Geological change confirmed as a factor behind the extensive diversity in tropical rainforests

The tropical rainforests of Central and South America are home to the largest diversity of plants on this planet. Nowhere else are there quite so many different plant species in one place. However, the entire region is increasingly threatened by human activity, which is why researchers are stepping up their efforts to record this astonishing biodiversity and find out how it developed. In a project undertaken by Johannes Gutenberg University Mainz (JGU) in collaboration with Dutch research institutions, the causes of this plant diversity were investigated by studying two closely related groups of trees of the Annonaceae family.

Cremastosperma brevipes, French Guiana [Credit: Paul J. M. Maas]

The researchers identified three relevant factors: the formation of the Andes mountain range, the disappearance due to natural causes of the extensive Pebas wetlands system that once existed in the Amazon region, and the formation of a land bridge between Central and South America in the form of the Panama Isthmus.

Cremastosperma and Mosannona are two genera of the Annonaceae or custard apple family the habitat of which is neotropical rainforests, where they extend from the lowlands up to elevations of 2,000 meters. They are primarily found in the Andes region of South America, but also as far north as Central America.

Mosannona costaricensis, Costa Rica [Credit: Reinaldo Aguilar]

The team of botanists led by Dr. Michael Pirie, who joined JGU as a researcher in 2013, looked at the distributions of the various species of both genera and their phylogenetic history in order to determine the influence of the geological upheavals on the continent.

For this purpose they compiled a time-calibrated phylogenetic tree based on DNA data, using the so-called molecular clock technique which is calibrated using the ages of the available fossils. In total, they analyzed 11 species of the genus Mosannona and 24 species of the genus Cremastosperma.

Formation of the Andes, the Isthmus of Panama, and the drying-out of the Pebas wetland system all promoted diversification

The research has produced a biogeographical scenario that confirms in this context the significance of the geological history of north-western South America during the late Miocene and early Pliocene periods about 5 to 10 million years ago.

Cremastosperma yamayakatense, Peru [Credit: Michael Pirie]

"We have actually discovered that the diversification of these two plant genera took place in parallel with major geological events, namely the formation of the Andes, the drying-out of the Pebas system, and the development of a land bridge to Central America," explained Pirie. Cremastosperma species, for example, were able to spread into what is today the Amazon basin and diversify, once the wetlands had silted up due to the deposition of material from the rising Andes.

One way in which diversification can be stimulated is by migration into a new ecosystem while another is adaptation to new conditions. "Natural changes over longer periods provide plants with a chance to adapt," added Pirie. On the other hand, rapid changes, such as those that have occurred in the recent past, do not give plants sufficient time to evolve.

Cremastosperma leiophyllum, Bolivia [Credit: Lars W. Chatrou]

While the development of the two genera in line with geological conditions could be said to be more or less as might be expected, the biologists did find one clear difference between them. Although their distribution patterns mostly overlap, Cremastosperma species and Mosannona species to some extent dispersed along differing routes. In the case of Cremastosperma, colonization of an area in what is now Guyana began from north-western South America at a time before the last parts of the Andes developed and could form a barrier. Mosannona, on the other hand, began to spread here at a far later date from its base in the Amazon basin.

Taxonomic update to include five new species

Dr. Michael Pirie will be continuing his research work in 2018 with the aid of a grant from the Heisenberg Program of the German Research Foundation (DFG). This will also involve publication of an extensive monograph in which a total of 34 Cremastosperma species will be described, including five new species that Pirie and his colleagues have recently discovered.

The study is published on Royal Society Open Science.

Source: Universitat Mainz [Febraury 26, 2018]

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Laser technology takes Maya archaeologists where they've never gone before

With the help of airborne laser mapping technology, a team of archaeologists, led by University of Arizona professor Takeshi Inomata, is exploring on a larger scale than ever before the history and spread of settlement at the ancient Maya site of Ceibal in Guatemala.

On the left is an aerial image of an area of Ceibal. On the right is the same area, as mapped by LiDAR
[Credit: Takeshi Inomata/University of Arizona]

In a new paper published in the journal PLOS ONE, Inomata and his colleagues explain how they commissioned the use of LiDAR, or light detection and ranging, technology to map a significantly larger area of Ceibal than ever before recorded.

LiDAR provides highly accurate, detailed 3-D maps of ground surface topography. Over the course of just a few days at Ceibal, a small airplane, equipped with lasers powerful enough to peer through the dense jungle canopy, soared above the site, mapping -- with a less than 10-centimeter margin of error -- the shape, size and location of ancient Maya pyramids, platforms, ceremonial centers, roads, water reservoirs and other structures previously undocumented by archaeologists.

