Figure 8.24. Characteristics of
myrmecophytic Cecropia trees. A,
Crown of tree showing radiating
long-petioled leaves. B, Apical stem
of sapling, showing bamboolike
stem segments (internodes)
composed of a hollow cylinder and
a leaf arising from upper rim of
internode. Internode chambers are
bounded internally by transverse
septa forming floor and ceiling. C,
Base of petiole showing velvetlike
pad of brown hairs (the trichilium,
plural trichilia) from which arise
white food bodies (Mullerian
bodies). D, Internode wall showing
preformed thin spot (prostoma,
plural prostomata) through which
ants enter. E, Longitudinal section
of Cecropia sapling stem, showing
white internal wall of recently
occupied internode, with founding
Azteca construct or queen at
prostomal scar. Note transverse
septum forming ceiling of internode
about queen. Photographs by
John T. Longino.
and they vary in their behavior (Longino 1991a).
Members of the A. muelleri complex (A. xanthochroa
and A. constructor in Costa Rica) have a central nest
in the trunk of the tree where the larvae are concen-
trated. Internal passageways are kept open between
the central nest and all the branch tips, where the
Mullerian bodies are produced. The workers are ex-
tremely aggressive, and small disturbances cause the
workers to rush out onto the branches and trunk. In
contrast, members of the A. alfari complex (A. alfari
and A. ovaticeps in Costa Rica) have a dispersed nest,
with larvae distributed throughout the tree crown in
branch tips. Active nest space is only in the branch
tips, and internal passageways are not maintained
between branches. The workers are relatively passive
and often do not emerge when the tree is disturbed.
Azteca coeruleipennis appears to be a dry forest spe-
cialist. Its nesting behavior is similar to the A. alfari
complex, but the workers are aggressive and readily
emerge when the tree is disturbed.
Myrmecophyte-ant interactions are rarely one-on-
one interactions of species pairs. More often, they are
multispecies communities of plants and ants (David-
son et al. 1991, Davidson and McKey 1993a, b). Such
communities usually contain several species of con-
generic myrmecophytes inhabited by several species
of congeneric plant-ants. Within these communities,
no strict host specificities exist. Each ant species can
occur in all the myrmecophyte species. However,
associations within the community are not random.
Often ant species and myrmecophyte species corre-
late with habitat and thus with each other (Davidson
and Fisher 1991, Longino 1991b). Ant species inhab-
iting Cecropia segregate by high light versus low light,292 Plant-Animal Interactions