Tenaghi Philippon, N.E. Greece - A 1.35 million Year Pollen Sequence

 Ruins from Philippi on the Aegean

The longest continuous European pollen record comes from the site of Philippi, in eastern Macedonia, N.E. Greece, established by Philip II in 356 B.C. but abandoned in the 14th Century after the Ottoman conquest.  It is now a UNESCO site for its Greek and Roman ruins.  Evaluation of the original age model using calibration based on vegetation changes and March and June perihelion configurations  suggests that the base of the pollen extends back to 1.35 million years.  

The pollen sequence from the Philippi basin provides the opportunity to examine long-term vegetation and individual taxa trends within the context of global climate changes.  Interestingly although this pollen sequence shows no changes in the magnitude of interglacial tree populations after the Mid-Brunhes climatic event around 430,000 years before present.  Instead the Tenaghi Philippon pollen sequence suggests major vegetation shifts in the composition of  interglacial cycles after MIS 16, which was a strong amplitude glacial which resulted in reduced diversity and a more 'modern' appearance of subsequent vegetation distributions.  


Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172–300 p.p.m.v.  Luthi (2008)    

Although species of oak managed to persist in the region, there were many extinctions, including Tsuga (Hemlock), Liriodendrum (Tulip Tree), Parthenocissus (Climbing Grape), Parottia (Persian Ironwood), Cedrus (Cedar), Carya and Eucommia (now native to China) that largely disappeared from the record after MIS 16 which was 650,000 years ago. Tzedakis (2006)

Persian Ironwood that disappeared from Philippi  650,000 years ago

Examples of some tree taxa that went extinct in Europe, and are now only found in S. E. Asia or North America:

Prior to Northern Hemisphere Glaciation, there were many more tropical taxa now only found in S. E. Asia and North America such as  Persimmon (Diospyros), Epipremnum (now only found in tropical forests), Snowbell or Snowdrop tree (Halesca), Karwinskia (Flowering Buckthorn -  Rhamnaceae family), Meliosma, Golden Larch (Pseudo Larix), Stewartia (flowering shrub related to camellia), Actinidia, Magnolia, Prosperpinaca, Fagus (Beech).  

The disappearance of the hardy magnolia from Europe is thought to be related to being out-competed by faster growing and more robust trees during the climate fluctuations of the last 2 million years rather than extinction due to Northern Hemisphere glaciation. Magnolia is a very old plant, considered an evolutionary relict that formerly had widespread distribution and early forms we but today is only found in North America (26 species) and S. E. Asia (80 species).  

As the climate warms, some species will do better:  for example, the horn growth of the endangered Alpine ibex is affected by European springtime temperatures between March and May - with earlier snow melts with more lush alpine grasses and herbs more favorable for the animal's vitality Buntgen (2013).  

Regrettably many other cold loving species will not be so fortunate....

A Tale of Two Extraordinary Adaptations

Desert Rhubarb (Rheum Palaestinum)

EXTREME ADAPTATIONS OF RHUBARB

The Desert Rhubarb (Rheum Palaestinum) in the
Negev Desert possesses unusually large rosette-shaped leaves for a desert plant. Most interestingly, its leaf morphology resembles the slopes it inhabits.  Piqued by this observation, University of Haifa researchers determined that is the only self-irrigating plant in that world known to have this capacity - collecting up to 16 times more water per year than other desert plants in the region.  The study has revealed the plant harvests 4.2 liters per year, akin to the rainfall of a mediterranean climate - in a desert region that receives  only 75 mm of rainfall a year.  Deep depressions in its leaves channel water towards its roots - creating its own mini leaf-oasis.  Yev-Ladun (2009) 



Meanwhile, high in the Himalayas above the treeline at 4000 meters where conditions are so extreme most plants cannot survive, Rheum nobile - the extraordinary Noble Rhubarb stands up to 2 meters tall, a hollow column of overlapping pale-yellow leaves rising from a base of green leaves.  Discovered in the 1840s by Joseph Hooker, Rheum Nobile stands tall on the harsh Himalayan scree-clad slopes withstanding both perishing cold and biting wind as well as an invisible-yet-deadly barrage of ultraviolet light. Amazingly, the translucent column functions as a protective greenhouse, enabling it to grow amazingly large at such an altitude.
A few botanical gardens and amateur enthusiasts grow Rhem nobile but it rarely flowers out of its natural habitat.  The flowers are extraordinary: the hollow columns are actually flower spikes.  Pale yellow leaves "bracts" grow from each spike that surround and hide the flowers inside.  Kew Gardens herbarium head David Simpson says it displays great botanical novelty.  Joseph Hooker noted that in winter, after the fruit and seeds have formed, the dead seed bearing stems are in dismal keeping with the surrounding winter desolation. Nicholls (2013)

In 1964 Sasuke Naoao wrote "the flowers open in a self-made warm room" that boosts pollination, he suggested by providing favorable conditions for insects.

