Browsing by Author "Omland, Kevin E."
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Item ANCESTRAL STATE RECONSTRUCTION OF MIGRATION: MULTISTATE ANALYSIS REVEALS RAPID CHANGES IN NEW WORLD ORIOLES (ICTERUS SPP.)(The American Ornithologists' Union, 2006-03-20) Kondo, Beatrice; Omland, Kevin E.During the past century, numerous theoretical articles explored the evolution of seasonal migration in birds; many of these focused on environmental or social conditions that may have led to the origin of migration. More recent work has focused not on the origin of migration, but on changes in migratory behavior that have occurred in modern species and their immediate ancestors. We used a novel approach, a multistate ancestral state reconstruction of migration, to examine patterns of migratory evolution in the New World orioles (Icterus spp.). Both the multistate and binary reconstructions indicated repeated gains in migration. However, the multistate method revealed details of how migration may be gained that the standard binary-state reconstructions would not have shown. Our maximum-likelihood reconstruction, using branch lengths based on a molecular phylogeny, suggested multiple instances of rapid gain of migration. Furthermore, we found that every migratory species’ migration type diff ered from that of its closest relatives. Surprisingly, no partially migratory species was closely related to a fully migratory species. These novel patt erns involving gain of migration demonstrate the utility of multistate ancestral reconstruction for examining changes in migratory behavior in closely related birds.Item As the raven flies: using genetic data to infer the history of invasive common raven (Corvus corax) populations in the Mojave Desert(Blackwell Publishing Ltd, 2007-10-01) Fleischer, Robert C.; Boarman, William I.; Gonzalez, Elena G.; Godinez, Alvaro; Omland, Kevin E.; Young, Sarah; Helgen, Lauren; Syed, Gracia; Mcintosh, Carl E.Common raven (Corvus corax) populations in Mojave Desert regions of southern California and Nevada have increased dramatically over the past five decades. This growth has been attributed to increased human development in the region, as ravens have a commensal relationship with humans and feed extensively at landfills and on road‐killed wildlife. Ravens, as a partially subsidized predator, also represent a problem for native desert wildlife, in particular threatened desert tortoises (Gopherus agassizii). However, it is unclear whether the more than 15‐fold population increase is due to in situ population growth or to immigration from adjacent regions where ravens have been historically common. Ravens were sampled for genetic analysis at several local sites within five major areas: the West Mojave Desert (California), East Mojave Desert (southern Nevada), southern coastal California, northern coastal California (Bay Area), and northern Nevada (Great Basin). Analyses of mtDNA control region sequences reveal an increased frequency of raven ‘Holarctic clade’ haplotypes from south to north inland, with ‘California clade’ haplotypes nearly fixed in the California populations. There was significant structuring among regions for mtDNA, with high Fst values among sampling regions, especially between the Nevada and California samples. Analyses of eight microsatellite loci reveal a mostly similar pattern of regional population structure, with considerably smaller, but mostly significant, values. The greater mtDNA divergences may be due to lower female dispersal relative to males, lower Nₑ, or effects of high mutation rates on maximal values of Fst. Analyses indicate recent population growth in the West Mojave Desert and a bottleneck in the northern California populations. While we cannot rule out in situ population growth as a factor, patterns of movement inferred from our data suggest that the increase in raven populations in the West Mojave Desert resulted from movements from southern California and the Central Valley. Ravens in the East Mojave Desert are more similar to ones from northern Nevada, indicating movement between those regions. If this interpretation of high gene flow into the Mojave Desert is correct, then efforts to manage raven numbers by local control may not be optimally effective.Item Coalescent analyses show isolation without migration in two closely related tropical orioles: the case of Icterus graduacauda and Icterus chrysater(John Wiley & Sons Ltd, 2013-10-09) Cortés‐Rodríguez, Nandadevi; Jacobsen, Frode; Hernandez‐Baños, Blanca E.; Navarro‐Siguenza, Adolfo G.; Peters, Jeffrey L.; Omland, Kevin E.The Isthmus of Tehuantepec has played an important role in shaping the avian diversity of Mexico, as well as the rest of the Western Hemisphere. It has been both a barrier and a land connector between North