INTER-NEST INTERACTIONS, NEST AUTONOMY, AND 
REPRODUCTIVE SPECIALIZATION IN AN AUSTRALIAN 
ARID-ZONE ANT, RHYTIDOPONERA SP. 12 
By P. Pamilo , 1 2 R. H. Crozier , 1 2 J. Fraser 3 
Introduction 
Rhytidoponera sp. 12 ANIC is a large Australian ponerine ant 
which lacks a morphologically-differentiated queen caste. As is the 
case for many other Australian species in this genus, some of the 
workers mate and assume the egg-laying role. As has been inferred 
for species in the R. metallica complex (Haskins and Whelden, 
1965) and observed for R. maniae (another large arid-zone species) 
and species in the R. impressa complex (Ward, 1981), colony- 
founding under this life-pattern is probably usually accomplished by 
fission (“hesmosis”), in which one colony divides into two. Unlike 
the situation where nest-founding follows a dispersive mating flight, 
colony fission is likely to lead to the new nest being located close to 
the parent one, leading to a population structure in which neighbor- 
ing nests are genetically related. A large study of the apportionment 
of genetic variation in a population of R. sp. 12 (Crozier et al., 1984) 
found that neighboring nests are indeed more similar genetically 
than expected by chance — they are related. 
The finding (Crozier et al., 1984) that neighboring nests are 
related raises the question of colony boundaries. Does each nest 
represent a separate colony, or do daughter-nests remain socially 
connected after fission, forming polydomous (multi-nest) colonies? 
The two alternatives are not, of course, completely clear-cut, in that 
intermediates could occur between single-nest colonies and truly 
'School of Zoology, University of New South Wales, Kensington, N.S.W. 2033 
AUSTRALIA 
Corresponding author: R. H. Crozier, School of Zoology, UNSW, P.O. Box 1, 
Kensington, NSW 2035 AUSTRALIA 
2 Present address: Center for Demographic & Population Genetics, University of 
Texas Health Science Center at Houston, P.O. Box 20334, Houston, TX 77025, 
USA. 
3 Biology Department, Boston University, 2 Cummington St., Boston, MA., 02215 
U.S.A. 
Manuscript received by the editor January 3, 1985. 
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