No abstract

Estudiamos la interacción entre la planta Cnidoscolus multilobus, sus visitantes florales y la araña depredadora Peucetia viridans. La dieta de P. viridans estuvo compuesta exclusivamente por artrópodos (arañas 32%, insectos 68%). El tamaño del cuerpo de las presas fue de 5.9 ± 1.0 mm, y el ámbito de las presas fue de 11.0 ± 0.4 mm (i.e. 0.14-1.3 más grande que la araña). Basándonos en la frecuencia de alimentación y el tiempo disponible para capturar y alimentarse de las presas, una araña puede capturar hasta 3.9 presas por día, esto dependiendo de la época del año. Entre junio y octubre de 1998 probamos si el número de visitas a las flores era afectado por la presencia/ausencia de la araña (efecto visual). Probamos cuatro tratamientos: (1) sin araña, (2) con araña, (3) con araña modificada (carapacho pintado con rojo), y (4) araña falsa. Encontramos dos patrones dependiendo de la respuesta de los visitantes florales a la araña “invisible” (pintada y falsa). Estos patrones estaban cercanamente asociados con la abundancia de visitantes. Utilizando panículas cubiertas, estimamos el efecto de la presencia de las arañas sobre la producción de semillas. Durante los meses con menos abundancia de visitantes florales (junio, julio y octubre), las panículas sin arañas produjeron significativamente más semillas. Mientras que en agosto y septiembre, los meses con el mayor número de visitantes florales, no se encontraron diferencias significativas entre tratamientos. Los resultados sugieren que los visitantes florales pudieron evitar aquellas inflorescencias con arañas vivas visibles, pero no les fue posible reconocer a las arañas sin pintura. Ya que muchos visitantes florales son potenciales polinizadores, las arañas podrían indirectamente reducir el número de semillas en C. multilobus durante los meses cuando los visitantes florales eran menos abundantes y las arañas no estaban saciadas.

Phenotypic traits such as songs are important in species recognition. Variation in acoustic traits can form barriers to gene flow and promote speciation. Therefore, understanding song divergence is crucial in groups with controversial taxonomy such as Olive Sparrows (Arremonops rufivirgatus), a widespread Neotropical species of songbird with multiple allopatric populations. Taxonomic authorities disagree on the number of Olive Sparrow subspecies, placing them into either two or three main groups. These groups may represent separate species based on morphological traits, but trait divergence within the complex has not been examined. We studied geographic variation in the characteristics of the songs of Olive Sparrows at two geographical levels: among three proposed groups and among five allopatric populations. In a second analysis, we evaluated the strength of acoustic divergence within the complex by comparing acoustic distances among groups and allopatric populations of Olive Sparrows with the acoustic distance among three recognized species in the genus Arremonops. We analyzed 802 songs from 174 individuals across 81 locations and measured 12 variables to describe the fine structural characteristics of the songs of Olive Sparrows, Green‐backed Sparrows (A. chloronotus), Black‐striped Sparrows (A. conirostris), and Tocuyo Sparrows (A. tocuyensis). We found significant acoustic variation in the Olive Sparrow complex at both geographical levels. Our divergence analysis also revealed that vocal divergence within the complex is similar to or greater than that found between recognized species in the genus. Together, these results suggest that acoustic diversity within the Olive Sparrow complex probably originated by isolation in tandem with selective and/or non‐selective factors.

Palacios F. Serum concentrations of corticosterone and sex hormones and their relationship in farmedMorelet's crocodile (Crocodylus moreletii).

Despite that snakes lack outer traces of an auditory system, they respond to acoustic stimuli in the air, in terrestrial substrates and in water, through a functioning cochlea and a somatic system. In reptiles, the use of vibrations has been primarily associated with communication among individuals. However, vibrations also can be a useful mechanism in predator-prey interactions, facilitating efficient hunting. The aim of our study was to examine the ability of horned pitvipers (Ophryacus smaragdinus) to detect and discriminate prey through their vibrations, which were recorded and played back with a transmitter of acoustic waves under a controlled experimental condition. We analyzed the capability of snakes to detect and discriminate potential prey (mouse and lizard) of different sizes, by playing back vibrations that prey species emitted when moving. Our results showed that O. smaragdinus has the ability to detect vibrations of its prey, but it does not discriminate among prey species or size based on the vibrations. We conclude that the auditory system of O. smaragdinus is an important first step to detect prey via vibrations, and that this species likely uses other complementary sensory strategies, such as chemoperception and or thermoperception, for prey recognition.