Fossil Beetle Assemblages Research Articles

Comparing fossil and extant beetles in central North Island forests, New Zealand

ABSTRACTRestoration efforts around New Zealand provide safe havens for native species that have been seriously compromised since the arrival of people and introduced mammals approximately 750 yrs ago. Maungatautari in the Waikato is currently the largest area of almost (except for mice) mammal-free estate on the New Zealand mainland. We examined attributes, such as beetle size variation, dispersal ability and trophic structure, of the beetle community at Maungatautari and compared it with the fossil beetle assemblage from two central North Island sites where forest was preserved under up to 2 m of tephra and volcanic ash from the Taupo eruption (232 ± 5 AD (1718 ± 5 cal. yr BP)) prior to the introduction of mammals. A total of 334 fossil, and 206 extant, beetle species were found. No difference was observed between the trophic composition and dispersal ability of taxa within the beetle communities sampled from pre-mammal ecosystem compared with Maungatautari. Greater numbers of large species were found at Maungatautari compared to the two fossil sites. However, this disguised the loss of several large flightless ground-dwelling weevil species that were found as fossils but are now considered extinct. Surprisingly, only 1.2% of the fossil beetle species identified are now thought to be extinct. The fossil beetle assemblages from the central North Island are invaluable datasets that describe the pre-mammal beetle fauna and provide an important benchmark for assessing restoration outcomes in New Zealand forest ecosystems.

Fossil beetles from Pilauco, south-central Chile: An Upper Pleistocene paleoenvironmental reconstruction

A new assemblage of fossil beetles of Upper Pleistocene age, dated between 15,754 and 14,697 cal yr BP, is described and interpreted based on cluster analysis. In this study, we present an analysis on the taxonomic composition, and the paleoenvironmental implication of the fossil beetle assemblage in the archaeo- paleontological site of Pilauco in Osorno, south-central Chile (40°34′S-73°07′ W). Around 17,370 cal yr BP at the onset of deglaciation the old Damas River abandoned its alluvial plain; afterwards wetlands grew up by deposition of peat and colluvial sediments. The fossil beetles were deposited in the PB-7 layer where human artefacts and vertebrate remains have been found in the same spatial and temporal context. The assemblage includes 13 families, documented by 285 skeletal remains of fossil beetles. Ten ecological groups were identified and related to riparian, epigean, Nothofagus sp. forests, and lotic environments such as streams and ponds. Dung and fungi beetles were also part of the fossil assemblage. Pollen and carpological investigations in the same strata point towards the presence of wetlands and evergreen North Patagonian rainforest communities in the Pilauco site during the Upper Pleistocene. However, this study reveals that the Pilauco fossil beetles do not completely conform to any of the known modern assemblages. Therefore, we interpret that the fossil beetle assemblage from Pilauco is the result of the coexistence of different small pockets of habitats in a reduced spatial setting during a period of deep environmental/anthropic changes at the end of the last glaciation. The carabids and dung beetles from these beds indicate that the wetlands may have undergone dry conditions for undetermined periods of time. Finally, we compare nearly contemporaneous beetle assemblages of the sites Pilauco and Monte Verde II to discuss differences and similarities between the sites.

Erosion of insect diversity in response to 7000 years of relative sea-level rise on a small Mediterranean island