and South America for many groups of birds. Furthermore, climatic change over the Pleistocene has resulted in ecological fluctuations that led to periods of connection and isolation of the highlands in this area. Here we studied the divergence of two species of orioles whose distribution in the highlands is separated by the lowlands of the Isthmus of Tehuantepec: Icterus graduacauda (west of the Isthmus) and Icterus chrysater (east of the Isthmus). We sequenced multiple loci (one mitochondrial gene and six nuclear introns) and performed coalescent analyses (Isolation with Migration) to test whether their divergence resulted from prior occupancy of the ancestral area followed by a vicariant event or recent dispersal from one side or the other of this Isthmus. Results strongly indicate a vicariant event roughly 300,000 years ago in the Pleistocene followed by little or no gene flow. Both mitochondrial and nuclear genes show that the Isthmus of Tehuantepec is a strong barrier to gene flow. Thus, these two species appear to not exchange genes despite their recent divergence and the close geographic proximity of their ranges.Item Colonization of South America from Caribbean Islands Confirmed by Molecular Phylogeny with Increased Taxon Sampling(American Ornithological Society, 2009-04-21) Sturge, Rachel J.; Jacobsen, Frode; Rosensteel, Bryan B.; Neale, Richie J.; Omland, Kevin E.A previous phylogeny of New World orioles (Icterus) suggested a possible example of island-to-mainland colonization. Using two mitochondrial genes (cytochrome b and ND2), that study showed that 43 of the recognized species/ subspecies are divided into three clades (A, B, C). Because of a lack of fresh tissue, however, two key taxa—the South American Orange-crowned Oriole (I. auricapillus) and the Caribbean Hispaniola Oriole (I. dominicensis dominicensis)—were missing from that analysis. To complete the phylogeny, we sequenced both genes for these taxa and reconstructed a well-supported phylogeny via parsimony and maximum-likelihood analyses. The addition of I. d. dominicensis to the phylogeny confirms that the Greater Antillean Oriole (I. dominicensis) is polyphyletic, and taxonomic revision of this species complex is warranted. Also, the placement of I. auricapillus and I. d. dominicensis within clade A has important implications for biogeography. The revised phylogeny implies that clade A orioles colonized mainland South America from Caribbean islands. Orioles thus provide a striking example of reverse colonization that contradicts the traditional assumption in island biogeography of mainland-to-island colonization.Item Congruence between nuclear and mitochondrial DNA: Combination of multiple nuclear introns resolves a well-supported phylogeny of New World orioles (Icterus)(Elsevier Inc., 2010-07) Jacobsen, Frode; Friedman, Nicholas R.; Omland, Kevin E.Darwin’s vision of a “Tree of Life” showing evolutionary relationships among all extant species seems an increasingly feasible goal, at least for vertebrate animals. However, virtually all published molecular phylogenies for closely related animals are based on a single locus – maternally inherited mitochondrial DNA. New approaches using multiple nuclear loci are needed to test published trees and better resolve the twigs of the entire tree of life. Here we use New World orioles (Icterus) to test an approach based on combined analysis of six independent Z chromosome introns. Combined analysis of multiple introns using traditional phylogenetic methods resolved a well-supported species phylogeny of New World orioles. In fact, all major lineages of orioles and several sub-clades that are well-supported by previously published mtDNA data are also strongly supported by the combined nuclear Z-intron tree. The male-biased Z-intron tree presented here is overwhelmingly congruent with the female-exclusive mtDNA tree. A slow rate of mutation relative to mtDNA resulted in generally poorly resolved gene trees when intron loci were analyzed separately. However, strong phylogenetic signal for all but the most recent divergences emerged once multiple loci were concatenated and analyzed in combination. Although there clearly are conditions under which concatenation analysis of nuclear DNA can be misleading, the congruence between mitochondrial and nuclear estimates of the Icterus phylogeny suggests that concatenation remains a powerful tool for inferring phylogenetic relationships for all but very recent divergences.Item Convergent Gains of Red Carotenoid-Based Coloration in the New World Blackbirds(American Ornithological Society, 2011-08-19) Friedman, Nicholas R.; Kiere, Lynna M.; Omland, Kevin E.Many birds have colorful plumage ornaments that utilize carotenoid pigments, and these are often displayed in signaling contexts. Researchers