Leaf-mining insects destroyed with the dinosaurs, others quickly appeared

After the asteroid impact at the end of the Cretaceous period that triggered the dinosaurs’ extinction and ushered in the Paleocene, leaf-mining insects in the western United States completely disappeared. Only a million years later, at Mexican Hat, in southeastern Montana, fossil leaves show diverse leaf-mining traces from new insects that were not present during the Cretaceous, according to paleontologists.”Our results indicate both that leaf-mining diversity at Mexican Hat is even higher than previously recognized, and equally importantly, that none of the Mexican Hat mines can be linked back to the local Cretaceous mining fauna,” said Michael Donovan, graduate student in geosciences, Penn State.Insects that eat leaves produce very specific types of damage. One type is from leaf miners — insect larvae that live in the leaves and tunnel for food, leaving distinctive feeding paths and patterns of droppings.Donovan, Peter Wilf, professor of geosciences, Penn State, and colleagues looked at 1,073 leaf fossils from Mexican Hat for mines. They compared these with more than 9,000 leaves from the end of the Cretaceous, 65 million years ago, from the Hell Creek Formation in southwestern North Dakota, and with more than 9,000 Paleocene leaves from the Fort Union Formation in North Dakota, Montana and Wyoming. The researchers present their results in today’s (July 24) issue of PLOS ONE.”We decided to focus on leaf miners because they are typically host specific, feeding on only a few plant species each,” said Donovan. “Each miner also leaves an identifiable mining pattern.”The researchers found nine different mine-damage types at Mexican Hat attributable to the larvae of moths, wasps and flies, and six of these damage types were unique to the site.The researchers were unsure whether the high diversity of leaf miners at Mexican Hat compared to other early Paleocene sites, where there is little or no leaf mining, was caused by insects that survived the extinction event in refugia — areas where organisms persist during adverse conditions — or were due to range expansions of insects from somewhere else during the early Paleocene.However, with further study, the researchers found no evidence of the survival of any leaf miners over the Cretaceous-Paleocene boundary, suggesting an even more total collapse of terrestrial food webs than has been recognized previously.”These results show that the high insect damage diversity at Mexican Hat represents an influx of novel insect herbivores during the early Paleocene and not a refugium for Cretaceous leaf miners,” said Wilf. “The new herbivores included a startling diversity for any time period, and especially for the classic post-extinction disaster interval.”Insect extinction across the Cretaceous-Paleocene boundary may have been directly caused by catastrophic conditions after the asteroid impact and by the disappearance of host plant species. While insect herbivores constantly need leaves to survive, plants can remain dormant as seeds in the ground until more auspicious circumstances occur.The low-diversity flora at Mexican Hat is typical for the area in the early Paleocene, so what caused the high insect damage diversity?Insect outbreaks are associated with a rapid population increase of a single insect species, so the high diversity of mining damage seen in the Mexican Hat fossils makes the possibility of an outbreak improbable.The researchers hypothesized that the leaf miners that are seen in the Mexican Hat fossils appeared in that area because of a transient warming event, a number of which occurred during the early Paleocene.”Previous studies have shown a correlation between temperature and insect damage diversity in the fossil record, possibly caused by evolutionary radiations or range shifts in response to a warmer climate,” said Donovan. “Current evidence suggests that insect herbivore extinction decreased with increasing distance from the asteroid impact site in Mexico, so pools of surviving insects would have existed elsewhere that could have provided a source for the insect influx that we observed at Mexican Hat.”Story Source:The above story is based on materials provided by Penn State. The original article was written by A’ndrea Eluse Messer. …

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Monarch butterfly numbers could be at historic lows this year, study suggests

