Reproductive isolation among Acropora Species (Scleractinia: Acroporidae) in a marginal coral assemblage

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

The ETS/IGS region in a lower animal, the seawhip, Junceella fragilis (Cnidaria: Anthozoa: Octocorallia): compactness, low variation and apparent conservation of a pre-rRNA processing signal with fungi

We determined the nucleotide sequence of an atypically short intergeneic spacer/external transcribed spacer (IGS/ETS) region in the seawhip, Junceella fragilis, and identified an 8-bp motif at the 5'-ETS/18S rDNA boundary closely resembling a fungal pre-rRNA A1 cleavage signal. This apparent conservation of processing signals was unexpected, as no corresponding sequence has previously been reported in any animal. The J. fragilis IGS sequence lacks repetitive motifs of the type typical of higher animals, but a microsatellite is present in the putative 3'-ETS. Comparisons of the IGS between geographically isolated populations of J. fragilis indicate an unexpected lack of sequence variation

Reproductive isolation among Acropora Species (Scleractinia:\ud Acroporidae) in a marginal coral assemblage

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