Showing posts with label Spain. Show all posts
Showing posts with label Spain. Show all posts

Tuesday, February 28, 2012

Polysternon isonae, A New Bothremydid Turtle

Researchers at the Institut Català de Paleontologia Miquel Crusafont (ICP), the Museu de la Conca Dellà (MCD) and the Universitat Autònoma de Barcelona (UAB) have published this week in the online edition of the journal Cretaceous Research the discovery and description of a turtle from the end of the age of dinosaurs.   Above left: a reconstruction of Polysternon isonae. (Credit: Oscar Sanisidro)

Josep Marmi, Angel Lujan, Angel Galobart from ICP, Rodrigo Gaete from MDC, and Violeta and Oms Oriol Riera from UAB have named this new species as Polysternon isonae, in recognition of the municipality of Isona I Conca Dellà (Catalonia, Spain), where the fossil remains of the specimen type have been found.

The abundance of dinosaur fossils that lived between 65 and 70 million years ago in the area currently occupied by the Pyrenees It is well known. In this range we find dozens of sites with bones, footprints and eggs of the last dinosaurs that inhabited our planet, the Tremp basin being one of the areas with the highest concentration of fossils.

However, lesser-known are the other organisms that completed the ecosystems at the end of the Cretaceous period, consisting of other vertebrates, invertebrates, plants, fungi, etc. A common feature of these ecosystems were turtles. In the Pyrenean sites, their fossils are relatively abundant and, in general, consist of isolated shell plates or small sets of plates that can help us get a general idea of the morphology and size of the animal. Instead, the entire shell finding is rare and even more exceptional are the findings where parts of the skeleton are preserved within the shell.

In recent years, in the municipality of Isona i Conca Dellà (Catalonia) numerous discoveries of turtle remains have been made, spread over several sites. One of these sites, that of Barranc de Torrebilles, has given fairly complete remains that allowed describing a new species: Polysternon isonae. The remains found consist of dozens of isolated plates derived from the fragmentation of shells through their sutures, and what is more important: a fragment of the ventral side of a shell and an almost entire shell, which without being totally complete, show morphological features of great interest to paleontologists and have allowed to describe this new species. These remains were recovered during two excavation campaigns conducted during the summers of 2008 and 2009.

So far, two species of the genus Polysternon were known : P. provinciale and P. Atlanticum (plus a possible third P. Mechinorum), distributed only in what is know the south of France and the Iberian Peninsula. They were animals adapted to swimming and living in fresh waters, in the deeper areas of rivers and lakes. Specifically, the shell of the new species P. isonae was oval, measuring about 50 centimeters long and 40 wide. The remains were found preserved in a very hard sandstone strata now exposed in the Barranc de Torrebilles. Just over 65 million years ago, when the animal died, this was not a lithified sandstone and consisted of fine sand that was washed away by river streams and that was deposited, along with the remains of other turtles of the Barranc de Torrebilles, at the bottom of one of these rivers.

Unlike other kinds of turtles, it seems that Polysternon did not survive the end of Cretaceous and went extinct with the dinosaurs. The close proximity of the site Barranc de Torrebilles to the geological level that marks the end of the Cretaceous extinction, indicates that Polysternon isonae was possibly one of the last species of the genus Polysternon.


J. Marmi, Á.H. Luján, V. Riera, R. Gaete, O. Oms, À. Galobart. 2012. The youngest species of Polysternon: A new bothremydid turtle from the uppermost Maastrichtian of the southern Pyrenees. Cretaceous Research; 35: 133 DOI: 10.1016/j.cretres.2011.12.004

Wednesday, April 6, 2011

Bufo viridis on the Iberian Peninsula

The green toad (Bufo viridis) was present 

in the Iberian Peninsula during the late 
Analysis of fossils found in the Cueva Victoria deposit in Cartagena (Murcia), has for the first time confirmed the presence of the green toad (Bufo viridis) in south eastern Spain at the end of the Early Pleistocene (more than 1.1 million years ago), in the provinces of Granada, Murcia and Castellón.

"Around 500 fossilised bones document the entire skeleton of the green toad, and provide key osteological clues that mean they can be unequivocally attributed to this species," says Hugues-Alexandre Blain, one of the authors of the study and a researcher in the Prehistory Department at the Rovira i Virgili University (URV) in Tarragona.

The study, which has been published in Comptes Rendus Palevol, shows that at this time the amphibian belonged to a different subspecies than the green toads of today. Changes in the climate and landscape, "which have taken place frequently over the past two million years," could be the reason for them having become locally extinct.

