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Taxonomy Of Cat Gecko
Aeluroscalabotes felinus
Complex in South East Asia
SITI NOR BAIZURAH BT ABD MALIK CHANG
This project is submitted in partial fulfillment of the requirement for the degree of
Bachelor of Science with Honours
(Animal Resource Science and Management)
Department of Zoology
Faculty of Resource Science and Technology
Universiti Malaysia Sarawak
2012
i
Acknowledgement
Foremost, I am indebted to my supervisor, Prof. Dr Indraneil Das for guiding and supporting me
towards the completion of this project. I would also like to extend my gratitude to Pui Yong Min
from the Institute of Biodiversity and Environmental Conservation (IBEC), for providing
assistance and equipment needed for the project. Most of all, I would like to extend my gratitude
towards my beloved parents, Mr. Chang Kat Min and Ms. Yung Moi Agus and all my family
members for their encouragements and financial support. I am grateful to my colleagues that
provide continuous encouragement and their willingness for comment on my work, especially
Esther Sheren A/K Joseph, Melynda Cheok Ka Yi, Khatijah Ismail, Nur Alwanie Bt Maruji,
Amaziasizamoria, Kirupaliny Susie, and special thanks are due to Mohd Izzuan Bin Abdul Rani
for incredible patience and moral support.
ii
Declaration
Hereby, I declare that this thesis is based on my original work except for quotations,
citations and references which have been appropriately acknowledged. I also declare that a paper
on this topic has not been submitted previously or concurrently for any degree in UNIMAS or in
any other institution.
Siti Nor Baizurah bt Abd Malik Chang
Animal Resource Science and Management Programme
Faculty of Resource Science and Technology
Universiti Malaysia Sarawak
iii
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ……………………………………………………… i
DECLARATION ………………………………………………………………… ii
TABLE OF CONTENTS ……………………………………………………….. iii
LIST OF TABLES AND FIGURES …………………………………………….. iv
ABSTRACT ……………………………………………………………………... v
1.0 INTRODUCTION ………………………………………………………… 1-3
1.1 Objective
1.2 Problem Statements
2.0 LITERATURE REVIEW …………………………………………………… 4-10
3.0 MATERIALS AND METHODS………………..…………………………… 11-19
3.1 Study Sites
3.2 Data Collection
3.3 Morphological Measurements
3.4 Analysis of Data
4.0 RESULTS…………………………………………………………………….. 20-32
5.0 DISCUSSION ………………………………………………………..……… 33- 40
5.1 Results of Discriminant Function Analysis and Cluster Analysis
5.2 Variation
5.3 Limitations
6.0 CONCLUSION AND RECOMMENDATIONS ……………………………. 41
REFERENCES
APPENDIX
iv
List of tables and figures
Pages
Figure 1: Phylogenetic relationships within Aeluroscalabotes 9
Figure 2: Materials utilized in phylogenetic analysis 10
Figure 3: Collection localities in Malaysia 11
Figure 4: (a) Body outline of a gekkonoid lizard, showing measurements taken
(b) Lateral view of a gecko head 14-15
Figure 5: Canonical discriminant functions using binary data 27
Figure 6: Canonical discriminants functions using measurement data 28
Figure 7: Result of cluster analysis (including data for tail) 29
Figure 8: Result of cluster analysis (excluding data for tail) 30
Table 1: List of measurements used and their abbreviations 15-17
Table 2: Status of tail 21
Table 3: Variables used for coloration patterns 22
Table 4: Comparison between current studies (2012), with those of 23-24
Grismer (2011), Taylor (1963)
Table 5: Eigenvalues for Discriminant Function Analysis (binary data) 25
Table 6: Wilk’s lambda for Discriminant Function Analysis (binary data) 25
Table 7: Standardized canonical discriminant function coefficients (binary data) 27
Table 8: Eigenvalues of Discriminant Function Analysis 28
Table 9: Wilks’s lambda of Discriminant Function Analysis 28
Table 10: Standardized canonical discriminant function coefficients 29
v
Taxonomy of Cat Gecko Aeluroscalabotes felinus complex in South east Asia
Siti Nor Baizurah Bt Abd Malik Chang
Animal Resource Science and Management Programme
Faculty of Resource Science and Technology
Universiti Malaysia Sarawak (UNIMAS)
ABSTRACT
This study focused on the genus Aeluroscalabotes, belonging to the family Eublepharidae in South-east Asia.
