生物在自然界的分布往往都不是均勻的，常有聚集（aggregation）的現象，隨著物種的不同，聚集的機制與尺度各有不同。東沙島面積僅約1.7平方公里且為連續沙灘、海岸林棲地，然而東沙島上的優勢物種皺紋陸寄居蟹（Coenobita rugosus）卻有高度分布不均的現象，因此本研究欲探討造成此物種在海岸上分布不均的現象和原因，一共提出三個假說。分別為陸域棲地偏好、入添數不均以及陸地族群個體移動，並以計算東沙島海岸林遮蔭面積、喜好食物海草碎屑的位置、逐月體型調查及標識放流的方式來驗證假說。本研究在全島周圍設了12個測站，自2017年9月至2018年8月總共進行12次逐月全島海岸皺紋陸寄居蟹數量調查，發現皺紋陸寄居蟹集中棲息在東沙島東南邊海岸的3個測站，有65%的數量聚集。東沙島外圍沙灘有海岸林覆蓋，能提供皺紋陸寄居蟹白天躲藏之處以及食物來源，作為另一食物的海草碎屑隨著季節風向不同而堆積在不同海岸上，而調查發現皺紋陸寄居蟹整年都聚集在東南海岸，分布與植被面積或海草碎屑皆無顯著相關，因此不支持陸域棲地偏好假說。標識放流的實驗結果顯示皺紋陸寄居蟹成體在7天內不會移動超過40公尺，6周內不會進行超過500公尺的大尺度的遷徙，否定陸地族群個體移動假說。為期一年之逐月調查中直接捕捉到大量幼蟹入添4次，並且用逐月的體型頻度回推出一年共有6次入添，且有70%的入添量集中出現在島東南方海岸測站G，該海岸也是皺紋陸寄居蟹的熱點，終年都有完整的體型群，此現象支持入添數不均假說，推測東沙島上皺紋陸寄居蟹的分布趨勢是由幼蟹入添的地點有關。

Aggregation in animal distribution is a common phenomenon among all species in different spatial scales. Various mechanisms causing the aggregation of animal distributions were described. The present study focused on the abundance heterogeneity of the terrestrial hermit crabs, Coenobita rugosus, on Dongsha Island, South China Sea. Coenobita rugosus is a common land hermit crab around Indo-Pacific Ocean, also the predominant on Dongsha Island. Dongsha Island is only 1.7 km2 in area with continuous beach and coast forest as habitat for C. rugosus. We conducted 12 monthly round-island surveys for local abundance and body sizes of the land hermit crabs during September 2017 to August 2018. The results indicated that 65% of Coenobita rugosus aggregated at the Southwest coastline which only contained 3 out of 12 sampling sites and occupied 12.5% of the total coastline. We hypothesized that the uneven distribution of Coenobita rugosus may originate from the (1) habitat preferences of the land population, (2) uneven numbers of post-larvae recruited to varies coastal localities, and (3) the migration by themselves. To testify our hypotheses, we compared the crab abundance with the land plant area and the availability of seagrass debris piles which were both considered as the important hiding area and food source, but there are no correlations between them. According to the results of mark and release experiments in small and large scales, the recaptured crabs were mostly found in the original location we released them (≤40m) in 7 days, and this species did not migrate over >500m in 6 weeks. Six recruitment pulse events were recorded in a year during our surveys, whether directly and indirectly. About 70% of the recruited crabs(PL<4mm) were found directly at one sampling site in Southwest part of Dongsha Island, which was also the most abundant for adult crabs(PL>4mm). We inferred that the patchiness of C. rugosus on Dongsha Island may originate from the uneven planktonic juvenile recruitment.

論文審定書…………………………………………………………i
誌謝………………………………………………………………………ii
中文摘要………………………………………………………………iii
英文摘要………………………………………………………………iv
前言……………………………………………………………………1
材料與方法……………………………………………………………4
結果………………………………………………………………………7
討論……………………………………………………………………10
參考文獻………………………………………………………………14

