Huw I. Griffiths

Slow molecular evolution in an ancient asexual ostracod

Genetic variability of the non–marine ostracod speciesDarwinula stevensoni was estimated by sequencing part of the nuclear and the mitochondrial genome. As Darwinulidae are believed to be ancient asexuals, accumulation of mutations should have occurred, both between alleles within lineages and between lineages, during the millions of years of parthenogenetic reproduction. However, our sequence data show the opposite: no variability in the nuclear ITS1 region was observed within or among individuals of D. stevensoni, despite sampling a geographical range from Finland to South Africa. Lack of allelic divergence might be explained by concerted evolution of rDNA repeats. Homogeneity among individuals may be caused either by slow molecular evolution in ITS1 or by a recent selective sweep. Variability of mitochondrial cytochrome oxidase (COI) was similar to intraspecific levels in other invertebrates, thus weakening the latter hypothesis. Calibrating interspecific, genetic divergences among D. stevensoni and other Darwinulidae using their fossil record enabled us to estimate rates of molecular evolution. Both COI and ITS1 evolve half as fast, at most, in darwinulids as in other invertebrates, and molecular evolution has significantly slowed down in ITS1 of D. stevensoni relative to other darwinulids. A reduced ITS1 mutation rate might explain this inconsistency between nuclear and mitochondrial evolution in D. stevensoni.

Chronology and stratigraphy of Late Quaternary sediments in the Konya basin, Turkey: Results from the KOPAL project

Abstract The Late Quaternary environmental history of the Konya plain, in south central Turkey, is used to examine sediment facies changes in a shallow non-outlet basin which has experienced major climatically driven changes in lake extent. Two principal types of sedimentary archive are used to reconstruct a palaeoenvironmental record, namely alluvial sequences on the Carsamba alluvial fan and sediments from residual lakes. The latter have been used to investigate broader climatic and vegetational histories via palaeolimnological techniques including pollen, diatom and stable isotope analysis. These changes are dated here by radiometric techniques including radiocarbon (AMS and conventional), OSL, and U–Th. Chronological agreement is generally good between the different dating techniques, although typically there is greatly reduced precision beyond ca. 25 ka. Lake sediment cores investigated have basal ages beyond the range of 14C dating, but contain hiatuses as a result of subsequent alternation between phases of lacustrine sedimentation and aeolian deflation. In contrast to most deepwater non-outlet lake systems, the Konya basin may have been occupied by a single extensive lake for as little as 10% of Late Quaternary time, mainly around the time of the LGM. This lake highstand was followed by an important arid interval. In the absence of unbroken chronostratigraphic sequences, palaeohydrological investigation of shallow non-outlet lakes may require analysis of basin-wide changes in sedimentation rather than reliance on single core records. Stratigraphic continuity in such sedimentary environments cannot be assumed, and requires independent chronological control through radiometric dating.

Persistence of asexuality through mixed reproduction in Eucypris virens (Crustacea, Ostracoda).

The ostracod species Eucypris virens exhibits geographical parthenogenesis, with rare sexual populations in southern Europe and widespread asexual populations elsewhere. DNA sequence data from the nuclear ITS1 and mitochondrial COI regions have been used to estimate genetic variabilities and reconstruct phylogenies. The observed divergence was exceptionally high, with intraspecific maxima of 10.3% (ITS1) and 20.9% (COI) among European lineages, levels reported for interspecific comparisons of other taxa. Phylogenetic reconstructions reveal multiple origins of asexual clones from sexual populations. However, we argue that such data can only provide a lower limit on the number of origins of asexual reproduction, and an upper limit on the age of asexual lineages. Congruence between gene trees for different loci can provide support for the inference of long-term apomictic reproduction. Nuclear and mitochondrial data differ in their placement of some asexual clones, possibly indicating that genetic exchange has taken place between sexual and asexual lineages. Such intraspecific hybridization is one route to combine the benefits of both reproductive modes, and it might explain how asexuality managed to persist in E. virens even in long, evolutionary terms.

