Comment on "Glacial survival of boreal trees in northern Scandinavia".

Parducci et al. (Reports, 2 March 2012, p. 1083) fail to present convincing evidence for glacial survival of Pinus and Picea in northern Scandinavia.

Founder takes all: density-dependent processes structure biodiversity.

Density-dependent processes play a key role in the spatial structuring of biodiversity. Specifically, interrelated demographic processes, such as gene surfing, high-density blocking, and competitive exclusion, can generate striking geographic contrasts in the distributions of genes and species. Here, we propose that well-studied evolutionary and ecological biogeographic patterns of postglacial recolonization, progressive island colonization, microbial sectoring, and even the 'Out of Africa' pattern of human expansion, are fundamentally similar, underpinned by a 'founder takes all' density-dependent principle.

Numts help to reconstruct the demographic history of the ocellated lizard (Lacerta lepida) in a secondary contact zone.

In northwestern Iberia, two largely allopatric Lacerta lepida mitochondrial lineages occur, L5 occurring to the south of Douro River and L3 to the north, with a zone of putative secondary contact in the region of the Douro River valley. Cytochrome b sequence chromatograms with polymorphisms at nucleotide sites diagnostic for the two lineages were detected in individuals in the region of the Douro River and further north within the range of L3. We show that these polymorphisms are caused by the presence of four different numts (I-IV) co-occurring with the L3 genome, together with low levels of heteroplasmy.

Phylogeography and demographic history of Lacerta lepida in the Iberian Peninsula: multiple refugia, range expansions and secondary contact zones.

Background: The Iberian Peninsula is recognized as an important refugial area for species survival and diversification during the climatic cycles of the Quaternary. Recent phylogeographic studies have revealed Iberia as a complex of multiple refugia. However, most of these studies have focused either on species with narrow distributions within the region or species groups that, although widely distributed, generally have a genetic structure that relates to pre-Quaternary cladogenetic events.

Quaternary phylogeography: the roots of hybrid zones.

The older history of hybrid zones is explored through consideration of recent advances in climatology, paleontology and phylogeography in the Late Cenozoic, particularly the Quaternary Period with its major climatic cycles. The fossil record shows that these ice ages and their nested millennial oscillations caused substantial changes in species distributions and with genetic evidence allows deduction of refugia and colonization routes in arctic, temperate, desert and tropical regions. The age of divergence between hybridizing lineages varies from the Late Pleistocene to the Late Miocene, implying much range change and varying selection on sister lineages.

Unexpected relationships of substructured populations in Chinese Locusta migratoria.

Background: Highly migratory species are usually expected to have minimal population substructure because strong gene flow has the effect of homogenizing genetic variation over geographical populations, counteracting random drift, selection and mutation. The migratory locust Locusta migratoria belongs to a monotypic genus, and is an infamous pest insect with exceptional migratory ability - with dispersal documented over a thousand kilometers. Its distributional area is greater than that of any other locust or grasshopper, occurring in practically all the temperate and tropical regions of the eastern hemisphere.

Microbial modification of host long-distance dispersal capacity.

Background: Dispersal plays a key role in shaping biological and ecological processes such as the distribution of spatially-structured populations or the pace and scale of invasion. Here we have studied the relationship between long-distance dispersal behaviour of a pest-controlling money spider, Erigone atra, and the distribution of maternally acquired endosymbionts within the wider meta-population. This spider persists in heterogeneous environments because of its ability to recolonise areas through active long-distance airborne dispersal using silk as a sail, in a process termed 'ballooning'.

Diversity and evolutionary history of the MHC DQA gene in leporids.

The European rabbit (Oryctolagus cuniculus) is used as a model for many human diseases, yet comparatively little is known of its genetics, particularly at important loci such as the major histocompatibility complex (MHC). This study investigated genetic diversity and evolutionary history of the DQA gene in a range of leporid species by analysing coding sequence diversity of exon 2 and intron 2 in 53 individuals of 16 different species. Fifty leporid DQA alleles were detected, including 13 novel European rabbit alleles.

Apparent 'sympatric' speciation in ecologically similar herbivorous beetles facilitated by multiple colonizations of an island.

Coexistence of recently diverged and ecologically similar sister species in complete sympatry represents a particularly compelling case for sympatric speciation. This study investigates the possible sympatric origin of two coexisting bark beetle taxa that utilize the same host plant on the island of La Palma in the Canary Islands. Aphanarthrum subglabrum and Aphanarthrum glabrum ssp.