Nowadays, B. viridis is distributed extensively throughout Eurasia and northern Africa, but until now its presence had never been demonstrated in the Iberian Peninsula. "Although the peninsula has favourable ecological conditions, the species is strangely absent," the expert says.

The south western limit of its current range in Europe is the border between Italy and France. In Spain, it is only found in the Balearic Islands, "where it is thought to have arrived recently, possibly having been introduced by the Phoenicians from northern Africa," says Blain.

Why did it disappear in the Iberian Peninsula?
There are various theories as to the causes that led to the green toad disappearing from the Peninsula during the Pleistocene. "Growing climate changes and in particular the cold period seen around one million years ago could be possible explanations," the scientist explains.

However, pressure from the natterjack toad (Bufo calamita), "which is stronger and more competitive," may have displaced the green toad and "made it locally extinct," leaving it "trapped" in south eastern Spain. The expert says that "we will only be able to find out what really caused the local extinction of B. viridis by carrying out studies on more deposits, covering a more extensive geographical area and longer time period."

In search of its ancestor
The green toad belongs to the family Bufonidae, but its ancestor is unknown. "Molecular studies suggest that green toads had an ancestor in Central Asia, but the oldest fossil record found to date is from the Early Miocene (more than 20 million years ago) in France and Spain," explains Blain.

In Spain, the closest living toad relative of B. viridis is the Natterjack Toad, which is found all the way to Ukraine. In Europe, "Bufo priscus could be a good candidate for the title of the European ancestor of B. viridis," says the scientist, who believes it is necessary to carry out a "serious review of all the fossils attributed to this group in Europe, Africa and Asia."

Hugues-Alexandre Blain, Luis Gibert, Carles Ferràndez-Cañadell. First report of a green toad (Bufo viridis sensu lato) in the Early Pleistocene of Spain: Palaeobiogeographical and palaeoecological implications. Comptes Rendus Palevol, 2010; 9 (8): 487 DOI: 10.1016/j.crpv.2010.10.002

Tuesday, April 5, 2011

Tadpoles and an Invasive Crustacean

After 30 years, the common frog can not activate their defenses against the American crayfish.

Iván Gómez Mestre and Carmen Díaz Paniagua, biologists from the Biodiversity Research Unit of the Principality of Asturias CSIC-Universidad de Oviedo and Station Biological relevance of Doñana (CSIC) respectively have confronted two groups of tadpoles with the American crayfish and have compared the degree of activation of their defenses. The researchers note that, despite the common frog tadpoles activated when they detect predators, are unable to perceive the American crayfish, which leaves no recourse for this invasive species.

"The common frog in the Doñana National Park has not yet adapted to the American red crayfish (Procambarus clarkii ) [photo]," said Iván Gómez Mestre. Both the common frog tadpoles in the wetlands of Donana, a town three decades has been in contact with this predator (between 10 and 15 generations), and tadpoles from populations that are faced by first time crab responded the same way: "The degree of activation of defenses is the same in both cases: null," says the biologist.

Tadpoles, explains, they have many defenses available to it, but when they detect the chemical signals (the smell dissolved in water) of a predator such as dragonfly larvae can morphological and behavioral changes.
"The changes in shape result in a wider tail and more pigmented, which attracts the predator to her leaving intact the vital organs and no tears or loss of tail have such serious consequences, since they can regenerate. And changes in behavior resulting in a reduction of activity that passed over unnoticed, "said Iván Gómez Mestre.

But these changes, despite improved survival in case of predators, have a price: "By reducing its activity, the tadpoles were fed less, grew more slowly and faced with the progress of your pond dry season, addition to give advantage to competitors for food, "says the researcher. Hence, the activation of defenses is not permanent and depend on the detection of the predator species by the tadpoles.
An evolutionary race

The results published today contribute to better understand the series of changes that occur in the Iberian ecosystems that invasive crab, native to the Southeastern U.S. and present from Doñana to Asturias. As indicated by Iván Gómez Mestre, among other effects "are known to be in areas that present the American crayfish is a proliferation of predatory birds, so that the pressure on amphibians increases even more."
"The question is whether common frog populations exposed to American crayfish have enough time before dying to adapt to the presence of an introduced predator so voracious. Can not venture a period in evolutionary terms, because each species responds differently, but a reference can be detected cases in the U.S. adaptation of bullfrog tadpoles by introduced fish against the man after 110 years of contact, "says researcher.

The species was detected 15 years ago in Asturian rivers. The American crayfish damage native ecosystems and particularly harmful to salmonids, small fish, amphibians, and vegetation waters. It has also displaced the native crayfish ( Austropotamobius pallipes lusitanicus) in almost all waterways.

