When east met west: the sub-fossil footprints of the west European hedgehog and the northern white-breasted hedgehog during the Late Quaternary in Europe

The distinct distribution of the west European hedgehog Erinaceus europaeus and the northern white-breasted hedgehog Erinaceus roumanicus and their separate refugial origins after the Pleistocene is a well-known example in the zoogeography of the Holarctic. Among the Late Quaternary faunal assemblages, the west European hedgehog is recorded at 269 sites whereas the northern white-breasted hedgehog is recorded only at 52 sites in Europe. The distribution patterns of the temporal and spatial Glacial records of the west European hedgehog show a general trend: a strong restriction to glacial refugia (the Iberian and Italian Peninsulas) during the Weichselian Glacial until the end of the Last Glacial Maximum, and a colonization of southern France during the early Late Glacial between 14 000 and 125 00 ¹⁴C years BP (15 000–12 800 cal. BC). Whereas the British Isles could have already been colonised by the end of the Pre-Boreal, in the rest of Central Europe E. europaeus was clearly distributed there in the Boreal for the first time. The west European hedgehog is an absolute Holocene faunal element in Central Europe. It appears in most parts of Central Europe during the Early Holocene, when the west European hedgehog met its eastern relative, which probably was similarly sensitive. After meeting each other, the distribution limit of both Erinaceus species in Central Europe seems to have been relatively constant in its geographic extent. Because of the clear climatic correlation, E. europaeus should be considered as an indicator species for temperate climatic conditions of the Holocene fauna. This should be considered during the reconstruction of climatic conditions with the help of the analysis of quaternary faunal material.     

Phylogeography of the white-tailed eagle, a generalist with large dispersal capacity

Aim Late Pleistocene glacial changes had a major impact on many boreal and temperate taxa, and this impact can still be detected in the present‐day phylogeographic structure of these taxa. However, only minor effects are expected in species with generalist habitat requirements and high dispersal capability. One such species is the white‐tailed eagle, Haliaeetus albicilla, and we therefore tested for the expected weak population structure at a continental level in this species. This also allowed us to describe phylogeographic patterns, and to deduce Ice Age refugia and patterns of postglacial recolonization of Eurasia. Location Breeding populations from the easternmost Nearctic (Greenland) and across the Palaearctic (Iceland, continental Europe, central and eastern Asia, and Japan). Methods Sequencing of a 500 base‐pair fragment of the mitochondrial DNA control region in 237 samples from throughout the distribution range. Results Our analysis revealed pronounced phylogeographic structure. Overall, low genetic variability was observed across the entire range. Haplotypes clustered in two distinct haplogroups with a predominantly eastern or western distribution, and extensive overlap in Europe. These two major lineages diverged during the late Pleistocene. The eastern haplogroup showed a pattern of rapid population expansion and colonization of Eurasia around the end of the Pleistocene. The western haplogroup had lower diversity and was absent from the populations in eastern Asia. These results suggest survival during the last glaciation in two refugia, probably located in central and western Eurasia, followed by postglacial population expansion and admixture. Relatively high genetic diversity was observed in northern regions that were ice‐covered during the last glacial maximum. This, and phylogenetic relationships between haplotypes encountered in the north, indicates substantial population expansion at high latitudes. Areas of glacial meltwater runoff and proglacial lakes could have provided suitable habitats for such population growth. Main conclusions This study shows that glacial climate fluctuations had a substantial impact on white‐tailed eagles, both in terms of distribution and demography. These results suggest that even species with large dispersal capabilities and relatively broad habitat requirements were strongly affected by the Pleistocene climatic shifts.     

Mitochondrial DNA variation in bull trout (Salvelinus confluentus) from northwestern North America: implications for zoogeography and conservation

Bull trout, Salvelinus confluentus (Salmonidae), are distributed in northwestern North America from Nevada to Yukon Territory, largely in interior drainages. The species is of conservation concern owing to declines in abundance, particularly in southern portions of its range. To investigate phylogenetic structure within bull trout that might form the basis for the delineation of major conservation units, we conducted a mitochondrial DNA (mtDNA) survey in bull trout from throughout its range. Restriction fragment length polymorphism (RFLP) analysis of four segments of the mtDNA genome with 11 restriction enzymes resolved 21 composite haplotypes that differed by an average of 0.5% in sequence. One group of haplotypes predominated in 'coastal' areas (west of the coastal mountain ranges) while another predominated in 'interior' regions (east of the coastal mountains). The two putative lineages differed by 0.8% in sequence and were also resolved by sequencing a portion of the ND1 gene in a representative of each RFLP haplotype. Significant variation existed within individual sample sites (12% of total variation) and among sites within major geographical regions (33%), but most variation (55%) was associated with differences between coastal and interior regions. We concluded that: (i) bull trout are subdivided into coastal and interior lineages; (ii) this subdivision reflects recent historical isolation in two refugia south of the Cordilleran ice sheet during the Pleistocene: the Chehalis and Columbia refugia; and (iii) most of the molecular variation resides at the interpopulation and inter-region levels. Conservation efforts, therefore, should focus on maintaining as many populations as possible across as many geographical regions as possible within both coastal and interior lineages.     

