Population Fluctuation Patterns Research Articles

The linkage between integrated pest management and agroecosystem management: a case study in the Bajío, México

Integrated pest management tactics are associated with and can be used simultaneously at various spatial and temporal scales. Integrating pest management tactics requires careful matching of tactics with their most relevant spatial scales, rather than forcing all tactics to be relevant at a single scale, such as an individual field for a single cropping cycle. A case study is provided of the evolution of control tactics from a focus on individual fields with a short time horizon, to improved pest management throughout a region. The case study is of diamondback moth control in the Bajio region of Mexico, a serious enough challenge to force cooperation at regional scales and cause the shift in tactics described. At the largest spatial and temporal scales, control included establishment of a host-free period that requires cooperation and practical changes in production practices throughout the agroecosystem. A time series analysis of diamondback moth population trends in the Bajio, measured by various kinds of data in different locations and over different time periods, was used to document changes in the pattern of pest population densities over time; changes in the pest population were then compared with changes over time in control strategies and in the agroecosystem itself. Although diamondback moth populations have increased and the pattern of population fluctuations has changed between 1988 and 2004, management of individual fields can still minimize pest damage through careful use of available control measures. The greater potential for improving control of diamondback moth, however, appears to be changing the agroecosystem itself at larger spatial and temporal scales, perhaps by production and processing of additional crops in the region.

Evaluating Pochonia chlamydosporia in a double‐cropping system of lettuce and tomato in plastic houses infested with Meloidogyne javanica

The effect of Pochonia chlamydosporia, a facultative fungal parasite of nematode eggs, alone or in combination with oxamyl was evaluated in a double‐cropping system of lettuce and tomato in unheated plastic houses infested with Meloidogyne javanica at two sites for two consecutive growing seasons. An additional treatment of methyl bromide fumigation was included to compare crop yield in nematode‐free vs. nematode‐infested soil. Final population densities, reproductive rate, root gall rating, and egg production were determined after each crop. Pochonia chlamydosporia was isolated from nematode eggs up to nine months after application to soil. The fungus survived in the rhizosphere for the entire growing season at one site, but only at low densities. Final population densities of M. javanica decreased after cultivation of lettuce and increased after tomato, and this pattern of population fluctuation was unaffected by treatment, experiment or site. The reproductive rate on lettuce was equal to or below 1, and it was similar among treatments in both experiments at both sites. Eggs were not found on lettuce roots. On tomato, the reproductive rate in the fungus + oxamyl treatment was significantly lower (P < 0·05) than other treatments in experiment 1 at both sites. Fungus + oxamyl consistently reduced root gall ratings on tomato in all cases, but numbers of eggs per g root varied depending on treatment. Methyl bromide‐treated plots remained free of M. javanica at the end of the 2‐year study.

Patterns of population fluctuations of the mulberry tiger moth, Thanatarctia imparilis (Butler)(Lepidoptera: Arctiidae) and effect of predation by the carabid beetle, Parena perforata (Bates)(Coleoptera: Carabidae) in the Kinki region.

Population changes of the mulberry tiger moth, Thanatarctia imparilis (Butler) (Lepidoptera: Arctiidae) and its carabid predator, Parena perforata (Bates) (Coleoptera: Carabidae) were surveyed at three disjunct study sites in the Kinki region, western Japan, from 1989 to 2001. At one of the three study sites, the population density of T. imparilis increased gradually, thereafter, decreased drastically, and then increased again. At this site, the number of P. perforata per prey colony changed closely with the density of T. imparilis. During the decline phase of T. imparilis, P. perforata was observed in over 80% of the prey colonies, and many egg masses of the beetle were deposited on each prey colony. It was observed that the effect of the predation acted strongly during the decline phase of T. imparilis. At another site, moreover, P. perforata was observed in over 80% of the prey colonies during the period of population decline of T. imparilis. At the third site of the three, however, the carabid beetles were observed in less than 10% of the prey colonies even during the decline phase of T. imparilis. At this site, the population density of T. imparilis decreased after high density had persisted for a few years and started to increase after low density had persisted for a few years. In addition, the change in amplitude between the highest density and the lowest density was ca. one-third that at the other two sites. It was suggested that the predator-prey interaction constitutes an important factor in explaining the different behaviors of T. imparilis populations at different localities.

