Genomic and acoustic differences separate Lilian’s Meadowlark (Sturnella magna lilianae) from Eastern (S. magna) and Western (S. neglecta) meadowlarks

Examining differences among recently diverged populations can provide insight into the traits and evolutionary mechanisms that drive or maintain divergence. The genus Sturnella includes 2 recently diverged species, Sturnella magna (Eastern Meadowlark) and S. neglecta (Western Meadowlark), the former of which has a complex of subspecies distributed across the Americas. Of the S. magna subspecies that occur in the United States, S. m. lilianae is the only one with a disjunct range, occurring in the southwestern United States and central Mexico. It also has markedly different song patterns than all other S. magna subspecies. In order to assess population differentiation, we performed whole-genome sequencing of 35 birds and analyzed song characteristics from 85 birds. Songs from each species and S. m. lilianae were diagnosable using linear discriminant function analysis and support divergence in song between all taxa. Phylogenetic analysis and admixture proportions support 3 distinct clades within North American meadowlarks, and tests of introgression failed to detect a significant signal. Overall, our results indicate that S. m. lilianae exhibits high levels of genetic and vocal differentiation from both S. magna and S. neglecta, with no evidence of introgression between any group, and forms a distinct evolutionary lineage. We thus recommend the elevation of S. m. lilianae to species status.

Using a multi-isotope approach to understand waterfowl movement in southern Africa

Many far-ranging species depend heavily on relatively small or temporary resources within a heterogeneous landscape. For waterfowl, most species rely on deep, permanent waterbodies as refugia from predators during annual flightless molt periods when synchronous loss and regrowth of the flight feathers occurs. The movements of ducks to and from molt sites are, however, poorly documented for most Afrotropical species and the dependencies of Afrotropical ducks on key sites are unclear, yet this information is integral to conservation and management efforts. We asked whether stable isotopes of wing feathers could be used to determine the molting origins of Afrotropical ducks in southern Africa. We analyzed isotope ratios of carbon, nitrogen, oxygen, and hydrogen in feathers from 4 different species across 5 different sites (wetlands, ponds, lakes) in South Africa, Zimbabwe, Mozambique, and Botswana. We observed differences among sites for all isotopes (P < 0.05), especially δ 13C and δ 15N. Based on these differences, we conducted linear discriminant function analysis (LDA) to assess the utility of these isotopes to assign birds to molt locations. We obtained a global classification accuracy = 0.59, although accuracies differed among sites. Our results demonstrate the potential of a multi-isotope approach to discriminate among specific molt locations and to provide an initial estimate of molt site. Rigorous documentation of molt site from wing feathers is plausible, but will require large sample sizes, extensive spatial coverage, and careful calibration.

Morphometric Analysis of Cranial Shape in Fossil and Recent Euprimates

Quantitative analysis of morphology allows for identification of subtle evolutionary patterns or convergences in anatomy that can aid ecological reconstructions of extinct taxa. This study explores diversity and convergence in cranial morphology across living and fossil primates using geometric morphometrics. 33 3D landmarks were gathered from 34 genera of euprimates (382 specimens), including the Eocene adapiforms Adapis and Leptadapis and Quaternary lemurs Archaeolemur, Palaeopropithecus, and Megaladapis. Landmark data was treated with Procrustes superimposition to remove all nonshape differences and then subjected to principal components analysis and linear discriminant function analysis. Haplorhines and strepsirrhines were well separated in morphospace along the major components of variation, largely reflecting differences in relative skull length and width and facial depth. Most adapiforms fell within or close to strepsirrhine space, while Quaternary lemurs deviated from extant strepsirrhines, either exploring new regions of morphospace or converging on haplorhines. Fossil taxa significantly increased the area of morphospace occupied by strepsirrhines. However, recent haplorhines showed significantly greater cranial disparity than strepsirrhines, even with the inclusion of the unusual Quaternary lemurs, demonstrating that differences in primate cranial disparity are likely real and not simply an artefact of recent megafaunal extinctions.

Morphometric and meristic differences between shallow- and deep-water populations of white hake (Urophycis tenuis) in the southern Gulf of St. Lawrence

Linear discriminant function analysis of morphometric and meristic characters was used to assess the extent of differentiation between shallow- (<100 m) and deep- (>200 m) water populations of white hake (Urophycis tenuis) from the southern Gulf of St. Lawrence (NAFO Division 4T). Although meristic characters provided some evidence for stock separation, the best statistical separation was obtained with morphometric characters. Morphometric discriminant functions derived from "learning" samples were able to correctly classify 82 and 84% of the "test" samples for both females and males, respectively. A greater relative snout length in fish sampled from along the Laurentian Channel compared with those from the Northumberland Strait area was the primary discriminating character for both sexes. Our morphological evidence and previous tagging and distributional studies suggest that the populations from these two areas represent separate stocks; therefore, the traditional management unit for white hake in NAFO Division 4T may no longer be appropriate.