Ebook "STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH"
Gleb I.Vasechko,
Cand.Sc.(Biology)
© Gleb Vasechko, 2005 All rights reserved.
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Created 20.03.2005
Last modification 15.06.2021
Gleb Vasechko.
PART I. A LIST OF THE AXIOMS. Continuation.
AXIOM 2. THE NATURE of ECOSYSTEM STABILITY to PLANT PESTS and its COMPONENTS. Continuation.
COMPONENTS of ECOSYSTEM STABILITY to PLANT PESTS
of the CATEGORY 2.3. ROUTINE WEATHER SUPPRESSION
This category of CESPPs embraces the cases of mortality and a decrease of fecundity of PPs under effects of weather situations. These effects are independent on other CESPPs or operate in cooperation with them.
An operation of suppressive effects of 2.3. "Routine weather suppression" is governed by the following regularities:
- The effects are directly dependent on potency of a weather situation, and inversely dependent on healthy of a herbivore population.
- The potency of a weather situation is an index of deviation from optimum for a herbivore species, for example in direction of decrease of negative air temperatures at hibernation or in decrease of low positive temperatures in the active stages of invertebrate herbivores (larval, pupal, adult); the potency gets greater at increase of duration of the situation.
- The healthy state or good physiological state of a herbivore population means a lack in it of the inapparent form of infection that is demonstrated in particular by high values such indices as body weight, normal sex ratio, etc. The weakened state is affection by the inapparent form of infection.
- The weather situations of high potency exert unselective mortality of population resulting in an extinction of a given species in an area. The situations of decreased potency exert selective mortality, i.e. kill weakened individuals within a herbivore population that results in a decrease of its density.
- Capacity of herbivore taxa to withstand to suppressive weather situations is diverse that is determined by evolutionary history of these taxa. Each taxon has own advantages and disadvantages to withstand the effects.
- Because potency of the effects of weather situations is determined by climates of areas, the range of a herbivore species can be subdivided on several regions with diverse probability of abundance/occurrence of these species. These regions are described by W.C. Cook (1929) as the zones of normal abundance (a), occasional abundance (b), possible abundance (c), and possible occurrence (d).
- Because evolutionary history of herbivore species is unequal, the W.C. Cook's zones in every of them are different as to their location.
- Weather situations are able to exert suppressive effects of herbivore species by means affection of host-plant resistance (CESPPs 2.1.1.2. and 2.1.1.4.) in direction to its increase.
The zonation of a species' range according to W.C. Cook (1929) is used as a frame for classification of CESPPs 2.3. "Routine weather suppression." The characteristics of the zones have been given by S.A. Graham (1939, pp. 72-73) as follows:
"Cook (1929) has analyzed the effect of physical factors on insects and divides the range of a species into several concentric zones. In the most favorable portion of the range lies the zone of normal abundance, within which physical conditions are invariably favorable for the species, and within which outbreaks are controlled or prevented by the action of nutritional and biotic ER (environment resistance).
Outside this zone lies the zone of occasional abundance, in which the physical conditions are always sufficiently favorable to permit the species to survive, but only occasional favorable variations will permit them to become exclusively abundant. Within such areas, continually favorable niches (Elton, 1927) occur in which the insects maintain themselves as they would in the zone of normal abundance. From these niches they spread when favorable variations permit. In this zone the abundance of the insects is regulated in the niches by biotic factors and in the usually unfavorable part of the zone by a return to usual conditions.
Next comes the zone of possible abundancein which conditions are usually so unfavorable that the insect cannot maintain itself except when favorable variations permit invasion from more favorable places. Here the numbers are regulated by physical factors when they return to normal.
Another zone might well be added, called the zone of possible occurrence,within which physical conditions are never sufficiently favorable to permit the insect to become numerous but within which it might occasionally be found in favorable niches."
The W.C. Cook's zones are unnecessarily concentric ones. In some areas, they have a lineal character.
The suppressive role of CESPPs 2.3. "Routine weather suppression" is close to zero in the zone of normal abundance. This is an ecological optimum of a PP species. The role grows to a crucial one in the zone of possible occurrence. This is an ecological pessimum of a PP species. In the latter, the effect of CESPPs 2.3. is so regular and potent that it keeps a PP species on the level below threshold of damage for dominants over unlimited period.
The prerequisites of CESPPs 2.3. "Routine weather suppression" (it is marked by the letter "P") are as the following:
2.3.P.1. Temporal lasting of weather situations.
2.3.P.2. Limitation of aggressiveness of PPs.
2.3.P.3 Proper structure of ecosystems, which provides microclimate tolerable for natural enemies of invertebrate herbivores.
2.3.P.4. Weather situation, which provides operation of CESPPs 2.1.2.1. Superevasion.
The classification of CESPPs 2.3. "Routine weather suppression" is given in the Table 2.
