by jeff levan and dr. allan landwer partitioning and allowed for greater anole diversity than...
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Niche Partitioning of Adult Males of Two Species of Jamaican Anolis in Simple Anthropogenic Versus Complex Forested Habitatby Jeff LeVan and Dr. Allan Landwer
Project Advisor: Dr. Gary Ferguson
Introduction
Lizard species that live together and compete for similar resources will often partition their
niche space and exploit certain ecological requirements, such as food type or perch height, in order
to minimize competition and eliminate the possibility of competitive exclusion. (Williams, 1969,
1983). Niche partitioning is one of the primary driving forces behind speciation, as individuals
choose or are forced to occupy a certain niche space with response to competition and over time
evolve specific adaptive characteristics that increase a species chance of survival.
We investigated the niche partitioning and community structure of several species of lizards
in the genus Anolis in Jamaica near the town of Ocho Rios. Caribbean Anolis lizards are a good
choice for analyzing community structure because they are common and are mostly unaffected by
repeated observation (Sugerman 1990). I investigated four native species, Anolis lineatopus, Anolis
grahami, Anolis opalinus, and Anolis garmani, as well an invasive species from Cuba, Anolis
sagrei. Each species occupies distinct physical niche space with relation to the other anoles
present (Fig 1). We compared the relative abundance and niches of the adult male anoles of the two
species (Anolis lineatopus and Anolis grahami) that occur in two separate locations with very
different habitat types. The first habitat type occurs around the Hofstra University Marine
Laboratory (HUML) on the north shore of Jamaica. The area is very disturbed and unnatural, and
the anoles live in close proximity with humans on walls, shrubs, and trees. The second habitat is
mature, natural, undisturbed forest habitat that occurs a few miles away in Cranbrook Flower
Forest (CFF).
Procedure
This study took place between 10 March and 12 March, 2006 in St. Ann’s Parish, Jamaica.
Two to three individuals hiked slowly along a trail traversing CFF and recorded the species, perch
height, and sun exposure (UVB exposure using a Solartech 6.2 meter, Harrison Township MI) for
each individual adult male Anolis lizard encountered. Only adult males were used because they are
large, conspicuous and easily identified by distinctively colored dewlaps. From these data we were
able to calculate the relative abundance, average perch height, temperature, and the sun exposure for
each species, in order to obtain a general understanding of the physical niche space in which each
Anolis species occurs.
We then compared the perch height and Ultraviolet-B irradiation of the two species that we
obtained from CFF to previous data obtained in niche partitioning studies executed in the disturbed
habitat around the HUML (Landwer et al. 1995; Landwer and Ferguson, 2002). Investigators
conducted studies in this area during the spring of 1983, 1987, 1994, 1996, 1998, and 2000.
Analyses of Variance (ANOVAs) were performed using Sigma Stat for windows 3.0 (SPSS, Inc).
Graphs were constructed using Sigma Plot 2002 for Windows (SPSS, Inc.)
Results
We found 50 male Anolis lineatopus, 15 male Anolis grahami, 6 male Anolis opalinus, and 2
male Anolis garmani during our hikes in CFF. In the studies conducted at the HUML, Anolis sagrei
was most abundant, Anolis grahami was second, and Anolis lineatopus was the least abundant. Both
Anolis opalinus and Anolis garmani are absent at HUML. Data on perch height and UVB exposure are
summarized in Table 1. Anolis opalinus occupied the lowest average perch height at CFF, followed
by Anolis grahami, Anolis lineatopus, and then Anolis garmani. At HUML, Anolis sagrei occurred at
the lowest perch heights, followed by Anolis lineatopus, and then Anolis grahami. At CFF, Anolis
opalinus occupied the areas of least UVB exposure, followed by Anolis lineatopus, and Anolis
grahami. At HUML, Anolis lineatopus occurred in the most shady regions, followed by Anolis
grahami, and Anolis sagrei.
The perch heights of Anolis lineatopus and Anolis grahami differ between the simple and the
complex habitat (fig. 2). Anolis lineatopus perched significantly higher at CFF than at HUML
(ANOVA p< 0.003). Anolis grahami perch heights were similar at both locations.
Figure 3 compares the average UVB exposure of Anolis lineatopus and Anolis grahami at
HUML and CFF. There was a significant difference in UVB exposure among the localities (ANOVA
p = .02). At both locations Anolis grahami exposed themselves to significantly higher UVB (ANOVA
p= .01), but the difference was greater at CFF.
Discussion
The complex habitat of Cranbrook forest afforded much more opportunity for niche
partitioning and allowed for greater anole diversity than Hofstra (5 species vs. 3 species). A
greater variety of perch heights and perch exposures are available in Cranbrook, and thus Anolis
lizards have more opportunity for niche specialization. The shadier, more complex habitat also
directly affects relative anole abundance, as Anolis lineatopus was much more competitive and
abundant in the forest habitat than in the sunny anthropogenic habitat, and Anolis sagrei is
completely absent from Cranbrook, despite being the most abundant species at HUML.
Anolis lineatopus and Anolis grahami occur at both HUML and CFF. The reason that the
perch height difference is greater at CFF is that a wide variety of sun exposures are available.