Aeluroscalabotes felinus is known to be the only representative of genus. The objectives of this study are to collect
data that contribute to further studies in taxonomy and systematic, while demonstrating morphological differences
including colouration patterns between populations of A. felinus in South-east Asia using morphometric techniques.
The result of cluster analysis showed differences between the populations in Peninsular Malaysia and Borneo, and
even within localities in western Borneo (Sarawak). Discriminant function analysis (DFA) revealed the strongest
characters to discriminate the populations are forehead and body dorsum colour, ratio of head width to snout vent
length and lamellae on fourth toe.
Key words: Aeluroscalabotes, monotypic, South-east Asia, morphometrics, Discriminant Function Analysis.
ABSTRAK
Kajian ini fokus pada genus Aeluroscalabotes kompleks dari famili Eublepharidae di Asia Tenggara.
Aeluroscalabotes felinus dikenali sebagai monotip dan wakil tunggal dalam genus tersebut. Objektif kajian ini
adalah untuk mengumpul data yang menyumbang kajian lanjutan dalam taksonomi dan sistematik sambil
mendemonstrasikan perbezaan morfologi termasuk corak warna di antara populasi A. felinus di Asia Tenggara
menggunakan morfometrik. Keputusan analisis cluster menunjukkan perbezaan antara populasi Semenanjung
Malaysia, Borneo, dan di dalam Kepulauan Borneo. Diskriminan fungsi analisis menunjukkan karakter utama untuk
membezakan populasi adalah warna di atas permukaan kepala,warna bahagian atas badan, nisbah kepala dan
lebar kepada muncung ke anus dan lamella di jari kaki ke-empat.
Kata kunci: Aeluroscalabotes, wakil tunggal, Asia Tenggara, morfometrik, Diskriminan fungsi analisis.
1
1.0 INTRODUCTION
Taxonomy is the discipline of naming and classifying organism scientific naming began
with Carlolus Linnaeus during the eighteenth century. It involves the process of discovering,
naming, describing and classifying organisms. Discovery of new organisms is the first step of
taxonomy. Taxonomists classify organisms and categorize them according to the Linnaean
system of naming from family, phylum, class, order, family, genus to species.
Order Squamata can be classified as a natural group in showing a cloacal opening, skulls
that are relatively more kinetic than other orders of reptiles and possess hemipenes, which are a
paired copulatory organ in males. Under the infraorder Gekkota, there are seven families
including the Gekkonidae, Carphodactylidae, Diplodactylidae, Eublepharidae, Phyllodactylidae,
Sphaerodactylidae, and Pygopodidae. According to Pianka & Vitt (2003), 25 species are
currently allocated to the family of Eublepharidae and are included in the genera
Aeluroscalabotes, Coleonyx, Eublepharis, Goniurosaurus, Hemitheconyx, and Holodactylus.
Aeluroscalabotes felinus, the cat gecko, is the only member of Eublepharidae in Borneo
and is currently considered monotypic. However, unpublished genetic work by Gamble et al. (in
prep.) suggests that this genus is not monotypic. The current project, using specimens collected
from Sarawak aims to demonstrate morphological differences between populations of geckos in
the genus Aeluroscalabotes and try resolving some of the systematic problems within the group.
2
These are forest-dwelling, slow-moving geckos that can be found in lowland rainforests
and peat swamp forests of Sarawak, Sabah and Kalimantan, and are also distributed in Peninsular
Thailand, the Malay Peninsula, Sumatra and Borneo (Taylor, 1963). It is nocturnal and arboreal,
being known to be active only during night on low vegetation of saplings and also on dead logs,
and feed on arthropods, such as crickets and cockroaches (Das, 2006).
Generally, they have slender bodies, fleshy eyelids and a rounded tail. They also possess
large retractable claws on each digit between a dorsal and two lateral scutes. As in other
members of the family of Eublepharidae, they produce eggs with leathery shell that measure 9.5
–13×17 –21.2 mm and generally one to two elongate eggs with parchment shells are produced.
According to Das (2010), A. felinus can be recognized by their colour which is usually brighter
in juveniles, sometimes with white spots and a vertebral stripe on the body and on tail, while in
some cases, tail-tip is white in colour.
