Quaternary history of the European roe deer Capreolus capreolus

• 1 The European roe deer Capreolus capreolus is a typical faunal element of the Holocene. It was already present in Europe at least 600 000 years ago and it has been known from both glacial and interglacial phases since then. With nearly 3000 fossil and subfossil records, it is one of the most frequent mammals in the Late Quaternary.
• 2 During the Middle and Late Weichselian Pleniglacial, the distribution of the roe deer was not restricted to the Mediterranean peninsulas but repeatedly reached regions of central Europe. In contrast to that, roe deer records from the Last Glacial Maximum (LGM, 21.0–14.5 ka ¹⁴C BP) are largely confined to the Mediterranean peninsulas – with the exception of south‐western France and the surroundings of the Carpathians where several records attest to its occurrence during the LGM.
• 3 During the Greenland Interstadial 1 (12.5–10.8 ka ¹⁴C BP), the species' distribution extended further north and the roe deer appeared north of the Alps and reached regions of central Germany. This seems to be correlated with the abrupt change to more favourable environmental conditions during this period. It is very likely that the roe deer disappeared north of the Alps during the Younger Dryas cooling (10.8–10.0 ka¹⁴C BP). The northern regions of the central European lowlands were recolonized by roe deer during the late Preboreal 9.7–9.5 ka ¹⁴C BP for the first time since the Weichselian Glacial.
• 4 The combined pattern of genetic data and fossil records of European roe deer suggests several regions in the Iberian peninsula, southern France, Italy and the Balkans as well as in the Carpathians and/or eastern Europe as glacial refugia. It further suggests that C. capreolus might have recolonized most parts of central‐northern Europe out of one or more eastern European (not Balkan) and/or Carpathian refugia. This recolonization wave might have blocked immigration from the traditional Mediterranean areas.

     

Do pathogens reduce genetic diversity of their hosts? Variable effects of sylvatic plague in black‐tailed prairie dogs

Introduced diseases can cause dramatic declines in—and even the loss of—natural populations. Extirpations may be followed by low recolonization rates, leading to inbreeding and a loss of genetic variation, with consequences on population viability. Conversely, extirpations may create vacant habitat patches that individuals from multiple source populations can colonize, potentially leading to an influx of variation. We tested these alternative hypotheses by sampling 15 colonies in a prairie dog metapopulation during 7 years that encompassed an outbreak of sylvatic plague, providing the opportunity to monitor genetic diversity before, during and after the outbreak. Analysis of nine microsatellite loci revealed that within the metapopulation, there was no change in diversity. However, within extirpated colonies, patterns varied: In half of the colonies, allelic richness after recovery was less than the preplague conditions, and in the other half, richness was greater than the preplague conditions. Finally, analysis of variation within individuals revealed that prairie dogs present in recolonized colonies had higher heterozygosity than those present before plague. We confirmed plague survivorship in six founders; these individuals had significantly higher heterozygosity than expected by chance. Collectively, our results suggest that high immigration rates can maintain genetic variation at a regional scale despite simultaneous extirpations in spatially proximate populations. Thus, virulent diseases may increase genetic diversity of host populations by creating vacant habitats that allow an influx of genetic diversity. Furthermore, even highly virulent diseases may not eliminate individuals randomly; rather, they may selectively remove the most inbred individuals.     

Towards the understanding of the origin of the Polish remote population of Polyommatus (Agrodiaetus) ripartii (Lepidoptera: Lycaenidae) based on karyology and molecular phylogeny