 

Rheum Nobile

                                                   

So even though this blog takes a slight detour from the glacial refugia topic, it is pertinent because it does make one question why if one angiosperm could manage such extreme adaptations, why were there not more? 

Weeds usually are noted for their phenotypic plasticity, but this example of the adaptation of Rhubarb (Rheum ssp) of the polygoniaceae family to survive in both extreme aridity and extreme cold is truly amazing.

 

The Tulip Tree and its fossil genome

Many tree species such as Hemlock (Tsuga), Sweet Gum (Liquid Amber), Magnolia and Tulip trees went extinct in Europe during the Pleistocene yet managed to survive the ice ages in North America and Asia. Their extinction is attributed to overall harsher climates through Europe, being closer to the ocean as well as zonal mountain ranges (i.e. the Pyrenees) that halted southerly migrations from the colder north. The larger continentality of the United States and north-to-south aspect of ranges was kinder to tree species during glacial phases.

Isolated relict populations do survive today such as Liquid Amber in Rhodes and Zelkova Abelica (Elm) in Crete and Sicily. 

Today and in the future, the genetic study of plants is and will continue to unravel valuable new information regarding plant evolution and distributions.

The Tulip Tree (Liriodendron tulipifera) in Eastern North America, related to the Magnolia (Magnoliaceae) family that disappeared in Europe due to the competition from more robust and faster growing tree species during the last 2 million years although today 26 magnolia species are found in North America and 80 in S.E. Asia.

 The Tulip Tree (Liriodendron tulipifera)

Interestingly in 2013, research groups from Indiana and Arkansas Universities determined that genetic material within the Tulip tree has remained largely unchanged since the time of the dinosaurs, making it a valuable archive of many genes lost during 200 million years of angiosperm evolution.  Jeffrey Palmer, coauthor of the study explained that due to the slow silent mutation rate, the genome appeared to have been frozen in time for millions of years Richardson (2013).  Prof. Ian Small of the University of Western Australia explained in commentary to the above article that Liriodendron belonged to an early lineage branch that is distinct from other groups to which most of the world's crops belong.

The Tulip Tree survived in North America through mega-scale Cenzoic cooling from greenhouse to icehouse conditions, major continental tectonic changes, orbital and millennial scale climate variability. 

It is also the state tree of Indiana, Kentucky and Tennessee.

The Iberian Peninsula

Cistus libanotis, an endemic plant of southwestern Iberian Peninsula

The Iberian Peninsula was a major Pleistocene Glacial Refugia in Southern Europe, a location where temperate species managed to survive throughout the Ice Ages.The very high level of endemism found in both plants and animals also suggests Iberia supported genetic differentiation as well as serving as a species repository for the northern latitudes of Europe after the Pleistocene Hewitt (1999).

                                


The Iberian Peninsula - A Glacial Cradle



In the last decade or so, many new creatures have been recognized to have migrated from the Iberian Peninsula to western and northern Europe after the Ice Ages, for example, the roe deer (Capreolus capreolus), the woodmouse (Apodemus sylvaticus), field voles (Microtis agrestis), the chaffinch (Fringilla coelebs), pond turtle (Emys orbicularis), and natterjack toad (Bufo calmita).  

                     Chaffinch (Fringella Coelebs) widespread emigrant from the Iberian Peninsula

The Iberian Peninsula located on the western edge of Europe has several large zonal (east-west) mountain ranges with a wide range of microclimates offering easy access to altitudinal shifts during rapidly-changing millennial climate events. 

It is a large 580,000 square km region, whose climate is impacted by both the North Atlantic Ocean and the Mediterranean Sea. In this region are found multiple climates: Desert, Mediterranean, Atlantic and Alpine.  For this reason, it is believed that there were multiple glacial refugia isolated by the harsh Pleistocene climate of the high central Iberian Plateau.

The Iberian Peninsula  soils have supported amazing floristic diversity. Studies of Iberian refugia plant taxa are ongong but there is some evidence of the Iberian Peninsula being a glacial refugia for ivy (Hedera, ssp), white oaks (Quercus, ssp), black alder (Alnus, ssp), silver fir (Aconitum lycoctonum), among others.  