Monarch butterflies may be named for their large size and majestic beauty, but once again their numbers are anything but king-sized — in fact, 2014 may go down as one of the worst years ever for the colorful insects, says a Texas A&M Monarch watcher who is proposing a national effort to help feed Monarchs.Craig Wilson, a senior research associate in the Center for Mathematics and Science Education and a longtime butterfly enthusiast, says reports coming from Mexico where the Monarchs have their overwintering grounds show their numbers are significantly down yet again — so much so that this year might be one of the lowest yet for the butterfly.It’s been a disturbing trend that has been going for most of the past decade, he points out. This year, Monarchs face a triple whammy: a lingering drought, unusually cold winter temperatures and lack of milkweed, their primary food source.Citing figures from the Mexican government and the World Wildlife Fund, Wilson says, “In 1996, the Monarch breeding grounds in Mexico covered about 45 acres, and so far this year, it looks like only about 1.65 acres. That means fewer Monarchs will likely reach Texas to lay eggs, perhaps the lowest numbers ever of returning butterflies.”Wilson says the colder-than-usual winter, which set record lows in many parts of Texas and even Mexico, has had a chilling effect on Monarchs.”Unfortunately, the harsh and lingering cold conditions mean that the milkweed plants that Monarch caterpillars must have to live have yet to start growing, and these are the only plants on which they can lay eggs to provide food for their caterpillars,” he adds.Wilson says that last fall, the number of Monarchs that were netted and tagged in the College Station area was one-fifth the number tagged in 2012.The dry conditions during the past decade and changing farming practices are hampering the growth of milkweed, the only type of plant the Monarch caterpillars will digest as the multiple generational migration heads north.Texas also has had dozens of wildfires in the past few years that have hampered milkweed growth, and even though there are more than 30 types of milkweed in the state, the numbers are not there to sustain the Monarchs as they start their 2,000-mile migration trip to Canada. Increased use of pesticides is also adversely affecting milkweed production in a huge way, he notes.”The severe drought in Texas and much of the Southwest continues to wreak havoc with the number of Monarchs,” Wilson explains, adding that the wintering sites in the Mexican state of Michoacn are at near-historic lows.”The conditions have been dry both here and in Mexico in recent years. It takes four generations of the insects to make it all of the way up to Canada, and because of lack of milkweed along the way, a lot of them just don’t make it.”But if people want to help, they can pick up some milkweed plants right now at local farmer’s cooperative stores,” he says, “and this would be a small but helpful step to aid in their migration journey and to raise awareness of the plight.”Wilson says there has to be a national effort to save Monarchs or their declining numbers will reach the critical stage.”We need a national priority of planting milkweed to assure that this magical migration of Monarchs will continue for future generations,” he says.”If we could get several states to collaborate, we might be able to promote a program where the north-south interstates were planted with milkweed, such as Lady Bird Johnson’s program to plant native seeds along Texas highways 35-40 years ago. This would provide a ‘feeding’ corridor right up to Canada for the Monarchs.”Wilson is currently adding a variety of milkweed plants to the existing Cynthia Woods Mitchell Garden on the Texas A&M campus. He recommends the following sites for Monarch followers: Journey North, Texas Monarch Watch and Monarch Watch.Story Source:The above story is based on materials provided by Texas A&M University. Note: Materials may be edited for content and length.

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Dry future climate could reduce orchid bee habitat

During Pleistocene era climate changes, neotropical orchid bees that relied on year-round warmth and wet weather found their habitats reduced by 30 to 50 percent, according to a Cornell University study that used computer models and genetic data to understand bee distributions during past climate changes.In previous studies, researchers have tracked male and female orchid bees and found that while females stay near their nests, male orchid bees travel, with one study concluding they roam as far as 7 kilometers per day. These past findings, corroborated by genetic data in the current study, reveal that males are more mobile than females.The study, published online in the journal Molecular Ecology, has important implications for future climate changes.”The dataset tells us that if the tendency is to have lower precipitation in combination with deforestation, the suitable habitat for the bees is going to be reduced,” said Margarita Lpez-Uribe, the paper’s first author and a graduate student at Cornell.The good news is that since male orchid bees habitually travel far, they can keep bee populations connected and healthy.”The males are mediating genetic exchange among populations, maintaining connectivity in spite of fragmentation of habitats,” said Lpez-Uribe. “This is a possible mechanism bees could use to ameliorate the negative impacts of population isolation resulting from future climate changes and deforestation.”By looking at current climate and bee distributions, Lpez-Uribe and colleagues assessed parameters of climate conditions that each of three bee species within the genus Eulaema could tolerate physiologically, including temperature and precipitation variability. She found that one of the three species, Eulaema cingulata, was three times more tolerant to a variety of climatic conditions.By proceeding with the caveat that physiological tolerance has remained constant — species tend to be evolutionarily conservative about shifting their niches — the researchers used computer models to simulate past bee distributions based on climate conditions in the Pleistocene. The results showed that in the past, during periods when the neotropics had lowered precipitation, each species experienced significant reduction in suitable habitat, with E. cingulata maintaining the largest geographical ranges.Climate and ecological niche computer model simulations were closely matched by genetic data of the two less-tolerant orchid bee species. The genetic data included mitochondrial markers, which are only inherited from females, and nuclear markers, which come from males and females. The mitochondrial DNA showed that individual bees in one geographic area were more closely related to each other than to bees from other areas. The findings suggest the maternal lines of these bees remained in the area and shared the same pools of DNA over time. But the bi-parental nuclear DNA showed more variation between individuals within an area, offering evidence that males traveled and shared their DNA with other regional groups.Orchid bees live in the neotropics, an ecozone that includes part of South and Central America, the Mexican lowlands and the Caribbean islands. …

