Abatus is a genus of irregular brooding sea urchins to the Southern Ocean. Among the 11 described species, three shared morphological traits and present an infaunal lifestyle in the infralittoral from the Subantarctic province; A. cavernosus in Patagonia, A. cordatus in Kerguelen, and A. agassizii in Tierra del Fuego and South Shetlands. The systematic of Abatus, based on morphological characters and incomplete phylogenies, is complex and largely unresolved. This study evaluates the shape variation among these species using geometric morphometrics analysis (GM). For this, 72 individuals from four locations; South Shetlands, Kerguelen, Patagonia, and Falklands/Malvinas were photographed, and 37 landmarks were digitized. To evaluate the shape differences among species, a principal component analysis and a Procrustes ANOVA were performed. Our results showed a marked difference between the Falklands/Malvinas and the other localities, characterized by a narrower and more elongated shape and a significant influence of location in shape but not sex. Additionally, the effect of allometry was evaluated using a permutation test and a regression between shape and size, showing significant shape changes during growth in all groups. The possibility that the Falklands/Malvinas group shows phenotypic plasticity or represents a distinct evolutionary unit is discussed. Finally, GM proved to be a powerful tool to differentiate these species, highlighting its utility in systematic studies.

Islands provide valuable opportunities to study how isolation affects phenotypic variation. Even though orchid bees are highly mobile, their movement can still be restricted by marine barriers. In this study, we assessed whether insular isolation impacts wing shape in the orchid bee Euglossa mixta across the Coiba archipelago and a nearby mainland site in Western Panama. Our study analyzed 271 individuals using geometric morphometrics, focusing on forewing venation landmarks, and evaluated the variation using multivariate analyses of shape variation and quantifying the shape of Mahalanobis distances. Additionally, we conducted a Mantel test to explore the relationship between geographic distance and morphological divergence. Our findings reveal that wing shape variation in E. mixta is largely conserved but shows fine-scale structuring consistent with spatial patterns expected in insular systems. These results suggest that even highly mobile pollinators may experience enough isolation for subtle phenotypic shifts to occur, highlighting the sensitivity of geometric morphometrics for detecting early stages of morphological differentiation.

Bilateral symmetry is a fundamental organizational trait in many metazoans. However, deviations from this symmetry, manifested as directional or fluctuating asymmetries, offer valuable insights into developmental, functional, and environmental processes. This study quantified and characterized bilateral asymmetry in three related species of the genus Abatus using a dual approach that integrates linear and geometric morphometrics. Our analyses reveal consistent patterns of directional asymmetry across different species, with specific trends showing that the left body sides tend to be larger. In contrast, fluctuating asymmetry exhibited an inverse relation with directional asymmetry. Also, linear morphometric analysis showed no significant correlation between directional asymmetry and either sex or body size, while geometric analyses only identified subtle shape deviations related to size but not to sex. These findings allow us to discuss the possible origins of this trait, mainly related to developmental constraints due to reproduction or growth, or carried over on a genetic basis. Our results highlight the importance of combining different morphometric approaches to clarify complex patterns of morphological variation and emphasize the significance of asymmetry analyses in understanding evolutionary and ecological processes in irregular echinoids.

Habitat loss and deforestation are among the main drivers of biodiversity decline in tropical ecosystems, yet their effects on developmental stability remain poorly understood in many insect groups. Orchid bees (Apidae: Euglossini) have been proposed as potential bioindicators of environmental quality due to their close association with forested habitats and sensitivity to habitat disturbance. Here, we evaluated the relationship between forest cover, wing morphology, and developmental stability in the orchid bee Euglossa imperialis across five protected areas of Panama exhibiting different levels of deforestation. A total of 290 individuals were analyzed using geometric morphometrics and fluctuating asymmetry (FA) of the forewing. Morphological variation was assessed through Principal Component and Canonical Variate Analyses, whereas developmental instability was quantified using Procrustes ANOVA and FA scores. Wing shape showed moderate differentiation among sites, with La Tronosa, the most deforested protected area, exhibiting the greatest morphological divergence. In contrast, FA displayed a clear association with habitat degradation. La Tronosa presented the highest levels of developmental instability, and generalized linear models revealed a significant positive relationship between deforestation and FA at both local and landscape scales, with landscape-level deforestation showing the strongest effect. Our results indicate that developmental instability is more sensitive than overall wing morphology for detecting the biological consequences of habitat alteration. These findings support the use of fluctuating asymmetry as an early indicator of environmental degradation and provide new evidence for the value of orchid bees as bioindicators in tropical ecosystems.