South-east Asia is a known area of high biodiversity due to its uniform temperature year-
around, high humidity and also high precipitation. The latitude ranges from 16°S to 20°N
latitude, the longitude from 95°C to 130°E. Countries included in the region are Brunei
Darussalam, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore,
Thailand, and Vietnam. Monsoonal seasons influence much of the climate in the northern parts
of the region, the southern parts being more seasonal.
Rainforests in northern South-east Asia have four different seasons, which are the winter
northeast monsoon, the summer southwest monsoon and another two intermonsoon seasons.
Borneo is the third largest island in the world and rich in species. Geographically, the island is
divided by the central highlands that run diagonally from Sabah state (Malaysia) in north-eastern
3
Borneo to south-western Borneo, roughly forming the border between West and Central
Kalimantan (Indonesia).
1.1 OBJECTIVES
To demonstrate morphological differences between populations of A. felinus in Borneo and
adjacent regions using (morphology) morphometric techniques and secondary literature.
To review data that will contribute to the taxonomy and systematic of A. felinus.
1.2 PROBLEM STATEMENT
A. felinus is known to be the sole representative of the genus Aeluroscalabotes (Grismer,
1988). However, unpublished genetic data reveal that several cryptic species within the
lineage exist (Gamble et al., in prep).
4
2.0 LITERATURE REVIEW
Taxonomy is the science of classifying organisms and the Linnaean system is currently
accepted worldwide for classification of plants and animals, both living and extinct. The
Linnaean system breaks down organisms into seven major divisions, known as taxa (singular:
taxon). These are: Kingdom, Phylum, Class, Order, Family, Genus and Species.
This research focuses on the genus Aeluroscalabotes (Reptilia: Squamata: Sauria:
Eublepharidae). The family of eublepharids geckos has six genera: Aeluroscalabotes, Coleonyx,
Eublepharis, Goniurosaurus, Hemitheconyx, and Holodactylus: only Aeluroscalabotes is found
on Borneo (Das, 2004).
Taylor (1963) diagnosed Eublepharidae as “true eyelids present, without “spectacle”;
pupil vertical: vertebrae procoelous; parietal bones united; digits straight, slender, without
lamellae claws usually partly concealed or retractile; postanal sacs and bones present; body
often compressed’.
According to Grismer (1988), the family Eublepharidae has a short tongue compared to
other family and their forehead can be identified based on the large symmetrical shields and the
most unique characters that this family possessed is the present of true eyelids and
Aeluroscalabotes felinus and its relatives have eyelids capable of closing. They have depressed
heads of elongate-triangular shape, distinct from their thin neck, and tapering and slightly
compressed tail (Günther, 1864).
Other characters include enlargement of postmentals, absence of axillary pockets, and
possession of transverse enlarged lamellae that are restricted to the base of digits (Das, 2004).
5
The five clawed digits that can be retracted suits their arboreal lifestyle permitting them to live in
trees or other vegetation off the ground.
The family is characterised by supratemporal bones in the skull and angular bones in the
mandible. It is the only family that possesses eyelids compare to the other gecko families on
Borneo. According to Das (2004), A. felinus distributed through Peninsular Thailand, the Malay
Peninsula, Sumatra and Borneo, where they inhabits lowland rainforests and peat swamp forests
reaching 800 m from sea level.
Kluge (1987), recognized “eyelid geckos” in the subfamily Eublepharinae of the family
Gekkonidae (Kluge, 1967) as constituting a single primitive lineage distant from all other
members of Gekkkota based on the cladistic analysis of morphological characters. Grismer
(1988) confirmed the monophyly of eublepharid geckos and formulated a detailed,
comprehensive phylogenetic hypothesis for the family.
The common name of Aeluroscalabotes is derived from its habit of curling up its tail
laterally around itself. This species is considered to be one of the more primitive members of the
Gekkota as shown by the fossil records of early geckos. Typically, males are smaller than
females.
The species is primarily nocturnal, insectivorous, and arboreal. It occupies lowland to
mid-level rainforest, often found on certain large fern-like plants. Usually, it prefers humid, cool,
undisturbed and secondary rainforests that are located near streams and usually forage at night in
the undergrowth (Cox, 1998). Their foraging activity starts at night and diets includes spiders
and crickets. They have dark eyes and can be marked by their slow movement, but can leap as
6
well. They have the ability to „shed‟ or „drop‟ their tail when pursued by predator, known as
caudal autotomy (Bauer et al., 1989), and sometimes use immobility as a defense mechanism.
