphological and biomechanical adaptations that affect nectar-feeding efficiency and foraging strategies. Using high-speed videography, we analyzed the feeding behaviors of both species, focusing on tongue kinematics, and feeding efficiency. Both species used a brush-tongue lapping technique but exhibited notable behavioral and kinematic differences, resulting in efficiency variations. P. discolor has a shorter, less flexible tongue than A. geoffroyi, though its tongue shows similar mobility capacities (licking frequency). Unlike A. geoffroyi, which hovers to feed, P. discolor lands, allowing for longer visits and greater nectar extraction per visit. However, P. discolor demonstrated lower feeding efficiency, likely due to its reduced tongue specialization for nectarivory. These findings reveal convergence in the general feeding mechanism but highlight differences in morphological and behavioral specialization that affect feeding kinematics and efficiency. Our study illuminates how foraging strategy and tongue morphology impact feeding efficiency, pointing to evolutionary pathways that promote niche differentiation within nectar- feeding bat communities.

biophysics↗

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↗

bioRxiv2023

Winging it: Unveiling how hummingbirds alter their flying kinematics during molt.

Hummingbirds are well known for their hovering flight, one of the most energetically expensive modes of locomotion among animals. Molt is a costly event in the annual cycle, in which birds replace their feathers, including all their primary feathers which, in hummingbirds, comprise most of the area of the wing. Despite this, the effects of molt on hovering flight are not well known. Here, we examined high-speed videos (14 individuals of three species from the Colombian Andes recorded at 1200 FPS) comparing molting and non-molting hummingbirds wing kinematics and wingtip trajectories. We found that molting hummingbirds extended their wings in sharper angles during both downstroke and upstroke compared to non-molting individuals (10{degrees} vs 20{degrees}, and 15{degrees} vs 29{degrees}, respectively), while other flight parameters remained unchanged. Our findings show that hummingbirds are capable of sustaining hovering flight kinematics even under impressive wing area reductions by adjusting their wing flapping behavior.

biophysics↗