Extensive gene flow of white-backed planthopper in the Greater Mekong Subregion as revealed by microsatellite markers.

The white-backed planthopper (WBPH), Sogatella furcifera (Horváth), is a destructive pest of rice in the Greater Mekong Subregion (GMS) countries including Cambodia, Laos, Myanmar, Thailand, Vietnam, and China's Yunnan Province. Our previous study not only confirmed the immigration sources of the WBPH in China's Yunnan Province were from Myanmar, Vietnam, and Laos, but also indicated that Cambodia was likely an additional migration source. To further clarify the migration sources and patterns of the WBPH in the GMS, we investigated the genetic structure of 42 WBPH populations using microsatellite loci markers. The analysis of genetic diversity, heterozygosity deficit, and heterozygosity excess based on the nuclear markers suggest that there is extensive gene flow between the 42 sampled populations from the GMS. The genetic structure confirmed the immigration sources of WBPH as revealed by mitochondrial markers and trajectory analyses methods in previous studies. These findings will aid in the sustainable regional management of this insect pest in the GMS.

Copulation duration, sperm transfer and reproduction of the two closely related phytoseiid mites, Neoseiulus womersleyi and Neoseiulus longispinosus (Acari: Phytoseiidae).

The effects of copulation duration on reproduction were studied in two important biological control agents, Neoseiulus womersleyi (Schicha) and Neoseiulus longispinosus (Evans), to better understand their reproductive potential. The number of eggs produced was significantly and positively related to the copulation duration in both species. Egg production was observed even in females which experienced only 15 min of copulation and increased as copulation period increased in both species. Both pre- and post-oviposition periods of N. womersleyi and N. longispinosus decreased with the increase of copulation durations, and they were significantly different between the two species. Copulation duration had no effect on the female adult longevity of N. womersleyi and N. longispinosus, but N. womersleyi showed higher adult longevity than N. longispinosus. Fecundity remarkably increased in both species when the copulation period exceeded 90 min. The size of the spermatophore inside the spermathecae increased in proportion to the copulation duration in both species. Fecundity was consistent with the sizes of the spermathecae and spermatophores. When copulation was extended, males first filled one spermatheca and then filled the other. The results obtained in this study suggest that copulation duration had similar effects on egg production in N. womersleyi and N. longispinosus. Egg production depended on the quantity of sperm transferred during copulation. The two species have similar reproductive potentials and mating properties under laboratory conditions.

Possible Source Populations of the White-backed Planthopper in the Greater Mekong Subregion Revealed by Mitochondrial DNA Analysis.

The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), is a serious pest of rice in Asia. However, little is known regarding the migration of this pest insect from the Greater Mekong Subregion (GMS) including Cambodia, Laos, Myanmar (Burma), Thailand, and Vietnam, into China's Yunnan Province. To determine the migration patterns of S. furcifera in the GMS and putative secondary immigration inside China's Yunnan Province, we investigated the population genetic diversity, genetic structure, and gene flow of 42 S. furcifera populations across the six countries in the GMS by intensive sampling using mitochondrial genes. Our study revealed the potential emigration of S. furcifera from the GMS consists primarily of three major sources: 1) the S. furcifera from Laos and Vietnam migrate into south and southeast Yunnan, where they proceed to further migrate into northeast and central Yunnan; 2) the S. furcifera from Myanmar migrate into west Yunnan, and/or central Yunnan, and/or northeast Yunnan; 3) the S. furcifera from Cambodia migrate into southwest Yunnan, where the populations can migrate further into central Yunnan. The new data will not only be helpful in predicting population dynamics of the planthopper, but will also aid in regional control programs for this economically important pest insect.