Poh-Kheng Ng, Phaik-Eem Lim* and Siew-Moi Phang Small ... · PDF file13 populations of...
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Botanica Marina 2015; 58(3): 175–187 *Corresponding author: Phaik-Eem Lim, Institute of Ocean and Earth Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia, e-mail: [email protected]; Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia Poh-Kheng Ng and Siew-Moi Phang: Institute of Ocean and Earth Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia; and Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia Poh-Kheng Ng, Phaik-Eem Lim* and Siew-Moi Phang Small-scale genetic structure of Gracilaria salicornia and its red algal parasite, G. babae (Gracilariaceae, Rhodophyta), in Malaysia Abstract: The present study compares genetic structure from the plastid rbcL, mitochondrial cox1, and nuclear internal transcribed spacer (ITS) sequences among 13 populations of Gracilaria salicornia and its red algal parasite, G. babae, in Malaysia. Owing to the unique biology of the red algal parasite, identical phylogeogra- phies were inferred from the rbcL and cox1 sequences in both G. babae and its host, G. salicornia. Despite the low genetic variation, rbcL and cox1 showed a concordant phy- logeographic split that largely corresponds to Peninsular Malaysia and East Malaysia, except for a sample from East Malaysia that was consistently grouped with samples from the peninsula. On the other hand, G. salicornia was separated from G. babae in the midpoint-rooted phylog- eny inferred from ITS data despite the failure to retrieve the two taxa in reciprocal monophyly. Gracilaria sali- cornia was less diverse and lacked apparent geographic structure. In contrast, the ITS data revealed considerable genetic diversity and fine-scale genetic structuring in G. babae within Malaysian waters, probably as a result of adaptation to the local host population. Keywords: Gracilaria babae; Gracilaria salicornia; ITS; Malaysia; phylogeography. DOI 10.1515/bot-2014-0071 Received 28 October, 2014; accepted 22 April, 2015 Introduction Southeast Asia is characterized by a complex geological history with fluctuating sea levels during glacial periods. Repeated exposure and flooding of the Sunda and Sahul shelves resulted in the isolation of marine taxa, provid- ing an important mechanism for population differen- tiation and incipient speciation. In addition, changes in the oceanographic dynamic system have been shown to have had a strong influence on marine algal species distribution and genetic connectivity in Southeast Asia (Kantachumpoo et al. 2014, Wichachucherd et al. 2014). Malaysia comprises two non-contiguous regions, partly on a peninsula of the Asian mainland (Peninsular Malaysia) and partly on the northern third of the island of Borneo (East Malaysia). These regions are separated by the South China Sea, the surface current of which is influ- enced by the southwest and northeast monsoons. The Malacca Strait runs along the western coast of Peninsular Malaysia and carries water from the Pacific Ocean via the South China Sea to the Andaman Sea off the Indian Ocean (Wyrtki 1961). Such oceanographic conditions could have promoted genetic connectivity in marine taxa. To date, reports on the genetic structure and phylogeography inferred from marine algal species in Malaysia have been based only on Gracilaria changii (B.M. Xia et I.A. Abbott) I.A. Abbott, J. Zhang et B.M. Xia from the peninsula (Yow et al. 2011, 2013). The red alga Gracilaria salicornia (C. Agardh) E.Y. Dawson is widely distributed from the tropics to the sub- tropics in the Indo-Pacific (Tseng and Xia 1999, Nelson et al. 2009, Yang et al. 2012). Lim and Phang (2004) reported the occurrence of G. salicornia along the western and southern coast of Peninsula Malaysia. Sterile, tet- rasporic, and female plants with cystocarps are always found throughout the year, implying the maintenance of populations through both asexual and sexual reproduc- tion in G. salicornia. Given the high reproductive potential exhibited, this species may thus be a good model for inves- tigating the genetic diversity, population connectivity, and barriers to gene flow of seaweeds in Malaysia. Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/10/15 8:27 AM
Transcript of Poh-Kheng Ng, Phaik-Eem Lim* and Siew-Moi Phang Small ... · PDF file13 populations of...
