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Post by brobear on Jan 6, 2023 9:00:19 GMT -5
Brown Bear - Taxonomy and Evolution - Subspecies www.primidi.com/brown_bear/taxonomy_and_evolution/subspecies Subspecies There is little agreement on classification of brown bears. Some systems have proposed as many as 90 subspecies, while recent DNA analysis has identified as few as five clades. DNA analysis recently revealed that the identified subspecies of brown bears, both Eurasian and North American, are genetically quite homogeneous, and that their genetic phylogeography does not correspond to their traditional taxonomy. As of 2005, 16 subspecies have been recognized. The subspecies have been listed as follows: 1- Ursus arctos arctos – Eurasian brown bear 2- Ursus arctos alascensis - Alaskan brown bear 3- Ursus arctos beringianus – Kamchatka brown bear (or Far Eastern brown bear) 4- Ursus arctos californicus – California golden bear (extinct) 5- Ursus arctos collaris – East Siberian brown bear 6- Ursus arctos crowtheri – Atlas bear (extinct) 7- Ursus arctos dalli - Dall Island brown bear 8- Ursus arctos horribilis – Grizzly bear 9- Ursus arctos isabellinus – Himalayan brown bear 10- Ursus arctos lasiotus – Ussuri brown bear (or Amur brown bear, black grizzly or horse bear) 11- Ursus arctos middendorffi – Kodiak bear 12- Ursus arctos nelsoni – Mexican grizzly bear (extinct) 13- Ursus arctos pruinosus – Tibetan blue bear 14- Ursus arctos sitkensis - ABC Islands bear or Sitka brown bear 15- Ursus arctos stikeenensis - Stickeen brown bear 16- Ursus arctos syriacus – Syrian brown bear 17- Ursus arctos marsicanus – Marsican brown bear (not officially recognised)
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Post by brobear on Jan 6, 2023 10:13:41 GMT -5
Molecular Phylogeography of the Brown Bear (Ursus arctos) in Northeastern Asia Based on Analyses of Complete Mitochondrial DNA Sequences academic.oup.com/mbe/article/30/7/1644/974412?login=false To further elucidate the migration history of the brown bears (Ursus arctos) on Hokkaido Island, Japan, we analyzed the complete mitochondrial DNA (mtDNA) sequences of 35 brown bears from Hokkaido, the southern Kuril Islands (Etorofu and Kunashiri), Sakhalin Island, and the Eurasian Continent (continental Russia, Bulgaria, and Tibet), and those of four polar bears. Based on these sequences, we reconstructed the maternal phylogeny of the brown bear and estimated divergence times to investigate the timing of brown bear migrations, especially in northeastern Eurasia. Our gene tree showed the mtDNA haplotypes of all 73 brown and polar bears to be divided into eight divergent lineages. The brown bear on Hokkaido was divided into three lineages (central, eastern, and southern). The Sakhalin brown bear grouped with eastern European and western Alaskan brown bears. Etorofu and Kunashiri brown bears were closely related to eastern Hokkaido brown bears and could have diverged from the eastern Hokkaido lineage after formation of the channel between Hokkaido and the southern Kuril Islands. Tibetan brown bears diverged early in the eastern lineage. Southern Hokkaido brown bears were closely related to North American brown bears. _____________________________________________________________________ I am not one to pretend to understand that which is over my head. There is a lot of information here concerning bear DNA for those interested.
