Posts tagged with "biogeography"
A multitude of ancient insects, but also spiders, mites, and plant parts found in a vast new amber deposit in India - some 150 kg of amber produced by an ancient rainforest in the Early Eocene, or 52-50 million years ago - are however less unique than would have been expected after 100 million years of island isolation.
Most of the included insects show links to modern insects as well as those that lived millions of years ago in different parts of the world, including Asia, Australia, and even South America (and thus not particularly Africa or Madagascar!). This could be explained by “land-bridge” connections (Where?). It is also possible for plants to drift hundreds of km on open ocean currents, and in the case of insects, some can fly, or get blown away, but …
The resin that later became amber originated from an ancient tropical rainforest, and likely produced by a sort of flowering hardwood trees that predominate in the forests of southeast Asia today. Many experts used to suggest that this type of tropical broadleaf rainforest first originated in the Miocene some 20 or 25 million years ago. That is yet another idea challenged by the recent amber discovery.
Besides the rainforest's age and India's biogeography it is astonishing to see the huge number of perfectly preserved specimens of insects, most of which have never been seen before. Unlike other types of amber found in deposits in the north (like the Baltic Amber), the Indian amber is quite distinct from that of resins produced by conifers, and much softer. This unique property made it possible completely to dissolve the amber and extract the ancient insects, plants and fungi.
The best known amber deposits are in the Dominican Republic, Mexico and the Baltic region, where some 80% of the world's known amber is found. There are tonnes of amber in the new Indian discovery with fossils from the terrestrial tropics, where the fossil record is otherwise not so good, because usually all the organic material gets rotten very quickly. With tonnes of amber now at the disposal a lot of secrets may be uncovered about world those many millions of years ago.
PS of 27 October 2010:
See also the excellent post at Rapid Uplift on Fossils In Amber From Eocene Cambay Basin India
The collision of the Indian continent with Eurasia affected the regional wildlife. Looking into the genetic evolution of a special frog species has now highlighted critical aspects of the timing of geological events responsible for the currents geography of Southeast Asia.
The findings are published in PNAS of 3 August 2010 as a freely available open access paper:
Che et al.
Spiny frogs (Paini) illuminate the history of the Himalayan region and Southeast Asia
I am grateful for the open access option. Thank you, PNAS.
Following the initial collision between India and Asia in the early Cenozoic (ca. 50–55 million years ago) or even earlier, about 70 million years ago, many effects associated with the major tectonic episode continued through the Oligocene (34 - 23 million years) and well into the Miocene (about 23 - 5 million years ago). During these times, associated geological processes occurred, ranging from the uplift (thickening) of the Himalaya–Tibetan plateau to lateral extrusion of the continental land-mass. However, details of the evolution in space and time related to the creation of the Himalayas and the Tibetan Plateau are still debated.
Most species of the tribe Paini (often called stone frogs in China) prefer to sit on moss-covered rocks near cold mountain streams. This long-conserved life history trait, coupled with their present distribution in Asia, makes this species group a potential model for examining geological evolution and environmental changes in Asia during the Tertiary. Their diversification can be related to massive mountains and deeply carved valleys acting as barriers, adaptations from streams to still water environments, adaptation to low oxygen levels on the Tibetan Plateau, and other drastic environmental changes.
The sequence of evolution supports a minority view of how the India/Asia collision played out. Rather than merely pushing the Himalayas upward, as some geologists believe, the Indian plate also pushed Southeast Asia and China aside and toward the Pacific Ocean, a process referred to as extrusion or escape tectonics.
The process sometimes known as escape tectonics, first elucidated by Paul Tapponnier, occurs during a collisional event where one of the plates deforms internally along a system of strike-slip faults. Between 1975 and 1981, Paul Tapponnier proposed, along with Peter Molnar, that most of today's deformation observed in Eastern Asia, where the greatest continental fault system occurs (20 earthquakes with a magnitude >8 since 1892), is the result of the penetration of India, at a speed of more than 5 cm per year, inside the Asian continent. India, modeled as a rigid block, has made its way over more than 2500 km, northward, inside Asia, causing the extrusion of the Indochinese peninsula and Southeast Asia. This extrusion also leads to the formation of two rifts, the most famous being that of Lake Baikal. This became the first coherent and global explanation for a great variety of deformations and structures observed in the Himalayan and Tibetan regions.
