Dendrochronology In Plains Prehistory: An Assessment

Abstract

Chronologies and climatological interpretations based upon annual growth rings of trees have been available to prehistorians within the Plains for more than half a century. Until the advent of radiocarbon dating, tree rings provided the only “absolute” chronology for most archeological complexes and subsequently, continued as an important adjunct to radiometric methods. Nonetheless, the validity of tree ring dates in the Plains must be questioned. Continuity of research has been lacking, there have been serious methodological problems, and the provenience of many specimens is in doubt. Moreover, there are significant conflicts between tree ring and recent radiocarbon dates.     

Mitochondrial genomes reveal slow rates of molecular evolution and the timing of speciation in beavers (Castor), one of the largest rodent species

Background

Beavers are one of the largest and ecologically most distinct rodent species. Little is known about their evolution and even their closest phylogenetic relatives have not yet been identified with certainty. Similarly, little is known about the timing of divergence events within the genus Castor.

Methodology/Principal Findings

We sequenced complete mitochondrial genomes from both extant beaver species and used these sequences to place beavers in the phylogenetic tree of rodents and date their divergence from other rodents as well as the divergence events within the genus Castor. Our analyses support the phylogenetic position of beavers as a sister lineage to the scaly tailed squirrel Anomalurus within the mouse related clade. Molecular dating places the divergence time of the lineages leading to beavers and Anomalurus as early as around 54 million years ago (mya). The living beaver species, Castor canadensis from North America and Castor fiber from Eurasia, although similar in appearance, appear to have diverged from a common ancestor more than seven mya. This result is consistent with the hypothesis that a migration of Castor from Eurasia to North America as early as 7.5 mya could have initiated their speciation. We date the common ancestor of the extant Eurasian beaver relict populations to around 210,000 years ago, much earlier than previously thought. Finally, the substitution rate of Castor mitochondrial DNA is considerably lower than that of other rodents. We found evidence that this is correlated with the longer life span of beavers compared to other rodents.

Conclusions/Significance

A phylogenetic analysis of mitochondrial genome sequences suggests a sister-group relationship between Castor and Anomalurus, and allows molecular dating of species divergence in congruence with paleontological data. The implementation of a relaxed molecular clock enabled us to estimate mitochondrial substitution rates and to evaluate the effect of life history traits on it.     

Evaluating the annual nature of juvenile rings in Bolivian tropical rainforest trees

Knowledge on juvenile tree growth is crucial to understand how trees reach the canopy in tropical forests. However, long-term data on juvenile tree growth are usually unavailable. Annual tree rings provide growth information for the entire life of trees and their analysis has become more popular in tropical forest regions over the past decades. Nonetheless, tree ring studies mainly deal with adult rings as the annual character of juvenile rings has been questioned. We evaluated whether juvenile tree rings can be used for three Bolivian rainforest species. First, we characterized the rings of juvenile and adult trees anatomically. We then evaluated the annual nature of tree rings by a combination of three indirect methods: evaluation of synchronous growth patterns in the tree- ring series, ¹⁴C bomb peak dating and correlations with rainfall. Our results indicate that rings of juvenile and adult trees are defined by similar ring-boundary elements. We built juvenile tree-ring chronologies and verified the ring age of several samples using ¹⁴C bomb peak dating. We found that ring width was correlated with rainfall in all species, but in different ways. In all, the chronology, rainfall correlations and ¹⁴C dating suggest that rings in our study species are formed annually.     

Rates of lateral channel migration along the Mala Panew River (southern Poland) based on dating riparian trees and Coarse Woody Debris

Two methods of estimating the lateral migration of a river channel have been proposed. The first method is based on Coarse Woody Debris (CWD) dating. The terraces of the Mala Panew River are mainly covered with plantations of Pinus sylvestris where individual trees grow at equal distances to each other. During times of high discharges trees fall onto the riverbed providing information on the extent of flood plain erosion. The ages of CWD and the surface of the eroded flood plain provide an estimation of the rate of lateral migration. The erosion rates measured at two sites in the Mala Panew River were between 0.24 and 0.36 m/year.Another way of reconstructing the rate of lateral migration is by dating trees growing on different-aged sandy meander bars. These levels are primarily covered with Alnus glutinosa and Alnus incana. The oldest trees growing on each level give information about the minimum age of that level, which allows us to reconstruct the rate of lateral migration. The lateral migration of the channel has also been estimated dating the oldest trees growing on mid-channel islands separated from the lateral banks. The values obtained for 10 sites of the Mala Panew channel oscillate between 0.07 and 1.83 m/year.Tree ring analyses also allow us to determine the impact of individual high discharges on the lateral migration rate of the Mała Panew channel. The lateral migration of the channel was most rapid in the years 1953–57 and 1966–68 as well as during the extraordinary flood in 1997.     

