Abstract:
Myrmecophyte plants house ants within domatia in exchange
for protection against herbivores. Ant-myrmecophyte mutualisms
exhibit two general patterns due to competition between ants
for plant occupancy: (i) domatia nest sites are a limiting resource and
(ii) each individual plant hosts one ant species at a time. However, individual
camelthorn trees (Vachellia erioloba) typically host two to four
ant species simultaneously, often coexisting in adjacent domatia on
the same branch. Such fine-grain spatial coexistence brings into question
the conventional wisdomon ant-myrmecophytemutualisms. Camelthorn
ants appear not to be nest-site limited, despite low abundance
of suitable domatia, and have random distributions of nest
sites within and across trees. These patterns suggest a lack of competition
between ants for domatia and contrast strongly with other antmyrmecophyte
systems. Comparison of this unusual case with others
suggests that spatial scale is crucial to coexistence or competitive exclusion
involving multiple ant species. Furthermore, coexistence may
be facilitated when co-occurring ant species diverge strongly on at
least one niche axis. Our conclusions provide recommendations for
future ant-myrmecophyte research, particularly in utilizing multispecies
systems to further our understanding of mutualism biology.