Chromosomal differentiation through an Alpine hybrid zone in the grasshopper Chorthippus parallelus

The grasshopper Chorthippus parallelus is genetically differentiated over its range into at least five major geographical subdivisions. Two of these subdivisions, designated as subspecies, meet and form a hybrid zone in the Pyrenees. These subspecies differ for a wide range of morphological, behavioural and chromosomal characters, which vary clinally across the zone. A further geographical subdivision exists within Italy. Here we present the first evidence for chromosomal divergence between populations of the grasshopper north and south of the Alps. Across two Alpine cols (Col de Larche, between France and Italy; Passo de Resia, between Austria and Italy), these populations differ in both structural and functional components of the X-chromosome. Northern Alpine individuals possess an active nucleolar organizing region (NOR) at the distal end of the X-chromosome and an associated region of heterochromatin (C-band). Both these features are absent from individuals from the south of the Alps. However, all individuals examined carry distally located rDNA on the X-chromosome. Clinal transition was examined in the distal C-band in transects through the two cols. The cline centres are roughly coincident with the tops of the cols. Both clines were of similar widths (Col de Larche, 21.88 km; Passo de Resia, 24.05 km), and therefore much wider than those for an X-linked distal C-band in the Pyrenean hybrid zone. This suggests that there are different selective pressures on the cytogenetic characters in the Alps. The results are discussed in the context of the historical population dynamics of the species in relation to the climatic changes associated with the Pleistocene ice ages.     

Adaptive Introgression Facilitates Adaptation to High Latitudes in European Aspen (Populus tremula L.)

Understanding local adaptation has become a key research area given the ongoing climate challenge and the concomitant requirement to conserve genetic resources. Perennial plants, such as forest trees, are good models to study local adaptation given their wide geographic distribution, largely outcrossing mating systems, and demographic histories. We evaluated signatures of local adaptation in European aspen (Populus tremula) across Europe by means of whole-genome resequencing of a collection of 411 individual trees. We dissected admixture patterns between aspen lineages and observed a strong genomic mosaicism in Scandinavian trees, evidencing different colonization trajectories into the peninsula from Russia, Central and Western Europe. As a consequence of the secondary contacts between populations after the last glacial maximum, we detected an adaptive introgression event in a genome region of ∼500 kb in chromosome 10, harboring a large-effect locus that has previously been shown to contribute to adaptation to the short growing seasons characteristic of Northern Scandinavia. Demographic simulations and ancestry inference suggest an Eastern origin—probably Russian—of the adaptive Nordic allele which nowadays is present in a homozygous state at the north of Scandinavia. The strength of introgression and positive selection signatures in this region is a unique feature in the genome. Furthermore, we detected signals of balancing selection, shared across regional populations, that highlight the importance of standing variation as a primary source of alleles that facilitate local adaptation. Our results, therefore, emphasize the importance of migration–selection balance underlying the genetic architecture of key adaptive quantitative traits.     

Genetic variation of Eryngium campestre L. (Apiaceae) in Central Europe

In Germany, Eryngium campestre is restricted to dry habitats along the rivers Rhine and Elbe and to a few areas in Central Germany. This distribution pattern is usually regarded as a typical pattern of postglacial immigration. In the present study, we investigated whether these two geographically distinct distribution areas are genetically differentiated and whether conclusions can be drawn regarding colonization history. To analyse the phylogeographic structure of E. campestre in Central Europe, 278 individuals from 29 populations within Germany and from further reference populations within Europe were analysed. We applied amplified fragment length polymorphisms to examine their genetic relatedness. Our analyses revealed three groups: a Mediterranean group additionally including two Rhine populations; a Rhine–Main group which further includes the westernmost population from the central German dry area; and one group which includes all eastern populations. Our results show that the two geographically distinct areas are genetically differentiated. As genetic diversity within the Elbe populations is very low, we conclude that this area, which was strongly affected through the late glacial maximum, was colonized relatively recently. High genetic diversity in the Rhine populations indicates a contact zone where lineages of different origin met. This would imply that today's patterns of genetic variation were caused through glacial range contractions and expansions. The present study is one of the first studies that deal with the postglacial distribution pattern of a dry grassland plant species in Central Europe and the results suggest that a survival of E. campestre at least during the Dryas cold stage might be possible.     