We have investigated the potential effects of global sea-level rise on Mediterranean coastal wetlands by studying the Coleoptera and pollen fossil remains in a 7000-year sedimentary record, which we obtained from a coastal marshy area on a small Mediterranean island (Cavallo, southern Corsica). Using beetle structural diversity and plant composition as recorded prior to marine and human influences as a ‘past analogue’, we reconstructed the impact of the Holocene relative sea-level rise on the coastal ecosystem. Our results show that beetle species richness and diversity were highest when freshwater was predominant, which was the case until about 6200 years ago. We also found that a major increase in salinity had occurred over the last 5300 years, experiencing a peak rate of increase at about 3700 years ago. These changes are clearly reflected in the fossil records of the following key taxa: halophilous beetles (Ochthebius sp., Pterostichus cursor), halophilous plants (Chenopodiaceae, Tamarix) and non-pollen palynomorphs (microforaminiferal linings). In particular, we note that the majority (60%) of wetland beetle fauna became locally extinct in response to the salinity changes, and these changes were exacerbated by the recent aggravation of human pressures on the island. The major part of this diversity loss occurred 3700 years ago, when the relative Mediterranean sea-level rose above −1.5 ± 0.3 meters. These findings demonstrate the value of fossil beetle assemblage analysis as a diagnostic for the response of coastal wetland biodiversity to past salinity increases, and serve as a means of forecasting the effects of sea-level rise in the future. The conservation of inland freshwater bodies could ultimately prove essential to preserving freshwater insect diversity in threatened coastal environments.

Long-term perspectives on biodiversity and ecological change during the Quaternary; comparisons from European fossil beetle assemblages

Long-term perspectives on biodiversity and ecological change during the Quaternary; comparisons from European fossil beetle assemblages

Paleoecology of an Interglacial Peat Deposit, Nuyakuk, Southwestern Alaska, U.S.A.

This paper reports the presence of interglacial beetle and pollen assemblages within a Pleistocene peat deposit exposed along the Nuyakuk River of southwestern Alaska. The fossil beetle assemblages contain a number of species not previously identified from eastern Beringian fossil assemblages. The Nuyakuk interglacial deposits are exposed within a 6-m-high terrace along the river, about 4 km beyond the moraine of the penultimate glaciation. Interglacial peat lies within the lowermost meter of the bluff and is overlain by fluvial gravel and loess. Insect fossils were extracted from five peat samples, yielding sixty-seven identified beetle taxa. The insect faunal diversity of the Nuyakuk assemblages is comparable to that found in regional Holocene peat samples. In contrast to assemblages of similar age from interior eastern Beringia, the Nuyakuk fauna contains significant numbers of aquatic, hygrophilous and riparian taxa. Four pollen samples from the Nuyakuk site were analyzed, providing spectra dominated by a few taxa, notably Alnus, Betula, Picea, Gramineae, Cyperaceae, Filicales, and Sphagnum, suggesting a rich alder-birch shrub tundra not much different from the modern regional vegetation. The pollen and insect fossil records also suggest climatic conditions similar to modern.

Re-envisioning the structure of last glacial vegetation in New Zealand using beetle fossils

A series of 18 fossil beetle assemblages are used to reconstruct the paleoenvironment of the northwest West Coast, New Zealand, over the period of the last interstadial–stadial transition (ca. 37,000–21,300 cal yr BP). The samples were recovered from an in-filled hollow within a dune field ca. 9 km south west of Westport (41°47′S, 171°30′E). This fossil beetle reconstruction is compared to an existing palynological reconstruction from the same site. The beetle assemblages indicate an environment of marshy shrubland interspersed with closed canopy coastal vegetation prior to glacial onset, and a mosaic of closed canopy patches and open tussock grassland during full glacial conditions. These interpretations, contrast with the palynologically based interpretation which indicates subalpine shrubland prior to glacial onset and widespread grassland with little woody vegetation during the period of maximum glacial cooling. This study is consistent with other non-pollen studies in New Zealand and indicates that the palynological interpretation of the paleoenvironment of the Westport region downplays the importance of closed canopy vegetation in the area during the transition from interstadial to full glacial (stadial) conditions. It challenges the interpretation of open vegetation at low elevations during glacial periods from pollen studies.

Refining mutual climatic range (MCR) quantitative estimates of palaeotemperature using ubiquity analysis

The Mutual Climatic Range (MCR) method, originally developed in the early 1980s to derive quantified palaeotemperature estimates from fossil beetle assemblage data, is based on assessments of the relationships between the modern distributions of beetle species and instrumentally measured climatic gradients. However, the MCR approach is based on presence/absence beetle data only, with no information on the spatial variation in relative dominance/importance of beetle species within their present climate ranges. This means that beetle–climate relationships are more difficult to test using conventional, probabilistic statistical methods. It is also unlikely that beetles have a normal (Gaussian) distribution in climate space, and hence calibration methods developed for correcting MCR values for bias in raw data are also questionable. In this paper, the underlying statistical weaknesses in the MCR method are examined, while an alternative approach, Ubiquity Analysis, is introduced. It is concluded that this approach offers much potential for reducing the uncertainties associated with MCR estimates.

