Genetic homogeneity and circum-Antarctic distribution of two benthic shrimp species of the Southern Ocean, Chorismus antarcticus and Nematocarcinus lanceopes

Abstract

During the last years, molecular studies revealed signiWcant population diVerentiation and cryptic species within various benthic and pelagic marine Antarctic taxa. This is unexpected due to the lack of obvious barriers to gene Xow and strong current systems. Using mitochondrial (COI, 16S rDNA) and nuclear (28S rDNA: D2) gene fragments, we tested whether two circum-Antarctic benthic shrimps with planktotrophic larvae, Chorismus antarcticus and Nematocarcinus lanceopes, show patterns of regional diVerentiation. For both species, the 16S and the 28S fragment were invariant. However, for COI we found 24 diVerent haplotypes for Chorismus antarcticus and 54 for Nematocarcinus lanceopes. No signiWcant diVerentiation was observed among populations or regions. Furthermore, we found signatures of a population expansion in the late Pleistocene hinting at an impact of large-scale glaciations in particular on the shallowwater shrimp Chorismus antarcticus, supporting a (re)colonization and demographic expansion of this shrimp species in response to climate oscillation.

Patrones de diversidad y estructura genética en especies antárticas y subantárticas de Nacella (Nacellidae)

“…Estos resultados permiten corroborar el impacto generado por los ciclos glaciales del Cuaternario sobre los patrones de diversidad y estructura genética en Antártica y Subantártica. Bajos niveles de diversidad como los registrados en la lapa antártica han sido registrados en otros invertebrados de la región incluyendo Chorismus antarcticus (Pfeffer, 1887) (Raupach et al 2010), Parborlasia corrugatus (McIntosh, 1876) (Thornhill et al 2008) y Sterechinus neumayeri (Meissner, 1900) (Díaz et al 2011). Como se esperaba dentro de un contexto latitudinal, los niveles de diversidad genética en N. concinna de Antártica fueron menores que los registrados en sus parientes subantárticos N. magellanica (Patagonia) y N. edgari (Isla Kerguelén), lo que sugiere un efecto demográfico más pronunciado de las glaciaciones a medida que aumenta la latitud.…”

On the comparison of population-level estimates of haplotype and nucleotide diversity: a case study using the gene cox1 in animals

“…In addition to quantitative comparisons against specific values, median values derived from the complete data set can be used as a cutoff for qualitative descriptions of low and high diversity. For example, in the study by Raupach et al (2010) on benthic shrimp species, estimates of h and p for samples of Chorismus antarcticus fall below the median value and thus could be categorized as low diversity, whereas samples of Nematocarcinus lanceopes fall above the median and thus could be termed high diversity (Table 1, Figure 2).…”

Introduction to the special issue on the Life in Antarctica: Boundaries and Gradients in a Changing Environment (XIth SCAR Biology Symposium)

“…The use of molecular tools to standardize comparisons ''barcoding'' and phylogeography has been shown to produce valuable sources of information which often reveal this hidden diversity. However, other studies have shown a certain molecular genetic homogeneity within the Antarctic benthos, revealing a great capacity for dispersal and genetic exchange between isolated populations (Raupach et al 2010;Arango et al 2011).…”