Contrasting migratory journeys and changes in hippocampal astrocyte morphology in shorebirds.

Semipalmated sandpiper (Calidris pusilla) migration to the Southern Hemisphere includes a 5-day non-stop flight over the Atlantic Ocean, whereas semipalmated plover (Charadrius semipalmatus) migration, to the same area, is largely over land, with stopovers for feeding and rest. We compared the number and 3D morphology of hippocampal astrocytes of Ch. semipalmatus before and after autumnal migration with those of C. pusilla to test the hypothesis that the contrasting migratory flights of these species could differentially shape hippocampal astrocyte number and morphology. We captured individuals from both species in the Bay of Fundy (Canada) and in the coastal region of Bragança (Brazil) and processed their brains for selective GFAP immunolabeling of astrocytes. Hierarchical cluster analysis of astrocyte morphological features distinguished two families of morphological phenotypes, named type I and type II, which were differentially affected after migratory flights. Stereological counts of hippocampal astrocytes demonstrated that the number of astrocytes decreased significantly in C. pusilla, but did not change in Ch. semipalmatus. In addition, C. pusilla and Ch. semipalmatus hippocampal astrocyte morphological features were differentially affected after autumnal migration. We evaluated whether astrocyte morphometric variables were influenced by phylogenetic differences between C. pusilla and Ch. semipalmatus, using phylogenetically independent contrast approach, and phylogenetic trees generated by nuclear and mitochondrial markers. Our findings suggest that phylogenetic differences do not explain the results and that contrasting long-distance migratory flights shape plasticity of type I and type II astrocytes in different ways, which may imply distinct physiological roles for these cells.

Mitochondrial introgression obscures phylogenetic relationships among manakins of the genus Lepidothrix (Aves: Pipridae).

Lepidothrix is the most diverse genus of the family Pipridae, with eight recognized species. Although the genus' monophyly has been supported by both molecular and morphological characters, phylogenetic relationships and species limits within Lepidothrix remain uncertain. In the present study, we combined molecular sequences of mitochondrial (ND2 and COI) and nuclear (MYO, G3PDh and I5BF) markers in a multilocus analysis, to evaluate relationships and inter-specific limits among L. iris, L. nattereri, and L. vilasboasi, which are known to hybridize in eastern Amazonia. The results revealed a complex pattern, whereby events of secondary contact and gene flow after isolation and genetic and phenotypic differentiation prevented the recuperation of reciprocal monophyly among the studied taxa. The mitochondrial data indicate that L. nattereri is divided into two non-sister groups, one monophyletic, and the other, paraphyletic, with L. iris iris being more closely related to one of the two L. nattereri groups, while L. iris eucephala forms an undifferentiated clade with L. vilasboasi, probably resulting from an extensive process of mitochondrial introgression. In agreement with a previous study based on Single Nucleotide Polymorphism (SNP) data, mitochondrial haplotype networks also support that L. vilasboasi does not represent a recent "hybrid swarm" between L. iris and L. nattereri, but instead a genetically divergent lineage with a separate species status. Finally, the sister relationship recovered herein between L. iris iris and some western populations of L. nattereri currently in allopatry is also apparently explained by mitochondrial introgression, as also supported for nuclear genes by SNP data, indicating a complex scenario of past contact and gene flow between currently geographically distant Lepidothrix lineages.