施習德。（2012）。東沙島潮間帶至陸域蟹類與寄居蟹調查。海洋國家公園管
理處。
郭城孟、楊曼妙、張家維、高美芳。（2010）。漂流萬里，東沙草木誌。海洋
國家公園管理處。
李亦騏。（2018）。東沙島、小琉球、墾丁的皺紋陸寄居蟹（Coenobita
rugosus）對貝殼之利用。碩士論文。台中：國立中興大學生命科學系。
許嘉軒。（2015）。驗證造成臺灣周遭生態島之皺紋陸寄居蟹蟹（Coenobita
rugosus）體型差異機制。碩士論文。高雄：國立中山大學海洋科學系。
Bertness, M. D. (1981). The influence of shell-type on hermit crab growth rate and
clutch size (Decapoda, Anomura). Crustaceana, 40(2), 197-205.
Burggren, W. W., & McMahon, B. R. (Eds.). (1988). Biology of the land crabs.
Cambridge University Press.
Doi, W., Mizutani, A., & Kohno, H. (2016). Larval Release and Associated Tree-
Climbing Behavior of the Land Hermit Crab Coenobita Violascens (Anomura: Coenobitidae). Journal of Crustacean Biology, 36(3), 279-286.
Elliott. J. M. (1993). Some methods for the statistical analysis of samples of benthic
invertebrates. Freshwater biological association scientific publication, 25, 1-
159.
Farrell, T. M., Bracher, D., & Roughgarden, J. (1991). Cross‐shelf transport causes
recruitment to intertidal populations in central California. Limnology and Oceanography, 36(2), 279-288.
Gebauer, P.; PASCHKE, K.; ANGER, Klaus. Costs of delayed metamorphosis:
reduced growth and survival in early juveniles of an estuarine grapsid crab, Chasmagnathus granulata. Journal of Experimental Marine Biology and Ecology, 1999, 238.2: 271-281.
Greenaway, P. (2003). Terrestrial adaptations in the anomura (Crustacea:
Decapoda). Memoirs of Museum Victoria, 60(1), 13-26.
Hamasaki, K., Ishiyama, N., & Kitada, S. (2015a). Settlement behavior and substrate
preference of the coconut crab Birgus latro megalopae on natural substrata in the laboratory. Journal of Experimental Marine Biology and Ecology, 468, 21-28.
Hamasaki, K., Hatta, S., Ishikawa, T., Yamashita, S., Dan, S., & Kitada, S. (2015b).
Emigration behavior and molting during the sea‐to‐land transition of terrestrial hermit crabs under laboratory conditions. Invertebrate Biology, 134(4), 318-331.
Hamasaki, K., Kato, S., Hatta, S., Murakami, Y., Dan, S., & Kitada, S. (2014). Larval
development and emigration behaviour during sea-to-land transition of the land hermit crab Coenobita brevimanus Dana, 1852 (Crustacea: Decapoda: Anomura: Coenobitidae) under laboratory conditions. Journal of Natural History, 48(17-18), 1061-1084.
Hamasaki, K., Kato, S., Murakami, Y., Dan, S., & Kitada, S. (2015c). Larval growth,
development and duration in terrestrial hermit crabs. Sexuality and Early Development in Aquatic Organisms, 1(2), 93-107.
Hamasaki, K., Fujikawa, S., Iizuka, C., Sanda, T., Tsuru, T., Imai, H., & Kitada, S.
(2018). Recruitment to adult habitats in terrestrial hermit crabs on the coast of Ishigakijima Island, Ryukyu Archipelago, Japan. Invertebrate Biology, 137(1), 3-16.
Hartnoll, R. G., & Clark, P. F. (2006). A mass recruitment event in the land crab
Gecarcinus ruricola (Linnaeus, 1758) (Brachyura: Grapsoidea: Gecarcinidae),
and a description of the megalop. Zoological Journal of the Linnean
Society, 146(2), 149-164.
Hartnoll, R. G., & Hawkins, S. J. (1985). Patchiness and fluctuations on moderately
exposed rocky shores. Ophelia, 24(1), 53-63.
Hsu, C. H., & Soong, K. (2017). Mechanisms causing size differences of the land
hermit crab Coenobita rugosus among eco-islands in Southern Taiwan. PloS One, 12(4), e0174319.
Huang, Y. H., Lee, C. L., Chung, C. Y., Hsiao, S. C., & Lin, H. J. (2015). Carbon
budgets of multispecies seagrass beds at Dongsha Island in the South China Sea. Marine Environmental Research, 106, 92-102.
Mau, M., Südekum, K. H., Johann, A., Sliwa, A., & Kaiser, T. M. (2009). Saliva of
the graminivorous Theropithecus gelada lacks proline‐rich proteins and tannin‐binding capacity. American Journal of Primatology: Official Journal of the American Society of Primatologists, 71(8), 663-669.
Nakasone, Y. (1988). Land hermit crabs from the Ryukyus, Japan, with a description
of a new species from the Philippines (Crustacea, Decapoda, Coenobitidae). Zoological Science, 5(1), p165-178.
Nakasone, Y. (2001). Reproductive biology of three land hermit crabs (Decapoda:
Anomura: Coenobitidae) in Okinawa, Japan. Pacific Science, 55(2), 157-169.
O'Beirn, F. X., Luchenbach, M. W., Nestlerode, J. A., & Coates, G. M. (2000).
Toward design criteria in constructed oyster reefs: oyster recruitment as a function of substrate type and tidal height. National Shellfisheries Association.
Pechenik, J. A. (1990). Delayed metamorphosis by larvae of benthic marine
invertebrates: does it occur? Is there a price to pay? Ophelia, 32(1-2), 63-94.
Pineda, J. (1991). Predictable upwelling and the shoreward transport of planktonic
larvae by internal tidal bores. Science, 253(5019), 548-549.
Pocheville, A. (2015). The ecological niche: history and recent controversies.
In Handbook of evolutionary thinking in the sciences (pp. 547-586). Springer, Dordrecht.
Sallam, W. S., & Mantelatto, F. L. (2010). Population features and breeding season of
the land hermit crab Coenobita scaevola (Forskäl, 1775) (Anomura, Coenobitidae) from Wadi El-Gemal, South Red Sea, Egypt. Nauplius, 18(1), 25-33.
Ueta, M., Melville, D. S., Wang, Y., Ozaki, K., Kanai, Y., Leader, P. J. & Kuo, C.
Y. (2002). Discovery of the breeding sites and migration routes of Black‐faced Spoonbills Platalea minor. Ibis, 144(2), 340-343.
Yu, Yat-tung; Wong, Chi-chun. (2016). The International Black-faced Spoonbill
Census: 15-17 January 2016. Hong Kong Bird Watching Society.