Effect of weather variables on the population fluctuation of muroid Calomys venustus in central Argentina

Abstract The effects of weather on population fluctuation patterns of the South American muroid Calomys venustus were studied. Box–Jenkins data series analysis and anova were used to describe the relationship between climatic variables and population. No relation was found between maximum temperatures or precipitation and the C . venustus population. Temperatures below 4 °C appear to affect populations of the overwintered cohort after a time lag of 5 months.

Effects of extra food on population fluctuation patterns of the muroid rodent Calomys venustus

Abstract Population dynamics in the South American muroid rodent Calomys venustus are described from a 14‐year continuous data series, using the auto‐regressive integrated moving average (arima) model. Population responses to experimental food addition were analysed in two experimental areas, over two periods, using intervention analysis. There was no consistent evidence that food quantity leads to peaks in population density. Significant increases were related to densities of transients and juvenile individuals.

Population dynamics of small rodents in a grassland between fragments of Atlantic Forest in southeastern Brazil

Summary Population dynamics and reproduction of four species of muroid rodents ( Akodon cursor , Bolomys lasiurus , Oligoryzomys nigripes , and Mus musculus ) were studied through capture-mark-recapture in a grassland between fragments of Atlantic Forest from March 1998 to February 1999. A. cursor and B. lasiurus accounted together for 93.5% of all captures. O. nigripes and M. musculus reached highest population sizes by the end of the dry season. A. cursor was most abundant during late drysol;early wet season, however, its population sizes were higher in the wet season than in the dry season. Populations of B. lasiurus were highest during the dry season, although their population levels varied less than those of A. cursor . The differences in the pattern of population fluctuations of the two latter species can be explained by differences in their feeding habits, as B. lasiurus feeds mostly on grass seeds (most abundant during the dry season), whereas the diet of A. cursor includes a high proportion of insects, which are most abundant during the wet season.

Various population fluctuation patterns of light‐attracted beetles in a tropical lowland dipterocarp forest in Sarawak

AbstractThe population fluctuation pattern of light‐attracted beetles was studied from August 1992 to September 1998 (for 73 months) using ultraviolet light‐traps set at three vertical levels in a tropical lowland dipterocarp forest in Sarawak, Malaysia. During our study, a general flowering occurred from April to July in 1996, and flowering on a small scale in 1997 and 1998. We analyzed the data for eight scarabaeid and six meloid species, some of which were anthophilous species. Various fluctuation patterns were observed among the beetle species in aspects of both seasonality and correlation with the supraannual phenological pattern. Three large chafer species (Scarabaeidae, Melolonthini) showed a clear seasonal fluctuation pattern with a peak once from March to May every year, the peak monthly catch greatly fluctuating annually. Other scarabaeid beetles did not show such a clear seasonal population pattern and hardly fluctuated annually. Populations of an anthophilous scarabaeid species, Parastasia bimaculata, a specific pollinator of Homalomena propinqua (Araceae), hardly fluctuated, probably because of its response to the constant flowering of its floral hosts. Monthly catches of an anthophilous scarabaeid, Anomala sp., and meloid beetles showed clear supraannual patterns in response to the general flowering and were significantly correlated with the flowering intensity with or without a lag of a month. The fluctuation pattern of meloids suggests a supraannual population fluctuation pattern of their hosts, i.e., megachilid/anthophorid bees.

