To paraphrase Larry Agenbroad, the former director of the Mammoth Site in Hot Springs, SD, Mammoth taxonomy is confused, and confusing. And it has been this way for a long while. Henry Fairfield Osborn, a giant of North American vertebrate paleontology dedicated decades of his life (and that of his assistants) to the production of a 1600-page, 2-volume, tome describing the Proboscidea, published posthumously in 1942. Through a specimen-by-specimen analysis, he described 16 species of North American mammoths across 3 genera. Since that time, North American mammoth species have undergone significant pruning, with most paleontologists recognizing 4-5 species across North America: M. meridionalis (Southern Mammoth), M. columbi (Columbian Mammoth), M. primigenius (Woolly Mammoth), and M. exilis (Channel Island Pygmy Mammoth). A fifth species, M. jeffersonii (Jeffersonian Mammoth) was considered an intermediate form showing characteristics of both Columbian and Woolly mammoths.
The story went something like this…Around 1.5 million years ago, the Southern Mammoth (M. meridionalis) emigrated to North America, settling along the west coast. Shortly after, the Eurasian Steppe Mammoth (M. trogontherii) joined its trunked brethren. Both were found in early deposits in the Anza Borrego Desert of southern California (and potentially the Great Plains and Florida). The Southern Mammoth died out or was swallowed up by the more successful Columbian forms, which radiated throughout most of North America. The BIG mammoths that fill western museums, like Archie at the University of Nebraska and the Angus Mammoth at Denver were initially considered to be too big to be run-of-the-mill Columbian mammoths and were anointed “Imperial” mammoths. Woollies migrated down the front of the continental ice sheets late in the game, during the Wisconsin glaciation sometime in the last 100 thousand years. Jeffersonian mammoths were the love-children of Woolly and Columbian mammoths. And the Island Pygmies were early Columbian mammoths that swam the channel or wandered across a land bridge.
This was a great story. It had action and explanation. And it was the framework that most museums used to explain their monstrous Mammuthus mounts (or miniscule mounts, in the case of the Pygmy Mammoth on display at the Santa Barbara Museum of Natural History). But two papers in the last 6 months have shown that the reality is actually much more complicated…and interesting.
The first paper was a study by Adrian Lister and Andrei Sher. There are few scientists who have seen as many mammoths as Lister (who literally wrote the book on the subject). In a project that spanned decades, Lister and Sher visited many North American collections housing early mammoths. From California to Florida and everywhere in between. They concluded that the earliest mammoths on the continent were, in fact, not M. meridionalis. Rather they were an odd assortment of poorly prepared/reconstructed material, individuals with heavily worn teeth, or simply Columbian mammoths from an early context. The clincher was that they had an excellent sample of Old World Southern Mammoths that didn’t overlap with any of the North American specimens. Any-of-them…
The second paper (Poinar et al. in press) came out this week. A few years ago, we hosted a sharp graduate student from McMaster University (Ontario) who was interested in our midwestern mammoths, Jake Enk. I bought him lunch. We talked at length about messed up mammoth taxonomy. Normal stuff. Ultimately, Jake sampled ~30 teeth for genetic studies (like this one), then moved on to major collections of Mammuthus in Nebraska, Denver, UC-Berkeley, and Santa Barbara. Given the success rate of previous aDNA studies, we expected that one or two of these specimens might actually give us some decent data. To my surprise, Jake was able to extract complete mitochondrial genomes from 67 mammoths from south of the Laurentide ice. An even bigger surprise, was that they were all chips off of the same block. They weren’t even different species.
Well…this was a surprise/not surprise. We had been looking at this issue through the morphology of midwestern mammoth teeth and found that there was a significant amount of overlap between different “species” and shared our data with Jake. The conventional wisdom that Columbian mammoth teeth were distinct from woolly and Jeffersonian mammoth teeth just wasn’t holding up. You could see multiple morphs within a small geographic area–and we had the dates to prove that we weren’t seeing the influx of “new populations” through time. Things seemed to get really complicated in ecotonal areas, like Iowa. During the Last Glacial Maximum Iowa was a transitional landscape between the more open steppic grasslands to the west (“Columbian” mammoth territory) and the forest steppe (think Taiga) of the east (“Jeffersonian” and “Woolly” Mammoth territory). We hit collections at the University of Iowa, Iowa State Historical Society, Putnam Museum (Davenport) and the Sanford Museum (Cherokee) hard, hoping to figure out where one species left off and the other began. We ended up scratching our heads over animals that had jaws that looked like Woolly mammoths, but teeth that were Columbian…or jaws that were Jeffersonian on one side, but Woolly on the other. We found localities like the mammoth bonebed in Mahaska County, that had one jaw that looked like a Columbian mammoth, but two more that were dead ringers for big Woollies. These were exactly the morphological patterns that we might expect if a) Mammoths were a single biological population capable of inter-breeding and producing viable offspring, and 2) the midwestern mammoths were in the middle of the mess, showing characters of both populations.
