have left behind their continental networks
(Olesenet al. 2002).
Unusual pollinators
The absence of many common continental pollina-
tors (bees, wasps, humming-birds, etc.) or dispersers
(some guilds of land-bird, non-volant mammals)
from remote islands has provided opportunities for
animals that do not usually perform these functions
to acquire or extend these roles. The best illustration
of this island feature comes from recent work on
lizards, which have adopted roles as pollinators
almost exclusively on islands, including New
Zealand, Mauritius, the Balearic islands, and
Tasmania. Olesen and Valido (2003) report that of 37
lizard species now known to act as pollinators, only
two species are from mainland areas, both in fact
peninsulas (Baja California and Florida).
The first published observations revealing
lizards as pollinators derive from Madeira in the
1970s, when Teira dugesiiwas observed drinking
nectar and licking the stigmatic lobes for pollen on
both native and introduced ornamental plant
species (Elvers 1977). Several species of Canarian
endemic lizards (Gallotiaspp.) are now known to
feed on nectar of Euphorbia, Echium, and Isoplexis.
Similarly, on the Balearic islands, Podarcis lilfordi,
an endemic lizard, is known to visit some 20 plant
species, including the flowers of the native
Euphorbia dendroides, for its highly concentrated
nectar (Traveset and Sáez 1997). Of special interest
is the role of Hoplodactylusgeckos in New Zealand
and of Phelsumaday geckos as pollinators in
Indian Ocean islands. These geckos are known to
visit many plant species (Whitaker 1987; Olesen
et al. 2002), transporting pollen over considerable
distances (Nyhagen et al. 2001). The introduction
of exotic predators (e.g. rats, mongooses, mon-
keys) has the potential to disrupt these pollinator
services, potentially leading to extinction of native
plant species.
Unusual dispersal agents
Again it appears that lizards have a disposition to
act as dispersal agents on islands, a role performed
less extensively by mainland lizard species. Of
some 200 lizard species reported to have a role in
seed dispersal, two thirds were island species
(Olesen and Valido 2003). Examples include 18
New Zealand lizard species, among them the
gecko Hoplodactylus maculatusand the skinks
Oligosoma grandeandCyclodina alani(Whitaker
1987). On the Balearic islands, Podarcis lilfordiand
P. pityusensisare known to feed on the fruits of
more than 25 species (Pérez-Mellado and Traveset
1999). All the endemic Canarian lacertids (seven
Gallotiaspecies) and skinks (three Chalcidesspecies)
are known to feed on fruit. Gallotializards eat fruits
of at least 40 native plant species, which is slightly
more than the half of the Canarian plant species
bearing fleshy fruits, and also feed on the fruits of
at least 11 introduced species (Valido and Nogales
1994).
Another ‘unusual’ plant dispersal agent comes
in the form of the giant tortoises (Geochelonespp.)
of the Galápagos (Racine and Downhower 1974)
and Aldabra atoll (Hnatiuk 1978). Today, the
Aldabran species (Geochelone gigantea) has been
introduced on several islets off Mauritius where
goats and rabbits have recently been eradicated,
as a functional substitute for extinct Mauritian
tortoises (Geochelone triserrataandG. inepta), which
are considered to have been the original dispersers
of the endemic Ile aux Aigrettes ebony (Diospyros
egrettarum). After a pilot study in a fenced enclo-
sure, viable fruits of the ebony were found dis-
persed in tortoise faeces away from the parent
trees (Zavaleta et al. 2001).7.6 Niche shifts and syndromes
Thus far in this chapter we have considered some
of the filters that might prevent lineages success-
fully establishing on islands and the implications
of small population sizes and of the possession of
particular life-cycle traits connected to breeding
systems. We have also begun, inevitably, to con-
sider emergent patterns of changing biological and
niche characteristics. Here, we continue this
process under the heading of some of the more
prominent island syndromes, starting with the loss
of dispersal powers.NICHE SHIFTS AND SYNDROMES 181