Description and interpretation of a fossil beetle assemblage from marine isotope stage 6 from Banks Peninsula, New Zealand

A penultimate glaciation‐age beetle fauna is described from a core record from Banks Peninsula, South Island, New Zealand. A total of 19 beetle species belonging to 5 families was recorded. The fossil beetles indicate a forest environment of montane affinity but in a coastal setting. The assemblage is dominated by phytophagous species, mainly weevils, associated with forest habitats. The beetle fauna includes Rhicnobelus metallicus, which is a forest canopy species; forest floor and swamp forest taxa; and Cecyropa modesta, which is specific to coastal dune systems. Fossil seeds were also identified. They include species from salt marsh and tidal flats, indicating an estuarine setting, which suggests that the beetle remains were washed into an estuary from an adjacent forest. The fossil beetle assemblage indicates cooler than modern conditions but not full glacial. This interpretation is consistent with the regional pollen record for this interval.

Arctic North American seasonal temperatures from the latest Miocene to the Early Pleistocene, based on mutual climatic range analysis of fossil beetle assemblages

Late Tertiary and early Quaternary fossil beds in the arctic regions of North America have yielded abundant, well-preserved remains of plants and arthropods, documenting the existence of coniferous forests in the high arctic latitudes. Nearly all of the beetle (Coleoptera) specimens in these fossil assemblages represent extant species. We have applied the mutual climatic range (MCR) method of paleotemperature analysis to fossil beetle assemblages from 11 sites to estimate mean summer (Tmax) and winter (Tmin) temperatures. We found that arctic Tmin values during the latest Miocene and Pliocene were substantially warmer than they are today. The MCR estimates therefore support the scenario derived from the paleobotanical data, namely that arctic Pliocene climates were far less continental. Several Pliocene-age assemblages from the high Arctic yielded Tmax estimates 9-10°C warmer than modern values at the sites. This is the same degree of warming required to allow coniferous forests to grow in the high Arctic. By 3 million years BP, a cooling trend is marked in the paleobotanical and fossil beetle evidence from Alaska. All assemblages dating between 5.7 and 2 million years BP yielded calibrated Tmax values between 12.4 and 13.8°C, regardless of location. Thus the insect fossil data support the theory that there was far less latitudinal gradation in temperatures during the Late Pliocene than there is today. Our reconstructions suggest regional climatic cooling (especially winter temperatures) began by at least 2 million years BP.

Mutual climatic range reconstructions of seasonal temperatures based on Late-Pleistocene fossil beetle assemblages in Eastern Beringia

The mutual climatic range (MCR) method of paleoclimate reconstruction has been employed by paleoentomologists for the last decade. A quantitative, calibrated method, MCR has many advantages over qualitative methods. The method has now been developed for arctic faunas. Climate envelopes for beetle species found in Eastern Beringia have been compiled using a 25 km gridded North American climate database that pairs climate parameters with modern collection sites. Linear regressions of predicted on observed values yielded equations used to calibrate the MCR estimates. This study presents the initial results from the MCR analysis of 46 fossil beetle assemblages from Alaska and the Yukon Territory. The assemblages range in age from about 150,000–9200 yr BP. Isotope stage six assemblages yielded estimates of mean July temperature (TMAX) 4–5°C colder than at present. Assemblages associated with the Old Crow tephra (OCt) (dated approximately 140,000 yr BP.) likewise indicated TMAX values well below modern levels. Isotope stage 5e faunas showed TMAX values as much as 3.5°C warmer than modern. Early Wisconsinan assemblages showed climatic cooling with TMAX levels dropping as low as 6°C colder than at present. A mid-Wisconsinan interstadial period is marked by warming of mean summer temperatures to near-modern levels at some sites. Last Glacial Maximum assemblages reflect cooling of TMAX to a level about 6.4°C colder than at present, although most assemblages from this period yielded mean January temperatures above modern levels. Warming of summer temperatures began at least by 12,500 yr BP, and warmer-than-modern TMAX values were recorded from all assemblages between then and 9200 yr BP.

