ABSTRACT
Resumen El orden Ciconiiformes incluye especies de aves zancudas de tamaño mediano a grande, con dinámicas de crecimiento corporal que pueden ser analizadas para esclarecer las tendencias microevolutivas del grupo. Las garzas (familia Ardeidae) provienen de un ancestro común, sin embargo, existen diferencias en la forma corporal de los adultos actuales y se ha sugerido un proceso de evolución por heterocronías. Sin embargo, los estudios de crecimiento previamente se han enfocado solo en las dimensiones lineales y no se han analizado los cambios alométricos. En el presente trabajo se describen los cambios de proporciones corporales durante el crecimiento en siete especies de ardéidos y se analizan bajo una hipótesis filogenética para identificar el patrón morfológico primitivo entre los géneros basales Butorides y Nycticorax. Para ellos se calcularon las proporciones pico / tarso en 353 pichones, medidos entre 1998 y 2006, y se evaluaron sus cambios en relación con la edad y el incremento del peso corporal. Las especies mostraron diferencias marcadas en la magnitud del cambio en las proporciones pico/tarso entre la eclosión y un momento análogo del crecimiento, excepto Bubulcus que tiende a crecer de forma casi isométrica. Los cambios alométricos al crecer conjuntamente con las proporciones al nacer, generan un crecimiento diferencial que produce las disímiles morfologías adultas que se expresan en el grupo de las garzas. La tendencia general de estos cambios es de un incremento ligero en el medio del crecimiento para luego descender a casi la misma proporción inicial. El crecimiento en las primeras etapas de vida tiende a ser más isométrico y las diferencias se acentúan en momentos más tardíos. La hipótesis de asumir a Nycticorax como morfotipo peramórfico es más parsimoniosa en las tendencias de cambio dentro del grupo, resultando en un alargamiento relativo con alometría positiva del pico y del tarso en todas las especies. Esta hipótesis sería consistente con una hipermorfosis gradual que alcanzaría su máxima expresión en Ardea.
Abstract The order Ciconiiformes include wading bird species of sizes from medium to high, with body growth dynamic that can be analyzed to enlighten micro evolutionary trends. Egrets and herons (family Ardeidae) evolved from a common ancestor, but there are differences in adult body shapes, and their evolution has been suggested to be based on heterochronic processes. However, previous researches on growth have focused only in lineal dimension, and alometric changes have not been studied. In the current paper I described changes in body proportions during growth in seven ardeid species, and analyzed body growth under a phylogenetic point of view, to identify the primitive morphology pattern among genus Butorides and Nycticorax. For this purpose, I calculated bill/ tarsus rate in 353 nestlings, measured between 1998 and 2006, and assessed their changes with age and body weight. All species showed marked differences in proportion changes extension between hatching and an analogous growth moment, except Bubulcus that grows almost isometrically. Alometric changes during growth and at hatch, generate a differential growth that produced the different adult morphologies expressed among egrets and herons. The general trends were toward a slight increase in the middle of the growth period up to a lowering to almost the same initial proportions. Growth in the first life stages tends to be more isometric and differences get higher latter in growth. The hypothesis of Nycticorax as peramorphic morfotype is more parsimonious with changes trends in the group, resulting in a relative extremities extension with positive alometry in bill and tarsus in all species. This hypothesis is consistent with a gradual hipermorphosis that reaches a maximum expression in Ardea. Rev. Biol. Trop. 65 (4): 1347-1357. Epub 2017 December 01.
ABSTRACT
Roseate Spoonbills (Platalea ajaja, Linnaeus) are wading birds present in two of the most important Brazilian wetlands: the Pantanal wetlands and Rio Grande do Sul marshes. Natural populations of these species have not been previously studied with variable nuclear molecular markers. In order to support decision making regarding the management and conservation of these populations, we estimated and characterized the distribution of genetic variability among five Brazilian breeding colonies. The average observed heterozygosity in Brazilian Roseate Spoonbill populations (Ho = 0.575) did not differ significantly from the value determined in a U.S. wild-caught sample of 15 individuals, using data generated by the same set of microsatellite loci. Considering that the U.S. population underwent a recent reduction in size, we discuss this result supposing that the U.S. population was not genetically affected or that both populations had suffered a bottleneck. Global F(ST) indicated the lack of genetic differentiation among colonies, indicating the occurrence of past and/or present gene flow among them. Analysis of molecular variance revealed that most of the genetic variation is distributed within the colonies. Results are explained by a recent origin of colonies or by high levels of gene flow. Management decisions should take into consideration the fact that, even in the presence of high genetic exchange, ecological adaptations to different environments are important for species survival.