Scots Pine (Pinus Sylvestris) - a tree that cannot withstand drought and that requires humidity - is believed to have survived the Pleistocene glaciations and is today found at 1000-2000 meters in Iberian Peninsula Mountains - but it is not part of the postglacial colonization of northern Europe.  Four species of white oak(Quercus) are also believed to be Iberian refugia   Gomez and Lunt (2007)

                                     Forest of Cork Oak (Quercus Super) - the Algarve
                                              Carsten Neihaus photographer (2004)
                                                       
Next week, more on Mediterranean Region as a glacial refugia during the last Pleniglacial.




Angiosperms and Gymnosperms

2013 marks Darwin's 200th birthday and 150 years of "The Origin of Species" ...

Darwin's Abominable Mystery: the Abundant and Amazingly Successful Angiosperm that so graces our planet in its myriad expressions of beauty....

Lemon Flowers

Spring  flowers in my Northern California garden before the dry Mediterranean summer takes over.

Nasturtiums

 

From the mid-Cretaceous onward, the flourishing and amazingly diverse angiosperm family become the dominant floral family on planet earth (see graph below).

Angiosperms, flowering plants presented a bit of a conundrum to Charles Darwin and generations of biologists after him.  How did angiosperms radiate and diversify with such dizzying and effortless array into the myriad 300,000 forms that may be found within the covers of any Botanical Encyclopedia and which are sprinkled throughout parks and gardens of the world?  A trip to any art gallery in the world will confirm not only the impact of flowers on culture but  to our sense of wellbeing and romance as well.  Even a little white daisy poking its head through a crack in a wall brings with it a certain ineffable beauty.

The angiosperms are pollinated plants producing flowers and fruit that diverged from gymnosperms.  Although angiosperm-like fossil pollen has been found that dates to the Middle Triassic in Germany Hochhuli, P.A. and Feist-Burkhardt, S. (2013) , the first small flowering plants became widespread within 120 MYA, replacing conifers (gymnosperms) as the dominant tree type around 60-100 MYA.  Davies, T. J. et al. (2004)

As in the graph  below, 125 MYA gymnosperms which include cycads and conifers were the major plant groups.  Angiosperms were rather small plants, growing alongside stream or even dry salty places where their thick leaves helped conserve water.  Then between 125 to 65 MYA, flowering plants exploded from a small minority into 80% of all plants.  According to a theory of Berendse and Scheffer (2009), the reason has to do with soil quality.  Although Gymnosperms flourished in poor soils, they did not improve soil quality.  Angiosperm litter replenished soils however, creating a positive feedback between improved soil fertility and angiosperm expansion. 


From Cox and Moore, Biogeography (2010)

So returning to the question of refugia, how does the topic of angiosperms relate?  Well, indirectly there are some interesting contrasts to highlight.  Note the map below showing the richness of tree species on a Latitudinal Diversity Gradient (LDG).

 

From Cox and Moore Biogeography (2010)

 

There are 644 tree species in Yasuni National Park, Ecuador - 

There are none at the North Pole.

There is a consistent latitidinal decline in life forms moving north

 

 

Simliar trends may be seen in mammals and birds.   Much greater diversity may be found closer to the equator.  It appears that the sun, warmth and moisture are kind to life on earth and that the cold, dry climes of far Northern Hemisphere are limiting factors for survival.  Note however that a correlation betwen latitude and evolution has not been fully resolved. Mittelbach, G.G. et al. (2007)

However, the following map which showing global diversity suggests a limiting trend of the Northern Hemisphere Pleistocene glaciation cycles.

 

 

 

Barthlott, Klier, Rafigpoor, Kreft, Kuper, Mutke & Nees Institut for Plant Biodiversity (2004)

 CLICK ON MAP TO ENLARGE

 

Finally, gymnosperms - the conifers -  largely outcompeted by the dazzling success of angiosperms adapted to harsher climates with needle-like leaves and structural cone shapes that did not facilitate much snow accumulation. 

 

Flowers are found at alpine locations but they tend usually to be small, hardy plants, such as Rosebay Willowherb (Epilobium Angustifolium) below.

 

 

 

 

This hardy little flower is one of the first to appear after a glacier retreats, such as this image from Glacier Bay in Alaska.

 

In a warming more humid world, perhaps this post might offer a ray of hope.......







 

Climate Change and Plants, historic and future uncertainties.....

Historically, plant species have adapted to climate change by moving to seek ways to survive within their optimal environmental envelope.  Pollen records from sediment cores have become important biological proxies of the rapid climate shifts during Pleistocene glacials, interglacials and stadials, supporting ice core and deep ocean proxy records. 

The Carp Lake, Washington, U.S. pollen record below dates 130,000 years and is of high resolution. 