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Post by brobear on Jan 7, 2023 7:58:42 GMT -5
Evolutionary history and palaeoecology of brown bear in North-East Siberia re-examined using ancient DNA and stable isotopes from skeletal remains Abstract Over 60% of the modern distribution range of brown bears falls within Russia, yet palaeoecological data from the region remain scarce. Complete modern Russian brown bear mitogenomes are abundant in the published literature, yet examples of their ancient counterparts are absent. Similarly, there is only limited stable isotopic data of prehistoric brown bears from the region. We used ancient DNA and stable carbon (δ13C) and nitrogen (δ15N) isotopes retrieved from five Pleistocene Yakutian brown bears (one Middle Pleistocene and four Late Pleistocene), to elucidate the evolutionary history and palaeoecology of the species in the region. We were able to reconstruct the complete mitogenome of one of the Late Pleistocene specimens, but we were unable to assign it to any of the previously published brown bear mitogenome clades. A subsequent analysis of published mtDNA control region sequences, which included sequences of extinct clades from other geographic regions, assigned the ancient Yakutian bear to the extinct clade 3c; a clade previously identified from Late Quaternary specimens from Eastern Beringia and Northern Spain. Our analyses of stable isotopes showed relatively high δ15N values in the Pleistocene Yakutian brown bears, suggesting a more carnivorous diet than contemporary brown bears from Eastern Beringia. *Plenty of information for those who can absorb it. I lack the education and possibly the gray matter.
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Post by brobear on Jan 7, 2023 10:00:21 GMT -5
Scientific taxonomy There are many methods used by scientists to define bear species and subspecies, as no one method is always effective. Brown bear taxonomy and subspecies classification has been described as "formidable and confusing," with few authorities listing the same specific set of subspecies. Genetic testing is now perhaps the most important way to scientifically define brown bear relationships and names. Generally, genetic testing uses the word clade rather than species because a genetic test alone cannot define a biological species. Most genetic studies report on how closely related the bears are (or their genetic distance). There are hundreds of obsolete brown bear subspecies, each with its own name, and this can become confusing; Hall (1981) lists 86 different types, and even as many as 90 have been proposed. However, recent DNA analysis has identified as few as five main clades which contain all extant brown bears, while a 2017 phylogenetic study revealed nine clades, including one representing polar bears. As of 2005, 15 extant or recently extinct subspecies were recognized by the general scientific community.
As well as the exact number of overall brown bear subspecies, its precise relationship to the polar bear also remains in debate. The polar bear is a recent offshoot of the brown bear. The point at which the polar bear diverged from the brown bear is unclear, with estimations based on genetics and fossils ranging from 400,000 to 70,000 years ago, but most recent analysis has indicated that the polar bear split somewhere between 275,000 and 150,000 years ago. Under some definitions, the brown bear can be construed as the paraspecies for the polar bear.
DNA analysis shows that, apart from recent human-caused population fragmentation, brown bears in North America are generally part of a single interconnected population system, with the exception of the population (or subspecies) in the Kodiak Archipelago, which has probably been isolated since the end of the last Ice Age. These data demonstrate that U. a. gyas, U. a. horribilis, U. a. sitkensis and U. a. stikeenensis are not distinct or cohesive groups, and would more accurately be described as ecotypes. For example, brown bears in any particular region of the Alaska coast are more closely related to adjacent grizzly bears than to distant populations of brown bears, the morphological distinction seemingly driven by brown bears having access to a rich salmon food source, while grizzly bears live at higher elevation, or further from the coast, where plant material is the base of the diet. The history of the bears of the Alexander Archipelago is unusual in that these island populations carry polar bear DNA, presumably originating from a population of polar bears that was left behind at the end of the Pleistocene, but have since been connected with adjacent mainland populations through movement of males, to the point where their nuclear genomes are now more than 90% of brown bear ancestry.
Brown bears are apparently divided into five different clades, some of which coexist or co-occur in different regions.