Late Pleistocene beetle faunas of Beringia: where east met west

AbstractAim To examine the issue of Beringian steppe‐tundra from an entomological standpoint, using fossil beetle data collected from late Pleistocene sites.Location North‐eastern Siberia (Western Beringia), the Bering Land Bridge (Central Beringia), and Alaska and the Yukon Territory (Eastern Beringia).Methods Analysis of habitat preferences of beetle species found in fossil assemblages, leading to classification of major habitat types characterized by the faunal assemblages.Results Fossil beetle assemblages indicative of steppe‐tundra are found mainly in the interior regions of Eastern Beringia, whereas these assemblages dominate nearly all late Pleistocene fossil sites in Western Beringia. Eastern Beringian faunas contain a much larger proportion of mesic to hygrophilous species and very few arid‐habitat species. In contrast to this, the habitat requirements of the Western Beringian faunas are more evenly spread across the moisture spectrum.Main conclusions The taxonomic patterns of the two sets of fossil assemblages are remarkably different. Eastern Beringian faunal assemblages contain substantial numbers of mesic tundra and riparian rove beetles (Staphylinidae); this element is almost entirely lacking in the Western Beringian fossil assemblages. Taphonomic bias tends to overemphasize moisture‐loving species at the expense of dry, upland species in the fossil record. Both Western and Eastern Beringian landscapes undoubtedly contained mosaics of habitats ranging from dry uplands (steppe‐tundra) through mesic tundra to bogs and riparian corridors.

Late Pleistocene Climates of Beringia, Based on Analysis of Fossil Beetles

Thirty-one fossil beetle assemblages from central and eastern Beringia (Alaska, the Yukon Territory, and the now-submerged Bering Land Bridge) have yielded seasonal temperature estimates for the interval 43,550–9250 14C yr before present (yr B.P.). Estimates of the mean temperature of the warmest (TMAX) and coldest (TMIN) months were derived by the Mutual Climatic Range method. Assemblages from northern and western sites show a mid-Wisconsin interstadial TMAX warming from 35,000–30,000 yr B.P.; this warming is less pronounced in assemblages for interior regions. There is little or no beetle evidence for the spread of coniferous forest in eastern Beringia during this interstade, except for in parts of the Yukon Territory. During the last glacial maximum TMAX values were depressed by about 2°–2.5°C in Arctic regions of Beringia, and by about 4°C in the interior; TMIN values were about 8°C colder in both regions. TMAX and TMIN values rose rapidly at northern sites after 12,000 yr B.P. Seasonal temperatures peaked at 11,000 yr B.P., just as the Bering Land Bridge was inundated. This was followed by a sharp climatic cooling between 11,000 and 10,000 yr B.P., the equivalent of a Younger Dryas cooling in eastern Beringia.

Late‐glacial climate in the Maritimes Region, Canada, reconstructed from mutual climatic range analysis of fossil Coleoptera

Mean July and January temperatures are reconstructed from radiocarbon‐dated fossil beetle assemblages from late‐glacial sites in the Maritimes Region of eastern Canada. Fossil‐bearing sediments date from 12700 14C yr BP (14950 cal yr BP) to younger than 10800 14C yr BP (12730 cal yr BP), spanning a period which includes stratigraphic, palynological, chironomid and coleopteran evidence for a climatic deterioration during the Younger Dryas in North America. Mutual Climatic Range data suggest several ‘events’ in the coleopteran record from the Maritimes that appear similar to climate events recorded in the GRIP ice‐core record, including the (Younger Dryas) cooling event from GI‐1a to GS‐1 beginning c. 12650 GRIP yr BP Some of the major temperature oscillations of Greenland Interstadial 1 may also be reflected in the coleopteran record of the Maritimes.

