Phylogeography of Maoricicada Cambelli (Hemiptera: Cicadidae): MtDNA Evidence Interpreted Using Phylogenetics and Nested Clade Analysis

<p>New Zealand, because of its wide range of habitats and rapidly changing, well-studied palaeohistory provides an excellent opportunity to investigate the impact of earth processes on the distribution of taxa. There are now a variety of studies on plants that investigate such patterns, and a growing number of studies on animal taxa. Most studies have supported the hypothesis that current patterns of distribution of New Zealand taxa were created by dispersal, mediated by landscape and climatic conditions over time, and have contradicted the panbiogeographic hypothesis that explained distributions via vicariant landscape changes such as lateral displacement along the Alpine Fault. This thesis presents a detailed phylogeographic history of a widespread, endemic New Zealand cicada, Maoricicada campbelli, that is abundant throughout much of the South Island and is also found in the central volcanic plateau of the North Island. Mitochondrial DNA sequences of 223 individuals from 70 populations of M. campbelli were studied using both traditional phylogenetic methods and nested clade analysis (NCA). As found in a previous study of 35 M. campbelli individuals, geographic structuring was strong, with two main clades (North Island+northern South Island versus Otago) representing diverse lineages that may in fact be different species. Population structuring within the northern South Island clade suggested that the central South Island was mostly uninhabitable during glacial periods and demonstrated a sister-group relationship between northern and southern Southern Alps populations to the exclusion of the more central Southern Alps populations. Population histories estimated from NCA support the hypothesis that most M. campbelli populations were formed through dispersal rather than via fragmentation or Alpine Fault vicariance. Three areas of ring-species-like secondary contact were found between the Otago and northern South Island clades, between lineages that had been isolated for approximately 2.3my. Further study is predicted to confirm the presence of additional suspected contact zones, and will demonstrate whether the different lineages are reproductively isolated or hybridising at these areas of secondary contact.</p>

Phylogeography of Maoricicada Cambelli (Hemiptera: Cicadidae): MtDNA Evidence Interpreted Using Phylogenetics and Nested Clade Analysis

<p>New Zealand, because of its wide range of habitats and rapidly changing, well-studied palaeohistory provides an excellent opportunity to investigate the impact of earth processes on the distribution of taxa. There are now a variety of studies on plants that investigate such patterns, and a growing number of studies on animal taxa. Most studies have supported the hypothesis that current patterns of distribution of New Zealand taxa were created by dispersal, mediated by landscape and climatic conditions over time, and have contradicted the panbiogeographic hypothesis that explained distributions via vicariant landscape changes such as lateral displacement along the Alpine Fault. This thesis presents a detailed phylogeographic history of a widespread, endemic New Zealand cicada, Maoricicada campbelli, that is abundant throughout much of the South Island and is also found in the central volcanic plateau of the North Island. Mitochondrial DNA sequences of 223 individuals from 70 populations of M. campbelli were studied using both traditional phylogenetic methods and nested clade analysis (NCA). As found in a previous study of 35 M. campbelli individuals, geographic structuring was strong, with two main clades (North Island+northern South Island versus Otago) representing diverse lineages that may in fact be different species. Population structuring within the northern South Island clade suggested that the central South Island was mostly uninhabitable during glacial periods and demonstrated a sister-group relationship between northern and southern Southern Alps populations to the exclusion of the more central Southern Alps populations. Population histories estimated from NCA support the hypothesis that most M. campbelli populations were formed through dispersal rather than via fragmentation or Alpine Fault vicariance. Three areas of ring-species-like secondary contact were found between the Otago and northern South Island clades, between lineages that had been isolated for approximately 2.3my. Further study is predicted to confirm the presence of additional suspected contact zones, and will demonstrate whether the different lineages are reproductively isolated or hybridising at these areas of secondary contact.</p>

Fragmentación y expansión demográfica en las poblaciones mexicanas de Pinus ayacahuite var. ayacahuite

This study explores the phylogeographic structure and the demographic hi story of the Mexican populations of Pinus ayacahuite var. ayacahuite. Three chloroplast microsatellites were amplified in 198 individuals from 14 populations. Twelve haplotypes were found and an average genetic diversity (He) of 0.705. Two maximally differentiated groups were determined with a spatial analysis of molecular variance. A significant correlation was detected between the genetic and geographic distances between these two groups, but not within them. A significant phylogeographic structure was found, produced by the existence of the two groups. Two demographic expansions were detected, the first in the entire species, the second only in the southernmost populations. Additionally, a nested clade analysis was pe1formed to complement our observations. The results showed that the Tehuantepec Isthmus was a corridor for species of temperate affinities in a cold period in early Pleistocene, and later acted as a barrier

Phylogeography of the blue land crab, Cardisoma guanhumi (Decapoda: Gecarcinidae) along the Brazilian coast

Several crab species are important fishery resources in Brazil and their overexploitation has lead to severe population declines in some regions. The management of populations of these species should take into account the degree of gene flow among populations in different estuaries. The goal of the present study is to assess the degree of geographical structure in the genetic diversity of the blue land crab, Cardisoma guanhumi, along the Brazilian coast. A fragment of the control region of the mtDNA (750 bp) was sequenced for 95 specimens collected across 5 Brazilian states. Analyses using F-statistics failed to indicate any evidence of geographical structure, a result that was corroborated by a nested clade analysis of the same dataset. Mismatch distribution analyses indicated that populations of the blue land crab have experienced an expansion during their recent evolutionary past. The obtained results are similar to those recently described for another sympatric crab, Ucides cordatus, particularly with respect to the extensive degree of gene flow. However, populations of C. guanhumi seem to be older than those of U. cordatus and do not show the north–south expansion found in that species.

Distinct Viral Populations Differentiate and Evolve Independently in a Single Perennial Host Plant

ABSTRACT The complex structure of virus populations has been the object of intensive study in bacteria, animals, and plants for over a decade. While it is clear that tremendous genetic diversity is rapidly generated during viral replication, the distribution of this diversity within a single host remains an obscure area in this field of science. Among animal viruses, only Human immunodeficiency virus and Hepatitis C virus populations have recently been thoroughly investigated at an intrahost level, where they are structured as metapopulations, demonstrating that the host cannot be considered simply as a “bag” containing a homogeneous or unstructured swarm of mutant viral genomes. In plants, a few reports suggested a possible heterogeneous distribution of virus variants at different locations within the host but provided no clues as to how this heterogeneity is structured. Here, we report the most exhaustive study of the structure and evolution of a virus population ever reported at the intrahost level through the analysis of a Prunus tree infected by Plum pox virus for over 13 years following a single inoculation event and by using analysis of molecular variance at different hierarchical levels combined with nested clade analysis. We demonstrate that, following systemic invasion of the host, the virus population differentiates into several distinct populations that are isolated in different branches, where they evolve independently through contiguous range expansion while colonizing newly formed organs. Moreover, we present and discuss evidence that the tree harbors a huge “bank” of viral clones, each isolated in one of the myriad leaves.