Observations on the Population Fluctuations and Life Histories of the Beetles Bruchidius ater (Bruchidae) and Apion fuscirostre (Curculionidae) on Broom (Sarothamnus scoparius)

Parnell, J. R.

doi:10.2307/2695

Cited by 35 publications

(34 citation statements)

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“…Beetle size was found to have a major influence on the fecundity of female beetles such that the largest females produced enough eggs to infest 2–3 times more seeds than the smallest beetles. The fitness benefits of large beetle size may extend beyond this as we also found indirect evidence that the survival rate of overwintering B. villosus beetles is size‐dependent (concurring with Parnell's () anecdotal observation in England that ‘no small beetles were found to emerge from hibernation’). This shift to larger mean beetle sizes post‐hibernation at the site with the smallest mean seed size (Palmerston North) strongly suggests that seed size may constrain overwinter survival in the beetles.…”

Section: Discussionsupporting

confidence: 89%

“…). Moreover, although other pre‐dispersal seed‐feeders which co‐occur with B. villosus in the UK, such as the seed‐weevil Exapion fuscirostre (Parnell ), are absent from NZ, native range studies indicate that total broom seed loss due to pre‐dispersal seed predators ranged from only 0.4–26% (Sheppard & Thomann ) implying that interspecific competition for resources is likely to be minor.…”

Section: Discussionmentioning

confidence: 99%

“…At each locality, we haphazardly selected 10 mature plants per site and collected 15 mature (dried and black) pods from each plant, prior to dehiscence, and put them in separate labelled bags. At the laboratory, each pod was opened and the total number of seeds per pod and the number of seeds infested with B. villosus (recognizable by a hole made in the seed coat when a beetle exits the seed; Parnell ) were counted. Emerged beetles were stored in labelled vials containing 70% alcohol, prior to being measured.…”

Section: Methodsmentioning

confidence: 99%

“…The potential relationship between beetle size and fecundity was investigated as follows: In October 2007 (before broom pods had formed and B. villosus oviposition had begun), adult B. villosus beetles were collected from broom flowers (where they congregate to feed on pollen; Parnell ) at the Palmerston North site (Table ). Beetles were then briefly immobilized by placing them in a fridge to cool them down, and the sex of each beetle was determined using a binocular microscope.…”

Section: Methodsmentioning

confidence: 99%

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Breaking and remaking a seed and seed predator interaction in the introduced range of Scotch Broom (Cytisus scoparius) in New Zealand

et al. 2015

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Summary Introduced plants may initially experience enemy release, but some of those interactions may be reinstated through biological control. These cases provide opportunities to explore the dynamics of broken and remade consumer–resource interactions. The European shrub broom (Cytisus scoparius) was introduced to New Zealand without a specialist seed predator (Bruchidius villosus) until a biological control programme reinstated this interaction in 1988. Broom produces substantially larger seeds throughout its non‐native range, and there are differences in seedling establishment beneath broom canopies between the native and introduced ranges. We hypothesized that large broom seeds produce seedlings with a survival advantage in shaded conditions, consistent with establishment under broom canopies in the introduced range. We also predicted that the seed‐feeding beetle would experience increased fitness in larger seeds. We found that seedling survival was correlated with seed weight in shaded conditions, consistent with the observed establishment of seedlings beneath broom stands in the non‐native range. Beetle size was positively correlated with seed weight, and female fecundity increased with body size. Comparison of the size distributions of beetle populations before and after hibernation provided indirect evidence that overwintering survival of beetles is also size‐dependent. These findings are consistent with observed higher levels of abundance of B. villosus in New Zealand, compared to native habitats. Selection gradients for seed size‐dependent seedling survival on broom occupancy were explored using the Rees–Paynter population model, demonstrating that a fitness benefit to the plant of large seed size through enhanced seedling survival beneath the parental canopy is only likely under low‐disturbance scenarios and moderate fecundity levels. Synthesis. The dynamics of biocontrol systems provide an underexploited opportunity to examine the impact of removal and reinstatement of species interactions. Differences in seed size between native and non‐native ranges may result from varying intensities of conflicting selection pressures acting on seed size. It remains to be seen whether a decline in seed size towards that seen in the native range will result from the biocontrol agent introduction, as we have demonstrated that selection pressures on seed size vary with disturbance‐mediated population turnover and fecundity.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Breaking and remaking a seed and seed predator interaction in the introduced range of Scotch Broom (Cytisus scoparius) in New Zealand