Cat eyed gecko are moderate sized and reach up to 122 mm in SVL (Das, 2004). Taylor
(1963) described the species of having triangular head that have double width of the neck. The
body and neck are compressed, with shorter tail compared to body. It has nearly uniform of small
scales on dorsal part and scales on the side of snout; supralabials ranges from 12 –13 and 12
infralabials.
Cat eyed geckos have “fingers and toes but slightly dilated in their basal half, with a
series of undivided, imbricate transverse plates below the dilated portion, the ungula half being
compressed and angularly bent ; all the fingers and toes clawed, each claw being retractile into
a compressed, bilobed sheath” (Günther, 1864). During Günther‟s (1864) time, three species
were known, two from the Asian mainland and one from Borneo.
This species is capable of climbing and show one narrow-toe that exhibits correlated
differentiation in toe morphology as the only arboreal eublepharids that possessed subdigital
setae and resemble other climbing and bent-toed geckos (Peattie, 2008). The digits of this species
resemble a row of enlarged subdigital scales proximal to the kinked portion of the digit.
Lack of lamellae (expanded toe pads, as seen in house geckos, Hemidactylus) disables
them from climbing walls and other smooth surfaces. However, a study by Peattie (2008) ound
the presence of subdigital climbing setae in Aeluroscalabotes felinus, that can be up to 9µm in
length and are 0.4 –0.5 µm wide.
Das (2006) wrote that Aeluroscalabotes felinus is typically red brown in colour, with
white spots on its body and sometimes, solid white on its body and in some cases on their belly.
7
Uniquely, they have varieties of body colours and patterns across their dorsum, some with red
broken stripes, while others are solid brown and few individuals can be grey.
Different sources give different colouration and pattern of the species. Cox (1998)
observed that some have no pattern on the dorsum and some show irregular longitudinal light
bands that may form a series of white dots. Günther (1864) described specimens from Asia
mainland as having a brown dorsum, with scattered pearl-coloured dots on flanks of body and
irregular white spots on the upper and lower parts of the tail. In addition, specimens from Borneo
have a few differences compared to the one found from “India” in having double series of light
ocellated spots along the back observed (Günther, 1864).
Taylor (1963) described the colour as, “dorsal and lateral parts of head and body
uniform brown with two lines of dim tan spots beginning on occiput, continuing on dorsum to the
base of tail; lower surfaces of head and venter cream, dotted with brown; upper lip, chin, and
throat cream; tail brown, on dorsal surface of a somewhat darker shade and with four cream
spots, with dark brown borders on their basal third; on subcaudal region several cream spots
usually associated with dark brown spots or flecks; distal part of tail uniform brown”.
Grismer (2011) described A. felinus as having a light to burnt orange dorsal ground
colour and elongate markings with conspicuous white markings on the original tail. Regenerated
tail usually lacks the markings and he also described the lower portion of flanks orange. Grismer
(2011) also mentioned that lizards from uplands above 350 meters usually have orangish ground
colour compared to brown and darker paravertebral markings on the body with larger white
markings on the tail o the lowland lizards. Iris colour of populations from Peninsular shows
8
difference as they tend to have a metallic silvery coloured iris, compared to populations of north
that possessed deep brown iris.
Previous researches on the taxonomy of A. felinus have sometimes produced confusing
results. Four species and one subspecies have been described, including Pentadactylus felinus
and Pentadactylus borneensis (Günther, 1864). According to Taylor (1963), three species from
genus Aeluroscalabotes described and only a single species recognized in Thailand and
Peninsular Malaysia. Grismer (1988) proposed that this genus is monotypic, based on a small
sample.
However, unpublished genetic differences observed (see Figure 1) suggest the existence
of several cryptic species within the lineage (Gamble et al., in prep). This issue suggests that
systematic and taxonomy of this genus has not been resolved, and further research is needed to
solve it. Based on the genetic data present, there is possibility that there are more than one
species under this genus. This research was thus conducted to collect new data based on
morphology using morphometric techniques.