Sedimentology, palaeontology and archaeology of late Middle Pleistocene River Thames terrace deposits at Purfleet, Essex, UK

Middle Pleistocene fluvial deposits of the Corbets Tey Formation at Purfleet, Essex, provide evidence of an un-named and previously poorly recognized interglacial, thought to corrrelate with Oxygen Isotope Stage (OIS) 9. Previous attributions of the sediments to the Ipswichian (Last Interglacial) Stage are refuted. New investigations have yielded rich molluscan, mammalian and ostracod assemblages that indicate fully temperate conditions and the distal influence of marine transgression. Pollen analyses suggest a previously unrecorded phase of interglacial vegetational development. Clast composition, geomorphological evidence and the occurrence of molluscs that favour large rivers all point to deposition by the Thames, rather than in a minor tributary, as suggested previously. Three separate Palaeolithic industries in stratigraphical superposition are recognized at Purfleet, these being Clactonian, Acheulean and Levallois. Purfleet is therefore a key locality in the understanding of the early human occupation and exploitation of southern Britain, as well as for the interpretation and correlation of the terrace sequence in the Thames Valley.

Mitochondrial phylogeography and population history of pine martens Martes martes compared with polecats Mustela putorius.

The flora and fauna of Europe are linked by a common biogeographic history, most recently the Pleistocene glaciations that restricted the range of most species to southern refugial populations. Changes in population size and migration, as well as selection, have all left a signature on the genetic differentiation. Thus, three paradigms of postglacial recolonization have been described, inferred from the patterns of DNA differentiation. Yet some species, especially wide‐ranging carnivores, exhibit little population structuring between the proposed refugia, although relatively few have been studied due to the difficulty of obtaining samples. Therefore, we investigated mitochondrial variation in pine martens, Martes martes, in order to understand the extent to which they were affected by glacial cycles, and compared the results with an analysis of sequences from polecats, Mustela putorius. A general lack of ancient lineages, and a mismatch distribution that is consistent with an expanding population, is evidence that the present‐day M. martes and Mu. putorius in central and northern Europe colonized from a single European refugium following a recent glaciation. There has also been interspecific mitochondrial introgression between M. martes and the sable M. zibellina in Fennoscandia.

Hybridization and the phylogenetic relationship between polecats and domestic ferrets in Britain

Ferrets (Mustela furo) were domesticated from polecats (M. putorius, M. eversmannii) over 2000 years ago. Following their introduction to Britain, they escaped and hybridized with native European polecats (M. putorius). Native polecats declined to the point of near extinction prior to World War I, but have recently begun to expand from a Welsh refugium. Concern has arisen as to the extent of polecat/ferret introgression, and in particular, whether the expanding population is of mainly hybrid origin. Therefore, mitochondrial DNA sequencing was used to investigate polecat genetic diversity in Britain. Two geographically distinct lineages were found, where one may be ancestral to the British polecat, and the other to the domestic ferret. The ancestral distribution of each lineage, or assortative mating is sufficient to explain the observed pattern. A further comparison between the distribution of the polecat phenotype and mitochondrial haplotype implies that the current population expansion may be mediated by dispersing male polecats hybridizing with female feral ferrets. However, the wild source of the ferret remains obscure. Relatively recent speciation from European mink (M. lutreola) and black-footed ferrets (M. nigripes), and/or the effects of hybridization result in an unresolved molecular phylogeny.

Evironmental change in southwestern Iran: the Holocene ostracod fauna of Lake Mirabad

