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Population Genetic Structure of the Pelagic Goby, Sufflogobius

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Population Genetic Structure of the Pelagic Goby, Sufflogobius CORE Metadata, citation and similar papers at core.ac.uk Provided by Nature Precedings Population genetic structure of the pelagic goby, Sufflogobius bibarbatus, in the Northern Benguela ecosystem, based on PCR- RFLP analysis of the mitochondrial control region and the ND 3 / 4 region M.Phil Thesis Nature Precedings : hdl:10101/npre.2009.3007.1 Posted 31 Mar 2009 Pallagae Mangala Chathura Surendra De Silva Department of Biology University of Bergen, Norway 2005 Population genetic structure of the pelagic goby, Sufflogobius bibarbatus, in the Northern Benguela ecosystem, based on PCR-RFLP analysis of the mitochondrial control region and the ND 3 ⁄ 4 region. By Pallagae Mangala Chathura Surendra De Silva A thesis submitted in partial fulfilment of the requirements for the degree of Master of Philosophy In Fisheries Biology and Fisheries Management Nature Precedings : hdl:10101/npre.2009.3007.1 Posted 31 Mar 2009 Department of Biology University of Bergen Bergen, Norway 2005 Table of Contents Acknowledgements…………………………………………………………………......2 Abstract…………………………………………………………………………………3 1. Introduction ……………………………………………………………………4 2. Materials & Methods …………………………………………………………..8 2.1. Sampling ……………………………………………………………………8 2.2. DNA Extraction……………………………………………………………10 2.3. PCR Methodology …………………………………………………………10 2.4. Restriction Fragment Length Polymorphism (RFLP) analysis …………12 2.5. Data Analysis ………………………………………………………………14 3. Results …………………………………………………………………………16 3.1. PCR products and Restriction Patterns ………………………………… 16 3.2. Haplotype numbers and Frequency Distribution………………………..16 3.3. Unique Haplotypes ……………………………………………………….19 3.4. Haplotype and Nucleotide Diversities ……………………………………19 3.5. Exact Test and Chi Square test …………………………………………..21 4. Discussion ……………………………………………………………………..23 4.1. General Overview …………………………………………………………23 4.2. Selection of Methods ………………………………………………………24 Nature Precedings : hdl:10101/npre.2009.3007.1 Posted 31 Mar 2009 4.3. Selection of Materials and Sampling Sites ……………………………….25 4.4. Variation within Areas ……………………………………………………26 4.5. Population Studies ………………………………………………………..27 4.6. Genetic Deviation through Haplotype Frequencies ……………………..28 4.7. Contributing Factors ……………………………………………………..29 5. Conclusions ……………………………………………………………………34 6. References ……………………………………………………………………..35 7. Appendix………………………………………………………………………..44 1 Acknowledgements I am very much grateful to my supervisor, Professor Gunnar Naevdal at Department of Biology, University of Bergen, Norway and co supervisor Dr K.B Suneetha at Department of Zoology, University of Ruhuna, Sri Lanka for their guidance and encouragement through out my study. The immense help given by Professor Anne Gro Salvanes at Department of Biology is highly appreciated. I am really thankful for your inspiring supervision, indispensable guidance, sincerity and invaluable suggestions on my work. It is very pleasant to work in the genetics lab in the Department of Biology and the technical assistance given by Solveig Thorkildsen during the laboratory work is very much appreciated. Special thanks for Dr Geir Dahle and Dr Torild Johansen for their enormous support in statistical analysis. I admire the support given by Berit Ogland and Kristin Paulsen through out my study period. Also it is highly commendable all the support and assistance given by all my friends during my difficult times. I am grateful to Pham Mai Huong for your lovely smile, affection and kindness towards me. I am very much flattered by the invaluable help given by my best friends Janna, David, Srisuda, Hilka, Janya, Stutada, Ketut and Diep. All of you deserved the credit for this work otherwise I am sure that I could have ended up with nothing. Nature Precedings : hdl:10101/npre.2009.3007.1 Posted 31 Mar 2009 Finally but not at last, my special gratitude to my parents, for taking me this journey this much. Although you are far away from me, you never forgot me and in my heart I was always living with you. I am very much pleased for your love, trust and everlasting kindness. 