Climate shaped the worldwide distribution of human mitochondrial DNA sequence variation

There is an ongoing discussion in the literature on whether human mitochondrial DNA (mtDNA) evolves neutrally. There have been previous claims for natural selection on human mtDNA based on an excess of non-synonymous mutations and higher evolutionary persistence of specific mitochondrial mutations in Arctic populations. However, these findings were not supported by the reanalysis of larger datasets. Using a geographical framework, we perform the first direct test of the relative extent to which climate and past demography have shaped the current spatial distribution of mtDNA sequences worldwide. We show that populations living in colder environments have lower mitochondrial diversity and that the genetic differentiation between pairs of populations correlates with difference in temperature. These associations were unique to mtDNA; we could not find a similar pattern in any other genetic marker. We were able to identify two correlated non-synonymous point mutations in the ND3 and ATP6 genes characterized by a clear association with temperature, which appear to be plausible targets of natural selection producing the association with climate. The same mutations have been previously shown to be associated with variation in mitochondrial pH and calcium dynamics. Our results indicate that natural selection mediated by climate has contributed to shape the current distribution of mtDNA sequences in humans

Evolutionary history of the greater white-toothed shrew (Crocidura russula) inferred from analysis of mtDNA, Y, and X chromosome markers.

We investigate the evolutionary history of the greater white-toothed shrew across its distribution in northern Africa and mainland Europe using sex-specific (mtDNA and Y chromosome) and biparental (X chromosome) markers. All three loci confirm a large divergence between eastern (Tunisia and Sardinia) and western (Morocco and mainland Europe) lineages, and application of a molecular clock to mtDNA divergence estimates indicates a more ancient separation (2.25 M yr ago) than described by some previous studies, supporting claims for taxonomic revision. Moroccan ancestry for the mainland European population is inconclusive from phylogenetic trees, but is supported by greater nucleotide diversity and a more ancient population expansion in Morocco than in Europe. Signatures of rapid population expansion in mtDNA, combined with low X and Y chromosome diversity, suggest a single colonization of mainland Europe by a small number of Moroccan shrews >38 K yr ago. This study illustrates that multilocus genetic analyses can facilitate the interpretation of species' evolutionary history but that phylogeographic inference using X and Y chromosomes is restricted by low levels of observed polymorphism

Elnagdy et al data

Experimental data collected to test impact of various male-killing bacteria on the fitness of their ladybird hosts

Evolutionary strata on the chicken Z chromosome: implications for sex chromosome evolution.

The human X chromosome exhibits four "evolutionary strata," interpreted to represent distinct steps in the process whereby recombination became arrested between the proto X and proto Y. To test if this is a general feature of sex chromosome evolution, we studied the Z-W sex chromosomes of birds, which have female rather than male heterogamety and evolved from a different autosome pair than the mammalian X and Y. Here we analyze all five known gametologous Z-W gene pairs to investigate the "strata" hypothesis in birds. Comparisons of the rates of synonymous substitution and intronic divergence between Z and W gametologs reveal the presence of at least two evolutionary strata spread over the p and q arms of the chicken Z chromosome. A phylogenetic analysis of intronic sequence data from different avian lineages indicates that Z-W recombination ceased in the oldest stratum (on Zq; CHD1Z, HINTZ, and SPINZ) 102-170 million years ago (MYA), before the split of the Neoaves and Eoaves. However, recombination continued in the second stratum (on Zp; UBAP2Z and ATP5A1Z) until after the divergence of extant avian orders, with Z and W diverging 58-85 MYA. Our data suggest that progressive and stepwise cessation of recombination is a general feature behind sex chromosome evolution

Data from: The direct effects of male-killer infection on fitness of ladybird hosts (Coleoptera: Coccinellidae)

Male-killing bacteria are common in insects, and are thought to persist in host populations primarily by indirect fitness benefits to infected females, while direct fitness effects are generally assumed to be neutral or deleterious. Here, we estimated the effect of male-killer infection on direct fitness (number of eggs laid, as a measure of fecundity, together with survival) and other life-history traits (development time and body size) in seven ladybird host/male-killer combinations. Effects of male-killers on fecundity ranged, as expected, from costly to neutral, however we found evidence of reduced development time and increased survival and body size, in infected strains. Greater body size in Spiroplasma-infected Harmonia axyridis corresponded to greater ovariole number, and therefore higher potential fecundity. To our knowledge, this is the first report of direct benefits of male-killer infection after explicitly controlling for indirect fitness effects. Neutral or deleterious fitness effects of male-killer infection should not therefore be automatically assumed