Ostracod faunal data are presented from a sediment core taken from extant Iranian Lake Mirabad. Ostracod faunal successions indicate relatively high concentrations of mainly nektonic taxa between c. 9265 and 6505 cal. 14C yr BP, followed by lower concentrations of mainly benthic forms after 6505 cal.BP. These results suggest that lake levels were low during the early Holocene, and that water levels rose during mid- Holocene times, notably after c. 4048 cal. 14C yr BP. These findings confirm and consolidate palaeoclimatic inferences based on previously published pollen diagrams from the region, but indicate an apparent timelag between the early to mid-Holocene forest advance and increased lake levels. This may be explained by changes in precipitation/evaporation ratios; the increase in winter precipitation was sufficient to allow the expansion of arboreal vegetation, but summer evaporation remained high. This also gives support to the idea that the delayed readvance of forests in eastern Turkey and western Iran in the early Holocene was hampered by dry conditions in the continental interior. The apparently out-of-phase response observed between the palaeoclimate record from Lake Mirabad and from other sites in northern Africa, the eastern Mediterranean and Arabia may be explained by shifting atmospheric circulation patterns and varying amplitudes of precipitation as a consequence of changes in insolation. To promote further ostracod palaeoecological research in the Near East, a checklist of non-marine Ostracoda known from modern Iran is presented as an appendix.

The recent palaeoecology and conservation status of Balkan Lake Dojran

Abstract Lake Dojran is a Balkan lake which is host to a number of endemic species and is of high conservation concern. We report the results of research into the present ecological status of the lake and its comparison with palaeolimnological data for recent human impact, based on modern zoobenthology, diatom and ostracod palaeoecology, sedimentology and 18 O/ 16 O and 13 C/ 12 C stable isotope ratios from shells of Darwinula stevensoni (Ostracoda) and Anodonta cygnea glochidia larvae (Mollusca). The results of the modern survey indicate that benthic faunal composition has changed substantially in recent years. However, in spite of documented eutrophication and major, human-induced fluctuations in lake level since the 1950s, the results of palaeoecological analyses indicate that Lake Dojran is still buffered from major ecological impact. The palaeolimnological datasets suggest, however, that an ecological threshold may have been reached, and remedial measures should now be considered. Ecological problems include not only a major decrease in water depth through water abstraction and the diversion of source waters for agricultural purposes, but also recent climatic aridity and anthropogenic pollution. However, geopolitical problems presently conspire against the formulation of a management strategy for the preservation of the lake and its endemic fauna and flora.

Modern and fossil ostracods from ancient lakes

Ancient lake systems contain incredibly rich archives of past biological and environmental change. Ostracods have long been associated with ancient lakes, largely because as a group they are common in such habitats, often occupy specific ecological niches and, generally, can be relatively easily studied. In addition, their excellent potential for preservation ensures that they frequently have a long fossil record, thereby providing a convenient means for investigating temporal changes in the lake system. Here we use a combination of biological and geological criteria to classify ancient lakes and, by means of a series of case studies using both extant and fossil exam-ples, go on to review some of the evolutionary and palaeoclimatic issues that can be addressed with respect to ancient lake ostracod faunas. We also high-light some of the current deficiencies in the field and make a call for more concerted research, not only from taxonomic and ecological standpoints, but also in the provision of rigorous chronological control for fossil sequences. The potential to couple both modern and fossil faunal data with new genetic analysis techniques will ensure that ostracod studies remain at the forefront of palaeoclimatic and evolutionary research in ancient lake environments.

Evolutionary biogeography of water shrews (Neomys spp.) in the western Palaearctic Region

We studied the morphology, DNA sequence, and Recent and Pleistocene distributions of three species of the water shrew genus Neomys (N. fodiens, N. anomalus, and N. teres) represented by samples from the Balkans and Asia Minor. Adaptations to semi-aquatic life (large body size, fringes of stiff hairs bordering the hind foot, and a tail keel) were most developed in N. fodiens and N. teres and least developed in N. anomalus. However, sympatric N. fodiens and N. anomalus did not differ significantly in relative braincase size. The three Neomys species clearly differed in glans penis morphology, N. teres being the most distinct, with a longer glans (length = 10.8-14.6 mm) than N. anomalus (7.0-8.0 mm) or N. fodiens (7.5-8.5 mm). Phylogenetic analysis placed N. fodiens as a sister-group to the anomalus-teres clade, based on both cytochrome b and 12S rRNA fragments. Palaeodistribution maps are presented for the three Recent taxa and the palaeospecies N. newtoni and N. browni. Possible evolutionary scenarios are ...