Levels and patterns of genetic variation in an Asian horseshoe crab species, <i>Tachypleus gigas</i> Müller, from the Malay Peninsula

<div><p></p><p>Horseshoe crabs are one of the oldest living organisms that still exist today. Given the overexploitation of horseshoe crabs around the world, and the lack of information on their populations, it is crucial that genetic variation studies are done to assess their levels and patterns of genetic variation for continuous monitoring and management of their populations. Here, five populations of the Asian horseshoe crab <i>Tachypleus gigas</i> sampled from along the coasts of the Malay Peninsula were studied using simple-sequence repeat (SSR) and inter-simple-sequence repeat (ISSR) markers. Different results were obtained using the two different types of markers in terms of the levels of genetic variation estimated, but both concurred that most of the genetic variations were distributed at the individual level rather than among populations of the species. Inbreeding was also observed using the SSR data, although the presence of null alleles could have influenced the estimation. Finally, both marker types revealed that <i>T. gigas</i> could have been subjected to the land barrier effect of the Malay Peninsula that causes populations from the Indian Ocean to be genetically differentiated from the populations from the South China Sea.</p></div

A summary of microsatellite genetic variation in the low solitary nests of <i>A. dorsata</i>.

<p>N_a is the number of different alleles, while N_e is the number of effective alleles. H_o, H_e and PIC indicate the observed and expected heterozygosity and polymorphism information content, respectively.</p

The spatial distribution of <i>A. dorsata</i> solitary nests from Marang, Terengganu, Malaysia (2010).

<p>Numbers 1 to 20 were the solitary nests, while numbers 21 to 23 were the aggregated nests.</p

Inferred queen genotypes of each solitary nest at each locus (Marang, Terengganu, Malaysia, 2010).

<p>Inferred queen genotypes of each solitary nest at each locus (Marang, Terengganu, Malaysia, 2010).</p

The hierarchical AMOVA based on microsatellite markers for showing the genetic differentiation of <i>A. dorsata</i> solitary nests.

<p>The hierarchical AMOVA based on microsatellite markers for showing the genetic differentiation of <i>A. dorsata</i> solitary nests.</p

A diagram of <i>A. dorsata</i> aggregation (high nesting) and low solitary nesting (Marang, Terengganu, 2010).

<p><b>A</b>: An aggregation on a bee tree of ∼ 40 metres in height. <b>LN</b>: Low solitary nests on a tree of between 2–5 metres in height. <b>N</b>: Nest.</p

Labelled pair wise relatedness matrix [30].

<p>The bold numbers (<b>1–20</b>) indicate <i>A. dorsata</i> solitary nests.</p

Graphical demonstration of the heterosis-based degree of dominance of the three anticancer andrographolides and their components in AP hybrids.

<p>AGP: AG percentage per plant (%), AGC: AG content per plant (g), AGY: AG yield per hectare (kg/ha), NAGP: NAG percentage per plant (%), NAGC: NAG content per plant (g), NAGY: NAG yield per hectare (kg/ha), DDAGP: DDAG percentage per plant (%), DDAGC: DDAG content per plant (g), DDAGY: DDAG yield per hectare (kg/ha). H1–H21 represent the 21 hybrids.</p

Correlations of the three phytochemicals in the seven parental AP.

<p>**, *Correlation is significant at the 0.01 and 0.05 levels, respectively (2-tailed). AGP: AG percentage per plant (%), AGC: AG content per plant (g), AGY: AG yield per hectare (kg/ha), NAGP: NAG percentage per plant (%), NAGC: NAG content per plant (g), NAGY: NAG yield per hectare (kg/ha), DDAGP: DDAG percentage per plant (%), DDAGC: DDAG content per plant (g), DDAGY: DDAG yield per hectare (kg/ha).</p

The distribution data of low solitary nests of <i>Apis dorsata</i> in Marang district.

<p>The distribution data of low solitary nests of <i>Apis dorsata</i> in Marang district.</p