scholarly journals Population- and Species-Based Variation of Webworm–Parasitoid Interactions in Hogweeds (Heracelum spp.) in the Netherlands

2020 ◽  
Vol 49 (4) ◽  
pp. 924-930
Author(s):  
Jeffrey A Harvey ◽  
Paul J Ode ◽  
Rieta Gols

Abstract In three Dutch populations of the native small hogweed (Heracleum sphondylium L. [Apiales: Apiaceae]), and one of the invasive giant hogweed (H. mantegazzianum Sommeier & Levier [Apiales: Apiaceae]), interactions between a specialist herbivore, the parsnip webworm (Depressaria radiella), and its associated parasitoids were compared during a single growing season. We found host plant species-related differences in the abundance of moth pupae, the specialist polyembryonic endoparasitoid, Copidosoma sosares, the specialist pupal parasitoid, Barichneumon heracliana, and a potential hyperparasitoid of C. sosares, Tyndaricus scaurus Walker (Hymenoptera: Encyrtidae). Adult D. radiella body mass was similar across the three small hogweed populations, but moths and their pupal parasitoid B. heracliana were smaller when developing on giant than on small hogweeds where the two plants grew in the same locality (Heteren). Mixed-sex and all-male broods of C. sosares were generally bigger than all-female broods. Furthermore, adult female C. sosares were larger than males and adult female mass differed among the three small hogweed populations. The frequency of pupal parasitism and hyperparasitism also varied in the different H. sphondylium populations. These results show that short-term (intra-seasonal) effects of plant population on multitrophic insects are variable among different species in a tightly linked food chain.

Author(s):  
Daniel L. Villeneuve ◽  
Brett R. Blackwell ◽  
Jenna E. Cavallin ◽  
Wan‐Yun Cheng ◽  
David J. Feifarek ◽  
...  

Forests ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 95
Author(s):  
Yuan Gong ◽  
Christina L. Staudhammer ◽  
Susanne Wiesner ◽  
Gregory Starr ◽  
Yinlong Zhang

Understanding plant phenological change is of great concern in the context of global climate change. Phenological models can aid in understanding and predicting growing season changes and can be parameterized with gross primary production (GPP) estimated using the eddy covariance (EC) technique. This study used nine years of EC-derived GPP data from three mature subtropical longleaf pine forests in the southeastern United States with differing soil water holding capacity in combination with site-specific micrometeorological data to parameterize a photosynthesis-based phenological model. We evaluated how weather conditions and prescribed fire led to variation in the ecosystem phenological processes. The results suggest that soil water availability had an effect on phenology, and greater soil water availability was associated with a longer growing season (LOS). We also observed that prescribed fire, a common forest management activity in the region, had a limited impact on phenological processes. Dormant season fire had no significant effect on phenological processes by site, but we observed differences in the start of the growing season (SOS) between fire and non-fire years. Fire delayed SOS by 10 d ± 5 d (SE), and this effect was greater with higher soil water availability, extending SOS by 18 d on average. Fire was also associated with increased sensitivity of spring phenology to radiation and air temperature. We found that interannual climate change and periodic weather anomalies (flood, short-term drought, and long-term drought), controlled annual ecosystem phenological processes more than prescribed fire. When water availability increased following short-term summer drought, the growing season was extended. With future climate change, subtropical areas of the Southeastern US are expected to experience more frequent short-term droughts, which could shorten the region’s growing season and lead to a reduction in the longleaf pine ecosystem’s carbon sequestration capacity.


2020 ◽  
Vol 40 (7) ◽  
pp. 869-885 ◽  
Author(s):  
Timo Domisch ◽  
Ji Qian ◽  
Izabela Sondej ◽  
Françoise Martz ◽  
Tarja Lehto ◽  
...  

Abstract Future climate scenarios for the boreal zone project increasing temperatures and precipitation, as well as extreme weather events such as heavy rain during the growing season. This can result in more frequent short-term waterlogging (WL) leading to unfavorable conditions for tree roots. In addition, it is decisive whether short-term WL periods during the growing season occur continuously or periodically. We assessed the effects of short-termed WL on 4-year-old Scots pine (Pinus sylvestris L.) saplings after shoot elongation started. Waterlogging (WL) lasted either continuously for 2.5 weeks (ContWL) or noncontinuously for 5 weeks, consisting of three repeated 1-week-interval WL periods (IntWL). Both treatments resulted in the same duration of soil anoxia. We studied soil gases, root and shoot growth and physiology, and root survival probability and longevity during the experiment. In the final harvest, we determined shoot and root biomass and hydraulic conductance and electrical impedance spectra of the root systems. Soil CO2 and CH4 concentrations increased immediately after WL onset and O2 decreased until anoxia. Waterlogging decreased fine root survival probability, but there was no difference between WL treatments. Shoot growth suffered more from ContWL and root growth more from IntWL. Needle concentrations of pinitol increased in the WL saplings, indicating stress. No WL effects were observed in photosynthesis and chlorophyll fluorescence. Increased starch concentration in needles by WL may be due to damaged roots and thus a missing belowground sink. Electrical impedance indicated suffering of WL saplings, although root hydraulic conductance did not differ between the treatments. Oxidative stress of short-term and interval WL can have long-lasting effects on shoot and root growth and the physiology of Scots pine. We conclude that even short-term WL during the growing season is a stress factor, which will probably increase in the future and can affect carbon allocation and dynamics in boreal forests.


