Chronosequences of ant nest mounds from glacier forelands of Jostedalsbreen, southern Norway: Insights into the distribution, succession and geo-ecology of red wood ants (Formica lugubris and F. aquilonia)

Red wood ant nest mounds were investigated on terrain deglaciated since the mid-18th century at three outlet glaciers of the Jostedalsbreen ice cap in southern Norway. Chronosequence methodology was combined with a geo-ecological approach in the context of autecology. Size and composition of 168 mounds, most of which belonged to Formica lugubris, were related to terrain age, vegetation characteristics and physical habitat types using non-metric multidimensional scaling (NMDS) linked to segmented bubble plots and inferential statistical techniques. Substantive insights include (1) colonisation occurs 50–80 years after deglaciation; (2) mounds up to 100 cm high occupy the glacier forelands with a density of 2.5–4.6 mounds/hectare; (3) the positive correlation between mound size and terrain age is weakened by the presence of numerous small mounds attributed to the expansion of polydomous colonies by budding; (4) although mounds are mostly composed of plant remains (litter), they contain up to 17% mineral material (mostly gravel) on relatively young terrain; (5) mound size and composition are related to the number of trees ( Betula pubescens) occurring within 5 m of each mound, which reflects the availability of biological resources for mound thatch and ant food, the latter being primarily honeydew from aphids; (6) where aphids are present on trees, the mounds tend to be relatively large, reflecting the presence of ant–aphid mutualism; (7) mounds are larger on moraines and till plains than on outwash deposits, probably reflecting the enhancement of tree growth because of greater moisture availability and soil fertility in the former habitat types; (8) a strong southerly preferred aspect in mound orientation indicates the importance of direct solar radiation in maintaining internal mound temperatures and (9) glacier-foreland landscapes are not simply time-dependent chronosequences reflecting succession but the product of spatio-temporal dynamics involving biotic and abiotic interactions, which we summarise in a conceptual geo-ecological model. The main methodological implications are that chronosequences can be used to investigate the autecology of keystone species using a geo-ecological approach and multivariate analysis.

Distribution and Size of Imported Fire Ant (Hymenoptera: Formicidae) Mounds in Recently Invaded Ball-and-Burlap Nurseries in Tennessee

A study was undertaken to describe size and distribution of imported fire ant mounds in south-central Tennessee ball-and-burlap plant nurseries to (1) improve survey and control measures and (2) assess the feasibility of airborne remote sensing for mound detection. Mounds were most numerous along roadsides and road cuts. Mounds in planted areas were larger than mounds along roadsides and road cuts, and mounds in open, grassy areas were of intermediate size (mean above-ground volume = 8.14, 4.36 and 5.32 L, respectively). An examination of mound size distribution in nursery landscapes indicated colony age-structure may not be consistent between landscape-date combinations, and mean mound size was smaller in July 2004 than in October 2003.

Temperature regulation in mounds of three sympatric species of megapode (Aves : Megapodiidae) in Papua New Guinea: testing the 'Seymour Model'

Most megapode species rake organic material into mounds in which they incubate their eggs. To test predictions of a model proposed for temperature regulation in incubation mounds (the ‘Seymour Model’), I collected data on the physical characteristics of these mounds of the sympatric wattled brush-turkey (Aepypodius arfakianus), brown-collared talegalla (Talegalla jobiensis) and New Guinea megapode (Megapodius decollatus) in Papua New Guinea. Data from mounds supported several predictions of the Seymour Model: (1) there is a critical mass needed for mounds to heat to incubation temperatures, (2) mounds are stable homeotherms, (3) mounds cool after they are abandoned, and (4) mounds with different proportions of organic material differ in size. Data did not support predictions that (1) mound size will change with changes in ambient air temperature, and (2) mounds in high-rainfall areas will be convex to shed water. Mounds of New Guinea megapodes and brown-collared talegallas were similar and differed from those of wattled brush-turkeys in size, composition, temperature profile and location of eggs. These differences were consistent with the Seymour Model. The Seymour Model is robust enough to explain differences in mounds of sympatric megapodes, which differ in their taxonomy, behaviour and ecology.

The vegetation of Brazilian ‘murundus’ – the island-effect on the plant community

ABSTRACTThe ‘campos de murundus’ (carthmound fields) are typical landscapes of the cerrado (savanna) region of Central Brazil and are characterized by many rounded earthmounds called ‘murundus’ which are scattered over a grassland surface. As these areas are normally liable to seasonal water-logging, the earthmounds are true habitat islands capable of bearing woody plants typical of the cerrado, which are normally very intolerant of root inundation. The vegetation of an area of murundus field at Cuiaba, in the State of Mato Grosso, Central Brazil, was surveyed for the purpose of evaluating the island-effect on the plant community growing on the mounds/islands. Two main aspects were considered: the influence of the size of the mound and the differences between the types of cerrado occurring on the mounds and on the areas surrounding the murundus field. Most plant species occurring on the mounds were also present in the flora of the surrounding cerrado. However, only a fraction of these species was able to colonize the mounds successfully. The number of species on the mounds was found to be significantly correlated with mound area. Speciesarea relationships were better described with the power model S = C(Az) than with the exponential model S = C + z (logA) (fitted with linear regression). The mound size also had a strong influence on the spatial distribution of the species on the surface of the mounds. The species were organized in an increasing number of concentric topographic belts corresponding to a gradient of soil depth above the Hooding level.