2 Abstract Polymorphism within the mitochondrial NADH-3,4 dehydrogenase(ND-3/4)) and control region (D-Loop) was studied by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of Sufflogobius bibarbatus (Pelagic Goby) population in the Northern Benguela ecosystem. Three major geographical areas representing the north-south axis (Ludritz, Walvis Bay and North of Ambrose Bay) were selected. Polymorphism was detected using three and two restriction enzymes respectively in ND- 3 / 4 and D-Loop regions, and a total number of 25 composite haplotypes were identified. The most common haplotype accounted for 36% of 238 individuals. Recorded haplotype diversities were quite high, ranging 0.70 to 0.86.The highest haplotype diversity was found in Walvis Bay followed by Ludritz and North of Ambrose Bay. Pairwise Fst values among regions indicated that significantly population differentiation existing. The Monte Carlo test revealed a significant difference among three geographical areas (P <0.05). Pairwise comparisons based on haplotype frequencies revealed significant differences between Ludritz and Walvis Bay (P < 0.05) and Ludritz and North of Ambrose Bay (P < 0.01) while no difference was found between Walvis Bay and North of Ambrose Bay (P >0.05).Similar observations were found by Exact test for haplotype frequencies. This study has shown existence of population subdivision of the pelagic goby in the Northern Benguela. Combination of factors like complex circulation pattern, physical barrier around Moeb Bay and adaptive selection can be Nature Precedings : hdl:10101/npre.2009.3007.1 Posted 31 Mar 2009 contributed to the observed divergence. Identified population sub structure will be vital in future decision and policy making of the proposed ecosystem based management in the Benguela region. 3 1. Introduction The Benguela ecosystem is one of the four most productive ecosystems in the world (Cushing, 1971). It is a unique coastal upwelling system in the world of ocean, bounded at both equatorward and poleward ends by warm water regimes. The region, where cool upwelled coastal waters to be found includes coast of Namibia and the western coast of South Africa. The Northern limit is bounded by Angola system and southern by Agulhas current retroflection area (Shannon, 1985). Previous studies have divided the Benguela ecosystem into two major oceanographic areas, a Northern and Southern region. The Northern Benguela represents Cunene river mouth to 290 S. The conventional border which divides the Northern and Southern Benguela is around Orange River mouth (290 S). And from the border the Southern Benguela extends to East London (280 E) (Jarre- Teichmann et al, 1998). The ecosystem is extremely vital for the region due to its supportive role in commercially valuable fisheries. Sufflogobius bibarbatus (Van Bonde, 1923), commonly known as pelagic goby, is endemic to the region and one of the key species in the Benguela ecosystem. Crawford (1987) describes the distribution of this species in coastal shelfwaters between 220S and 270S. More specifically the highest concentrations of pelagic goby can be found mainly between Walvis Bay and Ludertiz (Hewitson and Cruickshank, 1993). Also it is suggested that the distribution can be expanded as far north as Cunnene River (Cruickshank, 1980). The larval distribution has been recorded between 170 30`S and 330 30`S and over the 50–300m isobath (O`Toole, 1977; Shelton et al, 1986). The abundance Nature Precedings : hdl:10101/npre.2009.3007.1 Posted 31 Mar 2009 of the larvae could be seen through out the year, but peak abundance occurs during intense upwelling periods. Juveniles of this species are epipelagic and adults are found in deep waters. They prefer more open substrates and are particularly associated with soft substrate enrichd with benthic food (Gibbons et al, 2000). They spend much of their time in the water column during the night. It leads to the fact that pelagic goby use demersal habitats mainly for shelter (Gibbons et al, 2002). Early studies indicate that pelagic goby is mainly feeds on phytoplankton (Crawford, 1987). This is quite contradictory to recent studies where no phytoplankton has been recorded as their main food source (Gibbons et al, 2002). 4 Ecologically pelagic goby plays an important role in the Benguela ecosystem. It is one of the key prey species in the food chain. Shannon et al (1999) estimated that 1.5 million tons of gobies are prey for Benguela fish species such as hake (Merluccus capensis), penguin (Spheniscus demersus), Cape fur seal (Arctocephalus pusillus pusillus) and skate (Raja clarata). Their importance as a prey is clearly highlighted by reduction of hake and horse mackerel stocks, which reduce the predatory pressure on this species. During the same time Penguin and Cape fur seal shifted their prey items such as hake and horse mackerel to the pelagic goby (Hewitson and Cruickshank, 1993; Binachi, 1999). O`Toole (1977) reported that spawning of the pelagic goby and commercially important pilchard, Sardinops ocellatus, is occurring at the same time, hence they might be competing for same food resources. So in spite of few studies on pelagic goby, it is important to understand its role in the food web. In spite of the ecological role, still this species has a very limited commercial value in major fisheries in the region. It is estimated out that annual catch of this species as 0.001 Tons/ Km2/ year. This amount seems negligible
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