in behavioral ecology have focused on examining carotenoids in general, and red carotenoids in particular, because they may be an honest index of individual condition or quality. However, few studies have examined the evolutionary changes in carotenoid-based coloration across a phylogeny. We used reflectance spectrometry to examine carotenoid-based coloration across the New World blackbirds (Icteridae). We scored discrete character states based on these measurements and mapped them onto the icterid phylogeny. Our results indicate that red coloration has been gained six times in the blackbirds from a common ancestor that exhibited yellow ornamentation. This result was supported by both parsimony and likelihood methods of ancestral state reconstruction and by each of three different scoring methods. Thus, multiple lineages of icterids have convergently evolved red patches from a common ancestor that most likely used yellow. Several other studies have observed repeated gains of red coloration, which suggests that our observations may reflect a directional trend common among avian clades.Item Documentation of female song in a newly recognized species, the Puerto Rican Oriole (Icterus portoricensis)(2016-10-24) Campbell, Susanna K.; Morales-Perez, Alcides L.; Malloy, John F.; Muellerklein, Oliver C.; Kim, Jin A.; Odom, Karan J.; Omland, Kevin E.Evolutionary biologists often assume that male competition for females is the root of the evolution of elaborate coloration and song. However, recent findings show that in the ancestral history of songbirds, it is likely that song occurred in both males and females. Surprisingly, no data exist on female song for many species of birds. We investigated whether the Puerto Rican Oriole (Icterus portoricensis), a tropical songbird, exhibits both male and female song. For this project we marked individuals with sex-specific color bands and confirmed sex using genetic sexing. We repeatedly recorded both male and female orioles singing. Furthermore, female Puerto Rican Oriole song appears to be similar to male song, with no obvious differences in structure. Our study provides further evidence of the ubiquity of female song in tropical songbirds. Finally, our findings provide support that female song is ancestral in the Caribbean oriole clade, and that song dimorphism in temperate breeding species is a result of a loss of female song.Item Duetting behavior varies with sex, season, and singing role in a tropical oriole (Icterus icterus)(Oxford University Press, 2017-08-11) Odom, Karan J.; Logue, David M.; Studds, Colin E.; Monroe, Michelle K.; Campbell, Susanna K.; Omland, Kevin E.Females and males of many animals combine their vocalizations into coordinated acoustic duets. Duets can mediate both cooperation and conflict between partners, and are common in tropical, sedentary species that may use duets for multiple functions year-round. To elucidate the full range of duet functions, we need to study the individual-level behaviors that generate duets throughout the year. We evaluated multiple functions of duetting behavior in female and male Venezuelan troupials (Icterus icterus) during the breeding and nonbreeding seasons, including territory defense, maintaining contact with a mate, and paternity guarding. In both sexes during both seasons, song initiation rates were predicted by conspecific solo and duet rates. However, troupials were more likely to answer their mate to form duets after conspecific duets than after conspecific solos, supporting a territory defense function of duets. Troupials that answered their mate to form duets were also more likely to move toward their mate (than duet initiators and soloists), suggesting that duet participation also functions to maintain contact. During the breeding season, males were particularly likely to fly toward their mate after answering to form a duet. This finding may indicate that males answer to guard paternity, although other predictions of paternity guarding were not supported. Examining individual-level behaviors during both the breeding and nonbreeding season revealed multiple functions of troupial duets. Our results are consistent with social selection acting on females and males to maintain contact and territories year-round, and possibly sexual selection on males for functions tied to the breeding season.Item Evolution of Sexual Dichromatism. 1. Convergent Losses of Elaborate Female Coloration in New World Orioles (Icterus spp.)