Table 2. The classification of components of ecosystem stability to plant pests of the category 2.3. "Routine weather suppression" in arthropod herbivores (2.3.1. - 2.3.14.), vertebrate herbivores (2.3.15.), and phytopathogens (2.3.16)
| Codes and names of CESPPs of the category 2.3. | Effects on herbivores or phytopathogens | Codes of cooperators, independence of 2.3. and comments | W.C. Cook's zones where CESPPs were recorded |
| 1 | 2 | 3 | 4 |
2.3.1. Low ambient temperatures at hibernation even if they are not extraordinary ones |
2.3.1.1.Unhatching after hibernation |
2.5.3.1.5. Spontaneous or winter mortality of embryos |
(a) and (b) |
2.3.2. Weather stresses close to common (rains, droughts, frost, etc.) in the period of development of post-embryo stages |
2.3.2.1. Mortality under effect of the acute form of infection in the stages of larvae, pupae, and adult |
2.5.3.1.4. Mass mortality due to affection by the acute form of infection and parasitization |
(a) and (b) |
2.3.2.2. Mortality due to weakening by deficiency of food |
2.5.1. Deterioration and shortage of food |
(a) and (b) | |
2.3.2.3. Mortality due to affection by slow form of infection |
2.5.3.1.3. Mortality due to weather stress and parasites |
(a) and (b) | |
2.3.3. Cool and prolonged rains in the larval stage of defoliators |
2.3.3.1.Mortality of larvae at inducing of the acute form of infection |
2.5.3.1.5. or |
(b), (c) and (d) |
2.3.3.2. Mortality of neonate larvae due to restoration of operation of Antibiosis -CESPPs 2.1.1.2.1.2.2. |
2.1.1.2.1.2.1. |
(b), (c), and (d) | |
2.3.4. The sum of effective temperatures insufficient for completing of a life cycle of a species |
2.3.4.1. Mortality in the pupal stage due to too low ambient temperature |
Independent |
(d) |
2.3.4.2. Mortality in the egg stage due to impossibility of diapausation at low temperatures in fall |
Independent |
(d) | |
2.3.4.3. Mortality due to impossibility to finish development before disappearing of food |
Independent |
(d) | |
2.3.5. Onset of late frost over a season |
2.3.5.1. Mortality in the diverse stages |
Independent |
(d) |
2.3.6. Return of frost after thaw |
2.3.6.1.Mortality of young larvae in eggs |
2.5.3.1.5. or independent |
(a), (b), (c), and (d) |
2.3.7. Rains and dews in web-making defoliators |
2.3.7.1. Mortality under effect of parasites and predators due to disturbance of the web cover |
2.2.1.1. and 2.2.1.2. |
(b) and (c) |
2.3.7.2. Mortality of larvae due to inducing of the acute form of infection in the conditions of high humidity |
2.5.3.1.4. or 2.2.1.3. |
(b), (c), and (d) | |
2.3.8. Cool and prolonged rains in a flight period of moths |
2.3.8.1.Mortality of adults due to transformation of symbiotic (?) microorganisms in pathogens |
Independent |
(b), (c), and (d) |
2.3.9.Drought at the flight periods of moths in the species |
2.3.9.1.Decrease of fecundity of moths due to shortage of |
2.5.3.1.1.Decrease of fecundity |
(b), (c), and (d) |
2.3.10. Unfavorable conditions in sites of the dormancy period |
2.3.10.1. Mortality of larvae due to excessive moisture content in sites of hibernation |
Independent |
(b), (c), and (d) |
2.3.10.2. Mortality due to over-drying of the soil surface at summer dormancy |
Independent |
(b), (c), and (d) | |
2.3.11. Drought devastating food resource |
2.3.11.1. Mortality due to starvation and at emigration |
2.5.1.4.1. Mortality due to diverse factors |
(b) |
2.3.12. Drought in the pupal stage |
2.3.12.1. Decrease of polyvoltinism and increased mortality due to diapausation over the long period |
Independent |
(b) and (c) |
2.3.13. The sum of effective temperatures, which exceeds demand of a species |
2.3.13.1. Mortality in the egg stage due to impossibility of diapausation |
Independent |
(Ñ_) and (d) |
2.3.14. Enhancing of CESPPs 2.1. Plant resistance to plant pests |
2.3.14.1. Mortality due to enhancing of host-plant antibiosis |
2.1.1.2.1. Antibiosis to herbivores |
(b) and (c) |
2.3.14.2. Mortality due to enhancing of host-plant evasion |
2.1.1.4.1. Evasion from herbivores |
(a), (b) | |
2.3.15. Inability to feed under effect of weather stress in vertebrate herbivores |
2.3.15.1. Mortality due to starvation and decrease of fecundity |
2.4.2. In species, which spend the severe period both in active and inactive state, mortality or weakening under direct effect of weather stress |
- |
2.3.16. Enhancing of CESPPs 2.1.1.2.2. Antibiosis to phytopathogens |
2.3.16.1. Insusceptibility to phytopathogens |
2.1.1.2.2. Antibiosis to phytopathogens |
- |
2.3.17. Low winter temperatures inducing mortality of weakened part of populations of herbivores and phytopathogens |
2.3.17.1. Decrease of populations |
2.5. Effects of crowding |
(a), (b), (c) and (d) |
