Dissertation•
Pine Weevil Feeding Behaviour in Relation to Conifer Plant Properties
01 Jan 2014-
TL;DR: The results from a no-choice and a choice experiment indicate that the protective effect of MeJA-induced defences is, besides an overall reduction of feeding, mainly due to the reduced amount that a pine weevil can feed at one place.
Abstract: The pine weevil (Hylobius abietis (L.)) is a forest insect distributed over the Palearctic region. The adults feed on the phloem of young conifer plants causing high economic losses for the European forest industry. Still, there is very little knowledge about the structure of its feeding behaviour. Feeding behaviour can be studied in several different temporal resolutions, from differences in feeding after several weeks to diel patterns and short-term feeding, i.e. feeding patterns at the level of feeding events and meals. The aim of this thesis was to increase the knowledge about the pine weevils’ feeding patterns and the underlying behavioural mechanisms.
I studied the pine weevils’ time budget and diel behaviour as well as its short-term feeding behaviour based on video recordings. In addition, I assessed how changes in plant properties due to girdling or induction of plant defences with a chemical elicitor, methyl jasmonate (MeJA), affect the feeding pattern and preferences of the pine weevil.
Pine weevils allocated only 6 % of the time to feeding. Most of the time was spent away from the plant (70 – 80 %). Damaged plants appeared to attract the weevils because they spent more time while not feeding on damaged plants than on undamaged plants. Feeding behaviour was mostly concentrated to the second half of the dark phase, after a peak of locomotion behaviour during the first part of the dark phase. During the light phase, pine weevils mostly rested. Analysis of the short-term feeding behaviour showed that pine weevils made 4-5 meals per day, removing about 13 mm2 during about 24 minutes in each meal. Some of the feeding properties, such as how much time was spent not feeding during a meal, differed between male and female weevils. Girdling did not affect the time budget or feeding properties.
The induced plant defences with MeJA caused a reduction in meal duration. When meals consisting of only phloem, only needles or both were compared, the meal duration and the time until the initiation of a meal were more similar between the different meal contents on induced plants. In addition, the results from a no-choice and a choice experiment indicate that the protective effect of MeJA-induced defences is, besides an overall reduction of feeding, mainly due to the reduced amount that a pine weevil can feed at one place. Thus the risk of girdling and death of the plant is reduced.
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TL;DR: A method is proposed for the rigorous analysis of experiments with two food types offered simultaneously, providing both a parametric and a nonparametric procedure, and showing that when offered the three species of algae T. niger does not feed at random but shows a preference for U. nematoidea.
Abstract: A serious omission in ecological methodology is the absence of a rigorous statistical procedure to analyse multiple-choice feeding-preference experiments. A sample of 21 studies in the littoral marine context shows that results from such experiments are used to study a variety of conceptual issues, ranging from nutritional biology to ecosystem dynamics. A majority of such studies have been incorrectly analysed. The analytical problem has two facets: (1) lack of independence in the simultaneous offer of food types and (2) the existence of autogenic changes particular to each food type. Problem (2) requires the use of control arenas without the consumer. A recent advance allows the rigorous analysis of experiments with two food types offered simultaneously. Here I propose a method for the multiple-choice case. For the first problem I suggest the use of multivariate statistical analysis, providing both a parametric and a nonparametric procedure. The second problem is solved using basic statistical theory. I analyse data from an experiment with the sea urchin Tetrapygus niger feeding on three species of algae: Ulva nematoidea, Gymnogongrus furcellatus, and Macrocystis pyrifera. The parametric and nonparametric procedures yielded similar results, and showed that when offered the three species of algae T. niger does not feed at random but shows a preference for U. nematoidea. The method requires that the number of replicates in the treatment and control arenas be the same, and greater than the number of food types. The method is useful for other kinds of multiple-choice experiments.
258 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...During choice experiments, animals have access to several different food sources, most commonly two but more are possible, while they only have one food source during no-choice experiments (e.g. Roa, 1992; Zas et al., 2011; Meier et al., 2014)....
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TL;DR: The highest fold increase in monoterpene cyclase activity was consistently observed in Abies grandis, and the time-course of induction of activity following stem wounding in this species demonstrated a threefold increase at 2 days relative to unwounded controls.
Abstract: Levels of monoterpene cyclase activity were determined in extracts from wounded and unwounded saplings of 10 conifer species to assess whether oleoresin biosynthesis is induced by stem wounding. Species of Abies and Picea, with low to moderate levels of constitutive monoterpene cyclase activity, exhibited a five- to 15-fold increase in cyclase activity 7 days after wounding relative to unwounded controls. In contrast, species of genera such as Pinus, with high levels of constitutive cyclase activity, did not significantly respond to wounding by alteration in the level of cyclase activity. The highest fold increase in monoterpene cyclase activity was consistently observed in Abies grandis, and the time-course of induction of activity following stem wounding in this species demonstrated a threefold increase at 2 days relative to unwounded controls, rising to a maximum increase in the response at 9 days (greater than 10-fold) followed by an apparent decline. The wound response was localized, and both bark (phloem) and wood (xylem) tissues displayed increased cyclase activity at the wound site. The magnitude of the increase in cyclase activity was dependent on the severity of the wound.