(American Ornithological Society, 2008-02-05) Hofmann, Christopher M.; Cronin, Thomas W.; Omland, Kevin E.Studies of sexual dimorphism often focus on the evolution of elaborate male traits, whereas the evolution of elaborate females has been largely ignored. Yet a phylogenetic perspective suggests that changes in either male or female traits may lead to the evolution of sexual dimorphism. Furthermore, changes in the degree of sexual dichromatism can be caused by gains or losses of elaboration. One common form of elaboration found throughout the animal kingdom is the use of highly saturated and contrasting colors. To investigate further the evolution of female elaboration and sexual dichromatism, we took quantitative measurements of color from New World orioles (Icterus spp.) and then used ancestral-state reconstruction to infer evolutionary changes in male and female elaboration. Our findings suggest that male elaboration is ancestral and strongly conserved but that female elaboration has changed repeatedly, especially through the loss of saturation and contrast. Thus, changes in female—rather than male—color appear to lead to the evolution of sexual dichromatism in orioles. These repeated gains of strong sexual dichromatism through the loss of female elaboration were supported using multiple methods of character coding and reconstruction. Our phylogenetic results suggest that studies of sexual dichromatism cannot assume that color dimorphism arises through increased male elaboration. These findings have important implications for future studies investigating the ultimate causes of sexual dichromatism.Item Evolution of Sexual Dichromatism. 2. Carotenoids and Melanins Contribute to Sexual Dichromatism in New World Orioles (Icterus spp.)(American Ornithological Society, 2008-02-05) Hofmann, Christopher M.; Cronin, Thomas W.; Omland, Kevin E.Several recent studies have investigated how different proximate mechanisms of color production contribute to sexual dichromatism. These studies suggest that carotenoid pigments—which are frequently subject to sexual selection—are more strongly associated with sexual dichromatism than melanins. This reasoning implicitly assumes that increased male elaboration leads to sexual dichromatism. However, sexual dichromatism can be generated through multiple evolutionary pathways, including decreases in female elaboration. We examined whether evolutionary changes in carotenoid- and melanin-based plumage were correlated within New World orioles (Icterus spp.), a genus in which male elaboration is ancestral and only female elaboration varies. We found a significant correlation between evolutionary changes in the degree of carotenoid and eumelanin sexual dichromatism. These findings differ from those of previous comparative studies and suggest the possibility of interesting differences when different evolutionary pathways—such as changes in male versus female coloration—lead to sexual dichromatism.Item Extensive introgressive hybridization within the northern oriole group (Genus Icterus) revealed by three‐species isolation with migration analysis(Blackwell Publishing Ltd, 2012-08-29) Omland, Kevin E.; Jacobsen, FrodeUntil recently, studies of divergence and gene flow among closely-related taxa were generally limited to pairs of sister taxa. However, organisms frequently exchange genes with other non-sister taxa. The “northern oriole” group within genus Icterus exemplifies this problem. This group involves the extensively studied hybrid zone between Baltimore oriole ( Icterus galbula ) and Bullock’s oriole ( I. bullockii ), an alleged hybrid zone between I. bullockii and black-backed oriole ( I. abeillei), and likely mtDNA introgression between I. galbula and I. abeillei . Here, we examine the divergence population genetics of the entire northern oriole group using a multipopulation Isolation-with-Migration (IM) model. In accordance with Haldane’s rule, nuclear loci introgress extensively beyond the I. galbula – I. bullockii hybrid zone, while mtDNA does not. We found no evidence of introgression between I. bullockii and I. abeillei or between I. galbula and I. abeillei when all three species were analyzed together in a three-population model. However, traditional pairwise analysis suggested some nuclear introgression from I. abeillei into I. galbula , probably reflecting genetic contributions from I. bullockii unaccounted for in a two-population model. Thus, only by including all members of this group in the analysis was it possible to rigorously estimate the level of gene flow among these three closely related species.Item Female song is widespread and ancestral in songbirds(Macmillan Publishers Limited, 2014-03-04) Odom, Karan J.; Hall, Michelle L.; Riebel, Katharina; Omland, Kevin E.; Langmore, Naomi E.Bird song has historically been considered an almost exclusively male trait, an observation fundamental to the formulation of Darwin’s theory of sexual selection. Like other male ornaments, song is used by male songbirds to attract females and compete with rivals. Thus, bird song has become a textbook example of the power