Related past taxonomic studies by Yugees (2010) on the genus of Cyrtodactylus (family
Gekkonidae) from Borneo, provides reference for this study in which she determined the
differences between members of genus in Borneo, using 32 measurements including ratio of
morphological characters, in addition to colouration patterns, to distinguish the members from
one another and analysed data using cluster analysis and Discriminant Function Analysis (DFA).
9
Figure 1: Phylogenetic relationship within Aeluroscalabotes (Gekkota: Eublepharidae),
based on specimens from Peninsular Malaysia and Borneo (unpublished genetic differences
(Gamble, et al., in prep).
10
Figure 2: Materials utilised in phylogenetic analysis based on specimens from Peninsular
Malaysia and Borneo (unpublished genetic differences (Gamble, et al., in prep).
11
3.0 MATERIALS AND METHODS
3.1 Study site
This research used a total of 23 individuals from the museum of the Institute of
Biodiversity and Environmental Conservation (IBEC) and secondary literature (Grismer,
2011 and Taylor, 1963). Specimens obtained from several areas in Borneo, including
Gunung Mulu, Gunung Pueh, Gunung Penrissen, Gunung Gading and Kota Samarahan
located at the centre of UNIMAS was examined for morphological differences. One of the
locations is UNIMAS that located in Kota Samarahan, known to contributes the largest area
of peat swamp forest in Sarawak that is located at Kota Samarahan (01° 27‟ 48” N; 11º 27‟
03” E). The material examined from secondary literature ranges from area around Kuala
Lumpur (Taylor, 1963), Johor, Pahang and Perak (Grismer, 2011).
12
LEGEND
= Refer to Figure 1
= Additional location added
Figure 3: Collection localities in Malaysia (source: Gamble et al., in prep.)
According to Zainuddin (2006), most of vegetations consist of secondary peat swamp
forest which been logged over 50 years ago and now large areas of peat swamps forest of
UNIMAS destroyed for the construction of campus‟s building and roads. Gunung Pueh
(Latitude 1° 46' N, Longitude 109° 40' E) reached elevation up to 1291 meters and have
13
logged primary forest and houses number of species range from lowland to highland species
including Mountain Barbet (Megalaima monticola). Gunung Penrissen (Lat 1° 08' N, Long
110° 13' N) primarily the remnants of logged montane forest that reached altitude of 1,326
meters with few areas that already cleared for development.
Gunung Gading (Latitude 1° 43' N, Longitude 109° 50' E) in Lundu Division, and
covers an area of 5,432 hectares and reached elevation up to 906 meters. Type vegetation is
mixed dipterocarp forest and Diard‟s Trogon among the species that can be obtained at the
site. Gunung Mulu located in Miri Division (Lat 4° 03' N, Long 114° 15' E) and covers an
area of 52, 866 hectares and recorded maximum altitude of 2,376 meters. The vegetation
encompasses of montane sandstone, limestone forest and houses numbers of Montane
Borneo endemic species including Golden-naped Barbet and Whitehead‟s Trogon.
From the secondary literature, three locations from Peninsular Malaysia were added-
Johor (Endau-Rompin), Selangor, Pahang (Cameron highlands) and Perak (Temengor).
Endau Rompin National Park is a lowland dipterocarp forest that consists of contiguous area
of hilly sandstone with a unique assemblage of tropical lowland and hill forest. It
encompasses the watershed of rivers in Endau in Johor and Rompin in Pahang. For the
second location, which is in Selangor, no definite area stated in the secondary literature.
While, Cameron Highlands in Pahang known to located 1524m above sea level and with
temperatures less than 200C (Anonymous, 2012) and consists of different vegetations that
farmed by the residents such as strawberry farm and also tea plantations. Locations in Perak
(Temengor) not clearly described in the secondary literature so no definite information which
location selected for Grismer (2011) studies.
14
3.2 Data Collection
Measurements were taken following Grismer (2005) using digital calipers in mm
and microscopes were used for scale counts. A total of 51 measurements (including ratios
of certain characters, sex, patterns and scale measurements) were taken, and recorded.
The size determined by the measurement such as body length from snout to vent (SVL);
from vent to tip of the original tail (TL); measured at the widest part of the tail (HW);
(EarL) taken in vertical position as longest dimension of ear; (OrbD) measured as
greatest diameter between the orbits; and many more (Grismer & Leong, 2005). Ratios of
certain characters were used such as snout- vent length to tail length to determine body
proportions and the relationships to one another.
