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The main objective of this study was to evaluate biogeographical hypotheses of diversification and connection between isolated savannas north (Amazonian savannas) and south (Cerrado core) of the Amazon River. To achieve this, we used genomic markers (genotyping-by-sequencing) to evaluate the genetic structure, population phylogenetic relationships and historical range shifts of four Neotropical passerines with peri-Atlantic distributions: the narrow-billed woodcreeper (Lepidocolaptes angustirostris), the plain-crested elaenia (Elaenia cristata), the grassland sparrow (Ammodramus humeralis) and the white-banded tanager (Neothraupis fasciata). Population genetic analyses indicated that landscape (e.g., geographic distance, landscape resistance and percentage of tree cover) and climate metrics explained divergence among populations in most species, but without indicating a differential role between current and historical factors. Our results did not fully support the hypothesis that isolated populations in Amazonian savannas have been recently derived from the Cerrado core domain. Intraspecific phylogenies and gene flow analyses supported multiple routes of connection between the Cerrado and Amazonian savannas, rejecting the hypothesis that the Atlantic corridor explains the peri-Atlantic distribution. Our results reveal that the biogeographical history of the region is complex and cannot be explained by simple vicariant models., (© 2022 John Wiley & Sons Ltd.)

Identifying the ecological factors that shape parasite distributions remains a central goal in disease ecology. These factors include dispersal capability, environmental filters and geographic distance. Using 520 haemosporidian parasite genetic lineages recovered from 7,534 birds sampled across tropical and temperate South America, we tested (a) the latitudinal diversity gradient hypothesis and (b) the distance-decay relationship (decreasing proportion of shared species between communities with increasing geographic distance) for this host-parasite system. We then inferred the biogeographic processes influencing the diversity and distributions of this cosmopolitan group of parasites across South America. We found support for a latitudinal gradient in diversity for avian haemosporidian parasites, potentially mediated through higher avian host diversity towards the equator. Parasite similarity was correlated with climate similarity, geographic distance and host composition. Local diversification in Amazonian lineages followed by dispersal was the most frequent biogeographic events reconstructed for haemosporidian parasites. Combining macroecological patterns and biogeographic processes, our study reveals that haemosporidian parasites are capable of circumventing geographic barriers and dispersing across biomes, although constrained by environmental filtering. The contemporary diversity and distributions of haemosporidian parasites are mainly driven by historical (speciation) and ecological (dispersal) processes, whereas the parasite community assembly is largely governed by host composition and to a lesser extent by environmental conditions., (© 2019 John Wiley & Sons Ltd.)