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Post by brobear on Jan 7, 2023 10:09:45 GMT -5
Brown bear - www.researchgate.net/publication/284678859_Brown_bear Subspecies. By necessity, early classification relied heavily on paleontological and morphological data, but such classifications of ursids were inconclusive at best (Kurtén 1968; Kitchener 1994; Waits et al. 1999). Merriam (1918) proposed over 90 subspecies that described the geographic variants of U. arctos, but this classification is considered obsolete (Waits et al. 1998a). As summarized by Craighead and Mitchell (1982) and Waits et al. (1998a), Rausch (1963) identified two extant subspecies of brown bears in North America primarily from skull measurements. He classified bears from the mainland as U. arctos horribilis Ord and those from the Kodiak Island archipelago as U. a. middendorffi Merriam. Rausch (1963) reconsidered his earlier classification (Rausch 1953) of the bears from the Alaska Peninsula as being a distinct subspecies (U. a. gyas Merriam). Kurtén (1973) used skull measurements from Rausch (1963) to propose three North American subspecies, U. a. middendorffi from Kodiak Island archipelago, U. a. dalli Merriam of southern coastal regions of the Alaska panhandle, including the islands of Admiralty, Baranof, and Chichagof (ABC), and U. a. horribilis for all other brown bears. Finally, Hall (1984) used cranial and dentition dimensions to propose seven North American subspecies. Five were restricted to Alaska: (1) U. a. middendorffi (Kodiak islands), (2) U. a. gyas (Kenai Peninsula), (3) U. a. dalli (northwest panhandle), (4) U. a. sitkensis Merriam (southeast Alaska including ABC islands), and (5) U. a. alascensis Merriam (the remaining mainland). The subspecies U. a. stikeenensis Merriam was restricted to coastal British Columbia, Washington, and Oregon, and U. a. horribilis included all inland brown bear populations in Canada and the lower 48 states. The generally accepted current classification is that proposed by Rausch (1963), but this is likely to change based on DNA analysis. With the advent of DNA analysis and the technological advancements in this field, we now know considerably more about evolution of ursids and subspecific classification within species (Waits et al. 1999). Using mitochondrial DNA (mtDNA) of brown bears across their geographic range, several researchers have defined five mtDNA lineage groups defined as clades (Cronin et al. 1991; Taberlet and Bouvet 1994; Kohn et al. 1995; Randi et al. 1995; Taberlet et al. 1995; Talbot and Shields 1996; Waits et al. 1998a). Clade I brown bears are from southern Scandinavia and southern Europe; Clade II are from the ABC Islands; Clade III are from eastern Europe, Asia, and western Alaska; Clade IV are from southern Canada and the lower 48 states; Clade V are from eastern Alaska and northern Canada (Fig. 26.1). The mtDNA phylogeny does not support any of the historic taxonomic classifications (Waits et al. 1998a). There is no support for U. a. middendorffi, U. a. horribilis, or U. a. gyas. The classification by Kurtén (1968) and Hall (1984) of bears from the ABC islands and adjacent mainland probably is incorrect. Brown bears from the ABC islands constitute the oldest and most genetically unique mtDNA clade in the New World and are a sister taxa to the polar bear (Talbot and Shields 1996; Shields et al. 2000). However, as stated by Waits et al. (1998a:415), “a revision of the taxonomy of North American brown bears in accordance with the phylogenetic species concept (Cracraft 1983) would result in drastic changes in the current classification. The most frequently recognized subspecies, U. a. middendorffi, would be abolished, and 4 new subspecies distributions would be added. But it seems unreasonable to dramatically alter the current taxonomy based on the results from a single mtDNA region.” Additional research using additional genes, particularly from the Y chromosome, is needed for taxonomic clarification (Waits et al. 1998a).
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Post by brobear on Jan 8, 2023 4:52:51 GMT -5
Ursus arctos domainofthebears.proboards.com/thread/1382/bear-family-tree?page=2 However, recent DNA analysis has identified as few as five main clades which contain all extant brown bears, while a 2017 phylogenetic study revealed nine clades, including one representing polar bears. As of 2005, 15 extant or recently extinct subspecies were recognized by the general scientific community.