The perch heights of Anolis lineatopus most likely vary between the two locations because of a
greater amount of shade available at higher perch heights at Cranbrook. In the simple habitat of
Hofstra, the limited shady perch heights occur close to the ground.
Although competitive exclusion may be the primary factor in the evolution of niche
differences in these two species, the primary factor resulting in the differences between CFF and
HUML are alterations of the physical environment, i.e. more shade habitat at higher perches.
However, the presence of the low-perching Anolis opalinus at CFF only could be a factor
“driving” Anolis lineotopus to greater perch heights Over time the anoles will evolve
characteristics most suited to survival in a particular niche. For example, different Anolis species
vary in skin sensitivity to UV light according to how much sunlight they are exposed to
(Ferguson 2005).
Jamaican Anolis lizards illustrate how niche specialization can lead to morphological
adaptation, which can further lead to speciation, in order to maximize competitive advantage.
Works cited:
Ferguson G.W., W.H. Gehrmann, K.B. Karsten, A.J. Landwer, E.N. Carman, T.C. Chen, and M.F. Holick. 2005. Ultraviolet Exposure and
Vitamin D Synthesis in a Sun- Dwelling and a Shade-Dwelling Species of Anolis: Are There Adaptations for Lower Ultraviolet B and
Dietary Vitamin D3 Availability in the Shade? Physiological and Biochemical Zoology, 78(2):193-200
Landwer A.J. and G.W. Ferguson. 2002. Long-term structural and habitat use of male individuals of two native and one introduced Anolis
(Iguanidae) species on thenorth coast of Jamaica. Texas Journal of Science, 54:51-58
Landwer A.J., G.W. Ferguson, R. Herber and M. Brewer. 1995. Habitat Use of Introduced and Native Anoles (Iguanidae: Anolis) Along the
Northern Coast of Jamaica. Texas Journal of Science, 47: 45-52
Sugerman, R. A. 1990. Observer effects in Anolis sagrei. Journal of Herpetology, 24(3):316-317
Williams, E. E. 1969. The ecology of colonization as seen in the zoogeography of anoline lizards on small islands. Quarterly Review of
Biology, 44:345-389
Williams, E. E. 1983. Ecomorphs, faunas, island size and diverse end points in island radiations of Anolis. Pp. 326-370, in Lizard Ecology:
Studies of a model organism (R. B. Huey, E.R. Pianka, and T. Schoener, eds.), Harvard University Press: Cambridge, Massachusetts,
501 pp.
We thank The Hofstra University Marine Lab including Jason Williams, Steve Neuman, Kristene Proctor for their help in facilitating this
study. We thank Mr. and Mrs. Linton for permission to conduct the study at Cranbrook Flower Farm. We thank the project advisor Dr. Gary
Ferguson for help analyzing data and for providing photos.
Table 1 Perch height and UVB exposure of Anolis species at
HUML = Hofstra University Marine Lab; CFF = Cranbrook Flower Forest
Species Location Mean Perch
height CM
Standard
error
Mean UVB
exposure
!W/cm2
Standard
error
Anolis
lineotopus
HUML 93.6 8.8 13.6 4.6
Anolis
grahami
CFF 127.5 16.9 22.6 8.4
Anolis
garmani
CFF 365.8 92.4
4.2 2.7
Anolis
sagrei
HUML
Anolis
opalinus
CFF 101.6 12.2
58.3 7.1
5.2 1
17.8 4.8
45.6 7.7
Anolis
grahami
HUML 162.6 17.8
Anolis
lineotopus
CFF 162.6 8.9
Anolis grahami
Anolis lineatopus
Anolis opalinus Anolis sagrei Anolis garmaniAnolis habitat at Cranbrook (CFF) Anolis habitat at Cranbrook Anolis habitat at Hofstra (HUML) Anolis habitat at Hofstra
Figure 2. Mean and standard error of perch heights for adult male Anolis lineotopus and
Anolis grahami found at Hofstra University Marine Laboratory (HUML) and at
Cranbrook Flower Forest. Perch height is expressed in centimeters.
Figure 3. Mean and standard error of UVB exposure for adult male Anolis lineotopus
and Anolis grahami at Hofstra University Marine Laboratory (HUML) and Cranbrook
Flower Forest. UVB expressed in microwatts per square centimeter
Figure 1. This diagram shows where specific anole species occur in the canopy. Each species
prefers different perch heights and sun exposures.
Perch heights of adult male Anolis lineotopus and
Anolis grahami HUML and Cranbrook
Locality and species0.5 1.0 1.5 . . . 3.5 4.0 4.5
0
20
40
60
80
100
120
140
160
180
200
A. lineo topus Cranbrook
A. lineo topus HUML
A. grahami Cranbrook
A. grahami HUML
UVB exposure of males of Anolis lineotopus and Anolis grahamiin the field at HUML and Cranbrook
Locality and species0 1 2 3 4 5 6 7
0
5
10
15
20
25
30
35
A. lineotopus males HUML
A. grahami males at HUML
A. lineotopus males Cranbrook
A. grahami males Cranbrook