An intron loss of Dfak gene in species of the Drosophila melanogaster subgroup and phylogenetic analysis.

Drosophila focal adhesion kinase (Dfak) gene is a single-copy nuclear gene. Previous study revealed that Drosophila melanogaster and Drosophila simulans had lost an intron precisely within the tyrosine kinase (TyK) domain of this gene. However, this did not happen in several other Drosophila species, including Drosophila elegans, Drosophila ficusphila, Drosophila biarmipes, Drosophila jambulina, Drosophila prostipennis, Drosophila takahashii, and Drosophila pseudoobscura. In the current study, homologous sequences of Drosophila sechellia, Drosophila mauritiana, Drosophila yakuba, Drosophila teissieri, Drosophila santomea, and Drosophila erecta were amplified by polymerase chain reaction, and further sequencing analysis indicated that these species were missing a TyK domain intron, indicating they were closely related. The relationship of the D. melanogaster species group was reconstructed using TyK domain nucleotide sequences. The resulting phylogenetic tree revealed that these 8 species were the most related species in the melanogaster group. These results strongly support previously proposed classifications based on morphological and molecular data.

Comparative allozyme analysis of two geographic populations of Pararcyptera microptera meridionalis in China.

The genetic structure of the two populations of Pararcyptera microptera meridionalis (Ikonn.) from Hebei and Liaoning in China was analyzed with horizontal starch gel electrophoresis. Among 15 loci of 11 enzymes identified in zymograms, Adk-1, Fbp-1, Mdh-2 and G3pd-1 showed low variability with few alleles. Higher allelic polymorphisms were observed at Fbp-2, Mdh-1 and Me-1. The two populations demonstrated high percentage of polymorphic loci (93.3% and 100.0%) but low observable overall heterozygosity (0.061 and 0.086), that could be attributed to heterozygote deficiencies, which led to the genotype frequency deviating from Hardy-Weinberg expectations. It is reasoned that the strong movement capability of the insect makes the individuals likely to be exposed to drastically varied environments, which tends to maintain dynamic equilibrium of genetic polymorphisms. The F-statistics between the two populations was comparatively smaller ( F(st) = 0.084), but larger when compared with those in migratory locusts like Locusta migratoria manilensis. Nei's genetic identity (I) and Roger's genetic distance (D) also showed close genetic relationship of the two populations by their high genetic identity (I = 0.904) and small genetic distance (D = 0.256). However,considerably qualitative and quantitative differences were noted at loci Acp-1 (F(st) = 0.462) and Pgi-1 (F(st) = 0.182).

Genetic studies on eight populations of eight locust species from Shanxi Province, China.

The genetic structure of eight locust species in three families (Catantopidae, Oedipodidae and Arcypteridae) from Shanxi Province in China was compared using allozyme analysis with horizontal starch gel electrophoresis. Among 17 loci identified in zymograms, Ao-1, Est-3, G3pd-1, Idh-2 and Mdh-2 had low variability with a few alleles. High polymorphism was observed at Ldh-1, Me-1 and Gpi-1. Each of the eight species demonstrated high percentage of polymorphic loci (P = 64.7%-94.1%) but low observed heterozygosity (H0 = 0.024-0.087) due to heterozygote deficiency. It was noted that the migratory locusts usually had higher percentage of polymorphic loci (P = 88.2%-94.1%) than non-migratory species (P = 64.7%-94.1%). The only exception is Oxya chinensis(P = 94.1%). It is reasoned that the higher polymorphism is necessary for migratory species to cope with the environments that might be drastically different from the habitats before migration. The taxon relationships using cluster analysis based on Nei's genetic identity (I) and Roger's genetic distance (D) were the same at species and genus levels. The differences were found at family level, possibly due to the alternative algorithms. The cladogram using Roger's genetic distance (D) overlapped the relationship obtained from karyotypic analyses, which demonstrated that the species examined in Catantopidae displayed somewhat closer relationship to those in Oedipodidae than to those in Arcypteridae. It is suggested that the allozyme analysis is useful as molecular marker for locusts in phylogenetic reconstruction at the species and genus level, while additional data from other studies are necessary when used for higher taxa.

Genetic differentiation of different populations of four locust species in China.

