Age Structure and Size Variation in Three Closely Related Species of Casque‐Headed Frogs of the Genus <i>Trachycephalus</i> (Hylidae: Lophyohylini)

ABSTRACT Parreira. I.P. 2025. Age structure and size variation in three closely related species of casque‐headed frogs of the genus Trachycephalus (Hylidae: Lophyohylini)— Acta zoologica (Estocolmo). This study provides insights into longevity, sexual maturity and growth curves in closely related casque‐headed treefrogs distributed across distinct Brazilian biomes. Age estimation based on the counting of lines of arrested growth (LAGs) in bone tissue revealed a longevity of 6 years in Trachycephalus nigromaculatus and T. atlas , which is uncommon among Neotropical species. T. mambaiensis exhibited a distinct pattern of sexual maturity compared to the other species, suggesting divergent developmental strategies within the clade and possibly reflecting a higher reproductive investment at younger ages. A correlation between estimated age and snout–vent length (SVL) was observed in two of the three analysed species ( T. nigromaculatus and T. atlas ); however, this correlation may vary depending on the sampled locality and sample size. The growth model revealed distinct patterns within the clade: T. nigromaculatus exhibited a decline in growth rate corresponding to the age of sexual maturity, whereas T. atlas showed a non‐stabilised growth pattern. Our findings provide novel information for understanding the life history of explosive breeding species and emphasise the importance of museum specimens in ecological and evolutionary research.