Contributions to Zoology, 74 (3/4) (2005)J. Alexandrino; N. Ferrand; J.W. Arntzen: Morphological variation in two genetically distinct groups of the golden-striped salamander, Chioglossa lusitanica (Amphibia: Urodela)
Results

To refer to this article use this url: http://contributionstozoology.nl/vol74/nr03/a01

Testing causal hypotheses

Scores on the first PCA axis were significantly associated with geographic distance, group membership (Table 2) and latitudinal distance (Fig. 5). Scores on the second axis were not associated with either of the independent variables (Table 2).

FIG2

Fig. 4. Means and standard deviations for the a posteriori probability (P) of classification of individuals in each population to northern group 2, from Discriminant Analysis of six size adjusted morphometric variables in 18 populations of Chioglossa lusitanica.

FIG2

Fig. 5. Regression of mean factor scores of the fi rst Principal Component axis of 18 populations of female Chioglossa lusitanica against distance along a south-north axis.

Classification of individuals (both females and males) in group 2, following DA, increased gradually from south to north (Fig. 4). In females, head length and head width were associated with geographic distance and group membership, respectively. Size of the extremities was associated with geographic distance, with the exception of FLL# in males. Digit length and HLL# in males were also associated with group membership. Colour pattern was associated to neither geographic distance or group membership. Morphometric variability was not associated with any of the formulated independent variables (Table 3). Colour pattern variability was associated with hybridity and not with geographic distance or heterozygosity. Additionally, a trend was observed for colour pattern variability to decrease from south to north in group 2 populations (Fig.1).

 

Table 2: Partial Mantel test results for association between morphological differentiation across 18 populations of Chioglossa lusitanica versus geographic distance and group membership (see text for details). Dependent variables are A) top panel, the first and second PCA-axis and B) lower panel, individual size adjusted (#) morphometric variables and colour pattern.

Casual hypothesis

(independent variables)

Morphological distance

Geographic

Group

(dependent variable)

distance

Membership

A)

PCA 1 (females)

***

**

PCA 1 (males)

*

***

PCA 2 (females)

ns

ns

PCA 2 (males)

ns

ns

B)

HL# (females)

*

ns

HL# (males)

ns

ns

HW# (females)

ns

**

HW# (males)

ns

ns

FLL#(females)

***

ns

FLL (males)

ns

ns

HLL# (females)

***

ns

HLL# (males)

*

*

TFL (both sexes)

*

***

FTL (both sexes)

**

***

Colour pattern (both sexes)

ns

ns

ns – not significant, * - p<0.05,** - p<0.01, *** - p<0.001.

 

Table 3: Partial Mantel test results for association between morphological variability across 18 populations of Chioglossa lusitanica versus geographic distance, heterozygosity and hybrid versus non-hybrid population status.

Causal hypothesis

Morphological

(independent variables)

variability distance

Geographic

Heterozygosity

Hybridity

(dependent variable)

distance

PCA1 (females)

ns

ns

ns

PCA1 (males)

ns

ns

ns

PCA2 (females)

ns

ns

ns

PCA2 (males)

ns

ns

ns

Colour pattern

(both sexes)

ns

ns

**

ns - not signifi cant, ** - p<0.01