The genetic structure of eight populations of four locust species in three families (Catantopidae, Pamphagidae and Pyrgomorphidae) was examined by means of horizontal starch gel electrophoresis, the locusts were collected from Shanxi, Jiangsu and Hebei Province in China. The allele frequency and allozyme polymorphism of 12 enzymes (18 loci) were analyzed. Low variability with a few alleles was observed in Shirakiacris shirakii and Atractomorpha sinensis, however, Oxya Chinensis and Haplotropis brunneriana showed high polymorphism. In the eight populations of the four locust species, high percentage of polymorphic loci was observed (53.3%-100.0%). Owing to heterozygote deficiency of some species, all the four species demonstrated low overall heterozygosity (Ho = 0.034-0.139), which lead to the genotype frequency deviated significantly from Hardy-Weinberg equilibrium. However, many of the examined loci were fit for or close to H-W equilibrium in Atractomorpha sinensis. A certain differentiation in mean heterozygosity was found among the four species. Due to the difference of migratory capability, reproductive manner and living bound, mean heterozygosity (Ho) is higher in Haplotropis brunneriana (Ho = 0.089-0.139) and Oxya Chinensis (Ho = 0.073-0.090) than in Atractomorpha sinensis (Ho = 0.034-0.050) and Shirakiacris shirakii (Ho = 0.048-0.068). Genetic differentiation from F-statistics was also different at population level among four locust species. It was high in Haplotropis brunneriana (Fst = 0.32) and Atractomorpha sinensis (Fst = 0.31), and low genetic differentiations were observed in Oxya Chinensis (Fst = 0.20) and Shirakiacris shirakii (Fst = 0.18). It was confirmed that migratory capability, adaptability and surrounding factors had an important influence on the genetic differentiation of locust populations. The taxon relationships based on Nei's genetic identity (I) and genetic distance (D) were consistent with results obtained from karyotypic analyses. Oxya Chinensis and Shirakiacris shirakii in the same family have a higher genetic identity (I = 0.576) and a smaller genetic distance (D = 0.559); the species examined in Pampagidae displayed somewhat closer relationship to those in Pyrgomorphidae (D = 0.776, I = 0.464) than to those in Catantopidae (D = 0.908, I = 0.406). It is suggested that the allozyme analysis is an useful molecular marker for phylogenetic reconstruction of locust at both species and population levels.

Comparative allozyme analysis of Oriental migratory locust Locusta migratoria manilensis from two breeding areas in north China.

The allozyme analysis using horizontal starch gel electrophoresis was employed to compare the genetic structure in the population of oriental migratory locust Locusta migratoria manilensis from two breeding areas, Beidagang(Tianjin) and Huanghua(Hebei). The two areas are adjacent but with distinct ecological features, with the recorded locust outbreaks and migration. The zymograms showed that among nineteen loci four (Mdh-1, Pgm, Adk and G3pd) showed extremely low variability level with the frequency of the most common allele higher than 0.95 in the populations from both sites. The rest loci had 2 to 4 alleles but the allele frequencies between the two populations were all similar except Fbp and Got-2 loci. In the 27 chi 2-tests for the genotypes at polymorphic loci only two (Pgi and Got-1) of beidagang population did fit the Hardy-Weinberg's expectations. This is due to high frequencies of the most common homozygotes and the corresponding heterozygote deficiency. The allozyme data demonstrated that the locusts had remarkable genetic variability within each population, but little divergence between the populations. The genetic variability measurements were found similar: Percentage of polymorphic loci (P) was between 73.7% and 78.9%; The mean number of alleles per locus (A) was from 2.9 to 3.1; and the mean heterozygosity (Ho) was nearly identical (about 0.138). The F-statistics (FST = 0.053) also showed the genetic uniformity of the populations, corresponding to the high Nei's genetic identity (I = 0.938). These results of the allozyme analysis suggested that the two populations appeared to be a part of a large population. It is reasoned that the genetic polymorphism and differentiation at certain loci between the two populations may depend on at least two agnostic factors that are all related to migration. First, the unusual dispersal capability of L. m. manilensis tends to make a continuous genetic structure distribution. Second, the frequent migration also results in the individuals to be exposed to drastically various environments. Since the broad adaptability is crucial to survive the changing environments, the genetic variation at population level is necessarily required to offer the population resilience for successful survival and reproduction under those ecologically divergent abiotic and biotic conditions. Thus, the migration contributes to the maintenance of dynamic equilibrium of genetic polymorphism in this highly specialized subspecies.