Vol. 51 No. 1, 2012

Reproductive Isolation among Acropora Species (Scleractinia: Acroporidae) in a Marginal Coral Assemblage

Nuwei Vivian Wei^1,2, Hernyi Justin Hsieh³, Chang-Feng Dai², Carden C. Wallace⁴, Andrew H. Baird⁵, and Chaolun Allen Chen^1,2,6,*

^{1Biodversity Research Center, Academia Sinica, Nangang, Taipei 115, Taiwan
2Institute of Oceanography, National Taiwan Univ., Taipei 106, Taiwan
3Marine Biology Research Center, Taiwan Fishery Research Institute, Penghu 880, Taiwan
4Museum of Tropical Queensland, Townsville Q4810, Australia
5ARC Centre of Excellence for Coral Reef Studies, James Cook Univ., Townsville Q4811, Australia
6Life Science Institute, National Taitung Univ., Taitung 904, Taiwan}

^{Nuwei Vivian Wei, Hernyi Justin Hsieh, Chang-Feng Dai, Carden C. Wallace, Andrew H. Baird,and Chaolun Allen Chen (2012) Hybridization was proposed as being an important source of evolutionary novelty in broadcast-spawning reef-building corals. In addition, hybridization was hypothesized to be more frequent at the periphery of species’ ranges and in marginal habitats. We tested the potential for hybridization in 2 ways: observations of the time of spawning and non-choice interspecific fertilization experiments of 4 sympatric Acropora species in a non-reefal coral assemblage at Chinwan Inner Bay (CIB), Penghu Is., Taiwan. We found that colonies of more than 1 species rarely released gametes at the same time, thus limiting the opportunities for cross-fertilization in the wild. On the few occasions when different species released gametes in synchrony, interspecific fertilization in experimental crosses was uniformly low (the proportion of eggs fertilized ranged 0%-4.58% with a mode of 0%), and interspecific-crossed embryos ceased development and died within 12 h after initially being fertilized. Ecological and experimental analyses indicated that reproductive isolation exists in these 4 Acropora species even though they have the opportunities to spawn synchronously, suggesting that hybridization is not very frequent in this marginal coral habitat at CIB.}

^{Key words: Acropora, Hybridization, Synchronous spawning, Marginal coral community.}

^{*Correspondence: E-mail:cac@gate.sinica.edu.tw}