Biology Reference
In-Depth Information
4.1
Lizards
Most reports of nectar consumption by lizards are from islands, where lizards
reach higher densities than on the mainland, owing to reduced predation, and
where insects may be relatively scarce. In New Zealand, arboreal geckos
in the genus Hoplodactylus drink the copious nectar of Phormium tenax
(Agavaceae) and Metrosideros excelsa (Myrtaceae), transporting pollen on
their throats (Whitaker, 1987; Eifler, 1995). Diurnal geckos ( Phelsuma sp.,
Fig. 4C) are generalist flower visitors and pollinators on Mauritius and other
Indian Ocean islands (Nyhagen et al., 2001), and recently have been shown
experimentally to prefer coloured to clear sucrose solutions, thus explaining
their attraction to the coloured nectar of some Mauritian plants (Hansen
et al., 2006). Tasmanian snow skinks forage on abundant nectar of Richea
scoparia (Epacridaceae) without contacting pollen (Olsson et al., 2000), but
pollination of Euphorbia dendroides by lacertid lizards was demonstrated by
Traveset and Sáez (1997) in the Balearic Islands. It has been hypothesized
that pollination by lizards may have evolved on islands as a result of the
general scarcity of insects, with the consequences that island plants need pol-
linators and lizards need food (Olesen & Valido, 2003).
4.2
Birds
Nectarivory has evolved many times in birds, especially in tropical and sub-
tropical areas with long flowering seasons that can sustain birds on nectar all
year round. Convergent evolution is well illustrated by three major radiations
of nectarivorous birds on different continents: the American hummingbirds
(Trochilidae), Australasian honeyeaters (Meliphagidae), and the sunbirds and
sugarbirds (Nectariniidae) of Africa and Asia. The Meliphagidae is the domi-
nant passerine family in Australia, and the Trochilidae is the largest family
of non-passerine birds—now confined to the Americas, although humming-
bird fossils from the Oligocene have recently been reported from Germany
(Mayr, 2004). Numerous other families, mostly passerine birds, contain
species with varying dependence on nectar. These include the Hawaiian
honeycreepers, flowerpiercers, tanagers, and lorikeet parrots, as well as oppor-
tunistic nectar feeders such as white-eyes, bulbuls, weavers, orioles, barbets,
mousebirds, starlings, Darwin's finches, and some babblers and warblers
(Nicolson & Fleming, 2003b; Lotz & Schondube, 2006). It has been esti-
mated that around 10% of all bird species may use nectar as a resource at some
time (Wolf & Gill, 1986). Even in Europe, where bird pollination is extremely
rare (Ford, 1985; Ortega-Olivencia et al., 2005), opportunistic nectar consump-
tion can be energetically important for Sylvia warblers returning after
migratory flights (Schwilch et al., 2001). The relationship between bill length
Search WWH ::




Custom Search