Reproductive Modes in Onion Thrips (Thysanoptera: Thripidae) Populations from New York Onion Fields

Abstract

Thrips exhibit different reproductive modes including thelytoky (females produced from unfertilized eggs), arrhenotoky (males produced from unfertilized eggs and females produced from fertilized eggs) and deuterotoky (females and males produced from unfertilized eggs). We investigated patterns of reproductive modes in onion thrips, Thrips tabaci Lindeman, populations and potential effects of the bacterium Wolbachia and temperature on these modes. We also examined the possibility that male-producing T. tabaci populations were resistant to the frequently used insecticides, lambda-cyhalothrin and methomyl. In New York during 2002Ð2004, T. tabaci populations were sampled from 20 onion Þelds and reproductive mode was determined by identifying sex of progeny from virgins. Half of the populations were thelytokous and half were a mix of thelytokous, arrhenotokous and deuterotokous individuals, which we refer to as a male-producing population. In two of four cases, the reproductive mode of a population from the same onion Þeld changed across years, suggesting that populations either mix or an external factor caused the change. To address the latter, we speculated that Wolbachia or high temperature mediated reproductive modes. Samples of T. tabaci representing each reproductive mode were examined for Wolbachia using diagnostic polymerase chain reaction (PCR), but it was not detected. Cytological examination of ovaries from two additional thelytokous lines also showed no evidence of Wolbachia. Similarly, high temperature did not affect sex allocation ratios in either thelytokous or male-producing populations. Male-producing T. tabaci populations were not positively correlated with resistance to lambda-cyhalothrin, or tolerance to methomyl. The role of the different reproductive modes in T. tabaci populations in onion Þelds remains unclear.

Species richness of thrips and whiteflies and their predators in mustard fields

“…After settling down the less number of thrips started colonizing through multiplication that resulted in increased population richness over time and reached the peak of 72.50 thrips plant -1 on March19, 2016 with 27.8°C and 71% RH. The identical findings were reported by Bjorn (1995) for thrips infesting winter white cabbage, and Nault et al (2006) for onion thrips in New York onion field. The relative thrips richness in mustard on March, 2016 was statistically different from that in February 18, 2016 to November, 2015 that might be due to fluctuation in temperature and humidity across the months studied along with predators-prey interaction even though the higher richness of thrips from February 18 to march 19, 2016 was statistically similar (Table 1).…”

Onion Thrips (Thysanoptera: Thripidae): A Global Pest of Increasing Concern in Onion

“…T. tabaci also can reproduce by arrhenotoky (Kendall and Capinera 1990), in which unfertilized eggs develop into males and fertilized eggs into females. Deuterotoky is an uncommon parthenogenetic mode of reproduction in thrips and was reported for the Þrst time occurring in T. tabaci by Nault et al (2006). Deuterotoky occurs when unfertilized eggs develop into either males or females.…”

“…In addition, T. tabaci populations collected from the Þeld in 2000 and reared in laboratory conditions until 2004 did not produce males. In New York, Nault et al (2006) sampled T. tabaci in 20 onion Þelds from six different counties and found half of the population was thelytokous with the other half being a mix of thelytokous, arrhenotokous, and deuterotokous. The various reproduction systems of T. tabaci probably contribute to it becoming more problematic because, for example, thelytokous individuals are not dependent on Þnding mates and, if they are resistant to an insecticide, then their offspring will be as well.…”

Performance of Arrhenotokous and Thelytokous <I>Thrips tabaci</I> (Thysanoptera: Thripidae) on Onion and Cabbage and Its Implications on Evolution and Pest Management

“…T. tabaci of the two reproductive modes were found to coexist in the Þeld, and the frequency of these two reproductive modes varied temporally (Nault et al 2006). Comparative life table data of arrhenotokous and thelytokous T. tabaci can help explain their biological differences and provide important information about their population dynamics in the Þeld.…”

“…These two reproductive modes may coexist in populations collected in the Þeld (Nault et al 2006), but it is difÞcult to distinguish between thelytokous and arrhenotokous female adults morphologically (Jenser and Szé nási 2004). However, the two reproductive modes differ ecologically and genetically, including having different host preferences.…”