40Ar/39Ar dating in paleoanthropology and archeology

The potassium-argon (K-Ar) dating method has been widely used over the past 40 years to provide radioisotopic age control of hominid/hominoid evolutionary time scales. The wide appeal of the technique to paleoanthropology and archeology has been, in part, a result of its broad time range of applicability, from materials as young as a few thousand years old to an essentially unbounded upper age limit. Another reason for its appeal is the many geological circumstances in which datable materials are found. Beginning about two decades ago and accelerating into this decade, however, the conventional K-Ar technique has given way to ⁴⁰Ar/³⁹Ar dating as the method of preference. This technique is not only more precise and accurate when dating ideal materials, but also permits excellent ages to be obtained from situations that often stymie the conventional K-Ar technique, such as dating of contaminated tuffs and altered rocks. © 1998 Wiley-Liss, Inc.     

The genus Abies in Scotland

Summary

The genus Abies extends across much of the Northern Temperate Region in the form of about fifty species and ten well-marked geographical varieties. Thirty-two species and eight varieties have been found recently in Scottish gardens, policies and collections. Sixteen of these are potentially trees of great stature, and in no less than twelve of these sixteen, the largest and finest specimens in the British Isles are found in Scotland. The concentration of very big trees, still growing, is remarkable in three broad regions, Western Argyll, Central Perthshire with Angus, and NE Inverness-shire with adjacent parts of Ross-shire.     

Multigene Phylogenetics Reveals Temporal Diversification of Major African Malaria Vectors

The major vectors of malaria in sub-Saharan Africa belong to subgenus Cellia. Yet, phylogenetic relationships and temporal diversification among African mosquito species have not been unambiguously determined. Knowledge about vector evolutionary history is crucial for correct interpretation of genetic changes identified through comparative genomics analyses. In this study, we estimated a molecular phylogeny using 49 gene sequences for the African malaria vectors An. gambiae, An. funestus, An. nili, the Asian malaria mosquito An. stephensi, and the outgroup species Culex quinquefasciatus and Aedes aegypti. To infer the phylogeny, we identified orthologous sequences uniformly distributed approximately every 5 Mb in the five chromosomal arms. The sequences were aligned and the phylogenetic trees were inferred using maximum likelihood and neighbor-joining methods. Bayesian molecular dating using a relaxed log normal model was used to infer divergence times. Trees from individual genes agreed with each other, placing An. nili as a basal clade that diversified from the studied malaria mosquito species 47.6 million years ago (mya). Other African malaria vectors originated more recently, and independently acquired traits related to vectorial capacity. The lineage leading to An. gambiae diverged 30.4 mya, while the African vector An. funestus and the Asian vector An. stephensi were the most closely related sister taxa that split 20.8 mya. These results were supported by consistently high bootstrap values in concatenated phylogenetic trees generated individually for each chromosomal arm. Genome-wide multigene phylogenetic analysis is a useful approach for discerning historic relationships among malaria vectors, providing a framework for the correct interpretation of genomic changes across species, and comprehending the evolutionary origins of this ubiquitous and deadly insect-borne disease.     

