Ordning i klassen! Taxonomi & systematik – exempel från fåglarnas värld

Vad är en art? Varför betraktar somliga nordlig och sydlig gulärla som olika arter, medan andra klassificerar dem som samma art? Varför skiljer sig artantalet så mycket mellan olika listor över världens fågelarter, och vilken lista är rätt? Varför byter vissa arter släkte, och hur kommer det sig att vissa släkten omfattar många arter medan andra bara består av en enda art? Är falkar verkligen närmare släkt med tättingar än med hökar? Kan DNA-analyser besvara alla frågor

Integrative taxonomy of the Plain‑backed Thrush (Zoothera mollissima) complex (Aves, Turdidae) reveals cryptic species, including a new species

Background: The Plain-backed Thrush Zoothera mollissima breeds in the Himalayas and mountains of central China.It was long considered conspecific with the Long-tailed Thrush Zoothera dixoni, until these were shown to be broadlysympatric. Methods: We revise the Z. mollissima-Z. dixoni complex by integrating morphological, acoustic, genetic (two mitochondrialand two nuclear markers), ecological and distributional datasets. Results: In earlier field observations, we noted two very different song types of "Plain-backed" Thrush segregated by breeding habitat and elevation. Further integrative analyses congruently identify three groups: an alpine breeder inthe Himalayas and Sichuan, China ("Alpine Thrush"); a forest breeder in the eastern Himalayas and northwest Yunnan(at least), China ("Himalayan Forest Thrush"); and a forest breeder in central Sichuan ("Sichuan Forest Thrush"). Alpine and Himalayan Forest Thrushes are broadly sympatric, but segregated by habitat and altitude, and the same is probablytrue also for Alpine and Sichuan Forest Thrushes. These three groups differ markedly in morphology and songs.In addition, DNA sequence data from three non-breeding specimens from Yunnan indicate that yet another lineage exists ("Yunnan Thrush"). However, we find no consistent morphological differences from Alpine Thrush, and its breedingrange is unknown. Molecular phylogenetic analyses suggest that all four groups diverged at least a few million years ago, and identify Alpine Thrush and the putative "Yunnan Thrush" as sisters, and the two forest taxa as sisters. Cytochrome b divergences among the four Z. mollissima sensu lato (s.l.) clades are similar to those between any ofthem and Z. dixoni, and exceed that between the two congeneric outgroup species. We lectotypify the name Oreocincla rostrata Hodgson, 1845 with the Z. mollissima sensu stricto (s.s.) specimen long considered its type. No availablename unambiguously pertains to the Himalayan Forest Thrush. Conclusions: The Plain-backed Thrush Z. mollissima s.l. comprises at least three species: Alpine Thrush Z. mollissima s.s., with a widespread alpine breeding distribution; Sichuan Forest Thrush Z. griseiceps, breeding in central Sichuan forests; and Himalayan Forest Thrush, breeding in the eastern Himalayas and northwest Yunnan (at least), which is described herein as a new species. "Yunnan Thrush" requires further study

Evolution of ultraviolet vision in the largest avian radiation - the passerines

<p>Abstract</p> <p>Background</p> <p>Interspecific variation in avian colour vision falls into two discrete classes: violet sensitive (VS) and ultraviolet sensitive (UVS). They are characterised by the spectral sensitivity of the most shortwave sensitive of the four single cones, the SWS1, which is seemingly under direct control of as little as one amino acid substitution in the cone opsin protein. Changes in spectral sensitivity of the SWS1 are ecologically important, as they affect the abilities of birds to accurately assess potential mates, find food and minimise visibility of social signals to predators. Still, available data have indicated that shifts between classes are rare, with only four to five independent acquisitions of UV sensitivity in avian evolution.</p> <p>Results</p> <p>We have classified a large sample of passeriform species as VS or UVS from genomic DNA and mapped the evolution of this character on a passerine phylogeny inferred from published molecular sequence data. Sequencing a small gene fragment has allowed us to trace the trait changing from one stable state to another through the radiation of the passeriform birds. Their ancestor is hypothesised to be UVS. In the subsequent radiation, colour vision changed between UVS and VS at least eight times.</p> <p>Conclusions</p> <p>The phylogenetic distribution of SWS1 cone opsin types in Passeriformes reveals a much higher degree of complexity in avian colour vision evolution than what was previously indicated from the limited data available. Clades with variation in the colour vision system are nested among clades with a seemingly stable VS or UVS state, providing a rare opportunity to understand how an ecologically important trait under simple genetic control may co-evolve with, and be stabilised by, associated traits in a character complex.</p

