Abstract:
Puntius dorsalis and Puntius vittatus (Teleosteii: Cyprinidae) are widely distributed
indigenous species in Sri Lanka and adjacent countries. As no previous information
exists on their intraspecific geographic variation and whether the Sri Lankan species are
similar or different from Indian species, the present study aimed to describe the
morphometric character variations of Sri Lankan populations, and to carry out a
comparative analysis with some Indian specimens.
Specimens (n= 5-30) of P. dorsalis were collected from eight selected streams or tanks
with hydrological connection to different major river systems in Sri Lanka (Kalu
River, Nilwala River, Urubokka Oya, Menik River, Kirindi Oya, Mahaweli River,
Malwathu Oya and Kelani River). Specimens (n=5) collected from a single location in
Tamil Nadu (museum collection) were compared with Sri Lankan populations. Twenty
two morphometric characters of individual P. dorsalis fish using pre-decided landmark
points were obtained. Specimens (5-30) of P. vittatus from selected streams connected
to different river systems were used to collect data on 15 morphometries from digital
images of individual fish (two locations of Gin river and one each from Kalu, Nilwala,
Mee Oya, Kala Oya and Kelani River). Museum specimens from three locations in
India (WHT collection: Kerala, Veliyanadu and Nedu Mudi- Alleppey) were included
for P. vittatus. All the morphometric characters were standardized to remove size effect
prior to data analysis, and differences among the populations were tested by univariate
ANOVA and multivariate methods.
Caudal-Peduncle-Length (CPL) and Pre-Orbital-Length (PrOL) of P. dorsalis were
v significantly different (p<0.05, n=30 from Nilwala River) between males and females thus further data analysis for population comparison was done excluding CPL and
PrOL. Univariate ANOVA revealed significant heterogeneity in seven shape characters
among eleven samples, but no population-specific characters that can be used to
identify individual populations of P. dorsalis were found. In the discriminant function
analysis (DFA), Eye Diameter had the greatest power to discriminate P. dorsalis
populations. In principal component analysis (PCA) plot, separation of two groups of
populations was possible, where Canonical variate 1 (CV1) and CV2 explained 61.0%
of the total variation in data. In the cluster analysis, Indian sample clustered with
Nilwala River, Malwathu Oya, Menik River, Mahaweli River-Minneriya, Kalu River,
Kirindi Oya and Pattiyapola populations (clade A) whereas, Mahaweli River-
Polonnaruwa and Hasalaka populations made another clade in the same branch. It
seems that Kelani River population was different from all others, however, no external
morphometric differentiation was found in the ANOVA. Therefore, the findings
suggest that Sri Lankan specimens represent the same species of P. dorsalis that was
described from India, while considerable divergence may have occurred in the Kelani
River population.
In P. vittatus analysis, only Head-pre-dorsal diagonal (HPdD) was significantly
different between males and females (t-test, p=0.04, n=30 sample from Nilwala River),
thus further data analysis for population comparison was carried out after excluding it.
Univariate ANOVA showed no significant difference in any variables (p<0.05) among
three studied Indian populations. Considering only Sri Lankan populations, except Preorbital
L (PrOL), Dorsal fin base (FBD), Anal fin base (FBA), Maximum body depth
(MBD) and pre-anal L (PAL), all the others showed significant heterogeneity among
seven Sri Lankan populations, where Post orbital length (POL) had the greatest power to discriminate them. In PCA, separation of two groups of populations was possible,
where CV1 explained 72.5% of the total variation in data. In cluster analysis, Nilwala
River, Mee Oya, Kala Oya, and Kelani River populations made a separate clade
whereas Kalu and Gin River populations made another indicating considerable
divergence between the two. Three Indian locations cluster with Nilwala River, Kelani
River, Mee Oya and Kala Oya whereas Kalu River and two locations of Gin River
made another diverging clade. The results concluded that Indian populations represent
the characters of the first Sri Lankan clade, but the second Sri Lankan Clade
(‘Kalu+Gin’ Clade) seems to be specific to Sri Lanka and can be considered as a
diverging group. Hence, the measures should be taken to conserve any genetic diversity
present among them. The findings are expected to be important in issues related to
biodiversity and taxonomic assessment of Sri Lankan ichthyofauna.
Keywords: morphometric characters, phenotypic variation, cluster analysis, shape
variation, Puntius dorsalis, Puntius vittatus, diverging group