Modelling dispersal of a temperate insect in a changing climate.

We construct a novel individual-based random-walk model to assess how predicted global climate change might affect the dispersal rates of a temperate insect. Using a novel approach we obtained accurate field measurements of daily movements for individuals over time to parameterize our model. Males were found to move significantly further on average than females.

Reduced heterozygosity depresses sperm quality in wild rabbits, Oryctolagus cuniculus.

When close relatives are forced to reproduce, the resulting offspring inherit above average homozygosity and reduced fitness. Biologists now recognize inbreeding depression in the wild, a phenomenon that will probably increase as natural populations become depleted and fragmented. Inbreeding depression is most commonly expressed as compromised fertility and embryogenesis, but actual mechanisms remain poorly understood, especially for wild populations.

Wolbachia and other endosymbiont infections in spiders.

Maternally inherited endosymbiotic bacteria, such as Wolbachia, Rickettsia and Spiroplasma, have been shown to have wide-ranging effects on the reproduction of their hosts. We present data on the presence of each of these sorts of bacteria in spiders, a group for which there are currently few data, but where such infections could explain many observed reproductive characteristics, such as sex ratio skew. The Wolbachia and Spiroplasma variants that we find in spiders belong to the same clades previously found to infect other arthropods, but many of the rickettsias belong to two, novel, hitherto spider-specific bacterial lineages.

European colonization by the spined loach (Cobitis taenia) from Ponto-Caspian refugia based on mitochondrial DNA variation.

In the last 20 years, new species, asexual reproduction, polyploidy and hybridization have all been reported within the genus Cobitis. An understanding of the current distribution and baseline phylogeographical history of 'true' nonhybrid Cobitis species is crucial in order to unravel these discoveries. In the present work, we investigated the phylogeography of the spined loach, Cobitis taenia, using 1126 bp of the mitochondrial cytochrome b gene from 174 individuals collected at 47 sites.

The structure of biodiversity - insights from molecular phylogeography.

DNA techniques, analytical methods and palaeoclimatic studies are greatly advancing our knowledge of the global distribution of genetic diversity, and how it evolved. Such phylogeographic studies are reviewed from Arctic, Temperate and Tropical regions, seeking commonalities of cause in the resulting genetic patterns. The genetic diversity is differently patterned within and among regions and biomes, and is related to their histories of climatic changes.

The origin and radiation of Macaronesian beetles breeding in Euphorbia: the relative importance of multiple data partitions and population sampling.

Species-level phylogenies derived from many independent character sources and wide geographical sampling provide a powerful tool in assessing the importance of various factors associated with cladogenesis. In this study, we explore the relative importance of insular isolation and host plant switching in the diversification of a group of bark beetles (Curculionidae: Scolytinae) feeding and breeding in woody Euphor biaspurges. All species in the genus Aphanarthrumare each associated with only one species group of Euphorbia(succulents or one of three different arborescent groups), and the majority of species are endemic to one or several of the Macaronesian Islands.

Nuclear DNA analyses in genetic studies of populations: practice, problems and prospects.

Population-genetic studies have been remarkably productive and successful in the last decade following the invention of PCR technology and the introduction of mitochondrial and microsatellite DNA markers. While mitochondrial DNA has proven powerful for genealogical and evolutionary studies of animal populations, and microsatellite sequences are the most revealing DNA markers available so far for inferring population structure and dynamics, they both have important and unavoidable limitations. To obtain a fuller picture of the history and evolutionary potential of populations, genealogical data from nuclear loci are essential, and the inclusion of other nuclear markers, i.

Comparison of substitution rates in ZFX and ZFY introns of sheep and goat related species supports the hypothesis of male-biased mutation rates.

There is a growing body of evidence that males serve as the major generators of mutations, due to the larger number of cell divisions involved in sperm compared to egg production. In mammals, this hypothesis (referred to as "male-driven evolution") has been tested by comparison of nucleotide substitution rates on the X and Y sex chromosomes in a limited number of taxa, predominantly primates and rodents. This study asks whether male-driven evolution is a more general phenomenon among mammals, by comparison of paralogous ZFX and ZFY intron sequences in sheep and goat species (the tribe Caprini).

CLINES FOR HYBRID DYSFUNCTION IN A GRASSHOPPER HYBRID ZONE.

Two subspecies of the grasshopper Chorthippus parallelus meet in the Pyrenees forming a hybrid zone several kilometers wide. Crosses between the two pure taxa result in sterile male offspring and normal females (i.e.