CARP LAKE POLLEN RECORD - note absence of oak during LGM

Whitlock, C. and Bartlein, P. J. (1997)
 

During Last Glacial Maximum 18,000-20,000 years ago at Carp Lake, there was an increase of evergreens with an expansion of spruce in the late glacial but hemlock and cedar did not increase though there was an increase of sagebrush (Artemisia).This was a sagebrush/steppe environment, relatively cool and dry, not significantly wetter than the present.  There was a big shift at 80,000 years ago, a warmer isotope 5 period when oak came in. 

Current research suggests that in our rapidly warming 21st century, plants may be forced to move in excess of 1 km per year to keep up with the changing climate, according to Corlett and Westcott (2013)  In this article , the authors state that many plants will not be able to move fast enough to adapt with consequences for biodiversity and carbon storage.

Although ongoing research over the past 40 years is slowly elucidating historical patterns of past vegetation, there is still ongoing debate of many details of glacial refugia.  In order to have any pollen record, a sediment core from an anoxic sedimentary lake is required, lakes which in many arid parts have dried up.  Additionally, during the LGM,  many areas were cool and dry with minimal rain and low CO2 levels.  P. C. Tzedakis, B. C. Emerson and G. M. Hewitt (2013)believe there was an absence of temperate trees north of 45 degrees N and a west-east asymmetry in boreal tree distribution with a treeless Western Europe north of 46 degrees N, while restricted boreal populations persisted in Eastern Europe to 49 degrees N and higher latitudes east of the Fennoscandian ice-sheet. 

 

In future decades, vegetation will no doubt struggle to adapt to climate change within a certain climatic envelope but challenges will emerge from insects and new pathogens responding aggressively to a warming world.  Anyone who has visited the wet and humid Amazon rainforest will confirm that insects are not only bigger, they are more aggressive.  According to researchers at Exeter University, since 1960, viruses, nematode worms and any number of insects have been moving north at 3 km per year, posing a gradually increasing threat to global food supplies. Fisher et al. (2012)

 

 

Obviously we must be diligent as we work towards mitigation in our climate changing world.

 

 

 

Remote Queensland Rainforest "Lost World" - Newly-Discovered Refugium of Ancient Creatures

DISCOVERED ON OCTOBER, 2013 BY DR. CONRAD HOSKINS OF JAMES COOK UNIVERSITY and TIM LAMAN OF HARVARD UNIVERSITY ON A FOUR-DAY EXPEDITION FUNDED BY THE NATIONAL GEOGRAPHIC SOCIETY......

WHO KNOWS WHAT IS YET TO BE DISCOVERED AT THIS UNIQUE REMOTE PLATEAU AND WHAT CLIMATIC CONDITIONS ENABLED THESE RELICT POPULATIONS TO SURVIVE ONLY 900 MILES NW OF BRISBANE, AUSTRALIA?   (Sources:   Daily Telegraph, UK and Christian Science Monitor )

Unfortunately, the survival of all of the high-altitude Queensland rainforests are under threat from climate warming because as temperatures rise with altitude, the changing climatic zones will cause extinctions.

High on a remote 1.8 mile square upland plateau of Cape Melville, Queensland, accessible only by helicopter, three reptile species isolated for millions of years have been discovered:  a strange leaf-tailed gecko, a golden hued skink and a boulder-dwelling frog - ancient animals that have survived in this tiny niche since the Gondwana Rainforest!   



The Blotched Boulder Frog

The 20 cm nocturnal long leaf-tailed gecko emerges at nightfall to hunt on rocks and trees; the shade skink hunts insects in the mossy boulders.  The blotched boulder frog lives in cool, damp cracks of the boulders during the dry season, only emerging during summer rains to breed and feed on insects.

The 20 cm noctural leaf-tailed gecko

“That this gecko was hidden away in a small patch of rainforest on top of Cape Melville is truly remarkable. What makes it even more remarkable is that two other totally new vertebrates were found at the same time,” Dr Hoskin  announced.  He believes the Gecko's long legs are an evolutionary adaptation so the creature can scurry through the unusual, rocky environment looking for prey, while its eyes are likely to help it navigate the deep, dark crevices between boulders.

   



The golden-hued skink hunts for insects between boulders

______________________________________________________________________________________________________

Nothofagus, the Southern Beech Forests evolved 100 MYA, during the Dinosaur era when Australia was part of the supercontinent Gondwana.  Between 160 and 65 MYA, Gondwana split apart, forming today's southern hemisphere land masses: Antarctica, South America, Africa, Madagascar, Australia and New Zealand, New Guinea and New Caledonia.   The current distributions of Nothofagus are evidence of the continental drift.  The forests are found only in S. America (Chile and Patagonia), New Zealand, Australia, New Guinea and New Caledonia.

 

 

                                                                 Nothofagus Forest