Defining the Western Spruce Budworm's Nutritional Niche With Response Surface Methodology

Abstract

A response surface design was used to help define the "nutritional niche" of the western spruce budworm, Choristoneura occidentalis. We evaluated how calcium, magnesium, and phosphorus interacted to influence budworm fitness on artificial diets containing five different levels of the minerals. We quantified survival rates for several life stages using a three—generation bioassay. Data from the bioassay were used to estimate population growth over three complete generations. Performance of the budworm was affected by Mg (linear response for F1 generations; 0.83—1.95 mg/g tested) and P (quadratic response for P1 [parental] and F1 generations; 2.74—4.95 mg/g tested) but was largely unaffected by Ca (0.50—6.81 mg/g tested). Overall, the results suggested budworm performance is best when Mg is at low concentrations and P is at moderate concentrations, and that very high levels of Mg and P are detrimental to the budworm. On average, host trees had too much Mg and too little P for optimal response by budworms. Interactions between Mg and P imply that balances or ratios of minerals are important in budworm nutritional ecology. However, detectable effects from Mg, P, and Ca in the diets diminished as the bioassay continued into the F2 generation, and, consequently, the estimated number of larvae alive at the beginning of the F2 and F3 generations showed no relationship to concentrations of the test minerals. This result probably reflected: (1) the loss of some design points in the second and third generations of the biomass because larvae did not survive on diets that were markedly suboptimal and (2) increased variability in the population growth response as the experiment contributed into the F2 and F3 generations.

Lack of macronutrients in Eucalyptus urophylla S.T. Blake (Myrtaceae) seedlings affects feed and development of Podisus nigrispinus (Hemiptera: pentatomidae)

“…However, as shown here, it was observed that the lack of Mg in plants decreases the feed rate of the predators (CLANCY; KING, 1993).…”

Dietary phosphate affects food selection, post-ingestive P fate, and performance of a polyphagous herbivore

“…The caterpillar Manduca sexta exhibited faster growth and improved survival on artificial diets enriched in phosphate in the natural range, and also performed better on natural diets spiked with phosphate (Perkins et al, 2004). Similarly, higher leaf P levels were correlated with faster growth in spruce budworm caterpillars (Clancy and King, 1993), and the growth and survival of several lepidopteran larvae was better on wild and greenhouse-grown plants with higher %P, independent of %N (Apple et al, 2009). House crickets, Acheta domestica, grew and developed faster on artificial diets with a higher phosphate content (Visanuvimol and Bertram, 2011).…”

Dietary phosphorus affects the growth of larval Manduca sexta

“…However, observed effects of dietary phosphorus variation on insect herbivore growth in studies to date have not been consistent. Increasing dietary phosphorus has been shown to increase growth rates in caterpillars (Clancy and King, 1993) and crickets (McFarlane, 1991). Growth rates decreased in grasshoppers (Smith, 1960) and remained unchanged in mosquitoes (Dadd et al, 1973) in response to fluctuations in the amount of dietary phosphorus.…”

“…Growth rates decreased in grasshoppers (Smith, 1960) and remained unchanged in mosquitoes (Dadd et al, 1973) in response to fluctuations in the amount of dietary phosphorus. The range of dietary phosphorus in three of these studies was not compared with the variation in phosphorus of the insects' natural diets (Smith, 1960;Dadd et al, 1973;McFarlane, 1991), and in the sole exception the minimum dietary phosphorus concentration was almost double the minimum observed foliar phosphorus concentration (Clancy and King, 1993). All but one of the studies were performed using only artificial diets.…”