Recently, our understanding of the world has been deepened through studies of genetic variation among species, in addition to their physical and geographic discrepancies. This has given rise to a new discipline known as phylogeography. The term phylogeography was first coined in 1987, and thus did not turn up in my book from 1988, which was in fact a reprint of a 1985 edition.
Of course I went on with a bit of googling, and ran into an Open Access paper (Plos One) that would give the most feeble among us a linguistic headache. Let me quote from the abstract:
“It is generally accepted that the most ancient European mitochondrial haplogroup, U5, has evolved essentially in Europe. To resolve the phylogeny of this haplogroup, we completely sequenced 113 mitochondrial genomes (79 U5a and 34 U5b) of central and eastern Europeans (Czechs, Slovaks, Poles, Russians and Belorussians), and reconstructed a detailed phylogenetic tree … Phylogeographic analysis reveals that …”
Are you still with me? - Phylogenomics, phylogenetics, phylo-what ??? It is all Greek to me!
It is all about “phylum”. Phylum is a biological term derived from Ancient Greek φῦλον (phulon, meaning something like tribe, or race). My free definition is that a “phylum” is a group of species, or maybe rather a group of a group of species with similar distinctive characteristics. Characteristics that lie in their genes or DNA, which leads us to phylogenetics, the study of organism relationships based on evolutionary similarities and differences based on genes or genetics (from Ancient Greek γενετικός genetikos, “relative to birth” and γένεσις genesis, “birth, origin”), or the science of heredity if you like.
Slowly leading us to “phylogeography” - the study and understanding of the relationships found among living things and their location on Earth, why who is where. Why we have penguins near the South Pole, but no polar bears. And why we have polar bears near the North Pole, but no Penguins.
And just one of the other words used in the abstract mentioned above, haplogroup. One way to think about haplogroups is as major branches on the family tree of Homo Sapiens. These haplogroup branches characterise the early migrations of population groups. As a result, haplogroups are usually associated with a geographic region. (From the Greek: ἁπλοῦς, haploûs, "onefold, single, simple").
So in short the above mentioned paper is about DNA studies of the evolution from the first human settlers in Europe, via the stone age, expansions in eastern Europe, originating from industries that can be traced back 40–30 thousand years ago, an expansion of modern humans inhabiting the territory of the central part of East European Plain at least 24 thousand years ago, settlements in central Europe that appear to be continuous throughout the Last Glacial Maximum (approximately 20 thousand years ago).
Concluding that genetic data suggest that during the Last Glacial Maximum period, central European territories probably represented an area of intermingling between human migration (humans of different haplogroups) from refugial zones in the Balkans, the Mediterranean coastline and the Pyrenees.
(I hope I got it right, more or less - nobody said that reading scientific papers is easy).
Geology is not an isolated island, our eyes should be open for interfaces with other scientific disciplines - and vice versa, of course!
PS of 23 July 2010:
Oh Sorry, here is the reference to the Plos One paper:
Malyarchuk et al.
The Peopling of Europe from the Mitochondrial Haplogroup U5 Perspective
PLoS ONE 5(4): e10285.
Primates is a group that contains lemurs, lorisids, galagos, tarsiers, monkeys, apes, and humans.
A new model for primate origins is presented in Zoologica Scripta. The paper argues that the distributions of the major primate groups are correlated with Mesozoic tectonic features and that their respective ranges are congruent with each evolving locally from a widespread ancestor on the supercontinent of Pangea about 185 million years ago.
I like the tectonic approach in this new biogeographic reconstruction of primates. According to this “tectonic model’ divergence between strepsirrhines (lemurs and lorises) and haplorhines (tarsiers and anthropoids) is correlated with intense volcanic activity on the Lebombo Monocline in Africa about 180 million years ago. The lemurs of Madagascar diverged from their African relatives with the opening of the Mozambique Channel (160 million years ago), while New and Old World monkeys diverged with the opening of the Atlantic about 120 million years ago.
