Phylogenetic Relationship Between the Endosymbiont “candidatus Riesia Pediculicola” and Its Human Lice Host

Background: The human louse is one of the most ancient haematophagous ectoparasites that is related intimately to its host and has been of great concern to public health throughout human history. Previously, Pediculus humanus was classified within six divergent mitochondrial clades (A, D, B, F, C and E). Like all haematophagous lice, P. humanus directly depends on the presence of bacterial symbionts, known as “Candidatus Riesia pediculicola”, to complement their unbalanced diet. In this study, we evaluated the coevolution of human lice around the world and their endosymbiotic bacteria. Using molecular approaches, we targeted lice mitochondrial genes from the six diverged clades and Candidatus R. pediculicola housekeeping genes. Methods: A total of 126 lice were selected for molecular analysis of the cytb gene for lice clade determination. In parallel, four PCR primer pairs were developed targeting three housekeeping genes of Candidatus R. pediculicola: ftsZ, groEL and two regions of the rpoB gene (rpoB-1 and rpoB-2).Results: The endosymbiont phylogeny perfectly mirrored the host insect phylogeny, using the ftsZ and rpoB-2 genes, suggesting a strict vertical transmission and a host-symbiont co-speciation following the evolutionary course of the human louse. Conclusion: Our results unequivocally indicate that lice endosymbiont have experienced a similar co-evolutionary history, and that the human louse clade can be determined by their endosymbiotic bacteria.

Mitogenome and Phylogenetic Analysis of Typhlocybine Leafhoppers (Hemiptera: Cicadellidae)

Mitogenomes play an active role in determining the relationship between insect phylogeny and evolution and solve some problems encountered in traditional morphological classification. In order to increase the mitogenome data of leafhoppers the mitogenomes of Cassianeura cassiae and C. bimaculata were sequenced in this study and found to be 15,423 bp and 14,597 bp in length respectively. The gene structure was found to be similar to other published leafhopper mitogenomes, but we found the length of the control region of C. bimaculata to be the shortest in existing studies. The phylogenetic analysis of 13 PCGs resulted in a well-supported tree topology but species in Typhlocybini and Zyginellini were mixed. Meanwhile, this study also provided the phylogenetic analysis based on the body external morphology, female genitalia morphology and male genitalia morphology of 9 species of Typhlocybinae. The results showed that the female sternite VII of different species is quite different, but the female valvulae of different species in the same genus shows a certain consistency. The morphological phylogenetic tree is basically the same structure as the molecular phylogenetic tree. In the two different kinds of phylogenetic trees, Typhlocybini and Zyginellini clustered into one clade, showing a more closed relationship.