Many species of the subgenus Agrodiaetus have dotlike distribution ranges, and the delimitation of the majority of species is only possible on the basis of chromosomal and/or molecular data. In our research, we used a combination of chromosomal and molecular mitochondrial and nuclear markers to analyse the taxonomic identity and to study the phylogeographic history of an enigmatic Agrodiaetus population from South Poland. We discovered this population to be chromosomally and genetically indistinguishable from the widely distributed West Palaearctic species Polyommatus ripartii (Freyer, 1830). Moreover, this population was found to be genetically homogenous and to share the single identified COI+COII haplotype with populations from remote localities in Spain, Bulgaria and Ukraine. Coalescence‐based dating with COI+COII marker estimated that the Polish population originated most likely 10 600–14 300 years ago. This estimation corresponds well to the age (11 700–12 000 years) of palaeontological remnant of Onobrychis arenaria, a food plant of P. ripartii, found in Poland. Generally, the data obtained support the hypotheses that (1) the common ancestor of the Central European populations originated in a refugium in the North Balkan, (2) after the last glacial maximum, this ancestor became broadly distributed in Europe and (3) the Nida population in Poland represents a relict of this ancient distribution.     

Large‐scale longitudinal gradients of genetic diversity: a meta‐analysis across six phyla in the Mediterranean basin

Biodiversity is the diversity of life at all scales, from genes to ecosystems. Predicting its patterns of variation across the globe is a fundamental issue in ecology and evolution. Diversity within species, that is, genetic diversity, is of prime importance for understanding past and present evolutionary patterns, and highlighting areas where conservation might be a priority. Using published data on the genetic diversity of species whose populations occur in the Mediterranean basin, we calculated a coefficient of correlation between within‐population genetic diversity indices and longitude. Using a meta‐analysis framework, we estimated the role of biological, ecological, biogeographic, and marker type factors on the strength and magnitude of this correlation in six phylla. Overall, genetic diversity increases from west to east in the Mediterranean basin. This correlation is significant for both animals and plants, but is not uniformly expressed for all groups. It is stronger in the southern than in the northern Mediterranean, in true Mediterranean plants than in plants found at higher elevations, in trees than in other plants, and in bi‐parentally and paternally than in maternally inherited DNA makers. Overall, this correlation between genetic diversity and longitude, and its patterns across biological and ecological traits, suggests the role of two non‐mutually exclusive major processes that shaped the genetic diversity in the Mediterranean during and after the cold periods of the Pleistocene: east‐west recolonization during the Holocene and population size contraction under local Last Glacial Maximum climate in resident western and low elevation Mediterranean populations.     

A greener Greenland? Climatic potential and long-term constraints on future expansions of trees and shrubs

Warming-induced expansion of trees and shrubs into tundra vegetation will strongly impact Arctic ecosystems. Today, a small subset of the boreal woody flora found during certain Plio-Pleistocene warm periods inhabits Greenland. Whether the twenty-first century warming will induce a re-colonization of a rich woody flora depends on the roles of climate and migration limitations in shaping species ranges. Using potential treeline and climatic niche modelling, we project shifts in areas climatically suitable for tree growth and 56 Greenlandic, North American and European tree and shrub species from the Last Glacial Maximum through the present and into the future. In combination with observed tree plantings, our modelling highlights that a majority of the non-native species find climatically suitable conditions in certain parts of Greenland today, even in areas harbouring no native trees. Analyses of analogous climates indicate that these conditions are widespread outside Greenland, thus increasing the likelihood of woody invasions. Nonetheless, we find a substantial migration lag for Greenland''s current and future woody flora. In conclusion, the projected climatic scope for future expansions is strongly limited by dispersal, soil development and other disequilibrium dynamics, with plantings and unintentional seed dispersal by humans having potentially large impacts on spread rates.     