Evidence for Neandertal Jewelry: Modified White-Tailed Eagle Claws at Krapina

We describe eight, mostly complete white-tailed eagle (Haliaëtus [Haliaeetus] albicilla) talons from the Krapina Neandertal site in present-day Croatia, dating to approximately 130 kyrs ago. Four talons bear multiple, edge-smoothed cut marks; eight show polishing facets and/or abrasion. Three of the largest talons have small notches at roughly the same place along the plantar surface, interrupting the proximal margin of the talon blade. These features suggest they were part of a jewelry assemblage, --- the manipulations a consequence of mounting the talons in a necklace or bracelet. An associated phalanx articulates with one of the talons and has numerous cut marks, some of which are smoothed. These white-tailed eagle bones, discovered more than 100 years ago, all derive from a single level at Krapina and represent more talons than found in the entire European Mousterian period. Presence of eight talons indicates that the Krapina Neandertals acquired and curated eagle talons for some kind of symbolic purpose. Some have argued that Neandertals lacked symbolic ability or copied this behavior from modern humans. These remains clearly show that the Krapina Neandertals made jewelry well before the appearance of modern humans in Europe, extending ornament production and symbolic activity early into the European Mousterian.     

Whole genome duplication of intra- and inter-chromosomes in the tomato genome

Whole genome duplication(WGD)events have been proven to occur in the evolutionary history of most angiosperms.Tomato is considered a model species of the Solanaceae family.In this study,we describe the details of the evolutionary process of the tomato genome by detecting collinearity blocks and dating the WGD events on the tree of life by combining two different methods:synonymous substitution rates(Ks)and phylogenetic trees.In total,593 collinearity blocks were discovered out of 12 pseudo-chromosomes constructed. It was evident that chromosome 2 had experienced an intra-chromosomal duplication event.Major inter-chromosomal duplication occurred among all the pseudo-chromosome.We calculated the Ks value of these collinearity blocks.Two peaks of Ks distribution were found,corresponding to two WGD events occurring approximately 36-82 million years ago(MYA)and 148-205 MYA.Additionally, the results of phylogenetic trees suggested that the more recent WGD event may have occurred after the divergence of the rosidasterid clade,but before the major diversification in Solanaceae.The older WGD event was shown to have occurred before the divergence of the rosid-asterid clade and after the divergence of rice-Arabidopsis(monocot-dicot).     

Keep your feet warm? A cryptic refugium of trees linked to a geothermal spring in an ocean of glaciers

Up to now, the most widely accepted idea of the periglacial environment is that of treeless ecosystems such as the arctic or the alpine tundra, also called the tabula rasa paradigm. However, several palaeoecological studies have recently challenged this idea, that is, treeless environments in periglacial areas where all organisms would have been exterminated near the glacier formed during the Last Glacial Maximum, notably in the Scandinavian mountains. In the Alps, the issue of glacial refugia of trees remains unanswered. Advances in glacier reconstructions show that ice domes did not cover all upper massifs, but glaciers filled valleys. Here, we used fossils of plant and malacofauna from a travertine formation located in a high mountain region to demonstrate that trees (Pinus, Betula) grew with grasses during the Lateglacial‐Holocene transition, while the glacier fronts were 200–300 m lower. The geothermal travertine started to accumulate more than 14,500 years ago, but became progressively more meteogene about 11,500 years ago due to a change in groundwater circulation. With trees, land snails (gastropods) associated to woody or open habitats and aquatic mollusc were also present at the onset of the current interglacial, namely the Holocene. The geothermal spring, due to warm water and soil, probably favoured woody glacial ecosystems. This new finding of early tree growth, combined with other scattered proofs of the tree presence before 11,000 years ago in the western Alps, changes our view of the tree distribution in periglacial environments, supporting the notion of tree refugia on nunataks in an ocean of glaciers. Therefore, the tabula rasa paradigm must be revisited because it has important consequences on the global changes, including postglacial plant migrations and biogeochemical cycles.     

Impacts of different forest management methods on the stand spatial structure of a natural Quercus aliena var. acuteserrata forest in Xiaolongshan,China