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Maya decapitated and dismembered their enemies

Sep. 10, 2013 — Researchers of the Department of Anthropology of the Americas at the University of Bonn have discovered a mass grave in an artificial cave in the historical Maya city of Uxul (Mexico). Marks on the bones indicate that the individuals buried in the cave were decapitated and dismembered around 1,400 years ago. The scientists assume that the victims were either prisoners of war or nobles from Uxul itself.For the last five years, archaeologists of the department of Anthropology of the Americas of the University of Bonn have been excavating in the historical Maya city of Uxul in Campeche (Mexico) with the aim of researching the origins and the collapse of regional states in the Maya lowlands. The project headed by Prof. Dr. Nikolai Grube and Dr. Kai Delvendahl from the University of Bonn, as well as Dr. Antonio Benavides from the Mexican National Institute of Anthropology and History, which is funded by the Deutsche Forschungsgemeinschaft (DFG) has now made a sensational find: they have uncovered the skeletons of 24 people in an approximately 32 square meter artificial cave that had formerly been used as a water reservoir.”Aside from the large number of interred individuals, it already became apparent during the excavation that the skeletons were no longer in their original anatomical articulation,” says the archaeologist Nicolaus Seefeld, who studied the sophisticated water supply system of Uxul for his doctoral thesis and discovered the mass grave. All of the skulls were lying scattered around the interior of the cave, in no relation to the rest of the bodies. …

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Asian origins of native American dogs confirmed

July 10, 2013 — Once thought to have been extinct, native American dogs are on the contrary thriving, according to a recent study that links these breeds to ancient Asia.The arrival of Europeans in the Americas has generally been assumed to have led to the extinction of indigenous dog breeds; but a comprehensive genetic study has found that the original population of native American dogs has been almost completely preserved, says Peter Savolainen, a researcher in evolutionary genetics at KTH Royal Institute of Technology in Stockholm.In fact, American dog breeds trace their ancestry to ancient Asia, Savolainen says. These native breeds have 30 percent or less modern replacement by European dogs, he says.”Our results confirm that American dogs are a remaining part of the indigenous American culture, which underscores the importance of preserving these populations,” he says.Savolainen’s research group, in cooperation with colleagues in Portugal, compared mitochondrial DNA from Asian and European dogs, ancient American archaeological samples, and American dog breeds, including Chihuahuas, Peruvian hairless dogs and Arctic sled dogs.They traced the American dogs’ ancestry back to East Asian and Siberian dogs, and also found direct relations between ancient American dogs and modern breeds.”It was especially exciting to find that the Mexican breed, Chihuahua, shared a DNA type uniquely with Mexican pre-Columbian samples,” he says. “This gives conclusive evidence for the Mexican ancestry of the Chihuahua.”The team also analysed stray dogs, confirming them generally to be runaway European dogs; but in Mexico and Bolivia they identified populations with high proportions of indigenous ancestry.Savolainen says that the data also suggests that the Carolina Dog, a stray dog population in the U.S., may have an indigenous American origin.Savolainen works at the Science for Life Laboratory (SciLifeLab www.scilifelab.se), a collaboration involving KTH Royal Institute of Technology, Stockholm University, the Karolinska Institutet and Uppsala University.

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