Palaeontological and Biological Collections – Bridging the gap

Palaeontology and biology are closely related sciences, as are the collections associated with them. Nevertheless there are differences between the two types of collections and the scientific data that they yield with regards to taxonomy, climate and ecology. In order to bridge the gap between the two subjects, it is important to clarify what these differences are and how they can be used to supplement research that addresses future environmental/climatic issues. In biology, valuable traits of the whole organism serve for taxonomy. In the fossil record, a morphospecies concept needs to be used because specimens are mainly preserved fragmentarily and palaeontologists have to take advantage of morphological traits that are often disregarded by biologists. Another difference is that biological objects represent modern time, while the fossil record provides valuable information on a deep time perspective, i.e., in a third dimension. Yet, these two disciplines obviously depend on each other: while biologists provide palaeontologists with information about unfossilised soft parts, palaeontology can help to solve questions about life in the past. Using four current case studies from the Stuttgart Natural History Museum, we provide examples of how biological and palaeontological information stored in museum collections are linterlinked, and particularly how palaeontology can help to solve current and future problems. We also highlight the potential of palaeontological collections and demonstrate the necessity of digitizing large quantities of objects as well as the related basic information. Case studies are: Fossil leaves provide evidence for past atmospheric CO2 levels and climate change, which can be used for climate change models. Fossils help to understand current and future hazards e.g., fossils embedded in tsunami sediments can provide information on how tsunamis affect shelf marine ecosytems. Extensive taxonomic studies of Miocene land snails and the comparison with extant relatives allow the reconstruction of fossil environments. Combined with complementary methods, the biological, geological and meteorological factors controlling these environments can be reconstructed. Phylogenetic studies tell us how life evolved and how organisms have changed through time. An important factor for phylogeny is the time-aspect, such as the splitting of lineages. Phylogenetic trees based on modern taxa can only be validated by fossils. We will present an example of insect phylogeny. Fossil leaves provide evidence for past atmospheric CO2 levels and climate change, which can be used for climate change models. Fossils help to understand current and future hazards e.g., fossils embedded in tsunami sediments can provide information on how tsunamis affect shelf marine ecosytems. Extensive taxonomic studies of Miocene land snails and the comparison with extant relatives allow the reconstruction of fossil environments. Combined with complementary methods, the biological, geological and meteorological factors controlling these environments can be reconstructed. Phylogenetic studies tell us how life evolved and how organisms have changed through time. An important factor for phylogeny is the time-aspect, such as the splitting of lineages. Phylogenetic trees based on modern taxa can only be validated by fossils. We will present an example of insect phylogeny. These case studies not only show how biology and palaeontology are interlinked, but the first three studies are sound examples of how the knowledge of the past helps to understand the present. Furthermore, the first two studies are highly relevant for predicting the future. All of this information can only be used appropriately, if large proportions of data are available that include information on geology and age. For this reason, the Access to Biological Collection Data Extended for Geosciences (ABCD EFG) standard is so important, as it extends the two-dimensional view (Recent) into a third dimension (deep time). Our vision is an integrated modelling of past, present and future scenarios, whether for climate or ecosystem change, or geological hazards. Considering the deep time information, we can model how changes would take place under natural conditions, i.e., without anthropogenic influence. This requires the availability of large data sets of taxonomic information on the EFG level from all over the world.

Multiple large-scale gene and genome duplications during the evolution of hexapods

Polyploidy or whole genome duplication (WGD) is a major contributor to genome evolution and diversity. Although polyploidy is recognized as an important component of plant evolution, it is generally considered to play a relatively minor role in animal evolution. Ancient polyploidy is found in the ancestry of some animals, especially fishes, but there is little evidence for ancient WGDs in other metazoan lineages. Here we use recently published transcriptomes and genomes from more than 150 species across the insect phylogeny to investigate whether ancient WGDs occurred during the evolution of Hexapoda, the most diverse clade of animals. Using gene age distributions and phylogenomics, we found evidence for 18 ancient WGDs and six other large-scale bursts of gene duplication during insect evolution. These bursts of gene duplication occurred in the history of lineages such as the Lepidoptera, Trichoptera, and Odonata. To further corroborate the nature of these duplications, we evaluated the pattern of gene retention from putative WGDs observed in the gene age distributions. We found a relatively strong signal of convergent gene retention across many of the putative insect WGDs. Considering the phylogenetic breadth and depth of the insect phylogeny, this observation is consistent with polyploidy as we expect dosage balance to drive the parallel retention of genes. Together with recent research on plant evolution, our hexapod results suggest that genome duplications contributed to the evolution of two of the most diverse lineages of eukaryotes on Earth.

Multiple large-scale gene and genome duplications during the evolution of hexapods

Polyploidy or whole genome duplication (WGD) is a major contributor to genome evolution and diversity. Although polyploidy is recognized as an important component of plant evolution, it is generally considered to play a relatively minor role in animal evolution. Ancient polyploidy is found in the ancestry of some animals, especially fishes, but there is little evidence for ancient WGDs in other metazoan lineages. Here we use recently published transcriptomes and genomes from more than 150 species across the insect phylogeny to investigate whether ancient WGDs occurred during the evolution of Hexapoda, the most diverse clade of animals. Using gene age distributions and phylogenomics, we found evidence for 18 ancient WGDs and six other large-scale bursts of gene duplication during insect evolution. These bursts of gene duplication occurred in the history of lineages such as the Lepidoptera, Trichoptera, and Odonata. To further corroborate the nature of these duplications, we evaluated the pattern of gene retention from putative WGDs observed in the gene age distributions. We found a relatively strong signal of convergent gene retention across many of the putative insect WGDs. Considering the phylogenetic breadth and depth of the insect phylogeny, this observation is consistent with polyploidy as we expect dosage-balance to drive the parallel retention of genes. Together with recent research on plant evolution, our hexapod results suggest that genome duplications contributed to the evolution of two of the most diverse lineages of eukaryotes on Earth.