Life Tables and Mortality Factors for Saperda inornata (Coleoptera: Cerambycidae)1

Millar

Entomologia Exp Applicata

et al. 2001

The eucalyptus longhorned borer Phoracantha semipuncata (F.) is native to Australia and has become established in most of the regions of the world where its Eucalyptus L'Heritier host trees have been introduced. To study the population dynamics of the insect in its native range, we investigated the influence of host log age (fresh or aged), protection from ant predation, and protection from parasitism by specialist larval parasitoids on numbers of initial larval feeding galleries, larval mortality, larval survivorship, and parasitization. There were greater numbers of initial larval galleries when ants were excluded, and greater numbers on fresh logs than on aged logs. However, mortality of larvae was greater in fresh logs, as well as when larvae were exposed to parasitism. Survivorship was greater when ants and parasitoids were excluded. Larvae achieved a larger size in fresh logs and in logs protected from parasitism. Fresh host material may provide a fitness advantage because it is a higher quality resource, but greater infestation of that material also increases the probability of mortality from competition among larvae. The results suggest that there are potential ecological interactions among food quality, host resistance, natural enemies, and competition that must be considered in evaluating the population dynamics of this species in native and novel environments.

Section: Discussionmentioning

confidence: 53%

Influence of host log age and refuge from natural enemies on colonization and survival of Phoracantha semipunctata

Millar

Entomologia Exp Applicata

et al. 2001

“…At the beginning of their Þrst active period, larvae were small, fragile, and relatively exposed to woodpeckers, feeding in the phloem just under the outer bark surface. For other cerambycids, the poplar gall Saperda, Saperda inornata Say, P. semipunctata, and the sugi bark borer, Samanotus japonicus Lacordaire, early larval stages often endured the greatest relative mortality compared with other stages (Grimble and Knight 1970, Powell 1982, Shibata 1987. M. alternatus experienced evenly distributed mortality throughout its life cycle (Shibata 1987) and the southern pine sawyer, Monochamus titillator (F.), suffered the greatest mortality during the egg and mid-larval stages (Dodds and Stephen 2000).…”

Section: Discussionmentioning

confidence: 99%

Partial Life Tables From Three Generations of <I>Enaphalodes rufulus</I> (Coleoptera: Cerambycidae)

et al. 2012

We used life table analyses to investigate age specific mortality and to better understand the population dynamics of the red oak borer, Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae). We continually sampled populations within 177 trees at primarily two sites in the Ozark National Forest in Arkansas throughout three (2-yr) generations. The first cohort (adults emerged in 2003) was sampled during a severe population outbreak, whereas the second and third (2005 and 2007) were sampled during the population crash that followed. Generation mortality was 94% in 2003 and 99% in both 2005 and 2007. Estimates of apparent mortality indicated that the E. rufulus population crash likely occurred during or before the first overwintering period (2003-2004) of the generation that emerged as adults in 2005. We found limited evidence for density dependent mortality, which suggest that intraspecific competition after the first active feeding period was apparently not an important mortality factor during E. rufulus development. Life tables revealed that E. rufulus larvae generally experienced the greatest apparent mortality during the second summer of active feeding (80-94%) when larvae were feeding in, and moving between phloem and sapwood. The least apparent mortality was incurred during the following spring and early summer (26-67%) when late stage larvae and pupae were deepest and most protected within sapwood or heartwood tunnels. We found very little evidence for mortality from associated species. Scarring of vascular tissue in response to E. rufulus feeding occurred during early life stages and may be an important tree resistance mechanism and E. rufulus mortality factor.

“…Although a number of life table analyses have suggested that variation in fecundity is the most important factor regulating population dynamics (Grimble and Knight 1970, Redfern and Cameron 1978, Ryan 1986) these studies have not separated the effects of variation in female response due to host quality from variation in adult mortality. Berryman (1973) incorporated the effect of host quality (resin production) on the number of failed bark beetle oviposition attempts into a life table analysis, but oviposition failure is not a direct measure of reduced fecundity since females may be able to reattack after a failed oviposition.…”

Section: High Water Low Watermentioning

confidence: 99%

“…A few studies have described the effect of intraspecific host variation on oviposition behavior (see Rausher 1983, Papaj and Rausher 1987, and Singer 1988 for reviews), but such behavioral factors have not been incorporated into studies of herbivore population dynamics using life table analysis (e.g., Morris and Miller 1954, Dahlsten 1967, Grimble and Knight 1970, Redfern and Cameron 1978, Dixon and Houseweart 1982. We have included the effects of variable host quality on two Euura oviposition behaviors and mortality into a life table analysis.…”

Section: Introductionmentioning

confidence: 99%

Host Quality and Sawfly Populations: A New Approach to Life Table Analysis

Preszler¹,

Price²

1988

Ecology

103

In the field, population density of a shoot—galling sawfly Euura lasiolepis was on eighth as great and mortality was five times as great in dry habitats as in wet habitats. The effect of host water stress on Euura populations was experimentally tested by initiating Euura populations on potted Salix lasiolepis willow plants given various amounts of water. As in wild populations Euura mortality was much higher (2.5 times) on waterstressed Salix. The life table analyses of experimental Euura cohorts began with the potential number of eggs in the adult females of the preceding generation. This enabled us to describe the effects of female reproductive responses to host quality on Euura densities. These responses, failure to initiate a gall or to release an egg during gall initiation, resulted in a 27.5% reduction of the Euura cohort on hosts given a high—water treatment and an 85.1% reduction on low—water hosts. Excluding behavioral limits on the potential number of eggs laid, first—instar larval death was the largest and most variable Euura mortality factor of the experimental populations. Host water treatment accounted for 51.9% of the variance in first—instar larval mortality (P ° .001), with 13.6% of the first instars dying on hosts given high—water treatments and 54.5% dying on the low—water hosts. The threefold decrease in gall initiation and egg release on water—stressed hosts has probably been selected for by the fourfold increase in first—star larval mortality on these water—stressed hosts. From an evolutionary perspective the reproductive behaviors have amplified the effects of the first—instar mortality. From an ecological perspective the reproductive responses of the adult females were the critical factors regulating Euurra densities. Understanding the effect of variation in host quality on herbivore survivorship and behavior is essential to understanding the densities of local herbivore populations and should be routinely incorporated into life table analyses.