Stand spatial structure is a significant factor in forest processes that regulates growth and promotes sustainability. Close-to-nature forest management (CNFM), structure-based forest management (SBFM), and secondary forest comprehensive silvicuture (SFCS) are three forest management methods that have been promoted in China; however, how stand spatial structure is impacted by the different forest managements remains unclear. Understanding stand spatial structure characteristics in a forest under different forest managements is critical for forest management. In this study, we analysed and compared the spatial structure characteristics within a natural Quercus aliena var. acuteserrata forest under CNFM, SBFM, SFCS, and unmanaged control before tending, after tending and four years after tending using the three spatial structure parameters of uniform angle index, mingling, and dominance.Results(1) The SBFM and SFCS produced the random distribution pattern of a stand, and they could maintain a random distribution four years after tending. The SBFM significantly increased the degree of mixing in the forest, and the degree of mixing four years after tending was still significantly higher than before tending. (2) The SBFM was the only forest management method that could significantly reduce the proportion of micro-structures (non-randomly distributed trees with a low degree of mixing and inferior trees with a low degree of mixing) immediately, and the proportion of micro-structures after four years of tending was still significantly lower than before tending. (3) These three forest management methods cannot significantly increase the proportion of micro-structures (randomly distributed trees with a high degree of mixing and dominant trees with a high degree of mixing) immediately, while only when using the SBFM was the proportion of these after four years of tending significantly higher than before tending.ConclusionsCompared with other forest management methods, the SBFM can achieve the goal of optimizing the spatial structure of forests, which is conducive to the growth of trees and the improvement of forest stand productivity.     

Deciphering past human population movements in Oceania: provably optimal trees of 127 mtDNA genomes

The settlement of the many island groups of Remote Oceania occurred relatively late in prehistory, beginning approximately 3,000 years ago when people sailed eastwards into the Pacific from Near Oceania, where evidence of human settlement dates from as early as 40,000 years ago. Archeological and linguistic analyses have suggested the settlers of Remote Oceania had ancestry in Taiwan, as descendants of a proposed Neolithic expansion that began approximately 5,500 years ago. Other researchers have suggested that the settlers were descendants of peoples from Island Southeast Asia or the existing inhabitants of Near Oceania alone. To explore patterns of maternal descent in Oceania, we have assembled and analyzed a data set of 137 mitochondrial DNA (mtDNA) genomes from Oceania, Australia, Island Southeast Asia, and Taiwan that includes 19 sequences generated for this project. Using the MinMax Squeeze Approach (MMS), we report the consensus network of 165 most parsimonious trees for the Oceanic data set, increasing by many orders of magnitude the numbers of trees for which a provable minimal solution has been found. The new mtDNA sequences highlight the limitations of partial sequencing for assigning sequences to haplogroups and dating recent divergence events. The provably optimal trees found for the entire mtDNA sequences using the MMS method provide a reliable and robust framework for the interpretation of evolutionary relationships and confirm that the female settlers of Remote Oceania descended from both the existing inhabitants of Near Oceania and more recent migrants into the region.     

Recent origin of a large part of the forest cover in the Gabon coastal area based on stable carbon isotope data

Variations in the natural ¹³C abundance of soil organic matter (SOM) at different depths combined with SOM radiocarbon dating were used to reconstruct the history of the forest-savanna successions over the last millennium in the Gabon coastal area. A chronosequence was established by comparing the '¹³C profiles and the radiocarbon dating of a Gabon savanna with those of a Congolese savanna where the palaeoenvironments are already well known. The palaeoclimatic histories of the two savannas were shown to be strictly identical. The whole Gabon coastal area may well have been forested during the early Holocene, until about 4,000 years ago. The forest fragmented after this initial expansion. Savanna appeared circa 3,000 years ago but the forest did not disappear totally. A new forest transgression started 500-1,000 years ago and expanded over the open areas previously created or enlarged. The marked savanisation and the subsequent and currently ongoing forest expansion explain both the present forest-savanna mosaic and the abundance of secondary species such as Aucoumea klaineana in the coastal forest.Anthropogenic activities over the past decades and centuries have induced local fluctuations in the forest cover, superimposed on the climatic forest-savanna dynamic. This study also confirms that the monospecific, even-aged A. klaineana stands present in the area became established on abandoned cultivation clearings.     

Larvae of Aenetus virescens (Lepidoptera: Hepialidae) in decaying wood

Abstract

Larvae of Aenetus virescens (Doubleday) have previously been recorded only from the wood of live trees or shrubs. This paper describes the circumstances in which larvae occupy decaying wood in the forest habitat. Young larvae are considered to exist in dead wood for no more than a year. They then disperse to live trees, in which development is completed.     

