博士 / 國立臺灣大學 / 動物學研究研究所 / 94 / The studies of population structures and speciation are major concerns of evolutionary and conservation biology. Primary freshwater fishes have little or no tolerance to saltwater. Their migration, dispersal and distribution depend upon direct connections between drainage basins. Thus, the population structure dynamics and species formation are associated with historical events which resulted from changes of hydrological conditions. The investigation of freshwater fishes can lead to important insights in evolutionary biology, and the results can provide useful information for conservation and management. Therefore, in this study, I use the primary freshwater, Zacco spp, in Taiwan as a model to elucidate several important issues, such as systematics, evolutionary history, and conservation in freshwater fishes.
The Asian common minnow, Zacco, is a cyprinid genus of small and colorful fishes, which are dominant components in the freshwater ecosystems of East Asia, including Japan, Korea, China and Taiwan. There were 7-10 species recognized in this genus. Two species were formerly known in Taiwan; Z. pachycephalus (Günther) is endemic to Taiwan, and Z. platypus (Temmick ＆Schlegel) is wide-spread in East Asia. However, no Zacco were recorded in the eastern part of Taiwan until 17 years ago. The recent studies showed that the eastern populations of Z. pachycephalus were artificially introduced from unknown origins by anglers.
In my initial field survey, I noticed apparent intraspecific morphological polymorphisms in currently recognized Zacco species, which prompted the thought that more than two species might occur in Taiwan. Consequently, I tackled the problems of Zacco species complex by two different approaches: morphologically and genetically. For morphological analyses, I used both meristic and morphometric characters (CHAPTER II). Furthermore, I integrated several genetic markers in identifying genetically distinct morphotypes: (1) AFLP (CHAPTER II) (2) mtDNA D-loop (CHAPTER III) (3) microsatellites (CHAPTER IV).
Both morphological analyses and AFLP suggest two genetically distinct morphotypes in each of the two Taiwanese Zacco (Z. pachycephalus and Z. platypus). Therefore, I proposed that there are four Zacco species in Taiwan, which are referred herein as Z. pachycephalus,Z. sp, Z. platypus and Z. evolans. Furthermore, I analyzed the mtDNA D-loop sequences for Taiwanese and Japanese Z. platypus. Phylogenetic analyses confirmed that the Taiwanese Z. platypus originated from Lake Biwa of Japan through multiple introductions. Besides, I examined additional molecular markers, microsatellite loci, in Taiwanese Zacco. The results again supported the genetic divergence of the four newly identified Zacco species. I also examined the geographic distribution and demographic histories of these Zacco species. It is evident that the basis and origin of the intra- and interspecific divergences of Taiwanese Zacco resulted from “multiple invasions” and “insular vicariances”. It is also evidenced that the eastern artificially introduced populations originated from both northern and central populations of Z. pachycephalus.
Finally, I summarized the results of my studies in CHAPTER V: (1) Four Zacco species are recognized in Taiwan and one of them was introduced by human activity. (2) Distinct geographical distribution and population genetic structure of these four species indicate the influences of historical geographic events on Zacco populations. In addition, I also showed preliminary results of karyoptypic studies and mtDNA phylogenetic analyses. I proposed that the genus Zacco is not a monophyletic group, but is paraphyletic with the genera Opsariichthys and Candidia. Therefore, my further study aims to clarify the taxonomic status of the genus Zacco.
| Identifer | oai:union.ndltd.org:TW/094NTU05312027 |
| Date | January 2006 |
| Creators | Gwo-Chin Ma, 馬國欽 |
| Contributors | Hon-Tsen Yu, 于宏燦 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 114 |
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