Population dynamics of the spiny country rat ( Niviventer coxingi ) in a subtropical montane forest in central Taiwan

Population dynamics of the spiny country rat Niviventer coxingi were studied by mark–recapture methods from January 1982 to May 1983 in a subtropical montane forest at Chitou, central Taiwan. The population density was < 8 rats/ha. The annual pattern of population fluctuation was characterized by summer increase, autumn peak and spring decline. Adult recruits occurred mostly in summer and autumn 1982, whereas young rats joined the population as three cohorts: winter 1981, summer 1982 and winter 1982. Growth patterns differed between winter and summer cohorts, which was attributed mainly to the slow body weight increase in summer cohort males. Males, either adult or juvenile, survived the winter better than females, resulting in the shorter lifespans and the lower number of females in the population. Life-history traits in female N. coxingi, i.e. short reproductive lifespan, few litters per life time and prolonged maternal care, along with the low breeding intensity, rendered the number of females the limiting factor for population increase. However, females may improve the survival and maturation of their offspring by prolonged maternal care.

Various population fluctuation patterns of light-attracted beetles in a tropical lowland dipterocarp forest in Sarawak

Various population fluctuation patterns of light-attracted beetles in a tropical lowland dipterocarp forest in Sarawak

Spatially autocorrelated disturbances and patterns in population synchrony

Spatially synchronous population dynamics have been documented in many taxa. The prevailing view is that the most plausible candidates to explain this pattern are extrinsic disturbances (the Moran effect) and dispersal. In most cases disentangling these factors is difficult. Theoretical studies have shown that dispersal between subpopulations is more likely to produce a negative relationship between population synchrony and distance between the patches than perturbations. As analyses of empirical data frequently show this negative relationship between the level of synchrony and distance between populations, this has emphasized the importance of dispersal as a synchronizing agent. However, several weather patterns show spatial autocorrelation, which could potentially produce patterns in population synchrony similar to those caused by dispersal. By using spatially extended versions of several population dynamic models, we show that this is indeed the case. Our results show that, especially when both factors (spatially autocorrelated perturbations and distance–dependent dispersal) act together, there may exist groups of local populations in synchrony together but fluctuating asynchronously with some other groups of local populations. We also show, by analysing 56 long–term population data sets, that patterns of population synchrony similar to those found in our simulations are found in natural populations as well. This finding highlights the subtlety in the interactions of dispersal and noise in organizing spatial patterns in population fluctuations.

Measuring Patterns in Population Fluctuations

Measuring Patterns in Population Fluctuations

Measuring Patterns in Population Fluctuations

Measuring Patterns in Population Fluctuations

A Fundamental Problem in Key Factor Analysis

This paper reveals that key factor analysis, a popular method of life table analysis, cannot address the central issue of population dynamics: the pattern of population fluctuation and its causal mechanism. The basic idea of key factor analysis is to identify factors that contribute significantly to the variation in population. Several statistical methods to identify a key factor have subsequently been proposed in the literature. These are, in terms of the familiar relationship, K = k1 + k2 +... + kn, to correlate K with a k, regress K on a k, or regress a k on K, the last method being currently most frequently used. These methods, in effect, look for those k's whose variances and covariances constitute a significant part of the variance of K. The fundamental problem here is that the variation in population is inappropriately interpreted as the variance. I show that, in general, different factors play different roles in generating the pattern and that none of these aspects can be indicated merely by the variance of K and its components, the variances and covariances of the k's. I contend that, for judging which factor is major, criteria are multiple and subtle beyond the simplistic idea of key factors.

Individualistic responses of bird species to environmental change.

We investigated how the population dynamics of the same bird species varied in different environments, and how the population dynamics of different species varied in the same environment, by calculating long-term population trends for 59 insectivorous songbird species in 22 regions or strata of eastern and central North America using data from the North American Breeding Bird Survey. Of the 47 species that occurred in more than one region 77% increased in some regions and declined in others. Of the 22 regions 91% had some species that increased and others that decreased. There were only slightly more significant correlations between strata in species trends and between species for stratum trends than would be expected by chance. Because of nonlinearities in the data, the actual patterns of population fluctuations of the same species in different regions and of different species in the same region were even more heterogeneous than suggested by our analyses of linear trends. We conclude that these bird species respond to spatial and temporal variation in their environment in a very individualistic fashion. These individualistic responses show that the extrapolation of population trends gained from a few local studies to a larger spatial scale, and the use of a few indicator species to monitor the status of a broader community, are suspect.