Nest site selection and patterns of nest re-use in the Hooded Crow Corvus cornix

Capsule: Hooded Crows Corvus cornix selected nesting trees based on species, height, grouping and distance from an occupied house. Nest re-use was common and pairs that re-used old nests produced more fledglings than those that built a new nest.

Aims: To determine the features of trees that influenced whether they were used by Hooded Crows as nest sites, to establish what factors influenced nest re-use between years and to explore potential costs or benefits of nest re-use.

Methods: In a large area of Orkney, Scotland, the features of trees that contained a Hooded Crow nest were compared to those of trees where nests were absent. Patterns of nest re-use between years were examined in relation to the availability of alternative sites, previous nesting success and the number of equivalent options to the tree used previously within 200?m of this site.

Results: Hooded Crows favoured spruce and pine trees as nest sites, above the most locally abundant tree species, elder and willow. Preference for trees increased with tree height, local tree density and distance from occupied houses. Over half of the crows studied re-used an old nest when one was available and crows that re-used an old nest fledged more offspring than those that built a new nest. The likelihood of a new nest being built increased as the number of potential locations to build increased. Territories where a nest survived the winter were more likely to be reoccupied the following year than those where nests fell, while territories with fewer trees around the old site were most likely to be abandoned, suggesting that those were territories of lower quality.

Conclusions: Hooded Crows displayed strong preferences for nest sites that might favour nesting success by offering concealment, shelter and protection from ground-based predators. Nest re-use was common, especially when alternative sites were scarce, and appeared to facilitate greater reproductive output.     

Three-dimensional distribution of mass movement signals in disturbed Picea abies (L.) Karst.

Dendrogeomorphologic approaches enable annual absolute dating of various potentially hazardous geomorphic processes. This study tested the dating precision of three commonly used dendrogeomorphic approaches used for the extraction of geomorphic signals from the tree ring series of disturbed trees. The first approach is based on the onset of reaction wood occurrence, and the other two approaches are based on the detection of abrupt changes in tree ring eccentricity. Nine 165 cm long stems of maximally 27 year old Norway spruces (Picea abies (L.) Karst.) growing on unstable slope affected by mass movement events of known age were analysed. Several sampling directions on stems were analysed to reveal the best sampling strategy for each tested approach. The relationships between stem curvature and the dating precision of the approaches were also analysed. The results of dating precision showed crucial differences between the tested approaches. Tree stem curvature did not influence dating precision. Overall, we concluded that the approaches based on eccentric increments are less precise than those based on reaction wood analysis when juvenile P. abies trees that grow on landslide slope are sampled. The importance of this study is in providing new insight into dating precision by analysing the whole tree stems of trees influenced by mass movements. This is unique since the approaches based on eccentricity increments have not been previously tested in such a detail.     

Forty years of studies by Iranian entomologists on the Chrysopidae fauna of Iran (1961–2000) (Insecta,Neuroptera)

Abstract

The first check-list of the Iranian fauna of the neuropteran family Chrysopidae was published more than forty years ago (FARAHBAKHSH 1961). Since then, a number of Iranian authors have collected and reported on specimens of Chrysopidae, and have studied their biology, ecology, and taxonomy in various regions of Iran. This paper summarises their findings.     

Dendrochronological assessment of British veteran sweet chestnut (Castanea sativa) trees: Successful cross-matching,and cross-dating with British and French oak (Quercus) chronologies

Across Britain and continental Europe there are many ancient Castanea sativa trees of great significance for natural and cultural heritage, yet scant assessment has been made of them for dendrochronological information. This paper describes the dendrochronological analysis of 28 Castanea sativa trees (veteran historic trees, forest trees and coppice stems) sampled from 15 sites in southern Britain: 56 growth-ring sequences were collected for analysis, by boring living trees and by cutting transverse sections from dead fallen trees and previously cut stumps. Twenty-three single-tree sequences from 14 sites were cross-matched (t ≥3.5) and then cross-dated with 17 oak Quercus reference chronologies from England and northern France: a Castanea sativa master chronology spanning AD 1660–2014 has been created. The results demonstrate the viability of dendrochronological analysis of Castanea sativa wood; and confirm that Castanea sativa can be cross-dated with oak Quercus reference chronologies, inter-regionally and inter-nationally. The findings provide the potential means for dating Castanea sativa timbers sampled from palaeoenvironmental and historical contexts. The extraction of sawn sections from long-dead (up to 60 years in this study) trees and stumps is proven to be a reliable method for dating veteran trees in cultural landscapes and ancient woodlands; and for revealing the growth history of historic/iconic trees. The germination dates calculated for the Castanea sativa trees in this study span the period AD 1640–1943. The inaccuracy of estimating veteran Castanea sativa tree ages from girth measurements is highlighted.     

