Explaining Spatial Heterogeneity in Population Dynamics and Genetics from Spatial Variation in Resources for a Large Herbivore

The study aimed to assess the long-term population dynamics of questing Rhipicephalus appendiculatus and Rhipicephalus zambeziensis in two landscape zones of the Kruger National Park (KNP). Ticks were collected by dragging the vegetation monthly in three habitats (grassland, woodland and gully) at two sites in the KNP (Nhlowa Road and Skukuza) from August 1988 to March 2002. Larvae were the most commonly collected stage of both species. More R. appendiculatus were collected at Nhlowa Road than at Skukuza, with larvae being most abundant from May to August, while nymphs were most abundant from August to December. Larvae were most commonly collected in the gullies from 1991 to 1994, but in the grassland and woodland habitats from 1998 onwards. Nymphs were most commonly collected in the grassland and woodland. More R. zambeziensis were collected at Skukuza than at Nhlowa Road, with larvae being most abundant from May to September, while nymphs were most abundant from August to November. Larvae and nymphs were most commonly collected in the woodland and gullies and least commonly in the grassland (p < 0.01). The lowest numbers of R. appendiculatus were collected in the mid-1990s after the 1991/1992 drought. Rhipicephalus zambeziensis numbers declined after 1991 and even further after 1998, dropping to their lowest levels during 2002. The changes in numbers of these two species reflected changes in rainfall and the populations of several of their large herbivore hosts, as well as differences in the relative humidity between the two sites over time.

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The population dynamics of aphids on fire weed: a comparison of local populations and metapopulations

Canadian Journal of Zoology ◽

10.1139/z78-343 ◽

1978 ◽

Vol 56 (12) ◽

pp. 2554-2564 ◽

Cited By ~ 39

Author(s):

John F. Addicott

Keyword(s):

Population Dynamics ◽

Spatial Heterogeneity ◽

Rocky Mountains ◽

Median Number ◽

Marked Variation ◽

High Frequencies ◽

Local Populations ◽

Epilobium Angustifolium ◽

Population Processes ◽

Different Levels

Local populations of four species of aphids (Macrosiphum Valerianae, Aphis varions, A. helianthi, and A. salicariae) occur on shoots of fireweed (Epilobium angustifolium) in the Rocky Mountains of Colorado, U.S.A. Through exhaustive and repeated nondestructive sampling of the local populations on over 3800 shoots of fireweed, information was obtained on the dynamics of both the local populations and the metapopulation of each species. The dynamics of the metapopulation were analyzed in terms of the frequency of shoots occupied by aphids and the median number of aphids per occupied shoot. There were significant differences between species in both parameters, but high densities were not necessarily accompanied by high frequencies. Local populations were initiated throughout the summer, and there was marked variation in the duration and size of these populations. Most populations lasted only a few weeks, but others lasted up to 14 weeks. This turnover of local populations within the metapopulation implies that local populations must be studied in order to understand the dynamics of the metapopulation. There is a discussion of the relationships between population processes occurring at different levels of spatial heterogeneity.

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Contrasting effects of spatial heterogeneity and environmental stochasticity on population dynamics of a perennial wildflower

Journal of Ecology ◽

10.1111/1365-2745.12500 ◽

2016 ◽

Vol 104 (2) ◽

pp. 281-291 ◽

Cited By ~ 27

Author(s):

Elizabeth E. Crone

Keyword(s):

Population Dynamics ◽

Spatial Heterogeneity ◽

Environmental Stochasticity

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Improving simulated Amazon forest biomass and productivity by including spatial variation in biophysical parameters

Biogeosciences ◽

10.5194/bg-10-2255-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 2255-2272 ◽

Cited By ~ 40

Author(s):

A. D. A. Castanho ◽

M. T. Coe ◽

M. H. Costa ◽

Y. Malhi ◽

D. Galbraith ◽

...

Keyword(s):

Spatial Variability ◽

Spatial Heterogeneity ◽

Spatial Variation ◽

Primary Productivity ◽

Amazon Basin ◽

Net Primary Productivity ◽

Above Ground Biomass ◽

Biophysical Parameters ◽

Simulation Accuracy ◽

Forest Biome

Abstract. Dynamic vegetation models forced with spatially homogeneous biophysical parameters are capable of producing average productivity and biomass values for the Amazon basin forest biome that are close to the observed estimates, but these models are unable to reproduce observed spatial variability. Recent observational studies have shown substantial regional spatial variability of above-ground productivity and biomass across the Amazon basin, which is believed to be primarily driven by a combination of soil physical and chemical properties. In this study, spatial heterogeneity of vegetation properties is added to the Integrated Biosphere Simulator (IBIS) land surface model, and the simulated productivity and biomass of the Amazon basin are compared to observations from undisturbed forest. The maximum RuBiCo carboxylation capacity (Vcmax) and the woody biomass residence time (τw) were found to be the most important properties determining the modeled spatial variation of above-ground woody net primary productivity and biomass, respectively. Spatial heterogeneity of these properties may lead to simulated spatial variability of 1.8 times in the woody net primary productivity (NPPw) and 2.8 times in the woody above-ground biomass (AGBw). The coefficient of correlation between the modeled and observed woody productivity improved from 0.10 with homogeneous parameters to 0.73 with spatially heterogeneous parameters, while the coefficient of correlation between the simulated and observed woody above-ground biomass improved from 0.33 to 0.88. The results from our analyses with the IBIS dynamic vegetation model demonstrated that using single values for key ecological parameters in the tropical forest biome severely limits simulation accuracy. Clearer understanding of the biophysical mechanisms that drive the spatial variability of carbon allocation, τw and Vcmax is necessary to achieve further improvements to simulation accuracy.

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