Mid‐Wisconsin seasonal temperatures reconstructed from fossil beetle assemblages in eastern North America: comparisons with other proxy records from the Northern Hemisphere

Mutual climatic range (MCR) analysis was applied to 15 North American beetle assemblages spanning the interval from > 52 000 to 17 200 yr BP, bracketing a Mid-Wisconsin interstadial interval. The analyses yielded estimates of mean July (TMAX) and mean January (TMIN) temperatures. The oldest assemblage (> 52 ka) yielded TMAX values 7.5–8°C lower than present and TMIN values 15–18°C lower than present. A Mid-Wisconsin interstadial warming dating from 43.5–39 ka was rapid and intense. At the peak of the warming event, about 42 ka, TMAX values were only 1–2°C lower than modern. This level of amelioration apparently lasted only about 2000–3000 yr. By 23.7 ka, TMAX values declined to 11.5–10°C lower than modern, but another, small-scale amelioration is indicated by assemblages dating from 20.5 to 19.7 ka. The interstadial event recorded from the site at Titusville, Pennsylvania closely matches the timing and intensity of the climate change estimated from British beetle faunas in the Upton Warren interstadial. Another warm interval (ca. 31–32.5 ka) has been documented from fossil beetle assemblages in Europe and North America. Copyright © 1999 John Wiley & Sons, Ltd.

Insights on the Climatic Constraints on the Beetle Fauna of Coastal Alaska, U.S.A., Derived from the Mutual Climatic Range Method of Paleoclimate Reconstruction

The Mutual Climatic Range (MCR) method of paleoclimate reconstruction uses the climatic parameters associated with the modern range of species to produce climate envelopes for taxa found in fossil assemblages. The overlap of these climate envelopes produces a mutual climatic range for fossil assemblages. The method employs predatory and scavenging beetle species found in fossil assemblages. By comparing observed versus predicted mean summer and winter temperatures from MCR, we developed a set of calibration equations for fossil beetle assemblages in Alaska and the Yukon Territory. These equations showed that MCR predictions fit the observed mean temperatures of the warmest month (TMAX) reasonably well, but the predictions of mean temperatures for the coldest month (TMIN) for coastal sites were consistently below the observed values. Thus the beetle communities living in coastal Alaska today are indicative of colder winter temperatures than are indicated by the observed TMIN, and such lack of correlation is a difficulty in applying the MCR method and in estimating paleoclimates in Beringia. We postulate that periods of severely cold weather in coastal regions are sufficiently common to eliminate species adapted to maritime climates. Instead we find in coastal localities more cold-resistant species whose principal ranges are in interior regions. These species are adapted to continental climates (with extreme seasonality of temperatures), rather than maritime climates (with reduced seasonality).Another difficulty in estimating paleoclimates of Beringia is that the coastal geography has changed with each glacial/interglacial cycle. Glacial and interstadial sites that lie near the modern coast were subject to continental, rather than maritime climates.

Insights on the Climatic Constraints on the Beetle Fauna of Coastal Alaska, U.S.A., Derived from the Mutual Climatic Range Method of Paleoclimate Reconstruction

