Exploring the surface of the Moon and Mars: What kind of ground vehicles are required?

On the surface of the Moon and Mars, the astronauts must have at their disposal means for exploring a suitable area of the planet. A ground vehicle was tested for the first time outside Earth during the Apollo program, but the longer stay and the wider extent of the exploration will make similar vehicles designed for Mars larger, faster and more complex. In later missions, transportation on the planet will possibly require aerial vehicles and finally the realization of a whole transportation infrastructure. Furthermore, robotic rovers will be required to assist the astronauts in their exploration duties

Contrasting Patterns of Clinal Genetic Diversity and Potential Colonization Pathways in Two Species of Western Atlantic Fiddler Crabs.

Fiddler crabs (Brachyura, Ocypodidae), like many other marine organisms, disperse via planktonic larvae. A lengthy pelagic larval duration is generally assumed to result in genetic connectivity even among distant populations. However, major river outflows, such as of the Amazon or Orinoco, or strong currents may act as phylogeographic barriers to ongoing gene flow. For example, the Mona Passage, located between Puerto Rico and Hispaniola, has been postulated to impair larval exchange of several species. In this study, Cox1 mtDNA data was used to analyze population genetic structure of two fiddler crab species from the western Atlantic, comparing the continental coastline and Caribbean islands. The results indicate genetic homogeneity in Minuca rapax among Atlantic (continental) populations (Suriname, Brazil), whereas Caribbean populations show significantly restricted gene flow among the constituent islands and towards continental populations. Our data support the hypothesis of the Mona Passage hindering larval exchange. Contrastingly, Caribbean Leptuca leptodactyla populations appear to be devoid of detectable variation, while Atlantic-continental (i.e. Brazilian) populations show much higher haplotype and nucleotide diversities and display slight genetic differentiation among populations within the Atlantic region, though not statistically significant. Both species show a pronounced divergence between regions, supporting the presence of a phylogeographic barrier

Mitochondrial genetic structure of two populations of Uca urugayensis fails to reveal an impact of the Rio de la Plata on gene flow

The Rio de la Plata. located between Uruguay and Argentina, generates a tremendous freshwater influx from the estuary into the coastal sea. It is thus suggested to constitute a biogeographic barrier for many taxa exhibiting a marine planktonic larval dispersal. However, evidence for corresponding intraspecific dispersal constraint has yet to be provided. We compared mitochondrial haplotypes of ten individuals for each of two populations of Uca (Leptuca) uruguayensis north and south of the estuary to examine the potential effect of the Rio de la Plata on the species' distribution. The populations are separated by nearly 2,000 km and were collected in São Paulo State (Brazil) and Mar Chiquita (Argentina). We found no significant indication for restricted gene flow between them, based on 823 basepairs of the mitochondrial cytochrome c oxidase subunit I gene. The structure of the corresponding haplotype network and the estimated nucleotide diversities, however, suggest that the Argentinean population is genetically more diverse than the one from Brazil. In order to establish possible significant differences in haplotype distribution, further research including more populations and larger sample sizes will be necessary

Estimate of pairwise differences among <i>Minuca rapax</i>, derived from CO1 mtDNA (825 bp, N = 115).

<p>P values above diagonal, <i>ϕ</i>_<i>ST</i> values below diagonal. Significance level 0.05; +++: p < 0.001, +: p <0.05, -: not significant. Significant <i>ϕ</i>_<i>ST</i> values in bold type. Numbers in parentheses according to sample size. Arlequin 3.5.1.3. Groups define geographic regions as follows: Caribbean (Jam, Cub, DR, PR, StM) vs. Atlantic (Sur, Bra). Abbreviations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166518#pone.0166518.g001" target="_blank">Fig 1</a>, Bra—Brazil (pooled data from PA, SP).</p

Contrasting Patterns of Clinal Genetic Diversity and Potential Colonization Pathways in Two Species of Western Atlantic Fiddler Crabs

Fiddler crabs (Brachyura, Ocypodidae), like many other marine organisms, disperse via planktonic larvae. A lengthy pelagic larval duration is generally assumed to result in genetic connectivity even among distant populations. However, major river outflows, such as of the Amazon or Orinoco, or strong currents may act as phylogeographic barriers to ongoing gene flow. For example, the Mona Passage, located between Puerto Rico and Hispaniola, has been postulated to impair larval exchange of several species. In this study, Cox1 mtDNA data was used to analyze population genetic structure of two fiddler crab species from the western Atlantic, comparing the continental coastline and Caribbean islands. The results indicate genetic homogeneity in Minuca rapax among Atlantic (continental) populations (Suriname, Brazil), whereas Caribbean populations show significantly restricted gene flow among the constituent islands and towards continental populations. Our data support the hypothesis of the Mona Passage hindering larval exchange. Contrastingly, Caribbean Leptuca leptodactyla populations appear to be devoid of detectable variation, while Atlantic-continental (i.e. Brazilian) populations show much higher haplotype and nucleotide diversities and display slight genetic differentiation among populations within the Atlantic region, though not statistically significant. Both species show a pronounced divergence between regions, supporting the presence of a phylogeographic barrier

Haplotype and nucleotide diversity of <i>Minuca rapax</i> calculated with DnaSP ver. 5.00.07.

<p>5,000 replicates. Abbreviations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166518#pone.0166518.g001" target="_blank">Fig 1</a>.</p

Sample sites of <i>Leptuca leptodactyla</i>, represented by circles.

<p>BA—Brazil (Bahia State), Cur—Curaçao, DR—Dominican Republic, Jam—Jamaica, PA—Brazil (Pará State), SP—Brazil (São Paulo State), StM—St. Martin, Ven—Venezuela. Arrows point to potential biogeographic barriers, dashed line indicates suggested geographical regions.</p

Estimate of pairwise differences with Arlequin 3.5.1.3 among Caribbean populations of <i>Leptuca leptodactyla</i>, derived from CO1 mtDNA (825 bp, N = 58).

<p>P values above diagonal, <i>ϕ</i>_<i>ST</i> values below diagonal. Significance level 0.05; -: not significant. Numbers in parentheses correspond to sample size. Abbreviations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166518#pone.0166518.g002" target="_blank">Fig 2</a>.</p

Haplotype network of <i>Minuca rapax</i> constructed with TCS 1.21.

<p>Derived from CO1 mtDNA (825 bp, N = 119), 95% connection limit. Solid-lined circles represent sampled haplotpyes according to frequency and populations: Bra-PA—Brazil (Pará State), Bra-SP—Brazil (São Paulo State), Cub—Cuba, Col—Colombia, DR—Dominican Republic, Jam—Jamaica, PR—Puerto Rico, StM—St. Martin, Sur -Suriname, Ven—Venezuela. Reticulations were dissolved in favor of shortest distances. Dashed circles suggest geographic regions.</p