Limiting the success of stem borers (Prodoxus quinquepunctellus) in yuccas: indirect effects of ants, aphids, and fruit position

Abstract

1. Although the moth -yucca mutualism is often studied as a pairwise interaction, yucca plants are also the sole host for a variety of other visitors. One of these additional visitors is a stem-boring moth, Prodoxus quinquepunctellus.2. In this study, it is shown how the reproductive success of Prodoxus indirectly depends on the interactions between yuccas and their pollinators ( Tegeticula , Prodoxidae) as well as the indirect effects of ants and aphids.3. Aggressive wood ants foraging on yuccas will attack adult Prodoxus moths while attempting to oviposit. This reduces the number of eggs laid in yucca stalks, leading to fewer larvae feeding in the stalks.4. Once in the stalk, the survival of Prodoxus eggs/larvae depends upon the rate at which the flowering stalks dry out during fruit maturation. Portions of the stalk above the highest fruit dry out quickly and survivorship approaches zero in these dry sections, while larvae in green sections of the flowering stalk have significantly higher survival rates. The presence of aphids feeding on the stalk slows down the rate of stalk drying and could lead to increased survival of Prodoxus larvae. 5. Overall, ants have strong indirect effects on P. quinquepunctellus by controlling how many eggs are laid in the stalk and by influencing the distribution of aphids. However, it is primarily the presence and position of the fruit that can affect larval survivorship, and fruit position is a function of pollinator visits and resource limitation. These complex interactions illustrate the importance of studying the yucca -moth mutualism in a community context.

Stem tissue mass density is linked to growth and resistance to a stem‐boring insect in Alternanthera philoxeroides

“…In fact, the larvae of many phytophagous insects, including Coleoptera, Diptera, Lepidoptera and Hymenoptera, feed on or inhabit host plant tissues for certain stages or the whole of their life histories (Rathcke 1976; Eber et al . 1999; Snell & Addicott 2008). Thus, it is concievable that stem‐boring insect herbivores do bring selective pressure on both intraspecific and interspecific variations in plant stem traits.…”

“…The development of solid-stemmed wheat cultivars to minimize losses from the wheat stem sawfly (Cephus cinctus Norton) in the USA and Canada is another example of how stem traits play a critical role in plant resistance to insect herbivores (Hayat et al 1995). In fact, the larvae of many phytophagous insects, including Coleoptera, Diptera, Lepidoptera and Hymenoptera, feed on or inhabit host plant tissues for certain stages or the whole of their life histories (Rathcke 1976;Eber et al 1999;Snell & Addicott 2008). Thus, it is concievable that stemboring insect herbivores do bring selective pressure on both intraspecific and interspecific variations in plant stem traits.…”