Previous studies have shown that the esterase 6 (EST6) enzyme of D. melanogaster is mainly produced in the sperm ejaculatory duct of the adult male and comparisons of wild-type males with laboratory null mutants have suggested that the enzyme plays a role in reproductive fitness. In this study we have compared 18 field-derived lines each isoallelic for Est6 for differences in five components of male reproductive fitness. No consistent fitness differences were found among lines differing in respect of the two major allozyme classes EST6-F and EST6-S, despite other evidence that these two classes are not selectively equivalent in the field. However, differences in reproductive fitness were found among lines differing in the minor mobility variants that segregate within EST6-F and EST6-S. A failure to distinguish among these minor forms may explain the discrepancies in previous studies on the effects of the major EST6 allozymes on reproductive fitness. The most significant associations we have found between EST6 and reproductive fitness were due to variation in EST6 activity levels. Male EST6 activity levels were found to be positively correlated with their time to first mating, negatively correlated with the numbers of eggs laid and progeny produced by their mates, and negatively correlated with the frequency with which their mates remate. We conclude that some EST6 variants differ in components of male reproductive fitness operative in laboratory cultures. However, the evidence for fitness differences is stronger for variants affecting the amount, rather than the structure of the enzyme, and the direction of the differences varies between some of the fitness components tested.

We report heritable threefold differences in both larval and pupal esterase 6 activity among 17 isoallelic lines of D. melanogasrer extracted from a natural population. The activity differences in the two stages are only weakly correlated with each other or with previously determined values for esterase 6 activity in adults of these lines. The pre-adult activity variation is also unrelated to polymorphisms among the lines for six esterase 6 allozymes and six restriction sites in a region encompassing the esterase 6 coding DNA and the first kbp of 5' flanking DNA. However, two insertions, of 8.0 and 6.8 kbp, located about 1.4 kbp 5' of the esterase 6 coding region are associated with low activity in larvae and, to a lesser extent, in pupae, albeit not in adults. Restriction mapping reveals similarity between the 8.0 kbp insert and the 7.4 kbp retrotransposon 17.6. The differences in larval activity among lines are positively correlated with fitness as assessed from assays of pre-adult viability and development time but no significant associations between pupal esterase 6 activity and these measures are detected. Some effects of esterase 6 allozyme differences are also found for viability and development time but these effects could be explained by linkage disequilibrium between the 8.0 kbp insert and the EST6-9 allozyme.

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Spathoglottis is one of the most popular terrestrial orchids because it is attractive, easy to cultivate and continuously blooms throughout the year. It is a native orchid of Malaysia and listed as an endangered species. Therefore, this species needs to be conserved for commercial and environmental purposes. DNA barcoding is a technique for species identification, which uses a short DNA sequence from a standard and agreed-upon position in the genome. This technique plays an important role in biodiversity conservation for animals but is not yet well established in plants. Chloroplast DNA was chosen for this study aimed at building a DNA barcoding of Spathoglottis species. Seven species of Spathoglottis were used to carry out this study. They were Spathoglottis plicata, Spathoglottis gracilis, Spathoglottis aurea, Spathoglottis plicata alba, Spathoglottis unguiculata, Spathoglottis kimbaliana and a Spathoglottis hybrid. Eight regions (i.e., accD, matK, ndhJ, rpoB, rpoC1, ycf5, rbcL-a and trnH-psbA) in the chloroplast genome and two regions (i.e., ITS1 and ITS2) in the nuclear genome were selected and screened in order to define a universal barcoding region across all the seven selected species. The study found that the four chloroplast regions (i.e., matK, rbcL-a, rpoB and rpoC1) were successfully amplified from all the tested species. The DNA sequencing from each chloroplast region was compared among the species and analyzed to differentiate the intra-and inter-genetic variations. The analysis of chloroplast regions was done for single regions and as a combination of the four regions. The haplotypes for the multiple analyses showed sufficiently high resolution to enable differentiation between the selected Spathoglottis species. In conclusion, this study showed that the chloroplast DNA regions had high potential to be developed for DNA barcoding of Spathoglottis species. This is the first step towards the development of universal DNA barcoding technique for all native orchids in Malaysia.