Download Endemic Species of Grenada

Issue 12: May 13, 2011
Endemic Species of Grenada
By: Dr. Andrea EasterEaster-Pilcher
The field of conservation biology is focused upon enhancing the viability of threatened and
endangered species and the ecosystems which they depend upon. Like other oceanic (volcanic)
island chains (Hawaii and the Galapagos islands as notable examples), the islands of the Antilles
harbor numerous genetically unique endemic invertebrate and vertebrate species.
Endemic species have evolved their genetic uniqueness in, and are restricted to, a particular
geographic location. In fact, many endemic species are restricted to a single island of habitat. Perhaps
not surprisingly, given the increasing fragmentation of the world's landscapes, many endemic species
tend to be on the brink of extinction. With endemic species, local extinction is global extinction.
Invertebrates are notoriously facile in terms of adaptive radiation, spreading throughout island chains
and generating astonishing numbers of genetically unique species and subspecies. Drosophila in the
Hawaiian Islands have radiated into 1000+ distinct species and subspecies purportedly from the
introduction of a single continental species of Drosophila1. In the Antilles, Drosophila have behaved
no differently, evolving into numerous genetically distinct species and subspecies across the island
chain. Drosophila similus grenadensis is Grenada's own endemic subspecies and is clearly identified
by a phenotypic abdominal pigmentation pattern that is unique2.
It is likely that you have never heard of Grenada's endemic Drosophila similus grenadensis, but
perhaps you have heard of Grenada's most famous endemic species, the Grenada dove (Leptotila
wellsi). There are several species of doves and pigeons on Grenada, but only one species is the
critically endangered and endemic Grenada dove. In all probability, the dove in your backyard is not
the Grenada dove. The Grenada dove is a very shy and elusive bird, and it is helpful to enlist a guide
who knows where to look for them at the dove sanctuary in Mt. Hartman or the dove sanctuary in
Perseverance. According to Bonnie Rusk, a conservation biologist who has studied the Grenada dove
for over 17 years, the population of the dove declined by half between 1987 and 1990 to about 100
birds remaining. The dove population then experienced an increase between 1990 and 1998 to
about 190 birds, but Hurricane Ivan impacted the doves and the population now stands at
approximately 120 birds3.
Tips for identifying the Grenada dove: This dove is a medium size bird (12 inches) with a plain brown
back (no spotting, barring etc.), white belly and white forehead and crown. The breast of the dove
has a creamy pink hue and there is a telltale arched, vertical stripe of white feathers around the
shoulders. The eyes are white with dark pupils and the eye is encircled by a thin red eye ring. The
dove's audible call is a single, descending note, which lasts for about a second and then is repeated
every 7-8 seconds4.
GRENADA DOVE (Leptotila Wellsi
Wellsi)
PHOTO BY: Anthony "Jerry" Jeremiah
Major threats to the dove include habitat loss and fragmentation temporarily due to hurricanes and
for the long term due to clearing for agricultural lands, commercial development and development of
residential areas. Predation by invasive mammalian predators, primarily the Burmese mongoose
(Herpestes auropunctatus), and the black rat (Rattus rattus) are also factors in the dove's continued
decline.
Conservation measures continue to be implemented, but the Grenada dove remains critically
endangered.
"To despair of the entire situation is another reasonable alternative. But the unsatisfactory thing
about despair, in my view, is that besides being fruitless it’s far less exciting than hope, however slim5."
References:
1. Edwards Lab, Illinois State University: The “picture wings” and other Hawaiian
Drosophila – A case study in species evolution.
http://www.bio.ilstu.edu/edwards/hawaiiandrosophila/index.shtml
2. Hollocher, H., J. L. Hatcher and E. G. Dyreson. 2000. Genetic and
Developmental Analysis
of Abdominal Pigmentation Differences Across Species in the Drosophila Dunni Subgroup.
Evolution. 54(6), pp. 2057-2071.
3. Birdlife International (2011) Species factsheet: Leptotila Wellsi.
http://www.birdlife.org/datazone/speciesfactsheet.php?id=2581
4. Rusk, B. 2007. Grenada Dove Bird of the Month.
http://www.bu.edu/scscb/working_groups/Actions/bird_March_07_Grenada_Dove.htm
5. Quammen, D. 1996. The Song of the Dodo: Island Biogeography in an Age of Extinctions.
Scribner, New York.
About SGU Green House:
House:
SGU Green House is a publication created by Dr. Joanna Rayner and Dr. Clare Morrall to raise
awareness for environmental issues. Look for it fortnightly in the SGU Bulletin. Articles will include
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