So do these different “species” of mammoths mean anything? Why bother measuring teeth if all mammoths are the same? After the initial shock wore off I had plenty of time to think about this. As a morphologist, the idea that we are dealing with a single, morphologically variable population is actually…well…kind of liberating. Now we can explore how certain characters may have been selected for in different environments. We can think about functional morphology, broad-scale impacts of landscape/diet on body-size, or the morphological effects of introgressing populations. Before…the pygmy mammoths of California’s Channel Islands were an unrelated off-shoot of my midwestern behemouths, perhaps responding to nutritional stress and landscape changes in very different ways than their mainland cousins. Now, they are just another mammoth population that is using the same set of morphological and genetic tools to deal with the situation at hand. And we can learn from that.
Mammoths are fun to think about, even when we don’t know all of the answers. These papers (and a third that Jeff Saunders and I are hoping to finish up this week) illustrate the importance of retaining natural history collections in museums. A decade ago, there would have been no chance of getting this degree of genetic recovery out of fossil mammoths south of the ice. Even for “traditional” studies of morphology the only way to get sample sizes large enough to say meaningful things about the biogeography of a creature is to rely on the materials collected and accumulated through many generations.
Last week a bunch of the natural science curators here at the Illinois State Museum presented a poster at a small conference (downloadable PDF here). Normally, a conference poster isn’t a big deal or all that unique, but this may be a first. The theme of this year’s conference was “Taking stock before the connection” and was concerned with establishing accurate and relevant ecological baselines as goals for conservation activities. This isn’t the sort of conference you would normally see studies of zooarchaeological specimens or deer paleopathology, but this year we decided it was time to illustrate the relevance of ISM natural history collections to modern conservation biology.
We aren’t the first to do this. Different disciplines, typically considered the more “historic” sciences like archaeology and paleontology, have been working on these issues for at least a decade. In paleontology this approach is called “Conservation Paleobiology”, in archaeology it’s called “Applied Paleozoology”. Both approaches are very similar to the backwards looking “historical ecology” that goes hand in hand with restoration ecology. Practitioners of all these disciplines agree that in order to understand the wide range of variability in modern ecosystems, we need an understanding of processes and patterns that go deeper than the historical record. Let’s face it. The picture of historical ecological patterns we get from early Euro-American explorers or early settlers capture a snapshot in time that is not very representative of the larger picture. By the time these early chroniclers were traipsing across the Midwest and Great Plains, pre-contact ecosystems had already been largely altered or even obliterated. Horses were introduced by the Spanish in the late 1500s and by the 17th century had expanded throughout the western US. By the time fur traders first contacted Native groups in the eastern Great Plains, epidemics of European diseases had already decimated their communities. Before the first settlers built rough cabins in what is today central Illinois, years of warfare and genocide had reduced the human footprint to the point that the vegetation in many parts of the Midwest were released from human utilization and in successional stages. These are just a few examples of large-scale ecological changes brought about by the changes in the human landscape at contact. This begs the question often asked by planners prior to making decisions, what is the ecological baseline that should be the goal for conservation efforts? In many cases, these planners now recognize that there is no single baseline. No single date that we can point to and say, “this is the natural state”. Modern landscapes can be managed to provide basic ecosystem functions, or as one author puts it, “goods and services”. But what were those goods and services in pre-modern ecosystems? Are there metrics that we can use to document BOTH the modern and pre-modern to gauge which management schemes are appropriate? That was what we set out to do with this presentation. We presented five case studies that illustrate possible ways that paleoecological research on natural history collections (i.e., Paleontology, Archaeology, Botany, Zoology) can offer direct advice and specific answers to modern conservation science.
Case Study #1: Niche Characterization of North American Bison (C. Widga, T. Martin, A. Harn)
During the last 10,000 years, bison were a keystone herbivore in grassland ecosystems. They performed vital functions in nutrient cycling, vegetation succession and predator/prey dynamics. Bison were also present east of the Mississippi River in the eastern forests. The earliest record for bison in Illinois is ~8900 BP and sporadic records persist into the historic period (McMillan, 2006). Notable localities include: Anderson and Markman Peat Mines (Whiteside Co., ~3000-8900 BP), Ottawa Silica Co. (LaSalle Co., 4300 BP), and Lonza-Caterpillar (Peoria Co., 2300 BP)(Figure 3). Unfortunately, most historical documents describing bison date to a time period when ecosystems were rapidly changing. For a variety of reasons (e.g., changing human land-use), the historic record of bison is not analogous to the pre-modern baseline. Indeed, historical documents illustrate bison as seasonally mobile large herds, a picture that is completely incongruous with paleoecological patterns. Sub-fossil bison specimens archive valuable paleoecological information on how bison lived in the Midwest.