The resulting map covers 470 square kilometers that would have been extremely challenging for archaeologists to reach on foot, and includes the locations of more than 15,000 ancient Maya architectural remains. Previously, archaeologists had information on only about 8 square kilometers and fewer than 1,000 structures in the area.

"This kind of understanding was really unthinkable some years ago, and now suddenly we can have all these data," Inomata said. "The scale is completely different."

Inomata and his colleagues used the LiDAR data to reconstruct a timeline of growth and change at Ceibal, building upon what they already knew from previous excavations about when different styles of structures appeared between about 1,000 B.C. and A.D. 950.

At the top is an aerial image of a reconstructed temple at Ceibal. At the bottom is the same area, mapped by thousands
of individual laser points [Credit: Takeshi Inomata/University of Arizona]

"What we tried to do here was to set up a systematic method of analyzing this LiDAR data over a wide area, and then translate it into an interpretation of temporal sequences and social change," said Inomata, a professor and Agnese Nelms Haury Chair in Environment and Social Justice in the UA School of Anthropology.

Combining LiDAR and excavation data then allowed the archaeologists to reconstruct settlement patterns over a long period of time.

"Looking at the LiDAR image, you can see the specific types of architecture -- pyramids, long structures -- and we know from our excavations what time period they're from. So just looking at the shape of the structures, we can see this network of communities and ceremonial centers from specific periods," Inomata said.

Lasers Let Humans Explore Challenging Terrain

Mapping an archaeological site in a densely vegetated area such as the Guatemalan jungle is a daunting task -- one traditionally done on foot. Because of the challenging terrain, only about 1.9 square kilometers of Ceibal had been completely mapped previously -- by Harvard archaeologists in the 1960s -- while about 6 more kilometers were surveyed with less detail.

It was in that small area that Inomata and his colleagues have been conducting archaeological excavations for the last 13 years.

UA archaeologist Takeshi Inomata during an excavation at Ceibal
[Credit: Takeshi Inomata/University of Arizona]

Since joining the growing number of researchers who have used the LiDAR surveying method to help with interpretation of archaeological sites, Inomata and his team have gained access to data that would have been nearly impossible to obtain through on-foot surveys. The LiDAR survey, which was conducted by the University of Houston's National Center for Airborne Laser Mapping, even found a few things that the original on-the-ground mapping done in the 1960s missed.

"The maps that Harvard made were incredibly accurate, considering they were all ground survey, but with LiDAR we found a lot more buildings than were on the map previously, and their locations are very accurate," said paper co-author Melissa Burham, a UA graduate student in anthropology.

As a growing number of researchers turn to the LiDAR surveying method to aid in the interpretation of archaeological sites, Inomata and his team hope their colleagues in the field may follow a similar process to what they used at Ceibal, which they plan to apply again in their regional survey in the state of Tabasco in Mexico, where they will begin work in February.

"In archaeology, excavation is always important, but you can't excavate everything, so you look for patterns on a smaller scale that you can extrapolate over a larger region," said Burham, who co-authored the paper along with Inomata, UA anthropology professor Daniela Triadan and researchers from Guatemala and Japan. "That's really what this paper aims to do. This can help other people understand growth at other Maya centers and help with dating methods."

Source: University of Arizona [February 21, 2018]

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LiDAR scanning reveals sprawling ancient metropolis in Mexico

Using sophisticated laser surveying technology, archaeologists have discovered a “lost city” in western Mexico that may have been home to as many buildings as Manhattan.

One of Angamuco’s ‘neighbourhoods’, revealed using light detection
and ranging scanning [Credit: C Fisher]

A team of researchers, led by Colorado State University archaeologist Chris Fisher, was able to use LiDAR technology to determine that the ancient city of Angamuco had around 40,000 buildings spread over an area of 10 square miles. That’s roughly about the same number of buildings as Manhattan, but on a much smaller plot of land as the New York City borough is 22 square miles.

Fisher told Fox News that without the use of the LiDAR technology figuring out the number of buildings at the Angamuco site might have taken his entire career. But with just two flights using LiDAR, one in conjunction with the National Center for Airborne Laser Mapping, his team was able to determine the size of the city and also find previously uncovered structures.

“I almost started crying,” Fisher said of seeing the LiDAR images of the city for the first time. “It was incredible to see these buildings in such clear definition.”

