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Eurasian crows (1 Viewer)

aegithalos

Well-known member
Readers of this forum might be interested in this recently published article:

Phylogeographic patterns in widespread corvid birds
Molecular Phylogenetics and Evolution, vol 45, Pages 840-862
E. Haring, A. Gamauf and A. Kryukov (Dec 2007)

which treats principally Corvus corone (in the wide sense) among other species.

Abstract begins:

"Intraspecific genetic diversity and phylogeography of Corvus corone was investigated using the mitochondrial (mt) control region as a molecular marker. A split into two distinct mt lineages was observed. One represents individuals from a wide geographic range spanning from England to the Russian Far East (Kamchatka), while the other one was found in the Primorye and Khabarovsk regions (southern parts of Russian Far East) as well as Japan. ..."

and in the discussion:

"With respect to taxonomy the present data provide a
rather clear picture: The present data do not support
the recent proposal to treat the European carrion crow
and hooded crow as distinct species (C. corone, C. cornix;
Parkin et al., 2003). One might ask whether the
two mt clades represent two distinct species. In this case
the western species would comprise black as well as
black–grey forms, while the eastern one would only represent
the most eastern black populations. However, such
a split is not justified without corroboration by morphological,
behavioural and other data (e.g., vocalization)
and detailed analysis of the contact zone between the
two haplogroups."

So, back to square 1?

Cheers,

Keith
 

njlarsen

Gallery Moderator
Opus Editor
Supporter
Barbados
Maybe! I am not really sure which type of data were used to argue in favor of the split of C corone vs C corvix ?

Cheers
Niels
 

aegithalos

Well-known member
Maybe! I am not really sure which type of data were used to argue in favor of the split of C corone vs C corvix ?

Cheers
Niels

The reference cited is:

Parkin, D.T., Collison, M., Helbig, A., Knox, A.G., Sangster, G., 2003.
The taxonomic status of Carrion and Hooded Crows. British Birds 96,
274–290.

which I have not seen. However, it is referred to by:

A. J. Helbig, A. G. Knox, D. T. Parkin, G. Sangster, and M. Collinson. Guidelines for assigning species rank. Ibis, 144:518–525, 2002.

who list the existence of a stable hybrid zone as evidence for restricted gene flow and thus evidence for separate species (or 'semi-species'). They then cite the hooded and carrion crows as an example of this situation with a reference to Parkin et al in prep.

Cheers,

Keith
 

l_raty

laurent raty
The reference cited is:

Parkin, D.T., Collison, M., Helbig, A., Knox, A.G., Sangster, G., 2003.
The taxonomic status of Carrion and Hooded Crows. British Birds 96,
274-290.

which I have not seen.

Here is the abstract :

"The taxonomic status of Carrion Corvus corone and Hooded Crows C. cornix is reviewed. As well as the obvious differences in plumage between the two, there is good evidence for non-random mating and reduced fitness of hybrids between Carrion and Hooded Crows, which together provide sufficient evidence for them to be regarded as separate species under most species concepts. Differences in vocalisations and ecology support this distinction. It is therefore recommended that Carrion Crow and Hooded Crow be treated as separate species."

This is a good synthesis of the evidence that was available back then, with some meta-analysis of the results of different studies; certainly worth a reading if you're interested in this case.

If you are looking for weaker aspects in this split (other than the genetic data, that is...), they may include:

1) Assortative mating has been reported from many contact zones and is undisputable. However, assortative mating in itself is not necessarily very significant taxonomically, because it can also simply be a result of imprinting on the parents' phenotype (e.g., white and blue snow geese that have had two white or two blue parents also tend to pair "assortatively"; blue geese with a white and a blue parent do not). In the case of the crows, hybrid phenotypes might be at a disadvantage in an imprinting process, from the start, for an extremely trivial reason: see http://www.teorekol.lu.se/staff/fhaas/sdarticle.pdf
Hooded/pied phenotypes have been evolved a number of times independently in Corvus (asides from the hooded/carrion case, we find Corvus dauuricus in the jackdaw complex, C. albus in the raven complex, C. typicus in the Indonesian/Philippine crow complex...): switching from black to hooded doesn't seem too difficult in this genus. Yet, setting asides restricted hybrid zones, adults of any given population are never polymorphic, and never show a shaggy pattern with extensive intermixion of the black and pale colours, like many hybrids do. This suggests the existence of mechanisms preventing this to happen, at a more global level than the simple corone-cornix case.

