The sexual reproduction and population dynamics of the soft coral Asterospicularia laurae in southern Taiwan
Date Issued
2009
Date
2009
Author(s)
Lin, Yu-Chu
Abstract
Asterospicularia laurae (Utinomi 1951), a species of Xeniidae, has a restricted distribution on the shallow reef fronts at Hejie on the west coast of Hengchun Peninsula, southern Taiwan. Besides Taiwan, A. laurae has only been found in the Great Barrier Reef, Australia. This disjunct distribution is of particular interest. However, the information on life-history traits and ecology of A. laurae are lacking. In this thesis, the sexual reproduction and population dynamics of A. laurae at Hejie were studied by collecting samples every 1.5-2 months for histological studies and monitoring the changes of coral colonies in 5 belt transects from December 2007 to March 2009. Asterospicularia laurae is a gonochoric internal brooder, and the sex ratio is approximately 1:1. The smallest colony size of sexual maturation is 4-8 cm2, which indicates an early maturated case in octocorals. Gammetogensis was observed from late January to early July suggesting that the reproductive season is likely from February to July. Mature oocytes were approximately 260-300 μm in diameter. The planulae were found in coenenchyme from mid April to June thus planulation may occur during this period. The size-frequency distribution of A. laurae showed that the population was mainly composed of small colonies (< 4 cm2) during most of the sampling period, and then shifted to the dominance of large-sized colonies (> 64 cm2) in a short time due to the high intrinsic growth rate of colonies and fusion events. As a result, the total coverage also increased dramatically. The number of sexual recruits was 0.07-0.36 colonies/m2 per month and comprised approximately 1.5% to 8.2% of the total number of colonies throughout the study period. It revealed the contribution of sexual recruits to the population may be low. Benthic community associated with A. laurae was mainly composed of macroalgae (>50%). After the typhoon season, the size-frequency distribution were more centralized in the medium-sized colonies (4-64 cm2) due to the high whole-colony mortality of small colonies and high partial mortality of large colonies and the total coverage reduced by 28%. Meanwhile, the coverage of macroalgae decreased and the bare substrate increased. However, in March 2009, the total coverage of A. laurae was 6.21%, the highest during the study period, indicating the rapid recovery of A. laurae after disturbance. This study concluded that the population of Asterospicularia laurae in the area is highly contributed by asexual reproduction, reflecting an adaptation in a wave-swept and frequently disturbed habitat. However, due to the limited dispersal ability of asexual recruits and possibly high pre- and post-settlement mortality of sexual recruits, distribution of A. laurae was restricted distribution at Hejie, southern Taiwan.
Subjects
soft coral
sexual reproduction
population dynamics
disturbance
life histories
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-R95241214-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):f396cef7ff7f6fa91ad9854e0c57da33