Seasonal Migration of Meloidogyne chitwoodi and its Role in Potato Production

Seasonal vertical migration of Meloidogyne chitwoodi through soil and its impact on potato production in Washington and Oregon was studied. Nematode eggs and second-stage juveniles (J2) were placed at various depths (0-180 cm) in tubes filled with soil and buried vertically or in holes dug in potato fields. Tubes were removed at intervals over a 12-month period and soil was bioassayed on tomato roots. Upward migration began in the spring after water had percolated through the tubes. Nematodes were detected in the top 5 cm of tubes within 1-2 months of burial, depending on depth of placement. Potatoes were grown in field plots for 4 or 5 months before the tubers were evaluated for infection. One hundred eggs and J2 per gram soil placed at 60 and 90 cm caused significant tuber damage at the Washington and Oregon sites, respectively. At the Washington site, inoculum placed at 90, 120, and 150 cm caused potato root infection without serious impact on tuber quality, but inoculum diluted 2-8 times and placed at 90 cm did not cause root or tuber infection. Nematode migration was dependent on soil texture; 9 days after placement at the bottoms of tubes, J2 had moved up 55 cm in sandy loam soil (Oregon) but only 15 cm in silt loam (Washington). Thus, the importance of M. chitwoodi which occur deep in a soil profile may depend on soil texture, population density, and length of the growing season.     

Macroinvertebrate colonization of replacement substrate below a hypolimnial release reservoir

Loss of substrate from occasional high flows below reservoirs on the Trinity River prompted government agencies to replace the gravels to protect the anadromous fisheries resource. Several riffles were restored using 2.5 to to cm gravels. Three of these and two natural riffles, with gravels ranging up to 20 cm, were surveyed over a two-year period to determine the effect of this gravel replacement on the macroinvertebrate fauna. Replaced gravels were too small to support the diversity of organisms found on natural riffle gravels. In addition, temperature alteration by the hypolimnial release reservoir prevented colonization by all but a few organisms able to tolerate such conditions in the riffles below the dam. Large but unstable populations of Simulium, Baetis, and the Chironominae developed below the dam, aided by an abundant periphyton and detrital food supply and lack of competition and predation. It is concluded that habitat diversity through the use of a range of gravel sizes up to the size naturally found in productive riffles should be used in riffle restoration projects in order to increase habitat complexity, species diversity, density, and biomass important in maintaining fishery stocks.     

Allopatric origins of sympatric brook charr populations: colonization history and admixture

Natural selection is presumed to be the driving force behind the occurrence of phenotypically and genetically divergent populations in sympatry within many north temperate freshwater fishes. If, however, these populations have different ancestral origins, history could also contribute to their divergence. We previously found evidence for the role of selection in the evolution of divergent outflow and inflow breeding populations of migratory brook charr (Salvelinus fontinalis) inhabiting postglacial Mistassini Lake (Quebec, Canada). Here, we show that these populations do not have a common origin, through the use of admixture and spatial analyses with seven microsatellite loci. Divergent populations clustered into two different population groups when compared to samples from surrounding drainages, although inflow populations appeared to be more admixed between the two population groups than the outflow population. These results are noteworthy since outflow and inflow populations were monomorphic at mitochondrial DNA (338-bp sequence of the control region) and are only moderately differentiated (mean F(ST) = 0.10). Colonization by two ancestral populations was also consistent with known outflow direction changes throughout lake formation. In addition to providing insight into how phenotypic divergence in sympatry may have been affected by the nature (i.e. timing and direction) of colonization of ancestral populations, our results also suggest that ancestral populations may have differed in their ability to colonize certain lake habitats.     

Probable direction of the postglacial colonization of rivers on northern slopes of the Carpathian Ridge by Barbus carpathicus (Teleostei: Cyprinidae) evidenced by cline of genetic variation

A cline in microsatellite diversity appeared among populations of Barbus carpathicus in four adjacent river basins on the northern slopes of the Carpathian Ridge, with western populations more variable than eastern ones ( H _S equals 0·45, 0·32, 0·23 and 0·13, respectively). Overall genetic variation was low, likely reflecting population bottlenecks during postglacial expansions through the Danube–Vistula watershed and eastward into Carpathian tributaries of the Vistula River. Genetic similarities between populations in the westernmost tributary of the Dniester (Strwiąż River) and those in the adjacent Vistula tributary (San River) suggest that at least the western part of the Dniester basin was colonized from the Vistula River system.