Non-monophyly and intricate morphological evolution within the avian family Cettiidae revealed by multilocus analysis of a taxonomically densely sampled dataset

<p>Abstract</p> <p>Background</p> <p>The avian family Cettiidae, including the genera <it>Cettia</it>, <it>Urosphena</it>, <it>Tesia</it>, <it>Abroscopus </it>and <it>Tickellia </it>and <it>Orthotomus cucullatus</it>, has recently been proposed based on analysis of a small number of loci and species. The close relationship of most of these taxa was unexpected, and called for a comprehensive study based on multiple loci and dense taxon sampling. In the present study, we infer the relationships of all except one of the species in this family using one mitochondrial and three nuclear loci. We use traditional gene tree methods (Bayesian inference, maximum likelihood bootstrapping, parsimony bootstrapping), as well as a recently developed Bayesian species tree approach (*BEAST) that accounts for lineage sorting processes that might produce discordance between gene trees. We also analyse mitochondrial DNA for a larger sample, comprising multiple individuals and a large number of subspecies of polytypic species.</p> <p>Results</p> <p>There are many topological incongruences among the single-locus trees, although none of these is strongly supported. The multi-locus tree inferred using concatenated sequences and the species tree agree well with each other, and are overall well resolved and well supported by the data. The main discrepancy between these trees concerns the most basal split. Both methods infer the genus <it>Cettia </it>to be highly non-monophyletic, as it is scattered across the entire family tree. Deep intraspecific divergences are revealed, and one or two species and one subspecies are inferred to be non-monophyletic (differences between methods).</p> <p>Conclusions</p> <p>The molecular phylogeny presented here is strongly inconsistent with the traditional, morphology-based classification. The remarkably high degree of non-monophyly in the genus <it>Cettia </it>is likely to be one of the most extraordinary examples of misconceived relationships in an avian genus. The phylogeny suggests instances of parallel evolution, as well as highly unequal rates of morphological divergence in different lineages. This complex morphological evolution apparently misled earlier taxonomists. These results underscore the well-known but still often neglected problem of basing classifications on overall morphological similarity. Based on the molecular data, a revised taxonomy is proposed. Although the traditional and species tree methods inferred much the same tree in the present study, the assumption by species tree methods that all species are monophyletic is a limitation in these methods, as some currently recognized species might have more complex histories.</p

Old divergences in a boreal bird supports long-term survival through the Ice Ages

<p>Abstract</p> <p>Background</p> <p>Unlike northern Europe and most of northern North America, the Eastern Palearctic and the northwesternmost tip of North America are believed to have been almost unglaciated during the Quarternary glacial periods. This could have facilitated long-term survival of many organisms in that area. To evaluate this, we studied the phylogeography in east Asia and Alaska of a boreal migratory passerine bird, the Arctic Warbler <it>Phylloscopus borealis</it>, and compared our results with published data on especially North American species.</p> <p>Results</p> <p>In a sample of 113 individuals from 18 populations we identified 42 haplotypes of the mitochondrial cytochrome <it>b </it>gene, which separated into three clades: A - Alaska and mainland Eurasia (except Kamchatka); B - Kamchatka, Sakhalin and Hokkaido; and C - Honshu, Shikoku and Kyushu (i.e. Japan except Hokkaido). The oldest split among these clades, between A/B and C, is estimated to have taken place sometime between the mid Pliocene and early Pleistocene, and the second divergence, between clades A and B, in the early to mid Pleistocene. Within all of the three main clades, there are signs of population expansion.</p> <p>Conclusions</p> <p>The Arctic Warbler separated into three main clades in close succession around the Pliocene/Pleistocene border, with the two northern clades diverging last. All three clades probably experienced population bottlenecks during the Pleistocene as a result of range shifts and contractions, but nevertheless survived and maintained their integrities. Several other clades of Northeastern Palearctic birds are noted to have diversified during the Pliocene. In contrast, avian species or phylogroups presently occupying formerly glaciated North American ground are generally younger. The differences between these regions could be due to slower speciation rates in the Eastern Palearctic due to less fragmentation of forest habitats during glacial periods, or to longer survival of Eastern Palearctic clades as a result of less severe conditions in that region compared to northern North America. Several other Palearctic organisms show concordant biogeographical patterns to that of the Arctic Warbler, indicating common causes of their diversifications.</p

