Santa Fe Land Iguanas (Conolophus pallidus) cannot
resist the fruit of the cactus Opuntia ochios var.
barringtonensis. Image by marktucan.
Another indirect form of seed dispersal involving
lizards and birds occurs on the island of Santa Fe, in
the Galapagos Islands archipelago. The Santa Fe Land
Iguana (Conolophus pallidus) relishes fruits of the
cactus Opuntia ochios var. barringtonensis, consuming
them as soon as they fall to the ground. The seeds are
ejected when the iguanas chomp on the fleshy pulp,
and are then picked up and subsequently dispersed by
the Galapagos Mockingbird (Mimus parvulus).
Birds, although highly mobile, are endotherms, like
mammals, and have relatively high energy and water
requirements compared with lizards. Thus they are
also often at lower abundances on islands, again
leaving the frugivorous niche open to lizards.
Additionally, the isolation of many island environ-
ments means that insects may be at relatively low
abundances, forcing typically insectivorous lizards to
consume nectar, pollen and fruit. Indeed, across
several populations of Podarcis spp., lower arthropod
diversity and availability was found to be associated
with greater consumption of plant material.
Ancient Niche Expansion.
Researchers have also noted the predominance of
insular (island) species amongst those lizards known
Saurophily and saurochory appear to evolve in
environments where there are few insects (a potential to feed on nectar and fruits.
source of both food for lizards, and pollinators for
Because lizards are typically territorial and have
plants), and high densities of lizards, which encour-
relatively lower mobility, they may not be as effective
ages these species to expand their dietary niche to
pollinators as flying insects and birds, particularly
reduce competition. These conditions are especially
since if they visit flowers on the same plant, or
common on islands, which are typically difficult for
mammals to colonise due to their isolation and limited adjacent ones, this can result in inbreeding. Similarly,
the distance over which seeds are dispersed by lizards
resources. Free of mammalian predators, this allows
has been rarely evaluated, and is likely to be less than
lizards to reach far higher abundance, and in the
absence of large mammalian herbivores, these reptiles many other vertebrate seed dispersers. Nevertheless,
are able to include fruits in their diet and fulfil the role studies have documented that larger lizards, in
particular, may roam over considerable distances and
of seed dispersers.