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Above: Seven species of anoles found on the islands in the Eastern Tropical Pacific (ETP). Top row, left to right: Dactyloa agassizi (Isla Malpelo), Dactyloa gorgonae (Isla Gorgona), Norops townsendi (Isla Cocos). Bottom row: Norops medemi, Norops parvauritus, Dactyloa princeps, Dactyloa chocorum (all Isla Gorgona). |
There are 435 species
in the genus Anolis (sometimes divided into Norops and Dactyola)
and while they are one of the most heavily studied lizard clades most of the
work has been done on Caribbean species. However, there are seven eastern Pacific
Islands species that remain poorly studied. The seven species are known from the Islas
Cocos, Gorgona, and Malpelo. Anoles occupying these islands span the extreme
ends of the dactyloid phylogeny and are highly variable in their ecology and
natural history. In a new paper, Phillips et al. (2019) present a phylogenetic
analysis of eastern Pacific island anoles considering the greater anole
phylogeny and estimate the timing of divergence from mainland lineages for each
species. They found two species of solitary anoles (D. agassizi and N.
townsendi) diverged from mainland ancestors prior to the emergence of their
respective islands. They also present population-wide morphological data that suggests
that both display sexual size dimorphism, like single-island endemics in the
Caribbean. All lineages on Isla Gorgona likely arose during past connections
with South America, and ecologically partition their habitat. They also
highlight the importance of conservation of these species and island fauna in
general.
They found Dactyola
agassizi and Norops townsendi are ecological generalists unlike solitary
Lesser Antillean anoles. Norops townsendi appears to clearly conform to
this generalization, given that is was found ubiquitously on Isla Cocos in
terms of perch height, diameter, and type. Dactyloa agassizi has
distinctly unique behavioral characteristics that challenge the original
meaning of generalist as applied to the Lesser Antillean anoles. The food web
of Isla Malpelo appears to be very tight given the lack of vegetation and
scarcity of obvious food resources for all the island inhabitants. Everything
seems to revolve around the birds that visit the island, particularly the Nazca
Booby (Sula granti). Any food dropped by the birds, and all waste
products were immediately consumed by all Dactyloa agassizi, as well as the
lizard Diploglossus millepunctatus (commonly called the Malpelo Galliwasp) and crabs which congregate around
these resources. The crabs and Diploglossus attempt to capture any Dactyola
agassizi that venture too close, and the crabs will also consume eggs of
all species. Previous observers reported that D. agassizi ate both
insects and seeds, and that individuals would quickly consume potential food
items revealed when rocks were turned over. All D. agassizi departed
from typical anole behavior in being very curious, climbing on, and licking the
observers (clearly investigating food possibilities), never displaying any
defensive behaviors or territoriality. Therefore, insofar as their environment
allowed them, D. agassizi appeared to be an ecological generalist. Isla
Malpelo is unlike most other islands that are home to anoles, so it is not
surprising that D. agassizi departs from the general patterns observed
for solitary Caribbean anoles.
Citation
Phillips, J.G., Burton, S.E., Womack, M.M., Pulver, E.
and Nicholson, K.E., 2019. Biogeography, Systematics, and Ecomorphology of
Pacific Island Anoles. Diversity, 11(9),
p.141.