The absolute dating of Upper Pleistocene subSaharan fossil hominids and their place in human evolution

In the evolution of anatomically modern man and his subspecies most specialists have concentrated on investigating geographical areas other than Africa as the possible area of origin.In this study 20 fossil hominids and associated faunal remains from South and East Africa were dated by microanalysis, radiocarbon, and amino-acid dating in order to see whether modern man appears later, was sympatric, or even predated Neandertal man.These dates indicate that anatomically modern man occurs sympatrically and possibly even predates the Rhodesian group of Neandertals in Africa. Modern man might also be contemporary to and possibly even predate the occurrence of Neandertal in Europe.This would indicate that modern man did not evolve from but possibly gave rise to the Neandertals as off-shoots.Two possibilities for the evolution of modern man are suggested. First, that Homo sapiens capensis evolved about 90,000 to 100,000 years ago from possibly Homo erectus by way of a “basic” Homo sapiens and later gave rise to Homo sapiens rhodesiensis, Homo sapiens afer, and possibly Homo sapiens palestinus around 50,000 years ago with Homo neanderthalensis and Homo sapiens capensis evolving separately from Homo erectus. In this case Homo neanderthalensis would be a different species from Homo sapiens which includes Homo sapiens capensis, Homo sapiens rhodesiensis, Homo sapiens afer, and possibly Homo sapiens palestinus.Secondly, Homo sapiens capensis evolved by way of a “basic” Homo sapiens with Homo sapiens rhodesiensis and Homo sapiens palestinus branching off from Homo sapiens capensis around 50,000 years ago. Before that, around 90,000 to 100,000 years ago Homo sapiens capensis evolved first and was then followed by Homo sapiens neanderthalensis from a “basic” Homo sapiens stock, but diverged. This means, all Neandertals, Homo sapiens capensis, Homo sapiens sapiens and Homo sapiens afer can be considered as subspecies of Homo sapiens.The author favors the first scheme since on relative dating grounds the existence of Neandertal man in Europe before the earliest date of Homo sapiens capensis and a “basic” Homo sapiens seems to be fairly well documented. Irrespective of either one of these possibilities, modern man evolved in Africa and seems to have migrated into Europe and other parts of the world.New absolute dating techniques are mentioned in detail like the new radiocarbon-collagen method and amino acid dating.     

ACCURACY OF ESTIMATED PHYLOGENIES: EFFECTS OF TREE TOPOLOGY AND EVOLUTIONARY MODEL

A simulation study was carried out to investigate the relative importance of tree topology (both balance and stemminess), evolutionary rates (constant, varying among characters, and varying among lineages), and evolutionary models in determining the accuracy with which phylogenetic trees can be estimated. The three evolutionary context models were phyletic (characters can change at each simulated time step), speciational (changes are possible only at the time of speciation into two daughter lineages), and punctuational (changes occur at the time of speciation but only in one of the daughter lineages). UPGMA clustering and maximum parsimony (“Wagner trees”) methods for estimating phylogenies were compared. All trees were based on eight recent OTUs. The three evolutionary context models were found to have the largest influence on accuracy of estimates by both methods. The next most important effect was that of the stemminess × context interaction. Maximum parsimony and UPGMA performed worst under the punctuational models. Under the phyletic model, trees with high stemminess values could be estimated more accurately and balanced trees were slightly easier to estimate than unbalanced ones. Overall, maximum parsimony yielded more accurate trees than UPGMA—but that was expected for these simulations since many more characters than OTUs were used. Our results suggest that the great majority of estimated phylogenetic trees are likely to be quite inaccurate; they underscore the inappropriateness of characterizing current phylogenetic methods as being for reconstruction rather than for estimation.