In habitats dominated by short or mid-grass prairies, the cusps of bison teeth show flat wear by age 5-6 years. This is due to a high silica (i.e., grasses), high grit diet. However, pre-contact bison from the Midwest show a shearing wear pattern in cheek teeth (Figure 2). This pattern is present in herbivores who are browsers or mixed feeders from closed or partially closed habitats (e.g., deer, elk). Stable isotope data also indicate a diet dominated by C3 plants (i.e., shrubs, trees, sedges), despite the prevalence of tallgrass prairie (C4 dominant) in upland habitats (Widga, 2006).
Although large bison assemblages of 100+ animals are present during the early Holocene in the Great Plains, the smaller sizes of the eastern Plains assemblages are consistent with small-scale, temporary social groups that have been documented in modern conservation herds. The maximum herd size for midwestern bison assemblages is ~20 (Simonsen Site, NW Iowa). Other midwestern assemblages in MN, WI, and IL are smaller than this maximum. Females contributed less to overall herd populations in the archaeological assemblages than in modern herds, suggesting that managed sex ratios in the latter are uncommon in prehistoric bison groups (Figure 4). Although there may be economic and safety reasons for maintaining high numbers of females, these sex ratios should not be considered characteristic of natural variability in pre-contact bison herds. Furthermore, many modern herds maintain large juvenile populations (<4 years old), often approaching or exceeding half of the overall herd size. None of the archaeological assemblages contain more than a handful of juveniles.
Bison in the Midwest were ecologically distinct from their counterparts on the Great Plains. The pre-modern bison niche in Illinois can be characterized as small, local herds browsing shrubs and woody vegetation along river valleys.
Case Study #2: Baseline Expectations for the Distribution of Illinois Carnivores (M. Mahoney, E. Grimm)
Mountain lion (Puma concolor), gray wolf (Canis lupus), and American black bear (Ursus americanus) suffered sizeable reductions in distribution over the past 250 years when they were eradicated from much of eastern North America (Whitaker and Hamilton, 1998). All three species were extirpated from Illinois by 1870 (Hoffmeister, 1989). Today, large carnivore populations in many regions are healthy and increasing in size due to a combination of factors including species-specific protections at the state and federal level, protection of habitat, and regulation of hunting.
Two of these three apex predators are occasional migrants into Illinois (Figs. 1 and 2) and the third is likely to appear soon. It is a matter of time before they establish populations in Illinois as they expand from other parts of their ranges. What was the former distribution of these species in Illinois? What habitats are available today? Can we use past distributions to either predict where they might become established or to restore appropriate habitat types?
Historical records provide limited information on the distribution of large carnivores in Illinois as encountered by explorers, trappers, and early settlers and mostly serve to document the last known localities of large carnivores before their extirpation from Illinois in the mid-1800s (Hoffmeister, 1989, Fig. 2). These records have other known weaknesses. For example, mountain lion and bobcat (Lynx rufus) were not reliably distinguished until the early 1800s and wolves and coyotes were often conflated even after wolves were extirpated (Hoffmeister, 1989).
The Neotoma Paleoecology Database is an online resource for fossil and archeological site and sample information. It is a freely searchable compilation of datasets from numerous researchers and institutions. The primary components are fossil mammal (FAUNMAP) and North American pollen (NAPD) including data from sites spanning the last 5 million years. The Neotoma data (Fig. 3) expand our knowledge of the range of apex carnivores in Illinois both geographically and over time.
Bear is reported from over 40 Late Holocene localities (0-3500 BP). Wolf records (N=30) extend further south in Illinois than historical records indicate and some sites date to over 6000 BP. There are fewer mountain lion records (N=12), but they are widespread and occur up to 4000 BP. One intriguing result is the substantial overlap in site occurrences between gray wolf and black bear. Mountain lion co-occurs with bear at a few sites, and not at all with wolf. These data provide information on species’ occurrence over a deeper time span than is possible from historical records. This gives insight into the presence of animals on the landscape prior to and during past ecological changes, both natural and human mediated.