of sexual selection to lead to extreme neurological and behavioural sex differences. Here we present an extensive survey and ancestral state reconstruction of female song across songbirds showing that female song is present in 71% of surveyed species including 32 families, and that females sang in the common ancestor of modern songbirds. Our results reverse classical assumptions about the evolution of song and sex differences in birds. The challenge now is to identify whether sexual selection alone or broader processes, such as social or natural selection, best explain the evolution of elaborate traits in both sexes.Item Genetic signatures of intermediate divergence: population history of Old and New World Holarctic ravens (Corvus corax)(Blackwell Publishing Ltd, 2006-01-09) Omland, Kevin E.; Baker, Jason M.; Peters, Jeffrey L.Many studies of phylogeography, speciation, and species limits restrict their focus to a narrow issue: gene tree monophyly. However, reciprocal monophyly does not provide an ideal touchstone criterion of any aspect of evolutionary divergence. There is a continuum of divergence stages as isolated populations go from initial allele frequency differences to well‐differentiated species. Studying intermediate stages of divergence will increase our understanding of geographical speciation, species limits, and conservation priorities. We develop a conceptual framework and terminology for thinking about the stages of ‘intermediate polyphyly’. The Holarctic clade of common ravens (Corvus corax), found throughout much of Eurasia and North America, provides a case study of these stages of intermediate divergence. We used coalescent, phylogenetic, and population genetic methods to investigate the history and current status of this Old World–New World distribution using 107 mitochondrial control region sequences. Phylogenetically, New World and Old World samples are intermixed. However, most samples are grouped into small subclades that are restricted to either the New World or the Old World, and only one haplotype is shared between the hemispheres. Analysis of moleculalr variance (amova) results reflect this low haplotype sharing between hemispheres (Φs🇹 = 0.13, P < 0.01). Isolation with Migration (IM) coalescent results suggest a sustained period of divergence between the hemispheres and low levels of maternal gene flow. Although there has not been sufficient time to evolve reciprocal monophyly and some gene flow may occur, New World and Old World ravens are genetically quite distinct. We use this example to demonstrate these early stages of divergence as populations go from sharing only internal haplotypes, to sharing no haplotypes, to having population specific subclades. Studies of phylogeography, speciation and systematics will benefit from increased attention to these stages of intermediate polyphyly.Item Genomic evidence of speciation reversal in ravens(Springer Nature Limited, 2018-03-02) Kearns, Anna M.; Restani, Marco; Szabo, Ildiko; Schrøder-Nielsen, Audun; Kim, Jin Ah; Richardson, Hayley M.; Marzluff, John M.; Fleischer, Robert C.; Johnsen, Arild; Omland, Kevin E.Many species, including humans, have emerged via complex reticulate processes involving hybridisation. Under certain circumstances, hybridisation can cause distinct lineages to collapse into a single lineage with an admixed mosaic genome. Most known cases of such ‘speciation reversal’ or ‘lineage fusion’ involve recently diverged lineages and anthropogenic perturbation. Here, we show that in western North America, Common Ravens (Corvus corax) have admixed mosaic genomes formed by the fusion of non-sister lineages (‘California’ and ‘Holarctic’) that diverged ~1.5 million years ago. Phylogenomic analyses and concordant patterns of geographic structuring in mtDNA, genome-wide SNPs and nuclear introns demonstrate long-term admixture and random interbreeding between the non-sister lineages. In contrast, our genomic data support reproductive isolation between Common Ravens and Chihuahuan Ravens (C. cryptoleucus) despite extensive geographic overlap and a sister relationship between Chihuahuan Ravens and the California lineage. These data suggest that the Common Raven genome was formed by secondary lineage fusion and most likely represents a case of ancient speciation reversal that occurred without anthropogenic causes.Item Geographic Variation and Genetic Structure in the Streak-Backed Oriole: Low Mitochondrial DNA Differentiation Reveals Recent Divergence(American Ornithological Society, 2008-09-24) Cortes-Rodríguez, Nandadevi; Hernández-Baños, Blanca E.; Navarro-Sigüenza, Adolfo G.; Omland, Kevin E.Many avian species from the temperate zone show low levels of genetic diversity when compared with species from the tropics, although there are some interesting