2016 ◽  
Vol 35 (6) ◽  
pp. 645-666 ◽  
Author(s):  
Jinguang Zhang

Previous research found that speakers with more attractive voices receive more favorable evaluations (aka the vocal attractiveness stereotype). But sexual selection theory predicts that, to the extent that men perceive women with higher pitched voices as more attractive, women will be more hostile toward those women because they make more threatening mate rivals. Supporting this hypothesis, Study 1 ( N = 102) showed that female participants higher in trait dominance displayed heightened aggressive cognition after being primed with a romantic (but not a control) feeling and listening to a higher- but not lower-than-average female voice. Study 2 ( N = 111) showed that this heightened aggressive cognition was activated by a long-term but not a short-term mating motive. These findings supported sexual selection theory, challenged the vocal attractiveness stereotype, and suggested a mechanism that helps maintain the honesty of female voice pitch as a mate attraction signal.


1991 ◽  
Vol 18 (2) ◽  
pp. 199 ◽  
Author(s):  
DC McFarland

Ground parrots in Queensland were found in closed graminoid-heathlands and sedgelands between Maryborough and Coolum on the mainland, and along the west coast of Fraser I. Parrot distribution, when compared to historical data, shows a decline which is a result of habitat destruction or degradation in the northern and southern limits of the species range. The current population is estimated at 2900 birds, with the majority in the heathlands of Cooloola National Park, Wide Bay Military Reserve and the State Forest and the Great Sandy National Park on Fraser I. Ground parrot density varied between sites because of the interactive effects of vegetation type, heathland area, time since and frequency of fire, microhabitat diversity and proximity to recolonisers. Within sites, parrot numbers changed in the long term with time since fire (influence of temporal changes in vegetation structure and seed availability) peaking at 5-8 years after burning, and in the short term with the seasonal effects of dispersal and breeding. Although predators were present their impact on the main populations was considered minimal. All of these factors are, to some extent, influenced by human activities, e.g. clearing and burning of heathlands.


1976 ◽  
Vol 27 (1) ◽  
pp. 19 ◽  
Author(s):  
WJR Boyd ◽  
NA Goodchild ◽  
WK Waterhouse ◽  
BB Singh

Variations in the regional means of a number of growing-season climatic variables, and combinations of them, are not highly correlated with the long-term regional distribution of mean wheat yields in Western Australia or with their variation between years. The data suggest that the growing season is characterized by a cyclical alternation of favourable and unfavourable conditions for crop growth. This oscillating pattern varies in amplitude and wavelength as a result of unpredictable 'between'- and 'within'-season variation in the regional distribution of rainfall. In the central zone of the study area, wheat production is subject mainly to between-season variation whilst in more marginal areas yield variation is confounded by opposing and reciprocating within-season effects. The consequences for plant breeding are that specific regional environments expected on the basis of climate do not occur predictably in the short term. It is argued that breeding objectives, selection strategies and regional testing should initially avoid complications associated with specific marginal environments by concentrating on general adaptability within the central zone, which monitors between-season variation only. Subsequent evaluation for additional adaptive features specific to marginal areas should be undertaken.


1992 ◽  
Vol 40 (3) ◽  
pp. 327 ◽  
Author(s):  
DJ Rae ◽  
RE Jones

Nitrogen levels in commercial plots of sugarcane varied over the cane-growing season. However, when adjusted for seasonal effects, nitrogen did not have a detectable effect on the size of mealybug populations on cane. In laboratory experiments, the survival of immature Saccharicoccus sacchari and the size attained at the onset of the oviposition period was influenced by the level of nitrogen fertiliser applied to potted sugarcane. Survival of S. sacchari increased to a maximum at 320 mg L-1 soluble nitrogen in sugarcane and decreased at higher levels, while size increased with increased nitrogen over the whole range of concentrations tested. Nitrogen-driven changes in the abundance of S. sacchari predicted from laboratory data indicate that normal variations in nitrogen concentrations of field-grown sugarcane have little effect on the population dynamics of S. sacchari.


2014 ◽  
Vol 92 ◽  
pp. 6-18 ◽  
Author(s):  
Francis Orvain ◽  
Margot De Crignis ◽  
Katell Guizien ◽  
Sébastien Lefebvre ◽  
Clarisse Mallet ◽  
...  

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