One of the really interesting
bits of natural history is the presence of Giant redwoods and its cousins on
the west coast of the Americas . However one argues the case, one assumes that
a long evolutionary path exists, yet the available biome is astonishingly
small. It is a question that I would
like to see answered. It may have
actually been a recent emergence from what is obviously a very old lineage.
I do not get the impression from
the data generally that plant lineages truly go extinct very easily. I think that they more properly retreat into
refugia until conditions return in which they may prosper. Ne species do emerge and take their own place
but rarely are able to chase out completely competition.
That has not been true for animal
lineages who can easily be caught in a food crisis in which animals that were
never prey are hunted out because no choice exists. A real crash to the bottom is possible as a
result of simple mobility.
Imagine Africa
losing its ability to feed any large animal.
After the herbivores are hunted out, the hyenas will eat out all other
carnivores rather quickly.
That is surely what happened
during the Pleistocene .Nonconformity 12900 years ago. All the large carnivores who would have been
single hunters would have been taken by either a grizzly or a wolf pack in a
contracting environment. Wolves could
even clean out grizzlies if grizzlies did not hibernate. In the dead of winter, packs will congregate
in order to take down anything and a grizzly so surrounded would be harried to
death unless it were able to retreat to a cave it could easily defend.
Wynne Parry, LiveScience Senior Writer
Date: 04 May 2012 Time: 01:30 PM ET
Cypress trees, like these, are conifers found on all continents except Antarctica .
Early members of an ancient family of trees, the cypresses, grew on the supercontinent Pangaea, and when this giant continent split apart, it shaped the future of these trees, according to research that examined the evolution of these trees, which today include giant redwoods and sequoias.
More than 200 million years ago, Pangaea contained
all the modern continents, squished up against one another. The separation of
these continents isolated populations of living things, putting them on
different evolutionary paths.
Scientists have already found evidence of the separation of the
continents in the family histories of reptiles, amphibians and mammals.
"Until now, there has been no equivalent evidence for any plant
family," writes an international team of researchers in a study published
May 1 in the journal Proceedings of the National Academy
of Sciences.
The cypress
family, Cupressaceae, a group of conifers with scalelike leaves, is
believed to have originated more than 200 million years ago, when Pangaea was
still intact, according to the researchers.
By looking at changes in the DNA (deoxyribonucleic acid, the code that
makes up genes) of 122 species of cypress, the researchers were able to
reconstruct a timeline for their evolution. They also included fossil evidence
in the analysis.
The most recently evolved subfamilies of cypress, Cupressoideae and Callitroideae,
split from each other about 153 million years ago, as the two remnants of
Pangaea pulled away from each other. The northern half, Laurasia, contained
what would become North America, Greenland, Europe and much of Asia, while the
southern half, Gondwana, would later become South America, Africa, India , Antarctica and Australia .
The legacy remains. Living members of Cupressoideae occur
mainly in former Laurasian continents, while Callitroideae are found
on the fragments of what was Gondwana, write the researchers led by Kangshan
Mao of Lanzhou University , China .
Cypress are now found on all continents except Antarctica, they
note.
You can follow LiveScience writer
Wynne Parry on Twitter @Wynne_Parry. Follow
LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.
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