exceptions, and species whose ranges occur across the temperate–tropical boundary could have characteristics of either or both zones. The distribution of the Streak-backed Oriole (Icterus pustulatus) extends from northwestern Sonora in Mexico south along the Pacific coast to Costa Rica. In addition, there is a population on the Tres Marías Islands. Northern populations are migratory and dichromatic (sexes different), whereas southern populations are nonmigratory and monochromatic (sexes alike). We sequenced mtDNA (control region domain I) from 102 individuals across the range of this species. Maximum parsimony and maximum likelihood analyses did not support the existence of multiple species within Icterus pustulatus based on mtDNA. However, populations from the Tres Marías Islands seem to have been isolated long enough to have fixed differences from populations on the mainland. The species complex shows an uncommon phylogeographic pattern, with shallow haplotype trees and weak geographic structure, suggesting that it has undergone recent population expansion. We recommend that the insular populations be considered a separate species, Icterus graysonii, given the fixed differences from mainland birds in multiple characteristics, including mtDNA and plumage patterns.Item Himalayan black bulbuls (Hypsipetes leucocephalus niggerimus) exhibit sexual dichromatism under ultraviolet light that is invisible to the human eye(Springer Nature Limited, 2017-04-06) Hung, Hsin-Yi; Yeung, Carol K. L.; Omland, Kevin E.; Yao, Cheng-Te; Yao, Chiou-Ju; Li, Shou-HsienSexual dichromatism is a key proxy for the intensity of sexual selection. Studies of dichromatism in birds may, however, have underestimated the intensity and complexity of sexual selection because they used museum specimens alone without taking colour-fading into account or only measured conspicuous visual traits in live animals. We investigated whether the Himalayan black bulbul (Hypsipetes leucocephalus nigerrimus), which is sexually monomorphic to the human eye, exhibits sexual dichromatism distinguishable by a spectrometer. We measured the reflectance (within both the human visual perceptive and the ultraviolet ranges) of two carotenoid-based parts and eight dull and melanin-based parts for each individual live bird or museum skin sampled. According to an avian model of colour discrimination thresholds, we found that males exhibited perceptibly redder beaks, brighter tarsi and darker plumage than did females. This suggests the existence of multiple cryptic sexually dichromatic traits within this species. Moreover, we also observed detectable colour fading in the museum skin specimens compared with the live birds, indicating that sexual dichromatism could be underestimated if analysed using skin specimens alone.Item History and mechanisms of carotenoid plumage evolution in the New World orioles (Icterus)(Elsevier Inc, 2014-06) Friedman, Nicholas R.; McGraw, Kevin J.; Omland, Kevin E.While many recent studies focus on the functions of carotenoids in visual signaling, they seldom address the phylogenetic origins of plumage coloration and its mechanisms. Here, we used the New World orioles (Icterus) as a model clade to study the history of orange carotenoid-based coloration and pigmentation, sampling 47 museum specimens from 12 species. We examined the identity and concentration of carotenoids in oriole feathers using high-performance liquid chromatography, and used phylogenetic comparative methods to compare these observations to reflectance measurements of plumage. Each of the seven yellow oriole species we sampled used only lutein to color their feathers. Ancestral state reconstruction of this trait suggests that the oriole common ancestor had yellow feathers pigmented with lutein. We found keto-carotenoids in small concentrations in the plumage of each of the five species scored as orange. This correlation suggests that discrete gains and losses of keto-carotenoids are behind independent gains of orange coloration in orioles. In contrast, total carotenoid concentration was not associated with hue, and total concentration of keto-carotenoids poorly explained variation in hue among species where they were present. These findings suggest that orioles most likely evolved orange plumage coloration at least twice, each time by gaining the ability to metabolize dietary carotenoids by C4-oxygenation. Given that red coloration is generated by this same oxygenation process in a wide range of bird species, it raises the question of why, if orioles possess this metabolic capability, no red oriole species exist.Item Large female song repertoires and within‐pair song type sharing in a temperate breeding songbird(Wiley Online Library, 2020-12-03) Sikora, Jonathan G.; Moyer, Michelle J.; Omland, Kevin