Ecology of Bactrocera latifrons (Diptera: Tephritidae) Populations: Host Plants, Natural Enemies, Distribution, and Abundance

An intensive population census of Bactrocera latifrons (Hendel) identified 15 species of suitable host plants (11 solanaceous, 4 cucurbitaceous), 6 of them new host records. Lycopersicon pimpinellifolium (Jusl.) Mill., Solanum nigrescens Mart. & Galeotti, Solatium sodomeum L., and Solanum torvum Sw. were the most heavily infested host plants in feral habitats. Under backyard and commercial cultivations, Capsicum annuum L., Lycopersicon lycopersicum (L.) Karst. ex Farw., and Solanum melongena L. were the most heavily infested (larval density and percentage infestation). B. latifrons appears to outcompete melon fly, oriental fruit fly, and Mediterranean fruit fly in C. annuum, Capsicum frutescens L., L. pimpinellifolium, Physalis peruviana L., S. melongena, S. nigrescens, S. nigrum, S. sodomeum, and S. torvum. Extremely low (<1%) larval parasitization by Diachasmimorpha longicaudata (Ashmead) was observed. Larval parasitization by Tetrastichus sp. was also observed. More than 250 cm average annual cumulative rainfall probably excluded B. latifrons populations from areas where suitable host plants were abundant. Over the study period, the relative abundance of B. latifrons populations decreased as the elevation increased. B. latifrons population density levels were consistently low, and there was no discernible pattern of population fluctuation over time (months of collection). Comprehensive lists of all recorded host plants (world review) and natural enemies of B. latifrons are presented. The ecological attributes of B. latifrons populations and their adaptive significance in colonizing and establishing in new geographic areas are discussed.

The interplay of population dynamics and the evolutionary process

Long-term maintenance of genetic diversity is affected by ecological forces that are driven in turn by current levels of genetic variation. The strength of population regulation and the consequent patterns of population fluctuations determine the likelihood of genetic changes considered pivotal for rapid speciation. However, genetic diversity in the susceptibility to regulatory forces can reduce the magnitude of such fluctuations and minimize the likelihood of genetic revolutions. A group of populations that experiences local extinctions and recolonizations may hold lower levels of genetic diversity than in the absence of such extinctions, but local adaption, which provides enhanced genetic diversity, can reduce the likelihood of local extinctions. Tightly regulated populations experience different selection pressures than poorly regulated populations, although tighter regulation itself can evolve. When genotypic variation affects the outcome of interspecific interactions on a local scale, this effect, coupled with appropriate spatial variation, can enhance the resilience of the interactive system.

Population dynamics of stored-product mites.

Population fluctuation patterns were determined during 1959-70 in wheat bulks in 2 granaries typical of those used on Manitoba farms for 7 kinds of mites. The patterns were bradly similar in the 2 granaries. Outbreaks of all mites except Tarsonemus granarius and Aëroglyphus robustus were unaffected by the prolonged storage of grain; those of Acarus siro and Cheyletus eruditus occurred in unusually high numbers periodically every 2-5 years, whereas Glycyphagus destructor and Androlaelaps casalis were present in relatively low numbers from the first year of storage. A rise in T. granarius population corresponded with grain age and the succession of microfloral species. Tydeid mites occurred periodically.Pricipal component analyses of up to 26 variates including various fungal species on one grain bulk ecosystem provided a "kaleidoscopic" view of interrelations and dynamics of acarine populations in the grain bulks. The combination of correlated variates of which mites are a part, varied from year to year.Four factors that regulate acarine numbers, particularly those of A. siro and its natural predator C. eruditus, were identified. These are: (i) basic determinants (moisture, temperature, food, and the intrinsic rate of increase of the species); (ii) the main regulator (temperature); (iii) influencers (seed cracks, microflora, dockage, etc.); and (iv) seasonal and cyclic regulators (seasonality in temperature and several density-dependent factors). Generalized diagrams of prey-predator interactions and multivariate interrelations of each kind of mite are presented.