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Ant Biomass (ant + biomass)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Mechanisms of population regulation in the fire ant Solenopsis invicta: an experimental study

JOURNAL OF ANIMAL ECOLOGY, Issue 3 2001
Eldridge S. Adams
Summary 1We tested for density-dependent regulation of biomass in a population of the fire ant Solenopsis invicta and examined the mechanisms of population recovery following replicated colony removals. 2,All colonies were killed within the core area (1018 m2) of six plots, while six additional plots served as undisturbed controls. Over the next 5 years, colonies were mapped several times per year and the biomass of each colony was estimated from the volume of the nest-mound. 3,The average biomass and density of colonies within the removal areas gradually converged on those of control plots and were no longer detectably different after two years. Thereafter, ant biomass on experimental and control plots showed nearly identical seasonal and yearly fluctuations. 4Territories of colonies surrounding the removal areas rapidly expanded following the deaths of neighbours, while average territory size on control plots showed little short-term change. 5,Significantly more new colonies were established within core areas of experimental plots than within core areas of control plots during the first year following removals. 6,The per-colony probability of movement and the net influx of colony biomass were significantly higher in central regions of the experimental plots than in control plots during the first year. The directions of colony movements were clustered towards the centres of experimental plots in the first 2 years, but did not show significant directional trends on control plots. 7,In all 5 years of the study, annual mortality rates were lower for larger colonies, but the size-specific risk of mortality was not significantly affected by the experimental removal of competitors. 8,The growth rates of colonies, adjusted for initial size, were significantly higher in central regions of experimental plots than in control plots during the first two years of the study. In all years, colony growth rates declined with increasing colony size. 9,These results indicate that populations of S. invicta are regulated by competition among neighbouring colonies. Due to large intraspecific variation in colony size, the dynamics of ant populations are described more accurately by measures of total ant biomass than by colony density alone. [source]

Energetics of newly-mated queens and colony founding in the fungus-gardening ants Cyphomyrmex rimosus and Trachymyrmex septentrionalis (Hymenoptera: Formicidae)

PHYSIOLOGICAL ENTOMOLOGY, Issue 1 2007
JON N. SEAL
Abstract The energetics of colony founding is investigated in the fungus gardening ants (Attini) Trachymyrmex septentrionalis and Cyphomyrmex rimosus. Similar to most ants, inseminated queens of these two species found nests independently unaccompanied by workers (haplometrosis). Whereas most ant founding queens seal themselves in a chamber and do not feed when producing a brood entirely from metabolic stores (claustral founding), the majority of fungus gardening ants must forage during the founding phase (semiclaustral founding). Laboratory-reared T. septentrionalis individuals comprise 84 dealate females collected after mating flights in June 2004. Twenty are immediately killed to obtain values for queen traits and another 20 after worker emergence for queen, fungus garden and worker traits. Cyphomyrmex rimosus comprise 22 dealate females collected in June 2005; ten of which are immediately killed and similarly prepared. Newly-mated T. septentrionalis queens have 25% of their dry weight as fat; whereas newly-mated C. rimosus queens contain 11% fat. These amounts are 50,75% less than most independently founding ant species. Trachymyrmex septentrionalis queens lose merely 5% of their energetic content during colony founding, whereas the total energetic content of their brood is more than three-fold the amount lost by the queen. Incipient T. septentrionalis colonies produce approximately half as much ant biomass per gram of fungus garden as do mature colonies. Similar to most ants, T. septentrionalis produces minim workers that are approximately 40% lighter than workers from mature colonies. Regardless of their size, T. septentrionalis workers contain much lower fat than do workers of claustral species. These data indicate that fungus gardening is adaptive because colonies can produce much cheaper offspring, making colony investment much lower. [source]

Difference in Intensity of Ant Defense among Three Species of Macaranga Myrmecophytes in a Southeast Asian Dipterocarp Forest,

BIOTROPICA, Issue 2 2000
Takao Itioka
ABSTRACT To examine interspecific variation in the intensity of ant defense among three sympatric species of obligate myrme-cophytes of Macaranga (Euphorbiaceae), we measured the ratio of ant biomass to plant biomass, ant aggressiveness to artificial damage on host plants, and increase in herbivore damage on host plants when symbiont ants were removed. Increase in herbivore damage from two- and four-week ant exclusion varied significantly among the three species. The decreasing order of vulnerability to herbivory was M. winkleri, M. trachyphylla, and M. beccariana. The antip/ant biomass ratio (= rate of the dry weight of whole ant colonies to the dry weight of whole aboveground plant parts) and ant agressiveness also varied significantly among the three species; the orders of both the ant/plant biomass ratio and ant aggressiveness were the same as in the herbivory increase. These results indicated that the intensity of ant defense differs predictably among sympatric species of obligate myrmecophytes on Macaranga. In addition to the interspecific difference in the total intensity of ant defense, when symbiont ants were excluded, both patterns of within-plant variation in the amount of herbivore damage and compositions of herbivore species that caused the damage differed among species. This suggests that the three Macaranga species have different systems of ant defense with reference to what parts of plant tissue are protected and what herbivorous species are avoided by ant defense. Thus, it is important to consider the interspecific variation in ant defense among Macaranga species to understand the herbivore community on Macaranga plants and the mechanisms that promote the coexistence of multiple Macaranga myrmecophytes. [source]