E.; M. Rose, EvangelineFemale song has been significantly understudied in songbirds. While male song has been studied for centuries, female song has only begun to be explored in the last few decades. This is especially true in relation to understanding repertoire size and function. In male songbirds, song repertoires are thought to function primarily in mate attraction and territory defense. Only a few studies to date have explored repertoire size in female songbirds, and many of those focused on tropical duetting species. We quantified the size and explored the function of song repertoires in a temperate breeding songbird, the eastern bluebird. Female song in eastern bluebirds functions primarily in communication with a social mate in order to maintain long‐term pair bonds. Previous work in this species also documented that males have large repertoires serving a variety of purposes. We found that female bluebirds have similar song repertoire sizes to males. Also, females share their repertoires and song types more closely with their mate than shared with non‐mates. This is one of the first studies to document large female repertoires in a non‐duetting temperate species. Our findings indicate that large female repertoires and song type sharing in this species is integral to communication between social mates. Additionally, the large effect size of song type sharing with newly formed mates suggests open‐ended learning may be present in this songbird, a previously under‐documented phenomenon in females. This study provides the groundwork to explore the ontogeny and evolution of song repertoire size in female songbirds and to expand our understanding of song repertoires beyond their functions in males as an indicator of male fitness.Item Late Pleistocene divergence between eastern and western populations of wood ducks (Aix sponsa) inferred by the ‘isolation with migration’ coalescent method(Blackwell Publishing Ltd, 2005-07-01) Peters, Jeffrey L.; Gretes, William; Omland, Kevin E.During the Late Pleistocene, glaciers sundered many species into multiple glacial refugia where populations diverged in allopatry. Although deeply divergent mitochondrial DNA (mtDNA) lineages often reflect the number of refugia occupied, it is unlikely that populations that split during the recent Wisconsin glaciations will have reached reciprocal monophyly. We examined mtDNA control region sequences from eastern and western populations of wood ducks (Aix sponsa) to determine whether their current, disjunct distribution is consistent with the occupancy of two glacial refugia. We used the ‘isolation with migration’ coalescent method (im) to simultaneously estimate effective population sizes, maternal gene flow, and time since divergence. We found 24 unique haplotypes, none of which were shared between the eastern and western populations, but we did not find diagnostic monophyletic lineages suggestive of long‐term isolation in multiple glacial refugia. However, a high ΦST (0.31) indicates that eastern and western populations are well differentiated in mtDNA, and results from im suggest that these populations have been diverging, without extensive gene flow, for 10 000 to 124 000 years. Results from im further suggest that these populations most likely split about 34 000 years ago, and this time of divergence is consistent with the occupancy of multiple glacial refugia during the Late Wisconsin glaciation. Eastern wood ducks are characterized by high genetic diversity, a large effective population size, and a recent population expansion, while western wood ducks have much less genetic diversity, a smaller population size, and have not undergone a recent population expansion.Item A Molecular Phylogeny of the Blackbirds (Icteridae): Five Lineages Revealed by Cytochrome-B Sequence Data(American Ornithological Society, 1999-07) Lanyon, Scott M.; Omland, Kevin E.New World blackbirds (Icteridae) have long served as model systems for studies of avian ecology, evolution, and behavior. However, this work has been conducted in the absence of a strong phylogenetic hypothesis for the group. We sequenced 890 base pairs (bp) of the mitochondrial cytochrome-b gene for 28 of the 29 icterid genera and subgenera recognized by Blake (1968). We found strong evidence of five lineages of blackbirds: grackles and allies; caciques and oropendolas; orioles; meadowlarks and allies; and a monotypic cupnesting cacique lineage. However, we found little support for any further structure among these five lineages and no strong evidence supporting icterid monophyly. Our results set the stage for forthcoming work on relationships within lineages and for higher-level studies that address blackbird monophyly and relationships among lineages.
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