The effect of filtration method on the efficiency of environmental DNA capture and quantification via metabarcoding

Environmental DNA (eDNA) is a promising tool for rapid and noninvasive biodiversity monitoring. eDNA density is low in environmental samples, and a capture method, such as filtration, is often required to concentrate eDNA for downstream analyses. In this study, six treatments, with differing filter types and pore sizes for eDNA capture, were compared for their efficiency and accuracy to assess fish community structure with known fish abundance and biomass via eDNA metabarcoding. Our results showed that different filters (with the exception of 20‐μm large‐pore filters) were broadly consistent in their DNA capture ability. The 0.45‐μm filters performed the best in terms of total DNA yield, probability of species detection, repeatability within pond and consistency between ponds. However performance of 0.45‐μm filters was only marginally better than for 0.8‐μm filters, while filtration time was significantly longer. Given this trade‐off, the 0.8‐μm filter is the optimal pore size of membrane filter for turbid, eutrophic and high fish density ponds analysed here. The 0.45‐μm Sterivex enclosed filters performed reasonably well and are suitable in situations where on‐site filtration is required. Finally, prefilters are applied only if absolutely essential for reducing the filtration time or increasing the throughput volume of the capture filters. In summary, we found encouraging similarity in the results obtained from different filtration methods, but the optimal pore size of filter or filter type might strongly depend on the water type under study

Elnagdy et al data

Experimental data collected to test impact of various male-killing bacteria on the fitness of their ladybird hosts

UK Ladybird Survey: engaging people in recording ladybirds

We provide a brief overview of the history of recording ladybirds in Britain and the increase in participation since the arrival of the harlequin ladybird, Harmonia axyridis. We highlight the importance of effective communication and collaboration in engaging the tens of thousands of people who have contributed to ladybird recording in Britain

The global spread of Harmonia axyridis (Coleoptera: Coccinellidae): distribution, dispersal and routes of invasion

Contact : [email protected] UMR IBSV : Equipe ‘Biologie des Populations en Interaction’International audienceReleased as a biological control agent of aphids and coccids, Harmonia axyridis (Coleoptera: Coccinellidae) has spread from Asia to four additional continents. Since 1988 H. axyridis has established in at least 38 countries in its introduced range: three countries in North America, six in South America, 26 in Europe and three in Africa. In different continents the species has spread at rates estimated between 100 and 500 km year-1. Here, the global spread of H. axyridis is thoroughly reviewed. Mechanisms of short- and long-distance dispersal in coccinellids are discussed, as are the reasons for them, with particular emphasis on H. axyridis. Dispersal via anthropogenic means has been particularly important in the case of H. axyridis. Preliminary studies investigating the invasion routes of H. axyridis using genetic analyses (involving both microsatellite and mitochondrial DNA) are outlined

Living with the enemy: parasites and pathogens of the ladybird Harmonia axyridis

Harmonia axyridis is an invasive alien predator in many countries across the world. The rapid establishment and spread of this species is of concern because of the threat it poses to biodiversity as a generalist predator. Understanding the mechanisms that contribute to the success of this species as an invader is not only intriguing but also critical to our understanding of the processes governing such invasions. The enemy release hypothesis (ERH) could explain the rapid population growth of many invasive alien species. However, empirical evidence in support of the ERH is lacking. An alternative hypothesis that could explain rapid population growth is evolution of increased competitive ability (EICA). Here we provide an overview of the parasites and pathogens of coccinellids with a particular focus on H. axyridis as a host. We examine the differential susceptibility of host species and highlight the resilience of H. axyridis in comparison to other coccinellids. We recognise the paucity and limitations of available information and suggest that studies, within a life-table framework, comparing life history traits of H. axyridis in both the native and introduced ranges are necessary. We predict that H. axyridis could benefit from both enemy release and EICA within the introduced range but require further empirical evidence