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Post by brobear on Jan 8, 2023 6:55:34 GMT -5
Speciation in Bears sandwalk.blogspot.com/2012/07/speciation-in-bears.html I read an interesting article a few months ago. It was a study of the phylogeny of bears with an emphasis of the origin of polar bears. In theory, it should be possible to put a date on the speciation event and to identify the probably ancestor of the modern polar bear. The first thing you have to know is that polar bears and brown bears are not distinct species as defined by the biological species concept. This definition of "species" requires that there be no interbreeding with other populations, otherwise it's not a true species. (See Jerry Coyne's analysis of the problem with respect to humans.) Polar bears and brown bears can mate to form hybrids, although this doesn't happen very often in the wild because the two "species" are geographically separated. The interesting question is when did these two populations diverge. Many people thought the question had been answered a few years ago when Lindqvist et al. (2010) published the sequence of polar bear mitochondrial DNA ad compared it to that of other bears. The result is shown here on the left in a figure taken from the recent paper in Science (Hailer et al, 2012). The Lindvist et al. paper showed conclusively that polar bears are relatively young as a "species" (about 150,000 years) and that they clearly arose from within the brown bear clade. This result was somewhat surprising but not revolutionary. However, there were some experts on speciation who, questioned the conclusion; notably, Jerry Coyne [Do “polar bears” exist?]. They cautioned that using mitochondrial DNA could be misleading. The latest study in Science shows that their concerns were justified. Hailer et al. (2012) lookd at 14 nuclear genes and constructed the tree shown shown below on the right. This study indicates that polar bears diverged from brown bears about 800,000 years ago. Furthermore, the two populations of bear (brown and polar) form distinct clades. What does this mean? It probably means that about 150,000 years ago there was a brief fling between a male polar bear and a female brown bear. The female offspring, carrying brown bear mitochondria, mated with male polar bears and all of their progeny contained brown bear mitochondria with mixtures of brown and polar bear alleles in their nuclei. Over time, the brown bear mitochondria became fixed by random genetic drift in the polar bear population. This explains why the two trees differ and why you have to be cautious about using mitochondrial DNA in constructing phylogenies. The story doesn't end there. Just this week, a new paper appeared in PNAS confirming this result (Miller et al., 2012). Many of the authors are the same ones on the Lindqvist et al. (2012) paper. They are refuting the conclusions of their earlier paper by now showing that the sequence of nuclear genes indicate an earlier divergence of brown bears and polar bears. I put off blogging about the Science paper because there were more important things to do and because it would have been difficult to explain the problem and the explanation. Fortunately, Jerry Coyne has now taken up the task of explaining the result at: A new study of polar bears underlines the dangers of reconstructing evolution using mitochondrial DNA. Please read his explanation of gene flow in bears based on his extensive knowledge of speciation. The only issue I have with Coyne's explanation is that I don't think he gives enough emphasis to the idea that fixation of brown bear mitochondria in polar bears could be a genetic accident. UPDATE: Ed Yong of Not Exactly Rocket Science already wrote about this three months ago [Polar bear origins revised – they’re older and more distinct than we thought]. John Hawks emphasizes Jerry Coyne's warning about using mitochondrial DNA and discuss the implications for hominid evolution [Polar bear mtDNA replacement].
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Post by brobear on Jan 8, 2023 6:56:19 GMT -5
Brown bear clades:
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Post by brobear on Jan 8, 2023 8:11:57 GMT -5
(a) Map showing the sample location of the brown bears analysed using mtDNA, including information on what clades they belong to; ancient samples (dots), modern samples (triangles). The five Yakutian specimens investigated using ancient DNA and stable isotopes (grey dots) are indicated by a dashed circle. Our mitogenome study included 129 sequences (published n = 128, this study n = 1). (b) Schematic phylogeny of brown bear mitogenome clades, adapted from 13. Extinct clades 2c and 3c are not shown on the map. www.researchgate.net/figure/a-Map-showing-the-sample-location-of-the-brown-bears-analysed-using-mtDNA-including_fig1_331756023
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Post by brobear on Jan 8, 2023 8:19:15 GMT -5
*Note: I've been searching for information showing the various brown bear clades and which subspecies belongs to which clade. What brown bears are closely related and which are vastly separated. Thus far, I've come up empty.
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