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