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Ground Beetles Shed Light on the Environmental History of High Mountain Regions

Biologist at Rostock University Describes the Species Pterostichus leica

With over 35,000 known species, ground beetles – or Carabidae – are among the most speciose groups of animals in the world. Biologist Dr. Joachim Schmidt devotes his entire scientific work to the research of these frequently very small beetles, their ecology, distribution and phylogeny. He is particularly interested in the ground beetles of high mountain regions. These mostly wingless species have extremely limited dispersal ability and therefore colonize only small areas. This makes them valuable objects for researching the environmental history of high mountain regions. First, however, the biologist has to identify the countless species – such as Pterostichus leica, the Leica ground beetle from the Eastern Himalayas. The Leica M205 C stereo microscope with motorized focus drive, assembled on the TL5000 Ergo transmitted light base, the Leica DFC450 digital camera and the Leica LAS Montage software help him to study the new species in depth and to provide accurate and detailed documentation for scientific purposes. Using these instruments, he saves an enormous amount of time compared with the time he used to have to spend on the elaborate drawings in the species descriptions.


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Comprehensive mapping of biodiversity

Since 1989, Joachim Schmidt has traveled at least once a year to various high mountains in Europe, Asia and Africa, particularly to the Himalayas: “I’ve been there at least 25 times now. And yet I don’t think I know even half of this magnificent mountain system. I’m trying to systematically record the ground beetle fauna of all the altitudinal belts of the Himalayas in all accessible parts of the mountain. Every time I go I examine a different region. I’m also supported by my colleagues from museums and collections all over the world who send me beetle material for processing,” the biologist relates. He aims to map the horizontal and vertical distribution of all species and exactly record their links with the different habitats. On the basis of this data and additional molecular genetic analyses he then attempts to reconstruct the history of the distribution of the various species and evolutionary lineages in the course of the development of the mountains. But first he has to find the countless species, and to do this, he has to employ different methods. Many ground beetles can be found during the daytime under stones and dead wood. Particularly small species that live in leaf litter and moss are collected in a special bag sifter. Other species live on trees and bushes. Joachim Schmidt fetches these down with a beating tray. Ground beetles that are hidden in rock crevices during the day can be detected at night with a torch. In his mapping work, the biologist makes an exact note of the height above sea level and the habitat in which each of the species has been found, from the subtropical valley zone up through the various montane levels to the alpine belt.

“As a result of my own research trips and my work on museum material, I discover up to 50 new species of ground beetle every year,” Joachim Schmidt reports. In the high mountain ranges of Southern Asia and Africa there is a tremendous biological diversity that has not been adequately explored so far.” Meanwhile, the biologist’s study contains cabinets full of ground beetle species awaiting identification. Some of them have been sent to him on loan by various museums and collections; others he has discovered on his own research expeditions. “There are hundreds of new species in those cabinets, but they are not of interest to scientists yet because nobody else knows about them. First I have to describe them in detail and publish the results of my species diagnoses in the relevant journals,” says Joachim Schmidt. “It used to take me days to draw an illustration plate of the insects, some of which only measure a few millimeters. With the powerful optics, many different illumination options and LAS Montage software of the Leica M205 C Stereo Microscope I can produce high-quality documentation of the diagnostic features of the various species and make them available for specialist use. The possibilities of stack photography are a blessing for me. I save an incredible amount of time – that’s one of the reasons I chose the name Pterostichus leica.“

Beetle genitals change considerably in the course of evolution

The biologist mostly distinguishes different groups of ground beetle species on the basis of external features such as the shape and proportion of the various parts of the body and their surface structures, sensory organ features, etc. If he wants to distinguish closely related species within a group, he also has to look at the genital organs. “Male genitals in particular tend to undergo major morphological changes in the course of evolution. This probably serves a greater sexual differentiation between closely related species when their distributional areas overlap or are immediately adjacent.  If individuals of different species were able to mate, they would produce less viable offspring or none at all, and any acquired adaptations would be lost – a major disadvantage as far as fitness is concerned. Differently developed genitals in important parts limit the risk of mismatches,“ explains Joachim Schmidt.

The scientist therefore examines the genital organs of ground beetles as key features for differentiating the various species. Like the habitual features, genital features therefore have to be accurately documented in the description of new species and the revision of species groups. Here again, the Leica M205 C is a great help for Joachim Schmidt. Thanks to the excellent resolution, tiny genitals are sharply imaged even at high magnifications and ideally illuminated with the TL5000 Ergo transmitted light base.  He can therefore obtain outstanding imaging results with the Leica DFC450 digital camera and the Leica LAS Montage software even in this extreme range. This saves the scientist an enormous amount of time when documenting key features for the description and differential diagnosis of the different species.  