et al. 2015

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“…Generation survival was similar in all years despite the varying fruit abundances and weevil densities. The GS of c. 20% is higher than the 8-12% reported for a few other seed beetles, both Bruchidae and Curculionidae (Dickason, 1960;Parnell, 1966;Mitchell, 1977) and is not sufficient to prevent weevil population increases if fruit are available, unless overwintering mortality is quite severe. Rates of braconid parasitism showed no consistent trends with varying weevil densities; in contrast, combined parasitism by the chalcid species increased with the annual increase in weevil densities.…”

Section: Discussionmentioning

confidence: 62%

Abundance and survival of a seed‐infesting weevil, Pseudanthonomus hamamelidis (Coleoptera: Curculionidae), on its variable‐fruiting host plant, witch‐hazel (Hamamelis virginiana)

Steven

1981

Ecological Entomology

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Abstract. 1. The relative importance of seed abundance and of mortality factors in the population biology of Pseudanthonomus hamamelidis, a hostspecific predispersal seed predator on Hamamelis virginiana, is evaluated by analysis of weevil life tables and abundance estimates in three years with markedly different magnitudes of fruit production. 2. Fruit production of marked Hamamelis individuals averaged 336 m‐2 in 1978, increased three‐ to four‐fold in 1979, and declined again in 1980. More individuals fruited in 1979 than in the other two years. 3. The early larval stage of P.hamamelidis incurred the greatest mortality, with 42–58% dying from often undeterminable causes. Losses in the egg stage ranged from 22% to 31%. Three parasitoid species each accounted for minor mortality. Generation survival was similar in all three years, ranging from 21% to 28%. 4. The percentage of Hamamelis fruit crops infested by P.hamamelidis was high in 1978, averaging 76%, but was much lower in 1979, the year of abundant fruit. In 1980, when fruit were less abundant again, infestation was nearly complete. Egg densities on fruits were lower in 1979 than in the other two years. 5. The fluctuating fruit crops of Hamamelis are responsible for limitation of P.hamamelidis numbers during poor fruiting years. The occasional highly productive fruiting year results in satiation of weevil populations and concomitant seed escape by Hamamelis. Mortality factors appear less important in influencing weevil population dynamics.

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The Effect of Variability in the Phenology of the Reproductive Stages of Scotch Broom (Cytisus scoparius) on the Synchronization of the Life Stages of Broom Seed Beetle (Bruchidius villosus) in New Zealand

Harman

1999

Biological Control

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Observations on the Population Fluctuations and Life Histories of the Beetles Bruchidius ater (Bruchidae) and Apion fuscirostre (Curculionidae) on Broom (Sarothamnus scoparius)

Cited by 35 publications

References 4 publications

Breaking and remaking a seed and seed predator interaction in the introduced range of Scotch Broom (Cytisus scoparius) in New Zealand

Breaking and remaking a seed and seed predator interaction in the introduced range of Scotch Broom (Cytisus scoparius) in New Zealand

Abundance and survival of a seed‐infesting weevil, Pseudanthonomus hamamelidis (Coleoptera: Curculionidae), on its variable‐fruiting host plant, witch‐hazel (Hamamelis virginiana)

The Effect of Variability in the Phenology of the Reproductive Stages of Scotch Broom (Cytisus scoparius) on the Synchronization of the Life Stages of Broom Seed Beetle (Bruchidius villosus) in New Zealand

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