LiDAR uses a laser to measure distances to the Earth’s surface and can prove extremely valuable to study what is hidden in heavily forested areas. LiDAR is also used extensively in other applications, including autonomous cars where it allows vehicles to have a continuous 360 degrees view.

The city of Angamuco, which occupies a lava field on the eastern edge
of the Lake Pátzcuaro basin [Credit: C Fisher]

Fisher is quick to point out that Angamuco is not technically a “lost city” as it was first discovered in 2007 and his team has been conducting research there since 2009.

“We don’t call it a lost city,” he said. “We call it an undocumented city.”

Despite this, the archaeologist is not downplaying the impact the discovery could have his field of research and science overall.

“This is another demonstration that this is the 21st Century and we still know so little about our world and there is still so much to be discovered,” Fisher said. “This city is in a highly trafficked area of Mexico and nobody knew that it was right there the whole time.”

Angamuco was built around 900 AD by the Purépecha, a civilization that was a rival of the Aztec empire in central Mexico, and reached its peak population of around 100,000 residents somewhere between 1000 and 1350 AD.

Examples of sunken plazas, patios, and related features in Angamuco
[Credit: C Fisher]

"There are roughly a similar number of buildings but the size of the ancient buildings is obviously much smaller so the population density or number of people involved is not comparable," Fisher added.

At its height it was the largest city in western Mexico and much larger than the Purépecha imperial capital of Tzintzuntzan, although most likely not as densely populated.

“[Angamuco] was the real core of the empire,” Fisher said.

The city was built over a lava flow and has been hidden for centuries due to the dense forest and rugged terrain that surrounds it.

Colorado State University archeologist Chris Fisher has used the laser mapping technique
 in Mexico and Honduras [Credit: Colorado State University]

Researchers have found a number of interesting features that make Angamuco different from other pre-Colombian cities in Mexico. The majority of the city’s temples and open plazas sit in eight places around the edges of Angamuco, rather than the center, which is more common.

The city also had numerous gardens and the Purépecha were known for their ability to divert water flow to grow crops and cultivate green spaces.

“We can learn a lot from the Purépecha in regards to modern city planning,” Fisher noted. “They had green spaces, they did things with water that we’re still trying to implement. These guys had it all figured out.”

Radio carbon dating of artifacts discovered at the site suggests that the city went through two separate periods of expansion before its eventual collapse preceding the European arrival in the Americas in the 15th Century.

Author: Andrew O'Reilly | Source: Fox News [February 20, 2018]

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Ancient human remains, Ice Age animal bones found in giant Mexican cave

Archaeologists exploring the word’s biggest flooded cave in Mexico have discovered ancient human remains at least 9,000 years old and the bones of animals who roamed the earth during the last Ice Age.

Divers from the Great Mayan Aquifer project (L) exploring the Sac Actun underwater cave system, where Mayan and 
Pleistocene bones and cultural artifacts have been found submerged, near Tulum, Mexico [Credit: GAM/INAH]

A group of divers recently connected two underwater caverns in eastern Mexico to reveal what is believed to be the biggest flooded cave on the planet, a discovery that could help shed new light on the ancient Maya civilization.

The Yucatan peninsula is studded with monumental relics of the Maya people, whose cities drew upon an extensive network of sinkholes linked to subterranean waters known as cenotes.

Remains of a mask in the Sac Actun underwater cave in Mexico's Quintana Roo state 
[Credit: GAM/INAH]

Researchers say they found 248 cenotes at the 347-km (216-mile) cave system known as Sac Actun, near the beach resort of Tulum. Of the 200 archaeological sites they have discovered there, around 140 are Mayan.

Some cenotes acquired particular religious significance to the Maya, whose descendants continue to inhabit the region.

Remains of a Pleistocene bear from 2.5 million years ago, in the Sac Actun underwater cave 
in Quintana Roo state, Mexico [Credit: GAM/INAH]

Apart from human remains, they also found bones of giant sloths, ancient elephants and extinct bears from the Pleistocene period, Mexico’s Culture Ministry said in a statement.

The cave’s discovery has rocked the archaeological world.

Researchers from Mexico's National Institute of Anthropology and History (INAH), say they have discovered 
200 archaeological sites in the cave system [Credit: GAM/INAH]

“I think it’s overwhelming. Without a doubt it’s the most important underwater archaeological site in the world,” said Guillermo de Anda, researcher at Mexico’s National Anthropology and History Institute (INAH).

