Padrões de distribuições compartilhadas entre Aves amazônicas: inferências biogeográficas baseadas em congruência espacial

Abstract

The field of biogeography is constantly changing. New techniques in ecology, information theory, and genetics have driven advances and syntheses of knowledge not imaginable few decades ago. Comparative biogeography is one of its ramifications that seeks spatial patterns shared between species to classify and identify processes that operate in the geographic space. Spatial congruence, which defines biogeographic units, such as Endemic Areas and Ecoregions, but also chorological units, such as chorotypes, is assumed as appropriately addressed by concepts and methods. However, this spatial congruence has not been satisfactorily explored as a concept, nor has it been explicitly incorporated as a parameter into the bioregionalization methods used to recognize these units. In the first chapter problems and biases associated with concepts and methods currently used are identified, and a new method proposed. Two of its characteristics were not found combined in a single framework. One is the ability to detect independent patterns, derived from any species, and often spatially overlapped. The other is the possibility of describing gradients of distributions. For this we propose the differentiation between direct and indirect spatial congruences, and an algorithm to recognize groups of species that are equivalent to the concept of chorotype (Fattorini, S., 2015, J. Biogeog. 42:2246). These fundamental biogeographic units, which are based on spatial relationships between taxa, without the a priori establishment of areas, grids, or barriers, are described here by specific parameters: reference species, congruence level, depth, and the relation between richness and spatial coherence. Each species, when generating patterns, i.e. it is informative, can have partial chorotypes at each congruence threshold analyzed. The relaxation of congruence levels, and indirect comparisons allow the unveiling of less explored aspects, such as dispersion routes across barriers and the role of gradients in the species distribution. In the second chapter, the application of this method in Amazonian avifauna showed that the biogeography of this group is complex and structured, contrary to the results of recent analyzes that claim the absence of significant biogeographic structuring (Oliveira, Vasconcelos & Santos, 2017; Sci. Rep. 7:2992). The analysis rescued several of the Areas of Endemism traditionally recognized for terra-firme and varzea birds, but not all. More surprising, however, is to reestablish the perspective that there are patterns as or more representative in species, that bring together several traditionally described areas or, sometimes, only part of them. The two regions that stand out the most for species comprehensiveness and spatial cohesion were the West, both to the north and south of the Amazon river, and the Northeast (Guiana). In the West there are several very representative chorotypes, some of them spatially overlapping but compositionally independent. Several mainly linear patterns occupy the altitudinal gradients in the Pre-Andes region. Guiana has overlapping patterns associated with the altitudinal gradients of the Tepuis and other smaller regional patterns. The Southeast is well limited to the West by the Madeira river but has contradictory configurations associated with the biogeographical role of the Tapajós and Xingu rivers. The ‘species’ taxonomic level proved to be satisfactory for the rescue of these more evident patterns, but a further refinement in the taxonomic units will allow future analyzes with much more precise spatial resolution.