Divergensi Morfologi Antar Populasi Simpatrik Ikan Baung (Hemibagrus velox Tan et Ng) di Danau Singkarak Sumatera Barat.
ABSTRACT Hemibagrus velox is one of new potential catfishes species found in Sumatra. In order to explore intraspecific variation and morphological differentiation among sympatric populations of this species in Singkarak Lake at West Sumatra, field study and morphological analysis were conducted using direct observation and morphometric methods on three populations in Singkarak Lake (Sumani, Muaro Pingai and Sumpur) and one population in Ombilin River (outflow of Singkarak Lake). Unweighted Pair Group Method Aritmatic Average (UPGMA) was used to identify the pattern of morphological divergence and two nonparametric statistical tests (Kruskall-Wallis test and Mann-Whitney U test) were generated to analyze the morphological variations and differentiations. It was found some morphological divergences among sympatric populations with clear separation between lake and river populations, Sumani and Batang Ombilin River were the most different sympatric populations morphologicaly. There were three characters with highly significant variation and differentiation among populations such as second mandibular barbel length (PSB2), distance between anterior part of pectoral fin base to anterior part of dorsal fin base (T15), and distance between anterior part of pelvic fin base to anterior part of dorsal fin base (T17). These morphological divergences could be induced by ecological differentiations among populations.
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ABSTRACT: Arctic charr, Salvelinus alpinus (L.), commonly exhibits two coexisting morphotypes, dwarf and normal charr, which are characterized by differences in adult body size and colouration. We tested whether or not the morphotypic differences were genetically determined in rearing experiments with offspring of the two morphs and of their crosses. The experiments suggest that this ecological polymorphism in Arctic charr is largely environmentally determined. When reared under similar conditions, offspring of each of the two morphs differed little in size at the same age, and they had the same early developmental rate and maturation pattern. Moreover, the presence of parr marks along the flanks of the fish, one characteristic of dwarf charr, depended on body size and not on parental morph. Genetic differences between the morphs were suggested for growth rate during the second year of life, and for jaw morphology. Comparisons between charr life histories in captivity and in the wild suggest that ecological polymorphism in Arctic charr is chiefly a result of variation in growth conditions between different habitats.Biological Journal of the Linnean Society 01/2008; 48(1):63 - 74. DOI:10.1111/j.1095-8312.1993.tb00877.x · 2.54 Impact Factor
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ABSTRACT: Lake Femund, Norway, contains several sympatric ecotypes of whitefish, Coregonus lavaretus L. Deepwater whitefish, river whitefish, and shallow water whitefish can be easily distinguished by spawning habitat and gillraker number. Variation in morpho-logical and ecological characters and allozyme loci from 11 different spawning sites was analysed to compare the ecological poly-morphism with possible genetic sub-structuring of whitefish in the lake. Of the individual morphological and ecological characters, gillraker number best separated the spawning populations, followed by body length. In a hierarchical cluster analysis based on gill-raker number, body length and age of fish, the four deepwater sites grouped together as well as the three samples from, or closely related to, inlet rivers. The shallow water sites, however, were more dispersed. In the allozyme analysis, nine of the 38 enzyme loci were polymorphic at the 0.95 level. The amount of genetic variation was quite similar among localities with H exp = 0.046 -0.066. Allele frequencies differed significantly among localities at all polymorphic loci indicating distinct reproductive isolation between spawning sites. A consensus tree based on genetic distances grouped samples according to spawning depth and trophic morphology rather than regional proximity. All deepwater spawners grouped together with rather high support while geographically adjacent samples differing by their morphology or behaviour were dispersed. The patterns of differentiation based on allozyme variation and morphology are not fully concordant, but still the association between genetic differentiation and morphological and life history variables was highly significant. Thus, the morphological differences are not due to phenotypic plasticity within single spawning populations as is commonly seen in many other fish species. The possible evolutionary origins of reproductively isolated whitefish forms are discussed. The relatively close association between differences in gillraker counts and genetic difference indicates that the present management of Femund whitefish stocks based on gillraker counts is sensible.08/2004; 63(2):233-243. DOI:10.4081/jlimnol.2004.233
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ABSTRACT: Genetic data suggest that the littoral and pelagic forms of brook charr Salvelinus fontinalis in Lake Bondi are two populations with partial reproductive isolation and non-random mating. Genetic differentiation between the two groups was supported by differences in allele frequencies and by deviation from Hardy-Weinberg equilibrium when the two groups were pooled; no such deviation was observed when fish were divided into littoral and pelagic groups. In contrast to Lake Bondi, no clear evidence of genetic differentiation was observed in Lake Ledoux. Discriminant function analyses of morphological characters support the existence of littoral and pelagic groups in Bondi and Ledoux Lakes. In Lake Bondi, the two groups differed significantly in two shape variables (pelagic fish had shorter dorsal fins, and longer body length posterior to the dorsal fin than littoral ones) whereas in Lake Ledoux, the groups differed in four shape variables (pelagic fish had shorter pectoral fins, shorter dorsal fins, and a shorter and higher caudal peduncle than littoral ones). Discriminant analyses of these characters were effective in reclassifying fish into their appropriate groups in both populations, with an efficiency of 78% for juveniles in Lake Bondi and 69% for adults in Lake Ledoux. Differences in morphology between the two forms are consistent with adaptations required to forage in each zone, i.e. benthic form in the littoral zone and planktivorous form in the pelagic zone.Journal of Fish Biology 03/1999; 54(5):955 - 972. DOI:10.1111/j.1095-8649.1999.tb00850.x · 1.73 Impact Factor