The Mutual Climatic Range (MCR) method of paleoclimate reconstruction uses the climatic parameters associated with the modern range of species to produce climate envelopes for taxa found in fossil assemblages. The overlap of these climate envelopes produces a mutual climatic range for fossil assemblages. The method employs predatory and scavenging beetle species found in fossil assemblages. By comparing observed versus predicted mean summer and winter temperatures from MCR, we developed a set of calibration equations for fossil beetle assemblages in Alaska and the Yukon Territory. These equations showed that MCR predictions fit the observed mean temperatures of the warmest month (TMAX) reasonably well, but the predictions of mean temperatures for the coldest month (TMIN) for coastal sites were consistently below the observed values. Thus the beetle communities living in coastal Alaska today are indicative of colder winter temperatures than are indicated by the observed TMIN, and such lack of correlation is a difficulty in applying the MCR method and in estimating paleoclimates in Beringia. We postulate that periods of severely cold weather in coastal regions are sufficiently common to eliminate species adapted to maritime climates. Instead we find in coastal localities more cold-resistant species whose principal ranges are in interior regions. These species are adapted to continental climates (with extreme seasonality of temperatures), rather than maritime climates (with reduced seasonality).Another difficulty in estimating paleoclimates of Beringia is that the coastal geography has changed with each glacial/interglacial cycle. Glacial and interstadial sites that lie near the modern coast were subject to continental, rather than maritime climates.

Late Pleistocene and Holocene Seasonal Temperatures Reconstructed from Fossil Beetle Assemblages in the Rocky Mountains

Mutual Climatic Range (MCR) analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14,500 to 400 yr B.P. The fossil sites represent a transect of the Rocky Mountain region from northern Montana to central Colorado. The analyses yielded estimates of mean July and mean January temperatures. The oldest assemblage (14,500 yr B.P.) yielded mean July values of 10–11°C colder than present and mean January values 26–30°C colder than present. Postglacial summer warming was rapid, as indicated by an assemblage dating 13,200 yr B.P., with mean July values only 3–4°C cooler than modern. By 10,000 yr B.P., several assemblages indicate warmer-than-modern mean summer and winter values. By 9000 yr B.P., MCR reconstructions indicate that both summer and winter temperatures were already declining from an early Holocene peak. Mean July values remained above modern levels and mean January values remained below modern levels until 3000 yr B.P. A series of small-scale oscillations followed.

Late Wisconsin climate in northeastern USA and southeastern Canada, reconstructed from fossil beetle assemblages

Mean July and January temperatures are reconstructed from radiocarbon-dated fossil beetle assemblages, yielding a synthesis of palaeoclimatic history of the regions south of the Laurentide Ice Sheet in North America from 35 000 to 8500 yr BP. Mean July temperatures close to the last glacial maximum were 11–12°C colder than present; mean January temperatures were possibly 10–19°C colder. Mutual climatic range analyses of the beetle assemblages show warming of mean summer temperatures as early as 13.7 kyr, although ice-proximal sites were consistently about 5°C cooler than ice-distal sites. Late-glacial mean summer temperatures peaked between 12 and 11 kyr, then remained fairly constant through the early Holocene. Mean winter temperatures did not reach modern values until after 10 kyr.

Late Wisconsin climate in northeastern USA and southeastern Canada, reconstructed from fossil beetle assemblages

Late Wisconsin climate in northeastern USA and southeastern Canada, reconstructed from fossil beetle assemblages

Fossil Beetle Evidence for a Short Warm Interval near 40,000 yr B.P. at Titusville, Pennsylvania

A brief cold–warm–cold climate change during the middle Wisconsinan is described for the first time in North America, based on fossil beetle assemblages at Titusville, Pennsylvania. AMS dating of insect chitin and wood suggests the change occurred between 39,000 and 43,500 yr B.P. Basal peats in river terrace deposits contain arctic–subarctic beetle species representing a climate similar to that found at treeline in Canada, where mean July temperatures range from 10° to 13°C. These cold-adapted beetles were replaced by species representing a climate similar to the mixed coniferous–deciduous forests of southern Canada, where mean July temperatures range from 18° to 20°C. In turn, these warmer-adapted beetles were replaced by arctic–subarctic species in the upper part of the section, representing a climate with mean July temperatures in the range 10°–13°C. The brief warm interval is informally designated the Titusville interstade. The difference in temperature between the colder and warmer intervals is about 5°–7°C. The Titusville interstade is correlated with the Upton Warren Interstade of the British Isles which is of similar age and intensity. It is also correlated with the high sea-surface temperature interval between Heinrich events 4 and 5 represented in North Atlantic sediment cores.