Botanica Marina 2015; 58(3): 175–187
*Corresponding author: Phaik-Eem Lim, Institute of Ocean and Earth Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia, e-mail: [email protected]; Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, MalaysiaPoh-Kheng Ng and Siew-Moi Phang: Institute of Ocean and Earth Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia; and Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
Poh-Kheng Ng, Phaik-Eem Lim* and Siew-Moi Phang
Small-scale genetic structure of Gracilaria salicornia and its red algal parasite, G. babae (Gracilariaceae, Rhodophyta), in Malaysia
Abstract: The present study compares genetic structure from the plastid rbcL, mitochondrial cox1, and nuclear internal transcribed spacer (ITS) sequences among 13 populations of Gracilaria salicornia and its red algal parasite, G. babae, in Malaysia. Owing to the unique biology of the red algal parasite, identical phylogeogra-phies were inferred from the rbcL and cox1 sequences in both G. babae and its host, G. salicornia. Despite the low genetic variation, rbcL and cox1 showed a concordant phy-logeographic split that largely corresponds to Peninsular Malaysia and East Malaysia, except for a sample from East Malaysia that was consistently grouped with samples from the peninsula. On the other hand, G. salicornia was separated from G. babae in the midpoint-rooted phylog-eny inferred from ITS data despite the failure to retrieve the two taxa in reciprocal monophyly. Gracilaria sali-cornia was less diverse and lacked apparent geographic structure. In contrast, the ITS data revealed considerable genetic diversity and fine-scale genetic structuring in G. babae within Malaysian waters, probably as a result of adaptation to the local host population.
Keywords: Gracilaria babae; Gracilaria salicornia; ITS; Malaysia; phylogeography.
DOI 10.1515/bot-2014-0071Received 28 October, 2014; accepted 22 April, 2015
Introduction
Southeast Asia is characterized by a complex geological history with fluctuating sea levels during glacial periods. Repeated exposure and flooding of the Sunda and Sahul shelves resulted in the isolation of marine taxa, provid-ing an important mechanism for population differen-tiation and incipient speciation. In addition, changes in the oceanographic dynamic system have been shown to have had a strong influence on marine algal species distribution and genetic connectivity in Southeast Asia (Kantachumpoo et al. 2014, Wichachucherd et al. 2014).
Malaysia comprises two non-contiguous regions, partly on a peninsula of the Asian mainland (Peninsular Malaysia) and partly on the northern third of the island of Borneo (East Malaysia). These regions are separated by the South China Sea, the surface current of which is influ-enced by the southwest and northeast monsoons. The Malacca Strait runs along the western coast of Peninsular Malaysia and carries water from the Pacific Ocean via the South China Sea to the Andaman Sea off the Indian Ocean (Wyrtki 1961). Such oceanographic conditions could have promoted genetic connectivity in marine taxa. To date, reports on the genetic structure and phylogeography inferred from marine algal species in Malaysia have been based only on Gracilaria changii (B.M. Xia et I.A. Abbott) I.A. Abbott, J. Zhang et B.M. Xia from the peninsula (Yow et al. 2011, 2013).
The red alga Gracilaria salicornia (C. Agardh) E.Y. Dawson is widely distributed from the tropics to the sub-tropics in the Indo-Pacific (Tseng and Xia 1999, Nelson et al. 2009, Yang et al. 2012). Lim and Phang (2004) reported the occurrence of G. salicornia along the western and southern coast of Peninsula Malaysia. Sterile, tet-rasporic, and female plants with cystocarps are always found throughout the year, implying the maintenance of populations through both asexual and sexual reproduc-tion in G. salicornia. Given the high reproductive potential exhibited, this species may thus be a good model for inves-tigating the genetic diversity, population connectivity, and barriers to gene flow of seaweeds in Malaysia.
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