Hard physical labor

For field work, Joachim Schmidt usually flies to his high mountain destinations at the beginning of the regions’ rain seasons, as this is the beginning of the active period of the imagines for most ground beetle species. Apart from the many treks on foot in the mountains, hard physical labor awaits him there. For example, he has to turn heavy rocks over to look for beetles in the cavities of the soil and the rock debris. There are also many cubic meters of ground litter to be sieved. “Every time I go to the Himalayas I lose about ten kilograms of weight,” the biologist remarks. Schmidt’s work in the Himalayas is not only hampered by the rough monsoon weather, but also be the countless leeches that feel very much at home in the wet environment. “But it’s the warm and humid air masses in the Himalayas during the summer monsoon that make it possible to work in the alpine and subnival belts at all, as they rise to high altitudes and melt the snow. The activity period of the ground beetles here is restricted to this quite short period in the wettest but warmest part of the year.”

For Joachim Schmidt, ground beetles are biological tools or bio-proxies that help him understand the environmental history of high mountain regions. Fortunately, the species are closely linked with certain microclimate factors such as soil moisture and temperature. A particularly valuable property of this beetle group is the high degree of endemism in the high-montane and alpine altitude belts, especially in the mountains of medium and low latitudes. Whole swarms of species live in the Himalayas, on the Tibetan Plateau and in the Ethiopian Highlands whose habitats are restricted to extremely narrow geographic areas. “As they are wingless and crawl about in the ground’s cavity system, they are hardly able to disperse and therefore sometimes colonize tiny areas of only a few square kilometers,” the biologist reports. “In the course of evolution, the populations of various parts of the mountain system have developed into independent species because of the countless dispersal barriers in high-altitude environments. Some are even only endemic to a single mountain range or in a small tributary valley system.“

Pterostichus (Pseudethira) leica

An example of a local endemic ground beetle species, which he described in 2012, is Pterostichus (Pseudethira) leica, which is only found in one single mountain range in the Eastern Himalayas. All the other known species and sub-species of the Pterostichus subgenus Pseudethira, of which there are about 80, are local endemic in various parts of the High Himalayas. Once the biologist has compiled phylogenetic trees of these species groups applying morphological feature analysis and molecular-genetic methods, he can use the information in them to reconstruct the distribution history of this fauna group since its origination. “Ground beetles are a good paleoenvironmental proxy because they enable me to look back at the history of the mountain,” Schmidt relates. “If I exactly know the requirements of all the species of an endemic lineage in a specific mountain system and their horizontal distribution, and if the relationships between each species are sufficiently known, I can draw conclusions on the uplift and climate history in this mountain system.“

Ground beetles give a clue to temperatures in the last Ice Age

Besides their limited dispersal ability, high-mountain ground beetles are extremely rich in live forms and adapted to various mountain habitats. In his examination of the many different species groups, the biologist looks for recurring patterns. “From these patterns I draw conclusions that are of informative value to geomorphologists, geologists and climatologists,” Joachim Schmidt explains. “In the climate history of High Asia, for instance, the theory still exists today that Tibet was completely covered by a gigantic ice sheet (Tibetan ice sheet) up to two kilometers thick. I was able to disprove this theory by detecting ground beetles endemic to micro areas in Central Tibet.” With his research the biologist was also able to prove that the maximum temperature depression during the last Ice Age was much slighter than generally assumed – in fact only three to four Kelvin in southern Asia. This is the only explanation for the extant distribution of the ground beetle species in the Transhimalaya.

The biologist still has a lot of work to do in future. Besides his research expeditions and descriptions of the many new species already awaiting scientific analysis in his collector cabinets, Joachim Schmidt also examines ground beetle fossils. “Private collections in particular contain huge fossil treasures in the form of inclusions in Baltic amber that have hardly been scientifically explored yet,” says Schmidt. “If I succeed in clearly and systematically classifying a fossil, I can determine the minimum age of its evolutionary lineage. And if I manage to do that for various branches of a phylogenetic tree, I can date the evolutionary events with sufficient accuracy. As the evolution of the high-mountain ground beetle is directly linked to the uplift und environmental history of the particular high mountain range, I can use this knowledge for dating specific orogenic events. Top-quality optics are important for fossil analysis, too.” Another of his plans for the future is to examine amber fossils with the aid of x-ray microtomography. He hopes this will enable him to obtain information on the morphology of parts of the bodies of the beetles trapped in the amber that are inaccessible for light-optic investigation, such as the genital organs, which are of key significance for the exact determination of the systematic position of the particular fossil.