博士 / 臺灣大學 / 動物學研究所 / 98 / Abstract
The trichiurid fishes commonly called hairtails are important resources for various types of fisheries. Hairtails, being situated on the top of trophic pyramid, also play important roles in the demersal eco-systems. Due to highly specialized external appearance, the taxonomic status of hairtails is ambiguous as compared to the other fishes ranging from subfamily down to population levels. In this study, we used traditional measurements, geometric morphometrics and mitochondrial DNA as tool to reveal the phylogenetic relationships among genera, the species status of the genus Trichiurus and the population structure of T. japonicus in the western North Pacific.
The phylogenetic trees among 9 genera showed that both Aphanopodinae and Trichiurinae are monophyletic groups, but not for Lepidopodinae. We suggest putting Eupleurogrammus and Tentoriceps to Trichiurinae, because they all shared with apomorph of reduced anal and caudal fins. In addition, Assurger and Evoxymetopon showed so closed relationship that they should combine into a complete genus. Similarly, due to closed relationship between Lepturacanthus and Trichiurus and paraphyly of Lepturacanthus, we also suggest that they belong to a same genus.
The results from morphological and mitochondrial analyses showed that there are three valid species contained in the "T. lepturus" complex -- T. lepturus, T. japonicus and T. nanhaiensis. Traditional measurements showed that the ratio of measurements pairs were significant but overlapping. However, the shear (shape component, H) had fine resolution power to discriminate three species without overlapping. The first and second contributed of variables for the shear were represented body depth and preanal dorsal fin based length. Therefore, three species can be separated by using these two measurements compared to their total length. The phylogenetic relationships showed three distinct groups with no outliers. AMOVA showed that the major component of the variances concentrated among species (ΦCT = 0.967). The analyses of phylogeography of Trichiurus showed that all speciation events occurred around 8.5 million years ago in tropic waters among Indo-China, Sumatra and Borneo during the late Miocene.
The high haplotype diversities (0.97-0.99) with moderate nucleotide diversities (0.005 - 0.009) might result from historical bottleneck and subsequently population expansion. Populations in the area were sub-structured into two groups of the SCS and pan-ECS (ECS+TS+YS), confirmed by AMOVA (ΦCT = 0.165). These results indicate that the TS served as a barrier, which interrupts mixture between populations in the ECS and SCS. However, intermittent gene flow were also traceable in the phylogenetic analyses, indicating that the SCS gained a small number of migrants from the TS. Limited larval dispersal ability across marine boundaries and monsoon-influenced flow patterns in the TS well explain a non-panmictic structuring. Coalescent theory estimated that the populations were subdivided during the middle Pleistocene glacial maxima, and expanded when the ice sheets retreated. Two management stocks are suggested for conservation purposes; i.e., the ECS (including the TS) and the SCS, to strengthen current fishery regulatory programs.
| Identifer | oai:union.ndltd.org:TW/098NTU05312007 |
| Date | January 2010 |
| Creators | Chih-Hsiang Tzeng, 曾志翔 |
| Contributors | 丘臺生 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 122 |
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