A jumble of larks – cryptic taxa and paraphyletic species galore

| The original paper may be accessed for free through August 11 2016, using the following link: Stervander et al. 2016 MPE |

A couple of years ago, Alström et al. (2013) revealed that larks (Alaudidae) comprised unusually many examples of both cryptic taxa (whose evolutionary and taxonomic distinctness have gone overlooked, owing to phenotypic similarity to other taxa) and convergent evolution among unrelated species. One striking example of the latter was the species pair White-winged Lark Alauda leucoptera and Mongolian Lark Melanocorypha mongolica (Figure 1, upper panel), which display very similar plumage, and have been assumed to be closely related. Instead, they turned out to be of two different genera, separated since 11 million years ago. Likewise, the two clades which have traditionally formed the genus Calandrella, have been separated for 12 million years, and are not at all each other’s closest relatives, despite superficial similarities (Figure 1 middle panel). Urban Olsson, Per Alström, and others are currently looking closely into the clade which, following their recommendation, is now known as the genus Alaudala. Together with Per and Urban, Ulf Ottosson, Bengt Hansson, and Staffan Bensch, I dived into trying to sort out the phylogenetic relationships of the remaining Calandrella clade.

Figure 1 (from Stervander 2015). Larks (family Alaudidae) display strong adaptations in bill morphology and plumage, and recent studies have revealed both convergent evolution and cryptic taxa. Alström et al. (2013) demonstrated an extreme case of convergent evolution in the White-winged Lark Alauda leucoptera (top left) and the Mongolian Lark Melanocorypha mongolica (top right), previously thought to be congeneric. We confirmed that Calandrella [brachydactyla] dukhunensis (middle left) is a separate species from the Greater Short-toed Lark C. brachydactyla (middle right), more closely related to Hume’s Short-toed Lark C. acutirostris, though it morphologically resembles the Greater Short-toed lark. We also show that C. blanfordi daaroodensis and C. b. eremica form a clade that split over four million years ago from C. b. blanfordi and C. erlangeri, which are recently split sister taxa (bottom). Photos, with permission for use in Stervander (2015): Kari Eischer (top left), David Thorns (top right), Matt Poll (middle left), Juan Lacruz (middle right), Martin Stervander with permission from the British Museum of Natural History (bottom).

Figure 1 (from Stervander 2015). Larks (family Alaudidae) display strong adaptations in bill morphology and plumage, and recent studies have revealed both convergent evolution and cryptic taxa. Alström et al. (2013) demonstrated an extreme case of convergent evolution in the White-winged Lark Alauda leucoptera (top left) and the Mongolian Lark Melanocorypha mongolica (top right), previously thought to be congeneric. We confirmed that Calandrella [brachydactyla] dukhunensis (middle left) is a separate species from the Greater Short-toed Lark C. brachydactyla (middle right), more closely related to Hume’s Short-toed Lark C. acutirostris, though it morphologically resembles the Greater Short-toed lark. We also show that C. blanfordi daaroodensis and C. b. eremica form a clade that split over four million years ago from C. b. blanfordi and C. erlangeri, which are recently split sister taxa (bottom). Photos, with permission for use in Stervander (2015): Kari Eischer (top left), David Thorns (top right), Matt Poll (middle left), Juan Lacruz (middle right), Martin Stervander with permission from the British Museum of Natural History (bottom).

My curiosity dates back to the early 2000’s, when a small and isolated population of Red-capped Larks C. cinerea was rediscovered close to the Nigerian research institute APLORI, where I have been teaching. The Jos plateau, in central Nigeria, is a curious distribution outlier for this species, which is common in Southern Africa, but has its otherwise most northerly distribution in Congo – over 1,000 km away. Continue reading

Pipefish in the pipeline

I am currently intensifying the planning and development of my intended postdoc project, with visits to two research groups in the coming few weeks. I am very happy to spend my birthday in Dominic Wright’s group at Linköping University, on May 12, and then and join the Cresko Lab with Bill Cresko, Susie Bassham, Clay Small, and Allison Fuiten at the University of Oregon in early June. We will all chat about cool future studies, making use of an organism with extreme adaptations – the pipefish – and one of the foremost biological model systems – the zebrafish.

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Illustration ©: Joseph R. Tomelleri

Defended and done!

Stervander_thesis_cover_LUOn 18 December 2015, I finally defended my PhD thesis, entitled On Speciation in Birds – Genomic Signatures across Space and Time. (Cover artwork, the São Tomé grosbeak Neospiza concolor, by Peter Nilsson)

I was lucky enough to have Professor Trevor Price, University of Chicago, as faculty opponent, and I thoroughly enjoyed our discussions. Having written the landmark book Speciation in Birds, there is probably no single person who would be more fit as opponent. Below is a glimpse of the two of us fighting about exactly what tree topology that represent different colonization and speciation scenarios.

I currently finish some remaining work on finch radiations, while preparing postdoc grant applications. (Or perhaps you have a great project and good funding? Let me know…)

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Again and again and again – evolutionary charter trips to the Canary Islands

In a recently accepted paper in Molecular Ecology, we conclude that blue tits have colonised the Canary Islands from Africa no less than three times, but contrary to recent suggestions they did not back colonise mainland Africa from the islands. We combined traditional DNA sequencing on a large scale with massively parallel sequencing (“next generation sequencing”) and combine their respective strengths.

A demographic reconstruction reveals that the populations on the eastern Canary Islands Fuerteventura and Lanzarote have undergone recent population bottlenecks, while the long-term population sizes in northwest Africa have been stable, clearly supporting that the mainland populations have acted as a source for the colonisation of Fuerteventura and Lanzarote, and not the other way around.

Coalescense species trees of the Cyanistes tit complex. Values along branches represent posterior probabilities (PP), and * signifies PP = 1.0. For further information, see our paper.

Coalescense species trees of the Cyanistes tit complex. Values along branches represent posterior probabilities (PP), and * signifies PP = 1.0. For further information, see our paper. Illustrations (c) Martí Franch.

The phylogenetic relationships between the blue tit populations of the Canary Islands are truly intricate. Continue reading

Hello!

Looking happier than the bluebottle.

Welcome to my site! I am a keen ornithologist and evolutionary biologist, who just finished my PhD project at Lund University, Sweden, on speciation in birds. Does it seem like a rather broad theme? It is, and to cover it I am working with several study systems, of which many are made up by small radiations on isolated islands. I love doing field work, but for these projects I have spent the main part of my time in the lab, where I am applying both traditional genetic tecniques and state of the art “next generation” DNA sequencing. When asked to describe my project to non-biologists I say “think Darwin 2.0”, which should give a good hint! Read more about this in the Research section.