This situation has led to initiatives such as the Crab Project:

Ivan Gomez-Mestre and Carmen Díaz-Paniagua. (2011)  Invasive predatory crayfish do not trigger inducible defences in tadpoles Proc. R. Soc. B published online 30 March 2011doi:10.1098/rspb.2010.2762

Tuesday, February 22, 2011

The Fire & the Tortoise

Fire maintained ecosystems are often found in geographic regions with Mediterranean climates - southern California, southwest Australia, and of course the Mediterranean. Burning vegetation is an inconvenience, and even prescribed burns are often objected to by local citizens. But, burning-off left-over agricultural biomass has increased in many places. Suppressing fires can lead to the build-up of fuel -dead, dry vegetation- in fire maintained ecosystems and result in increased hazards to both humans and wildlife. How wildlife populations deal with fire is of interest for understanding adaptations to fire and for conservation. Ana Sanz-Aguilar and colleagues have examined how the Iberian Spur-thighed Tortoise, Testudo gracea ibera, manges to coexist with fire at the Cumbres de la Galera Biological Reserve in the Sierra de la Carrasquilla, in Spain. Their study area supported a high density population (about 20 tortoises per hectare) of Spur-thighed Tortoise and they estimated tortoise populations in areas that had frequent fires and areas that had not been burned. The Spur-thighed Tortoise is a long-lived species of the Mediterranean shrublands and the tortoises spend much of their lives sheltered under the vegetation or underground in burrows. These tortoises also bury themselves for hibernate and aestivate, so that they are protected from extreme temperatures, predators and possibly from fires. They found fire caused direct and delayed reductions in local survival, with young individuals being the most affected. Fire-related mortality was highest in juveniles and subadults than adults; this seemed to be related to differences in burrowing behavior. Summer fires had a lesser impact on adults because they spend summer and winter underground in burrows or by burying themselves to avoid temperature extremes. Juveniles and subadults tend to use more superficial burrows or take cover under the vegetation only a few centimeters in depth, thus and are exposed to higher temperature and smoke. The study areas that had fire frequencies similar to those occurring in areas uncontrolled for burns (less than one fire every 20–30 years) tortoise populations were able buffer the effects of fires. But, when fire frequency increased the probability of extinction dramatically increased, except for the largest populations. Thus, T. graeca is able to cope with natural fire frequencies, but the effects of more recurrent fires may severely threaten the species.

Citation:Sanz-Aguilar, A., J. D. Anadon, A. Gimenez, R. Ballestar, E. Gracia, and D. Oro.. 2011. Coexisting with fire: The case of the terrestrial tortoise Testudo graeca in mediterranean shrublands. Biological Conservation (2011), doi:10.1016/j.biocon.2010.12.023

Sunday, February 13, 2011

Fire & Tortoises

Humans have altered Mediterranean landscapes and ecosystems for more than 8000 years, and despite human influences the region is considered a biodiversity hotspots. In the last few decades fire suppression policies have modified the ecosystems’ functioning, but prescribed burning has been considered a management tool to prevent extensive wildfires and restore the dynamics of fire-maintained ecosystems. Anna Sanz-Aquilar and colleagues (2011) assessed the impact of fire on survival rates, reproduction and movement of the Mediterranean Spur High Tortoise, Testudo graeca ibera, at the Cumbres de la Galera Biological Reserve, in the Sierra de la Carrasquilla, Spain. They found fire impacted survival of mostly of young individuals, with dramatic mortality of juveniles with the burned areas during the first and the second year after the fire. The reduction in vegetation cover after a fire could increase the visibility of young and vulnerable individuals to predators interfere with thermoregulatory behavior, or effect food availability. They found no differences in fecundity and movement patterns of tortoises between burned and unburned areas. Their, population models showed areas with fire frequencies of less than one fire every 20–30 years the tortoise populations seemed to cope with the effects of fires with little damage to the populations. But, when this fire frequency was surpassed, the probability of population extinctions exploded for all populations, except for those with the largest numbers of individuals. Thus, tortoise populations may be able to deal with naturally occurring fire frequencies, but the effects of more frequent fires may severely threaten the species. 

Sanz-Aguilar, A., J. D. Anadón, A. Giménez, R. Ballestar, E. Graciá and D. Oro. 2011. Coexisting with fire: The case of the terrestrial tortoise Testudo graeca in mediterranean shrublands. Biological Conservation, In Press. doi:10.1016/j.biocon.2010.12.023