2) The reduced success of reproducing hybrids seems real too. But:
- It is statistical only. I.e., these birds do reproduce successfully; they are just less successful at doing it on average than the pure parental phenotypes. Furthermore, despite a lower mean value, the success of hybrids is more variable than that of pure phenotypes, which implies that some hybrids probably do not conform to the rule, and perform pretty well after all.
- The data supporting this reduced success come exclusively from the Italian hybrid zone. This is a bit disturbing - not that much because large areas where contact also occurs have never been studied, but because this particular hybrid zone is actually pretty peculiar: it is the only one in Europe that is known to coincide with a strongly marked ecotone (a transition between two ecologically highly distinct zones), and the only one that has been geographically stable historically (elsewhere, the width of the hybrid zones remains rather constant, but their geographical location has been known to change).
The mechanisms that limit the width of phenotypic hybrid zones in the crow complex obviously do not require the presence of an ecotone, as they appear to be efficient even where no ecotone exists. On the other hand, on both sides of a strongly marked ecotone, by itself, we could expect local adaptive divergence, and this could, conceivably at least, result in a reduced reproductive success of "hybrid" birds breeding along the ecotone (irrespective of any phenotypic consideration). If there is a deficiency of migration across it, an ecotone could also probably quite easily "trap" (stabilise geographically) a non-adaptive, fluctuating phenotypic transition zone - once both will be coincident, it will be much more difficult for the phenotypic transition zone to start moving again.
It is a bit problematic to draw conclusions about gene flow restriction mechanisms across hybrid zones in general, using exclusively data from an area where an additional process restricting gene flow could be at play, while knowing very well that this additional effect is absent elsewhere.

3) Differences in vocalisations, again, have been described only from Italy; there is no evidence that these differences are consistent across the entire range of the taxa. There is also no evidence that the birds use their calls to discrimate among them.

4) The differences in ecology refer to differential use of various habitats for feeding by the two forms. This has, again, been studied in Italy only, and the two published studies, performed in different parts of the Italian hybrid zone, were actually not entirely concordant in their results. Behaviourally, corvids are highly adaptive birds, and these differences might as well reflect different traditions in different (sub)-populations.

Best,
Laurent -
 
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Hotspur

James Spencer
United Kingdom
Try asking martin collinson, one of the authors who posts on here as docmartin. He should be able to help with the criteria used for the split.
 

Richard Klim

-------------------------
Brodin et al

Brodin, Haas & Hansson (in press). Gene-flow across the European crow hybrid zone – a spatial simulation. J Avian Biol. [abstract]

Parkin, Collinson, Helbig, Knox & Sangster 2003. The taxonomic status of Carrion and Hooded Crows. British Birds 96(6): 274–290. [pdf]

Madge 2009 (HBW 14):
Corvus (corone) cornix is recognised as a distinct species by HBW, IOC, Clements/eBird, BOURC, CSNA, OSME and ABC;
but not by BirdLife, H&M3, AERC TAC or OBC.

PS. Haring et al 2007 pdf.
 
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Peter Kovalik

Well-known member
Slovakia
J W Poelstra, H Ellegren & J B W Wolf. An extensive candidate gene approach to speciation: diversity, divergence and linkage disequilibrium in candidate pigmentation genes across the European crow hybrid zone. Heredity 111, 467-473 doi:10.1038/hdy.2013.68

[PDF]
 

Peter Kovalik

Well-known member
Slovakia
Bossu CM, Baglione V, Grabherr M, Kruszewicz A, Lantz H, Müller I, Poelstra J, Vijay N, Wikelski M, Wolf J. Islands of genomic divergence across the hooded and carrion crow hybrid zone: linking genes and ‘magic traits’. XIV Congress of the European Society for Evolutionary Biology. Lisbon, 2013.

***

Vijay, N, Poelstra J, Bossu C, Baglione V, Grabherr M, Kruszewicz A, Lantz H, Müller I, Wikelski M, Wolf J. Speciation genomics in the European crow: a magic hybrid zone where sexual selection and few major effect loci may promote speciation. XIV Congress of the European Society for Evolutionary Biology. Lisbon, 2013.

[Abstracts]
 

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