A Bird in the Hand Versus Two in the Bush? The Specialist Leafhopper Dalbulus maidis (Hemiptera: Cicadellidae) Does Not Discriminate Against Sub-optimal Host Plants (Zea spp.)

Abstract

The corn leafhopper [Dalbulus maidis (DeLong & Wolcott)] is a specialist on Zea (Poaceae) that coevolved with maize (Zea mays mays) and its teosinte (Zea spp.) relatives. This study tested the hypothesis that host acceptance by females varies among Zea hosts, and is correlated with variation in defensive levels across those hosts. Prior studies revealed differences in plant defenses among Zea hosts and corresponding differences in corn leafhopper performance. Thus, host acceptance was expected to be correlated with defensive levels and offspring performance across Zea hosts, following the hypothesis that offspring performance mediates host preference. In parallel, host acceptance was expected to be correlated with transitions in life history strategy (perennial to annual life cycle), domestication status (wild to domesticated), and breeding intensity (landrace to hybrid variety) in Zea because variation in defensive levels and corn leafhopper performance were shown in prior studies to be correlated with those transitions. The study's hypotheses were tested by comparing, under no-choice conditions, host acceptance by corn leafhopper of a suite of Zea hosts encompassing those transitions: perennial teosinte (Zea diploperennis), Balsas teosinte (Zea mays parviglumis), and landrace and commercial hybrid maize. The results did not show differences in host acceptance for oviposition or feeding among the hosts. Thus, under no-choice conditions, all Zea hosts may be similarly acceptable for feeding and oviposition, despite marked ovipositional preferences under choice conditions and poorer offspring performance on teosintes relative to maize shown previously. The results suggested also that oviposition frequency per plant by females was not correlated with their offspring's performance.

Larval dispersal of the invasive fall armyworm, Spodoptera frugiperda, the exotic stemborer Chilo partellus, and indigenous maize stemborers in Africa

“…In the present study, FAW neonate larvae exhibited greater ballooning activity than stemborers. Several studies suggested that in the cases where larval dispersal is limited, females select for high‐quality hosts (van Huis, 1981; Thompson, 1988; Roitberg et al, 1999; Zlotina et al, 1999; Gripenberg et al, 2010; Refsnider & Janzen, 2010; Bellota et al, 2017). Thus, the higher dispersal indicates that FAW is less involved in high‐quality host assessment and also more polyphagous than any of the stemborer species.…”

Nonsensical choices? Fall armyworm moths choose seemingly best or worst hosts for their larvae, but neonate larvae make their own choices

“…Thus, the propensity for dispersal of neonate larvae may override the moth’s host choices and be adaptive, while female ovipositional preferences may be dynamic, i.e. shaped by variables other than their offspring’s performance, such as risk of parasitism or egg mortality, which may be high and differ among hosts [ 2 , 65 , 66 ]. For example, recent field studies showed that fall armyworm egg-stage mortality on maize was 73 to 81% [ 16 ], and that parasitism and predation risks of fall armyworm larvae were three- to four-fold higher on the maize wild ancestor Balsas teosinte ( Zea mays parviglumis ) compared to maize [ 33 ].…”

Do assortative mating and immigrant inviability help maintain population genetic structuring of an herbivore on a crop and a wild relative?

“…Females were removed after 5 d, and discarded, and seedlings were placed inside a cage, and leafhopper eggs allowed to hatch into nymphs. Fifteen days later, the number of nymphs per seedling was recorded, and the leaf section exposed to ovipositing females was excised from the seedling for subsequent recording of oviposition (below); the timing and spread of egg hatch and adult emergence times were known from prior studies (Dávila‐Flores et al ., ; Bellota et al ., ). Beginning at this time, cages were examined daily to record the emergence of adult leafhoppers.…”

“…Adults were removed as they appeared, and the time (days) to emergence and gender were recorded. The excised leaf section, exposed to oviposition, was stained per McBryde () to facilitate counting the number of eggs that were originally laid on a seedling; this procedure as applied to corn leafhopper was successfully used in prior studies (Bellota et al ., , ; Dávila‐Flores et al ., ). The following data were recorded for each seedling: numbers of eggs, nymphs, and adults, gender of adults, and development times (= the period from oviposition to emergence of adults).…”