Present and past ecological niche models for the Great Tit (Parus major)

This presentation was given as part of the GIS Day@KU symposium on November 14, 2018. For more information about GIS Day@KU activities, please see http://gis.ku.edu/gisday/2018/PLATINUM SPONSORS: KU Department of Geography and Atmospheric Science KU Institute for Policy & Social Research GOLD SPONSORS: KU Libraries State of Kansas Data Access & Support Center (DASC) SILVER SPONSORS: Bartlett & West Kansas Applied Remote Sensing Program KU Center for Global and International Studies BRONZE SPONSORS: Boundles

Asymmetric introgression reveals the genetic architecture of a plumage trait

Genome-wide variation in introgression rates across hybrid zones offers a powerful opportunity for studying population differentiation. One poorly understood pattern of introgression is the geographic displacement of a trait implicated in lineage divergence from genome-wide population boundaries. While difficult to interpret, this pattern can facilitate the dissection of trait genetic architecture because traits become uncoupled from their ancestral genomic background. We studied an example of trait displacement generated by the introgression of head plumage coloration from personata to alba subspecies of the white wagtail. A previous study of their hybrid zone in Siberia revealed that the geographic transition in this sexual signal that mediates assortative mating was offset from other traits and genetic markers. Here we show that head plumage is associated with two small genetic regions. Despite having a simple genetic architecture, head plumage inheritance is consistent with partial dominance and epistasis, which could contribute to its asymmetric introgression. Hybrid zones are windows into the evolutionary process. Semenov et al. find that the head plumage differences between white wagtail subspecies have a simple genetic basis involving two small genetic regions, in which partially dominant and epistatic interactions help to explain how this sexual signal has become decoupled from other plumage traits

Past hybridization between two East Asian long-tailed tits (Aegithalos bonvaloti and A. fuliginosus)

Introduction: Incomplete lineage sorting and hybridization are two major nonexclusive causes of haplotype sharing between species. Distinguishing between these two processes is notoriously difficult as they can generate similar genetic signatures. Previous studies revealed that the mitochondrial DNA (mtDNA) differentiation between two East Asian long-tailed tits (Aegithalos bonvaloti and A. fuliginosus) was extremely low, even lower than intraspecific differentiation in some other long-tailed tits. Using a combination of multilocus and coalescent analyses, we explored the causes of the anomalous lack of mtDNA differentiation between the two species.Results: The mtDNA divergence between the two species was shallow, while the nuclear DNA (nuDNA) divergence was considerably deeper. The IMa analyses based on the mtDNA dataset suggested relatively high gene flow from A. fuliginosus to A. bonvaloti, while negligible gene flow in the opposite direction. In contrast to mtDNA, the migration rates at autosomal and Z-linked nuDNA loci were negligible or much lower. The NEWHYBRIDS analysis assigned all individuals except one to pure parental species with high posterior probability. The Bayesian skyline plot showed that both species underwent population expansions during the Last Glacial Maximum (LGM), and the ecological niche modelling suggested that their ranges overlapped more during the LGM than at present.Conclusions: We suggest that historical hybridization, in combination with selective sweep and/or genetic drift might be the main causes of the extremely low mtDNA differentiation between the two species. The hybridization probably occurred mainly between A. fuliginosus females and A. bonvaloti males. The LGM distribution expansion might have facilitated hybridization, while the post-LGM distribution contraction could have facilitated some mtDNA sorting. Ongoing hybridization between the two species might be very limited, but further studies with more samples from the contact zone are needed to test this conclusion

Comparative genomics reveals insights into avian genome evolution and adaptation

Birds are the most species-rich class of tetrapod vertebrates and have wide relevance across many research fields. We explored bird macroevolution using full genomes from 48 avian species representing all major extant clades. The avian genome is principally characterized by its constrained size, which predominantly arose because of lineage-specific erosion of repetitive elements, large segmental deletions, and gene loss. Avian genomes furthermore show a remarkably high degree of evolutionary stasis at the levels of nucleotide sequence, gene synteny, and chromosomal structure. Despite this pattern of conservation, we detected many non-neutral evolutionary changes in protein-coding genes and noncoding regions. These analyses reveal that pan-avian genomic diversity covaries with adaptations to different lifestyles and convergent evolution of traits