Patterns of differentiation in a colour polymorphism and in neutral markers reveal rapid genetic changes in natural damselfly populations

The existence and mode of selection operating on heritable adaptive traits can be inferred by comparing population differentiation in neutral genetic variation between populations (often using F(ST) values) with the corresponding estimates for adaptive traits. Such comparisons indicate if selection acts in a diversifying way between populations, in which case differentiation in selected traits is expected to exceed differentiation in neutral markers [F(ST )(selected) > F(ST )(neutral)], or if negative frequency-dependent selection maintains genetic polymorphisms and pulls populations towards a common stable equilibrium [F(ST) (selected) < F(ST) (neutral)]. Here, we compared F(ST) values for putatively neutral data (obtained using amplified fragment length polymorphism) with estimates of differentiation in morph frequencies in the colour-polymorphic damselfly Ischnura elegans. We found that in the first year (2000), population differentiation in morph frequencies was significantly greater than differentiation in neutral loci, while in 2002 (only 2 years and 2 generations later), population differentiation in morph frequencies had decreased to a level significantly lower than differentiation in neutral loci. Genetic drift as an explanation for population differentiation in morph frequencies could thus be rejected in both years. These results indicate that the type and/or strength of selection on morph frequencies in this system can change substantially between years. We suggest that an approach to a common equilibrium morph frequency across all populations, driven by negative frequency-dependent selection, is the cause of these temporal changes. We conclude that inferences about selection obtained by comparing F(ST) values from neutral and adaptive genetic variation are most useful when spatial and temporal data are available from several populations and time points and when such information is combined with other ecological sources of data.     

Long-Term Trends in Faunal Recolonization After Bauxite Mining in the Jarrah Forest of Southwestern Australia

Abstract Fauna serve a key role in many forest ecological processes. Despite this, few studies have considered long‐term faunal recolonization after mining and rehabilitation of forest ecosystems. In the jarrah forest of southwestern Australia, permanent fauna monitoring sites have been established in bauxite mined areas rehabilitated in 1990 and in a range of representative unmined forest control sites. At each site mammals, birds, reptiles, and ants were surveyed in 1992, 1995, and 1998. The aims of the monitoring were to develop a better understanding of faunal recolonization trends, to produce recommendations for promoting fauna return, and to consider which techniques and fauna groups are best suited for monitoring recolonization. The results showed that successional trends varied between fauna groups. Generalist foraging mammals recolonized rapidly, whereas small predators took longer. Feral mice were initially abundant and then declined. Birds gradually recolonized, and after 8 years bird communities were very similar to those in unmined forest sites. Reptile species took longer, and after 8 years numbers of species remained lower than in unmined forests. Species richness and diversity of ants in 8‐year‐old rehabilitation were comparable with those of unmined forest in some rehabilitated sites but were lower in others. The composition of ant communities was still different from that of unmined sites. Ant species that only use disturbed forest declined rapidly in abundance as rehabilitation aged. The results suggest that although the rates of faunal recolonization will vary, with time most or all mammal, bird, reptile, and ant species should inhabit rehabilitated bauxite mines. The densities of many are likely to be similar to those in unmined forest, but for others it is too early to know whether this will be the case. Techniques for promoting fauna return are discussed. This study demonstrates that no single fauna group is suitable for use as an overall “indicator” of faunal recolonization; different fauna species and groups reflect different aspects of faunal succession.     

Phylogeography of postglacial range expansion in Nigronia serricornis Say (Megaloptera: Corydalidae)

We have examined the effects of post-Wisconsinan glacial range expansion on the phylogeography of the saw-combed fishfly, Nigronia serricornis Say (Megaloptera: Corydalidae) because aquatic insects are under-represented in postglacial studies (and in phylogeography in general), and because the effects of ecological degradation on the population genetics of environmental indicator species like N. serricornis cannot be measured unless the underlying phylogeography is understood. Sequence data from a 630-base fragment of the mitochondrial cytochrome oxidase I (COI) gene were subjected to amova and nested clade analysis for 30 populations (n = 344) of N. serricornis. Both the amova and nested clade analysis revealed substantial population structure; 44.4% of the variance occured among populations. Three northward migrations are apparent: one from Tennessee into Illinois, Indiana, Wisconsin, Michigan and Ontario, a second that radiated eastward from Pennsylvania, and a third that moved along the coast from North Carolina into Connecticut, Massachusetts, Maine and then into New York. The latter two of these migrations were the result of contiguous range expansions, while the former expansion, out of Tennessee, appears to have been rapid with little gene flow from the source population. Additional clades included a group of haplotypes in central Kentucky that appear to have expanded along preglacial drainages, and clades in North Carolina and Georgia that have remained centrally located. Haplotype diversity decreased from south to north, a pattern that has been widely reported for animal and plant populations that expanded with the retreat of the Wisconsinan glaciation.