Regulation of Population Density Due to Individual Differences and Patchy Environment

Łomnicki, Adam

doi:10.2307/3544426

Cited by 151 publications

(76 citation statements)

References 22 publications

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“…To understand the dynamic behaviour of a population we must also understand the causes of the differences in the behaviour of individuals (Lomnicki 1980(Lomnicki , 1988. Underpinning studies of populations with an understanding of individual variation will increase the predictive power of population ecology (Sutherland 1997).…”

Section: Introductionmentioning

confidence: 99%

Comparing individual and spatial influences on foraging behaviour in Antarctic fur seals Arctocephalus gazella

Staniland

Reid²,

Boyd³

2004

Mar. Ecol. Prog. Ser.

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We investigated intra-specific and geographic variation in the behaviour of female Antarctic fur seals Arctocephalus gazella by serially sampling 11 individuals throughout their breeding season using satellite tracking, time-depth recorders and radio transmitters. There was significant variation between individuals in trip durations and the maximum distance reached from the breeding beach, but not in the direction of travel. We recognised 4 categories of trip duration, depending on the location of foraging: long deep-location, long intermediate-location, short intermediate-location and short shallow-location, based on the maximum distance reached from the breeding beach and the mean depth of water where diving occurred. Trip category accounted for a greater amount of the variation between trips than the identity of the seal. Seals on long deeplocation trips spent proportionally less time diving, had a lower dive rate, and dived to shallower depths for shorter durations with less bottom time than seals on short shallow-location trips. There was no significant difference in the total number of dives within trips between trip categories or between individual seals. There was also no significant difference in either the mean size of krill taken by individual seals or the incidence of fishes in their diet. These data suggest there is a strong individual component to where a seal forages especially in terms of the distance it travels from the breeding beach. However, we suggest that it is where an individual forages, not who that individual is, that determines how it will behave in terms of its diving. While individual seals may exploit areas of previous feeding success, their diving behaviour within these areas is likely to be determined by the spatial and temporal distribution of the prey within them.

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Section: Introductionmentioning

confidence: 99%

Comparing individual and spatial influences on foraging behaviour in Antarctic fur seals Arctocephalus gazella

Staniland

Reid²,

Boyd³

2004

Mar. Ecol. Prog. Ser.

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“…However, many studies have shown the importance of dispersal to the dynamics of metapopulations in heterogeneous landscapes (Reddingius and den Boer 1981;Roff 1974a, b;Lidicker 1975;Hamilton and May 1977;Comins et al 1980;Gaines and McClenaghan 1980;Lomnicki 1980;Fahrig and Merriam 1985).…”

Section: Introductionmentioning

confidence: 99%

The elements of connectivity where corridor quality is variable

1990

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Small mammals in heterogeneous environments have been found to disperse along corridors connecting habitat patches. Corridors may have different survivability values depending on their size and the degree of cover they provide. This deterministic model tests the effects of varying corridor quality on the demographics of a metapopulation of Peromyscus leucopus. Two types of corridors are defined based on the probability of survival during a dispersal event.Results indicate that mortality during movement through corridors influences metapopulation demographics. We found that:1. Any connection between two isolated patches is better than no connection at all in terms of persistence and population size at equilibrium. 2. Metapopulations with exclusively high quality corridors between patches have a larger population size at equilibrium than do those with one or more tow quality corridors. 3. Increasing the number of high quality corridors between patches has a positive effect on the size of the metapopulation while increasing the number of low quality corridors has a negative effect. 4. The addition to a metapopulation of a patch connected by low quality corridors has a negative effect on the metapopulation size. This suggest the need for caution in planning corridors in a managed landscape. 5. There is no relationship between the number of corridors and the metapopulation size at equilibrium when the number of connected patches is held constant. 6. Geometrically isolated patches connected by low quality corridors are most vulnerable to local extinctions.We conclude that corridor quality is an important element of connectivity. It contributes substantially to the effects of fragmentation and should be carefully considered by landscape planners.

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“…12). As a result, of the relationships found on many individual beds a n d for most ages and seasons, adult mortalities on the may have contributed significantly to population stability (Lomnicki 1980, Ambrose 1986). However, while the movement of mussel clumps by storms is well known (Seed…”

Section: Discussionmentioning

confidence: 99%

Population dynamics of Mytilus edulis along environmental gradients:density-dependent changes in adult mussel numbers

McGrorty¹,

Jd²

1995

Mar. Ecol. Prog. Ser.

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The densities of each a g e class of adult (>l yr old) mussels Mytilus edulis were measured in autumn and spring over 8 yr on each of 12 intertidal mussel beds in the Exe estuary, southwest England. The possibility that density-dependent changes in adult numbers in each of 9 yearly age classes occurred over the summer and winter periods was explored directly on individual beds and indirectly by combining data from all beds. There was direct evidence of density-dependent changes in both seasons in some age classes on some beds. The indirect tests suggested, however, that density-dependence was much more widespread over beds, age classes and seasons than had been suggested by the direct tests. The critical density above which density-dependent losses occurred, and to which the density-dependence tended to return numbers irrespective of the abundance of the mussels at the start of summer or winter, varied considerably among beds in several age classes. These critical densities were correlated most closely with the time for which a bed was exposed over low tide but were also influenced by the distance of a bed from the estuary mouth and the softness of its substrate. Between them, these 3 variables defined the environmental gradient of intertidal mussels in the Exe estuary. The residual, density-independent variations in the changes in numbers of several age classes of adult mussels about the density-dependent relationships were correlated with weather variables (temperature, gales and rainfall) in several cases and in both seasons. Surprisingly, there was evidence of widespread density-dependent immigration of adult mussels, especially in summer and in the younger age classes. While the passive movement by adult mussels in storms is well established, it is not known whether active movements occur in these older mussels. Although much of the density-dependence was due to mortality, immigration was therefore often a n important component of the densitydependent relationships detected on individual beds. However, immigration on some beds countered losses on others. Perhaps because of this, density-dependence was often masked, and thus not detected, at the estuary scale in all but the youngest mussels whose estuary-wide abundance was dominated by 2 large mussel beds, where their numbers tended to CO-vary. Thus, strong densitydependence at one scale may not be detected at a higher scale.

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Regulation of Population Density Due to Individual Differences and Patchy Environment

Cited by 151 publications

References 22 publications

Comparing individual and spatial influences on foraging behaviour in Antarctic fur seals Arctocephalus gazella

Comparing individual and spatial influences on foraging behaviour in Antarctic fur seals Arctocephalus gazella

The elements of connectivity where corridor quality is variable

Population dynamics of Mytilus edulis along environmental gradients:density-dependent changes in adult mussel numbers

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