
The finch is on both islands. I guess the nuthatch distribution could be habitat related.Corsica would have been linked to Sardinia, so why the nuthatch and finch now on one island only.
The finch is on both islands. I guess the nuthatch distribution could be habitat related.Corsica would have been linked to Sardinia, so why the nuthatch and finch now on one island only.
I also find the redpolls very confusing. I know that things are very messy in Greenland, but in other places ID of the different types takes work, but is possible.If Redpolls are all one despite Arctic being 15% bigger than Lesser and morphologically different, I'm not sure of the boundaries any more.
Sorry my mistake. In China at the moment, so working ‘from memory’.The finch is on both islands.
Have a reference on that? Would like to read more about it.Yeah...different processes = different dates. I just assume from a biotic isolation standpoint otherwise sedentary species would have been able to move over the Doggerland until pretty recently.
A cursory online look says that Britain was completely covered by glaciers as recently as 22,000 years ago. Any sort of endemic subspecies would have to be younger than that. Although there are pretty distinct forms in North America that are not much older. IIRC Juncos only started diverging in the Late Pleistocene, as did Yellow-rumped Warblers.
The whole effects of geography on shaping speciation and diversity in Eurasia vs the Americas is honestly fascinating. The whole east-west axis of mountains in Eurasia + the Mediterranean meant that the temperate and warmer weather faunas just got pulverized with each glacial. Doggerlands rapid flooding means that a lot of critters never made it to across to Great Britain. In the Americas the axis of mountains is largely north-south, so critters had few barriers stopping them from moving south. Hence why you get patterns like there being more native turtle species in Wisconsin than there is in all of Europe.
To be fair (caveat mammals are not birds) in humans there is a difference of about 15% in average height between the places with largest and smallest individuals (and even greater in weight). Humans are a bit of a weird subject there, but from a BSC point of view, we're a single taxa.15% is quite drastic, but i accept its variable. Hornemann's and Lesser just seem like different species to me.
But that's an interesting point, so thank you.
Look to humans! We are one species. The difference in weight and appearance does not change that.I'm just totally confused by it all to be honest.
If Redpolls are all one despite Arctic being 15% bigger than Lesser and morphologically different, I'm not sure of the boundaries any more.
Divers/loons, Wagtails, Crossbills, geese etc.
The land rise after the last (of many) glaciations is interesting: we live by the seashore here in Norway, only that was a few thousand years ago, now we are 186 meters above. We have a cabin on a small island on a lake in mid-Norway (great for birding!) and in the silt/beaches (132 m above mean sea level) you find marine seashell shells.Sorry my mistake. In China at the moment, so working ‘from memory’.
But my point was really that lots of places weren’t physically isolated in the last ice age, due to lower sea levels.
That said, lowlands will have been flooded by rising sea levels, so species and subspecies could still have evolved in mountain ranges still isolated from other ranges, but for a time part of the same island - say the highlands of PNG, which presumably were once a mountain range in northern Australia. So perhaps the Nuthatch could have evolved in Corsica and been prevented from reaching now Sardinia by unsuitable lowlands. I suppose finches are less sedentary than Nuthatches and the finch could perhaps have crossed any lowland divide.
The answer to your question is 'yes' - there are many subspecies that probably should not be recognised. Also, there are many populations in Asia and S America that lack a name or should have one, and many cases where subspecies ranges should be studied properly and restated.Reading up on subspecies, I sometimes come upon statements that read something like: "Not readily diagnosable" sometimes not even with measurements. For example I tried to learn about Taiga Bean Goose subpopulations, but apparently it's impossible to distinguish Anser fabalis fabalis from A. f. johanseni.
...
Therefore, I would like to ask the birdforum crowd:
What's the use of subspecies that are not diagnosable (except perhaps by range) or only by minute characteristics? Do we need fewer subspecies?
I don't think that's correct. The maximum extent of ice during the last ice-age didn't extend to south and south east England.A cursory online look says that Britain was completely covered by glaciers as recently as 22,000 years ago. Any sort of endemic subspecies would have to be younger than that
I asked Gemini:I don't think that's correct. The maximum extent of ice during the last ice-age didn't extend to south and south east England.
I asked Gemini:
About 22,000 years ago, during the Last Glacial Maximum (LGM), ice sheets reached their greatest extent.
* Northern Hemisphere: Ice sheets covered much of North America, Europe, and Asia. In North America, the ice sheet extended as far south as the northern United States. In Europe, it covered all of Scandinavia and the British Isles, extending into northern France and Germany. In Asia, ice sheets covered much of Siberia.
* Southern Hemisphere: Ice sheets were smaller in the Southern Hemisphere, but still covered parts of Antarctica, South America, and New Zealand.
The LGM had a significant impact on the Earth's climate and environment. Sea levels were much lower than they are today, and the Earth was much colder. The LGM also caused significant changes in plant and animal distributions.
The LGM began to end about 20,000 years ago, and the ice sheets began to retreat. This marked the beginning of the Holocene epoch, which is the current geological epoch.
A cursory online look says that Britain was completely covered by glaciers as recently as 22,000 years ago. Any sort of endemic subspecies would have to be younger than that. Although there are pretty distinct forms in North America that are not much older. IIRC Juncos only started diverging in the Late Pleistocene, as did Yellow-rumped Warblers.
Gemini is Google. And remember: the channel didn't exist then.Sometimes it is better to just google, instead of asking AI....
Within 5 seconds one can find this map of the extent of the ice in the last glaciation in Europe:
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So yes, parts of England and Ireland were icefree and there was certainly no ice in Northern France (not sure where gemini made that up)
While England wasn't completely covered in ice, the habitats would be significantly different and I would assume that many species currently represented by "subspecies" must indeed have arrived later, given that there wouldn't be much of suitable habitat (unless you were a steppe/tundra bird).
Gemini is Google. And remember: the channel didn't exist then.
Quote from Bethan Davis' blog: In Britain, the Last Glacial Maximum was reached around 27-21 ka[3], but different parts reached their maximums at different times. Like many ice sheets at their maximum, it was constrained at its northern limits by the steep drop in the sea floor at the continental shelf edge. Likewise in Patagonia, the ice sheet reached the continental shelf edge and could go no further on its Pacific, western margin[6]. In the Antarctic Peninsula, the Antarctic Ice Sheet reached the continental shelf edge at around 25,000 years ago[9].
A recent publication, Quaternary Glaciations – Extent and chronology, a closer look, edited by Ehlers, Gibbard and Hughes[10], provides detailed information on each of these ice sheets at their maxima. It even provides GIS shapefiles that you can download to examine the LGM of each ice sheet yourself:
More importantly, the Channel is "only" 8-10 000 years old.Even in the Riss ice age, southern England was ice free:
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Saale glaciation - Wikipedia
en.wikipedia.org
I totally agree with you wrt species: subspecies is an old, well-tested descriptive in zoology. It denotes a genetically distinct population of a species which is still interbreedable within the species. And always remember: even within species there will be incompatible breeders.Considering subspecies in general, I would leave them as a current mess, because 1) even a very small genetic difference can result in a population which is ecologically different and irreplaceable and / or visually very different, 2) a subspecies is really the only rank lower than species.
About the history of Britain - the part not covered by ice was tundra, continuous across Eurasia. There was no forest birds, and tundra birds were not isolated from other populations in Eurasia.