For scale counting, six types of scale measurements were taken, including both
right and left supralabials and infralabials, mid-ventral scales and subcaudal scales.
Colour pattern was further divided to six categories including the absence or presence
vertebrate stripes and the upper head coloration whether as in dorsum or paler. The list of
measurements provided in Table 1.
However, the colour of iris could not be used as specimens used were preserved
specimens, in 70 % ethanol. Scale counting conducted in both right and left sides, while
only in right sides for the body measurements. For the measurements of finger of fourth
length (Fin4L), lamella on finger fourth (Fin4Lam), lamella on fourth finger (Toe4Lam)
taken on the right sides only. Additional data obtained from Grismer (2011) and Taylor
(1963).
16
Table 1: List of measurements used
No.
List of measurements used
1
Snout vent length (SVL)
2
Tail length (TL)
3
Tail width (TW)
4
Tail depth (TD)
5
Axilla to groin (A-G)
6
Forearm length (FAL)
7
Tibia length (Tbl)
8
Head width (HW)
9
Head length (HL)
10
Head depth (HD)
11
Jaw width (JW)
12
Orbit diameter (OrbD)
13
Interorbital (IO)
14
Distance of orbit to snout (OrbSn)
15
Distance of orbit to ear (OrbEar)
16
Ear length (EarL)
17
Right of supralabials scales (RSL)
18
Left of supralabials scales (LSL)
19
Right of infralabials scales (RIL)
20
Left of infralabials scales (LIL)
21
Scales count at mid ventral of body (MVSR)
22
Subcaudals (SC)
17
23
Length of finger four (Fin4L)
24
Lamellae count at finger four (Fin4LaM)
25
Lamellae count at toe four (Toe4Lam)
26
Ratio of tail length to snout vent length (TL:SVL)
27
Ratio of tail length to the tail width (TL:TW)
28
Ratio of tail length to the tail depth (TL:TD)
29
Ratio of tail width to snout vent length (TW:SVL)
30
Ratio of tail depth to snout vent length (TD:SVL)
31
Ratio of the axilla to groin distance with snout vent length (A-G:SVL)
32
Ratio of forearm length to snout vent length (FAL:SVL)
33
Ratio of tibia length to snout vent length (TbL:SVL)
34
Ratio of head width to snout vent length (HW:SVL)
35
Ratio of head width to head length (HW:HL)
36
Ratio of head width to head depth (HW:HD)
37
Ratio of head length to snout vent length (HL:SVL)
38
Ratio of head depth to snout vent length (HD:SVL)
39
Ratio of jaw width to snout vent length (JW:SVL)
40
Ratio of orbit diameter to snout vent length (OrbD:SVL)
41
Ratio of interorbital to snout vent length (IO:SVL)
42
Ratio of orbit to snout to snout vent length (OrbSn:SVL)
43
Ratio from orbit to ear to snout vent length (OrbEar:SVL)
44
Sex of the individual
45
Colour pattern (see Table 3)
18
3.3 Analysis of data
To analyze the data, it involves process of inspecting and modeling the data such as
analyzing the data in simplest form to distinct individuals. Data were analysed using
comprehensive system Statistical Package for Social Sciences software (SPSS) and Multivariate
Statistical Package (MVSP). Program used from SPSS for this study is discriminate function
analysis (DFA) and cluster analysis from MVSP. Both programs used after considering the
advantageous and the suitability of method for the objective of this research. Ratios of certain
characters used to determine the relationship of body proportions to another using the concept of
allometry.
3.3.1 Discriminant Function Analysis
Discriminate Function Analysis (DFA) runs through SPSS 18.0 and easy access patterns in
grouping of samples. Basically, it used to predict membership in two or even more mutually
exclusive groups. Other than that, it also investigated differences between groups to indicate
which attributes separate groups and determine the predictor variables to discriminate between
populations (Hedderson, 1991). This analysis gives better options to build a predictive model of
group that have their own relationship based on observed characteristics and in this study, based
on morphological observation. The advantage of this method is that it allowed nominal measure
for the dependant variable. It is able to classify cases in more than two categories which the line
regression technique unable to handle.