Notes: anthropoids are: monkeys, apes, and humans (a subgroup of primates).
The Lebombo monocline in the Kaapvaal craton contains Jurassic igneous rocks associated with rifting during the break-up of Pangea.
Press Release from Buffalo Museum of Science
PS of 27 January 2010
Scientists remain skeptical: http://news.yahoo.com/s/livescience/20100127/sc_livescience/newtheoryofprimateoriginssparkscontroversy
For most of the past few million years, the shallow ocean shelf surrounding the peninsula and islands of Malaysia and Indonesia has been exposed, creating a land area about the size of Europe. That habitat shrank dramatically each time sea levels rose.
The map shows the situation sixteen thousand years ago, when surrounding seas were 110 meters lower than today. Massive ice sheets covered parts of North America, northern Europe, and several other regions during the last ice age. This huge volume of ice lowered global sea level by around 120 meters as compared to today. After the ice sheets began to melt and retreat, sea level rose rapidly, with several periods of even faster spurts.
The figure shows a generalised curve of sea level rise since the last ice age.
The closing of the “Indonesian Seaway” (east of Borneo/Kalimantan) has by the way been seen as triggering the Ice Ages.
|November 2013January 2014|
A Nobelist on the Nature Effect
This year Randy Schekman won the Nobel Prize in Medicine. Last week he wrote a piece for the Guardian on how the "big dog" journals Cell, Nature and Science do damage to science. Most notably, he pledged that his laboratory would avoid "luxury journals" like these. What's the harm they do? As Sc ...
A Geological Advent Calendar
I was raised in a household with Advent calendars: charmingly detailed printed scenes studded with little numbered die-cut doors. Each day in December, the child would search for the door corresponding to that day and open it, to expose a tiny charming scene that was in some way relevant to the ...
Geo-Quiz of the Week: Caves
I used to be a caver—spent a fair amount of my late teens visiting wild caves. Then I moved to a place with no caves, moved again, and many years later I'm not sure I could repeat anything I used to do underground. But I still enjoy a tour of a good show cave, especially when they lay on t ...
Mindat.org Seeks Support
Anyone who looks online for deep, solid information on minerals has encountered Mindat.org, which presents more kinds of data than you can shake a rock hammer at, plus photos contributed over the years by collectors. I didn't realize that Mindat began as Jolyon Ralph's personal site 13 years ago ...
An Open-Access Anthropocene Journal
The American Geophysical Union, whose Fall Meeting I'm attending all this week, is taking the Anthropocene concept seriously. Today David Grinspoon delivered the annual Sagan Lecture on the subject, under the title "Terra Sapiens," putting some more flesh on the ideas I described 10 years ago as ...
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"allgeo" via Chris
What’s the Real Story With Clean Coal?
Coal-fired power plants are responsible for one third of all U.S. carbon dioxide emissions each year. Recently President Obama proposed a plan to combat climate change including a measure that will regulate emissions from new and existing coal-fired power plants. The plants will likely only be a ...
Antarctica – a general introduction
Bedrock map of Antarctica obtained by the BEDMAP2 project of the British Antarctic Survey By Bianca There have been quite a few articles about Antarctica by now, but none of them actually about Antarctica itself. For most people the seventh continent is isolated from everything, and that is actu ...
It's been a while since I posted but, as usual, things have been busy. I don't get pay, recognition, or much else for writing a blog - it's mostly for my own benefit and to encourage my writing. If others find it interesting or useful, that's an extra benefit! Anyway, a few da ...
Thin section porosity estimation using ImageJ ...
I have made a short video that shows how to use the free software ImageJ to estimate porosity from an image of a thin section cut from a rock sample. The video can be found here. Screen shot from video with porosity highlighted red and results window indicating 17.19% porosity.
I've been holding onto a couple of blogs that appear to be defunct, or which have officially ended. So I'm taking the following off my bloglist: A Gentleman's C - the first blog I followed regularly. Isis the Scientist - this one is officially done, not "sorta done but I'll still keep posting" ...