蝦虎魚類的分子系統分類
Other Title
Moleculars systematics of gobioid fishes
Journal Issue
62
Start Page
14
End Page
17
Date Issued
1999
Author(s)
Advisor
杜銘章
李信徹
Abstract
ABSTRACT In this study, I used genetic marker to analyse the phylogenetic relationships between eleotrids and gobiid within gobioids. The main achivement can be described as the following five sections: (1) The conserved regions of tRNAPHE and 16S rRNA in the vertebrate mitochondrial genome were compared in order to design the primers, 12SR and 12SL. These universal primers can be broadly used to amplify a 1.2-kb DNA fragment by polymerase chain reaction (PCR) over a wide range of major vertebrate lineages represented by the species listed in the text. There is little length variation of the PCR product among different taxa. Further sequence analysis revealed that the fragment contains complete lengths of 12S rRNA and tRNAVAL, and that the length of 16S rRNA is 200 bp. In tests through all representative taxa investigated, the above 2 primers could amplify the complete 12S rRNA gene from all representative taxa investigated. As the 12S rRNA gene is widely used for phylogenetic analyses among different hierarchies, these primer sets are useful for vertebrate phylogeny. (2) These primer sets were further used to investigate the phylogenetic relationships of Gobioidei. The molecular phylogeny of gobioid fishes studied comprising 33 genera and 43 valid species were examined by using complete mitochondrial 12S rRNA and tRNAVAL genes. Both parsimony and neighbor-joining analyses reveal comparable results and are congruent with that of morphological studies. The Odontobutis, which always formed at the root of the phylogenetic trees, can be treated as sister group of all other non-rhyacichthyid gobioids. Within eleotrid fishes, the monophyly of Eleotrinae (Hoese and Gill 1993) is strongly supported by molecular data. The Butinae is closer and should be treated as sister group of five-branchiostegal rays group. Of the five-branchiostegal rays, except of sicydine, can be divided into two groups according to their epural counts. The fish with one epural, Gobiinae of Pezold (1993) plus microdesmid, is resolved as a monophyletic group and sister to that with two epurals, Oxudercinae and Gobionellinae of Pezold (1993). However, with one epural, sicydine is more close to Oxudercinae and Gobionellinae rather than Gobiinae. Since the progressed reduction of epural number has been observed along this lineage. The sicydine should be treated as derived group within the group with two epural. (3) The 12S rRNA sequences of 43 gobioid species and nine diverse assortments of fishes were further analyzed and employed to establish a "core" secondary structure model for fish 12S rRNA. Of 43 stems recognized, 41 of which were supported by at least some compensatory evidence among vertebrates. An analysis of compensatory substitution shows that the percentage of co-variation is 68% and the weighting factor for phylogenetic analyses to account for the dependence of mutations should be 0.66. Different stem/loop weighting schemes were applied to the analyses of phylogenetic relationships of Gobioidei which show that down-weighting paired region due to non-independence is irrelevant in the present phylogenetic analysis. The biased nucleotide composition (A% > T%, C% > G%) in loop regions was also observed on its mammalian counterpart. The exceed of A and C in loop region may be due to asymmetric mechanism of mtDNA replication which leads to the spontaneous deamination of C and A. This process may also contribute to the preference for transitions over transversions in both loop and stem regions. (4) For further understanding the relationship between Eleotris dispersal and sea current, the reproductive cycle of Eleotris acanthopoma was investigated. For over 1 year, gonad gross morphologies of fish were examined by using light microscopy and the plasma 17 beta-estradiol (E2) and testosterone (T) were analyzed by using ELISA. In male E. acanthopoma, plasma T concentrations show a single seasonal cycle, with a peak in summer (June to August) following the profile of gonadosomatic index. In females, plasma E2 concentrations are significantly elevated during summer in accordance with the GSI. Low temperatures and a short photoperiod in winter correlate well with the arrest of gonad maturation. Annual patterns of plasma E2 and T levels are similar to those of GSI changes existing in Eleotris acanthopoma of either sexes. These findings indicate that both temperature and photoperiod dominantly affect the reproductive cycle of Eleotris acanthopoma. (5) The systematic of genus Eleotris was carried out by isozyme electrophoresis and DNA sequences analysis. Both data sets achieve the similar conclusion, which indicates that the E. acanthopoma is sister group to E. melanosoma and E. fuscus. Among 17 loci analyzed, ADH-1 and MDH-2 can be used as biochemical key to identify these three species in Taiwan. E. faciatus were not found during this study period. Since the morphological characters of E. faciatus described by Chen (1968) can not distinguish from E. fuscus collected from Orchid Island. I suppose that the E. faciatus is synonymous to E. fuscus. E. oxycephalus was not collected either due to its rareness in Taiwan. The E. oxycephalus collected from Mainland China show distantly related with other three species. The phylogeny of this genus may need further investigation. The distributions of Eleotris species around Taiwan are different: E. fuscus is confined to the east coast whereas the E. acanthopoma and E. melanosoma to the west. Samples of E. acanthopoma from different localities show extremely low level of differentiation (FST = 0.019), indicates the genetic structures of this species among different collecting site are homogenous. Both differentiated distributions between species and homogenous genetic structures within species are due to the association of reproductive cycle with seasonal changed water current.
Subjects
親緣關係
生殖週期
reproductive cycle
分子演化
粒線體12S核醣核酸二級結構
塘鱧魚類
蝦虎魚類
eleotrid fishes
gobioidei
mitochondrial 12S rRNA secondary structure
molecular evolution
phylogenetic relationships
Publisher
國立臺灣師範大學
Type
doctoral thesis