De Anda is also director of the Gran Acuifero Maya (GAM), a project dedicated to the study and preservation of the subterranean waters of the Yucatan peninsula.

According to the INAH, water levels rose 100 meters at the end of the Ice Age, flooding the cave system and leading to “ideal conditions for the preservation of the remains of extinct megafauna from the Pleistocene.”

The Pleistocene geological epoch, the most recent Ice Age, began 2.6 million years ago and ended around 11,700 years ago.

Source: Reuters [February 20, 2018]

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Acoustic imaging reveals hidden features of megathrust fault off Costa Rica

Geophysicists have obtained detailed three-dimensional images of a dangerous megathrust fault west of Costa Rica where two plates of the Earth's crust collide. The images reveal features of the fault surface, including long grooves or corrugations, that may determine how the fault will slip in an earthquake.

Perspective view of the shallow megathrust looking seaward towards the trench; the frontal prism has been cut away.
The color scales indicate depth below seafloor, and grey denotes the seafloor [Credit: Edwards et al., 2018]

The study, published in Nature Geoscience, focused on the Costa Rica subduction zone where the Cocos plate slowly dives beneath the overriding Caribbean plate. Variations in texture seen in different portions of the fault surface may explain why Costa Rica has complex, patchy earthquakes that do not seem to slip to shallow depths, unlike some other megathrust faults, said first author Joel Edwards, a Ph.D. candidate in Earth and planetary sciences at UC Santa Cruz.

"Our new imagery shows large variability in the conditions along the megathrust, which may be linked to a number of earthquake phenomena we observe in the region," Edwards said.

Megathrusts, the huge continuous faults found in subduction zones, are responsible for Earth's largest earthquakes. Megathrust earthquakes can generate destructive tsunamis and are a serious hazard facing communities located near subduction zones. Understanding the mechanisms at work along these faults is vital for disaster management around the globe.

Edwards worked with a team of geophysicists at UC Santa Cruz, the U.S. Geological Survey, the University of Texas-Austin, and McGill University to obtain 3-dimensional imagery of the fault interface using cutting-edge acoustic imaging technology. The long grooves, or corrugations, they observed along the interface are similar in size to those found along the base of fast-flowing glaciers and along some ocean ridges. The images also showed varying amounts of smoothness and corrugations on different portions of the fault.

"This study produced an unprecedented view of the megathrust. Such 3-D information is critical to our ability to better understand megathrust faults and associated hazards worldwide," said coauthor Jared Kluesner, a geophysicist at the USGS in Santa Cruz.

The acoustic dataset was collected in spring 2011 on the academic research vessel Marcus G. Langseth. The ship towed an array of underwater microphones and sound sources behind it as it made a series of overlapping loops over the area of the fault. The data were processed over the next 2 years and have since been used in a number of studies looking at different aspects of the subduction zone process. This particular study focused on the interface between the sliding plates, which serves as a record of slip and slip processes.

"The 3-D site selection was really good and the resulting acoustic dataset showed extraordinary detail," said Edwards, noting that coauthor Emily Brodsky, professor of Earth and planetary sciences, was the first to recognize the corrugations. Such features had been observed in exposed faults on land, but never before in a fault deep beneath the surface.

"I had an early rendition of the interface that vaguely showed long grooves, and during my qualifying exam, Brodsky saw them and asked, 'are those corrugations!?' I didn't know, but I knew they were real features. Slip-derived corrugations was a really neat hypothesis, and we dug into it after that," he said.

The area in this study had long been a target for drilling into the megathrust by the Costa Rica Seismic Project (CRISP). Coauthor Eli Silver, professor emeritus of Earth and planetary sciences at UC Santa Cruz, and others in the CRISP program decided to pursue a 3-D seismic study, which must precede any deep drilling, and the project was funded by the National Science Foundation in 2009. "At present, two drilling expeditions have been accomplished with shallower targets, and, though not yet scheduled, we are hopeful that the deep drilling will occur," Silver said.

Researchers hope to use similar imaging techniques on other subduction zones, such as the Cascadia margin along the northern U.S. west coast, where there is a long history of large megathrust earthquakes and related tsunamis. "Conducting this type of 3-D study along the Cascadia margin could provide us with key information along the megathrust, a plate boundary that poses a substantial hazard risk to the U.S. west coast," Kluesner said.

Author: Tim Stephens | Source: University of California - Santa Cruz [February 12, 2018]

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