Case Study #3: Resilience of Deer to Traumatic Limb Injuries (T. Martin, D. Lawler)
Investigations of large archaeological faunal assemblages often reveal unique incidences of animal pathology. Although interesting as curiosities, pathological specimens can disclose insights on past animal populations and the human groups that were exploiting these animals. Four specimens from the Fort St. Joseph (20BE23) and Fort Ouiatenon(12T9) sites illustrate incidences of trauma suffered by white-tailed deer (Odocoileus virginianus) at eighteenth-century trading posts that were inhabited by French settlers and their Native American wives and trading partners. Gross examination and application of x-ray radiography and micro-computed tomography shows a pattern of severely broken front legs on individual deer that survived their initial injuries long enough to permit bone healing and remodeling before the deer ultimately became the victims of Native American or French hunters. Specifically, environmental sheltering from predation, food and water availability in immediate surroundings, and fractured bone ends in reasonable apposition could accomplish functional healing through the downward pull of gravity, heavy limb weight, and limited movement. Individual diagnoses can reveal details about the traumatic injury, malnutrition, and/or infections, and the resiliency of the animal in surviving injuries that initially might be considered to be fatal.
Case Study #4: Pre-Modern Fisheries and Aquatic Ecosystems (B. Styles, T. Martin, M. Wiant)
Although wetland ecologists draw on a variety of modern and historical resources to achieve conservation goals, many system-altering events occurred prior to documentation. The Illinois River and its flood plain were dramatically transformed between 1870 and 1930 by the construction of locks and dams, levees, and the Sanitary and Ship Canal. Drawing on a long-term Illinois River valley archaeological research program, zooarchaeologists have acquired a deep-time perspective on changes to terrestrial and aquatic ecosystems.
A total of 59 fish species have been recorded from four Illinois valley archaeological sites. However, only 12 species, Buffalo, Redhorse sucker, Black and Brown bullheads, Channel catfish, Bass, Sunfish, Bowfin, Gar, Freshwater drum, Northern Pike, and Pike spp., were found in every assemblage. Analysis of proportional data based on the Minimum Number of Individuals indicates that a few species dominate the combined assemblage (Figure 1). These include: Black bullhead, Indeterminate catfish, Bowfin, and Gar, each of which accounts for more than 20% of the total number of individuals. All of these species are common in Illinois River floodplain backwater lakes. However, it is difficult to discern whether this particular distribution represents food preference, the exploitation of particular habitats with specific technology, or some combination thereof.
Case Study #5: Freshwater Mussel Fauna in the Illinois River Basin, Compositional Variation and Change (R. Warren)
Malacologists have compiled invaluable lists of freshwater mussel species native to the Illinois River Basin based on museum collections and historical records. However, lists alone tell us little about the compositions and habitat associations of mussel communities before they were transformed by dam construction and other human impacts during the 19th and 20th centuries. This study uses archaeological shell collections to explore compositional variation among native mussel communities in the Illinois Basin, and to develop a proxy baseline for looking at the magnitude of compositional change in modern mussel faunas. The archaeological material includes 49 shell samples from 30 archaeological sites (Figure 1). The samples represent prehistoric and historic Native American mussel collections that were deposited in village or mortuary contexts. They range in age from 200-9500 BP, although most date to the late Holocene (<2000 BP). Fifty species occur in the total sample of 29,407 identified specimens.
In the archaeological samples, species diversity increases downstream in the Illinois Basin. Species composition is highly variable in the basin as a whole. In most samples the leading dominant species is either the threeridge (Amblema plicata) or the spike (Elliptio dilatata), but five other species predominate in at least one sample. A multivariate ordination of abundance data using detrended correspondence analysis (DCA) orders samples and species along two principal axes of variation (Figure 2). Correlations of sample DCA coordinates with independent environmental variables, mussel habitat scores, and proportions of modified shell indicate that compositional variation reflects (1) down-valley geographical differences among mussel communities, (2) local access to an array of aquatic habitats (large river, creeks, and backwater lakes and sloughs), and (3) cultural selection, in a few cases, of certain species as raw material for creating shell artifacts (Figure 3).
Analysis of mussel samples likely gathered from the Illinois River mainstem shows evidence of community variability and habitat associations that are missing in modern mussel faunas. Samples dominated by the spike (E. dilatata) and mucket (Actinonaias ligamentina) are indicative of a shallow large river with coarse substrate, whereas samples dominated by the threeridge (A. plicata) are indicative of a deeper large river with fine substrate. Shoal habitats are indicated not just in the upper Illinois River, which was historically infamous for its dangerous rapids, but also in the central and lower sections of the valley where reaches of deeper water also occurred. A 1960s mussel survey of the river showed a significant decline in species diversity during the 20th century, when about half of the species were extirpated. Baseline data from the archaeological model indicate there was also a narrowing of mussel community variability and a constriction of habitat associations. These changes may be related to historical human impacts on the stream including pollution, sedimentation, and dam construction.
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