217 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...It might not have been enough time to reach peak levels in defence responses (Lewinsohn et al., 1991), although conifers can respond to damages within a few hours (Ralph et al....
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TL;DR: In this article, a non-linear curve-fitting procedure, such as NLIN in SAS, is applied to split behaviour into bouts, and traditional analysis of variance can then be used to decide whether the behavioural events are split into bouts.
214 citations
"Pine Weevil Feeding Behaviour in Re..." refers methods in this paper
...In these studies the meal criteria were determined using a different statistical approach, which has an underlying assumption of events starting at random (Sibly et al., 1990; Mitchell & Low, 1994)....
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TL;DR: Some general princ iple s are shown to be the basis of all the ecological rhythms and plays especially clearly the synchro nization of the biological processes with rhythmic factors of the environ ment.
Abstract: biological rhythms is very wide. The cycle s can range from some millis econds to some years. The rapid osci lla tions are especially characteristic of physiological rhythms which ensure the synchronization of all the internal process es in an organism. Such rhythms may be exemplifi ed by the rhythmic events in the "enzym e-substrate" system or by the pulsations of the heart muscle. Oscillations with daily or longer periods rank as a rule among ecolog ical rhythms which provid e for adapt a tion of plants and animals to fluctuations of enviro nmental factors. Internal oscillators are assumed to control such rhythms ; they are synch ronized by external timing elements (Zeitgeber = time-giv ers) which can be also termed as synch ronizers or entraining agents. Photope riod is especially im portant as this agent. The possession of int ernal oscillators enable s orga nisms to prepare in good ti me for the chang es of ecological conditions dur ing each day (daily rhyt hms), month (l unar rhythm s), or year (s eas onal rhyth ms). Adaptive implication and, cor res pondi ngly, mode of display ing the three type s of rhythms varies considerably. That's why, until recently, circadian and seasona l rhythms in arthropods have been investigated quite indepen dently. Daily rhythms were studied as biolo gical oscillations related to time measuring. As to inve stigations into seasonal cyclic phenomena , most atte n tion was paid to syst ems of neurosecr etory control of development and dia pause as well as to ecological aspects of the problem. The two points of view have been flected in reviews by Hark er (90) and de Wilde (207 ), published in previous volumes of Annual Review of Entomology. The material accumulated shows that some general princ iple s are th e basis of all the ecological rhythms. It dis plays especially clearly the synchro nization of the biological processes with rhythmic factors of the environ ment. The adaptations to lunar and seasonal periodicity evolve by way of 1 The follow in g abbrev iati ons are used in the text: PhPR (ph otop eriodic rea cti on); T of a free-running rhyth m); LL (constant ligh t); DD (constant darkness) ; LD (light-dark cycles which can be further specified as
201 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...Diel rhythms are also important for interand intra-species relationships (Danilevsky et al., 1970; Harmsen et al., 2011)....
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TL;DR: The terpenoid and phenolic constituents of conifers have been implicated in protecting trees from infestation by bark beetles and phytopathogenic fungi, but it has been difficult to prove these defensive roles under natural conditions.
Abstract: The terpenoid and phenolic constituents of conifers have been implicated in protecting trees from infestation by bark beetles and phytopathogenic fungi, but it has been difficult to prove these defensive roles under natural conditions. We used methyl jasmonate, a well-known inducer of plant defense responses, to manipulate the biochemistry and anatomy of mature Picea abies (Norway spruce) trees and to test their resistance to attack by Ips typographus (the spruce bark beetle). Bark sections of P. abies treated with methyl jasmonate had significantly less I. typographus colonization than bark sections in the controls and exhibited shorter parental galleries and fewer eggs had been deposited. The numbers of beetles that emerged and mean dry weight per beetle were also significantly lower in methyl jasmonate-treated bark. In addition, fewer beetles were attracted to conspecifics tunneling in methyl jasmonate-treated bark. Stem sections of P. abies treated with methyl jasmonate had an increased number of traumatic resin ducts and a higher concentration of terpenes than untreated sections, whereas the concentration of soluble phenolics did not differ between treatments. The increased amount of terpenoid resin present in methyl jasmonate-treated bark could be directly responsible for the observed decrease in I. typographus colonization and reproduction.
170 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...affect the behaviour of herbivorous insects towards their host (e.g. Miller et al., 2005; Erbilgin et al., 2006; Heijari et al., 2008)....
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