Phylogeographic Analysis Suggests a Recent Population Bottleneck in the Rare Red Sea Tridacna squamosina

Giant clams are an important ecological component of coral reefs in the Red Sea, as they enhance the reef’s productivity and provide habitat that can increase diversity. Three species of giant clams, namely Tridacna maxima, T. squamosa, and T. squamosina have been described within the Red Sea. However, due to its scarcity, information about the distribution and ecology of T. squamosina in the Saudi Arabian Red Sea is still lacking. This study used DNA barcoding to confirm the identity of the rare T. squamosina in the Farasan Banks. Six mtCOI fragments (500 bp) of T. squamosina were successfully amplified using the SQUA-primers for the first time. We used our data along with 18 reference sequences (16S) from the online database to assess the genetic diversity and population structure of T. squamosina. Low genetic diversity among the T. squamosina populations inferred from the 16S sequences implies a recent bottleneck for this species, which is supported by their historically higher diversity based on the coalescent-based estimator. Given the small population abundance and limited genetic variation of T. squamosina, it may warrant immediate local protections such as biobanking and fertility preservation programs as well as effective integrated coastal zone management plans.

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A Multidisciplinary Approach for the Mapping, Automatic Detection and Morphometric Analysis of Ancient Submerged Coastal Installations: The Case Study of the Ancient Aegina Harbour Complex

Remote Sensing ◽

10.3390/rs13214462 ◽

2021 ◽

Vol 13 (21) ◽

pp. 4462

Author(s):

Nikos Georgiou ◽

Xenophon Dimas ◽

Elias Fakiris ◽

Dimitris Christodoulou ◽

Maria Geraga ◽

...

Keyword(s):

Morphometric Analysis ◽

Multidisciplinary Approach ◽

Coastal Zone Management ◽

Cost Effective ◽

Statistical Parameters ◽

Remotely Operated Vehicle ◽

Acoustic Data ◽

Zone Management ◽

Management Plans

The documentation of underwater cultural heritage (UCH) is the basis for sustainable maritime development including its protection, preservation, and incorporation in coastal zone management plans. In this study, we present a multidisciplinary, non-intrusive downscale approach for the documentation of UCH implemented on the coastal area of Aegina Island, Greece, where a unique submerged harbour complex is preserved. This approach succeeded in obtaining information that serves both geomorphological and archaeological purposes in a time- and cost-effective way, while obtaining information of centimeters to millimeters scale. The geomorphology of the area was mapped in detail through marine geophysical means while ancient submerged conical rubble structures and breakwaters were documented using automatic seafloor segmentation techniques, revealing previously unknown sites of archaeological interest. The structures’ parameters were extracted from the acoustic data to analyze their morphometry, while photogrammetry was realized using a Remotely Operated Vehicle to expose their micro-structure. The spatial distribution of the structures revealed the construction of a well-planned harbour complex with multiple passages and different possible functionalities. Finally, through the structures’ morphometric analysis (geometry and terrain statistical parameters) their preservation status was revealed, demonstrating the anthropogenic impact on the submerged ancient structures due to the modern harbor activity.

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Classification of Genus Acanthopanax in Korea and Genetic Diversity Using Allozymes

Silvae Genetica ◽

10.1515/sg-2005-0030 ◽

2005 ◽

Vol 54 (1-6) ◽

pp. 206-210 ◽

Cited By ~ 2

Author(s):

M. K. Huh ◽

H. W. Huh

Keyword(s):

Genetic Diversity ◽

Representative Sample ◽

Genetic Relationships ◽

Woody Species ◽

Small Population ◽

Geographic Ranges ◽

Low Level ◽

Low Genetic Diversity ◽

Population Sizes

Abstract Genus Acanthopanax is a long-lived woody species that is primarily distributed throughout Asia. Many species of this genus are regarded as medically and ecologically important. We evaluated a representative sample of the nine taxa with allozymes to estimate genetic relationships within the genus. As some Korean populations were isolated and patchily distributed, they exhibited a low level of genetic diversity. The narrow geographic ranges, artificial distribution of habitats, and small population sizes are proposed as factors contributing to low genetic diversity. Acanthopanax seoulense was similar to A. sessiliflorus, while a cluster of the A. rufinerve population is distant from any other species. A. senticosus is closely related to A. seoulense and A. sessiliflorus, whereas other species (A. koreanum) are more distinct from the Korean populations. Korean species are clustered together and clearly differentiated from the Chinese and Russian Acanthopanax taxa, genus Acanthopanax

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Photosynthetic performance of giant clams, Tridacna maxima and T. squamosa, Red Sea

Marine Biology ◽

10.1007/s00227-008-1019-7 ◽

2008 ◽

Vol 155 (2) ◽

pp. 211-221 ◽

Cited By ~ 40

Author(s):

Carin Jantzen ◽

Christian Wild ◽

Mohammed El-Zibdah ◽

Hilly Ann Roa-Quiaoit ◽

Christoph Haacke ◽

...

Keyword(s):

Red Sea ◽

Photosynthetic Performance ◽

Giant Clams ◽

Tridacna Maxima

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Genetic Diversity Within and Among Populations of Shorea Robusta Roxb. Ex Gaertn. In Bangladesh and Its Implications for Conservation

Bangladesh Journal of Botany ◽

10.3329/bjb.v50i2.54098 ◽

2021 ◽

Vol 50 (2) ◽

pp. 405-412

Author(s):

Pragga Saha Sharmi ◽

Md Abul Kashem ◽

Rifat Samad ◽

Mohammad Zabed Hossain

Keyword(s):

Genetic Diversity ◽

Population Size ◽

Isolation By Distance ◽

Genetic Erosion ◽

Mantel Test ◽

Small Population ◽

Deciduous Forests ◽

Shorea Robusta ◽

Low Genetic Diversity ◽

Geographical Regions

Fragmentation and reduction of natural population size render threats to the conservation of forest resources through depletion of genetic diversity. Hence, information on genetic structure of Sal (Shorea robusta Roxb. ex Gaertn.) populations is relevant for proper management and conservation of the tropical deciduous forests. The present study focused on assessing the genetic diversity of the populations of Sal which was the dominant tree species of the deciduous forests of Bangladesh. Plant leaf samples were collected from the three populations of Sal distributed in the three geographical regions including Madhupur tract in the districts Tangail and Gazipur and that of the districts of Cumilla and Dinajpur. DNA band profiles were generated using eight ISSR primers for a total of 13 samples taken from the three populations. Statistical analysis was done using PopGen 32 and GenAlEx 6.5 softwares. Principal coordinate analysis done on the DNA band profiles revealed that Sal populations of Madhupur tract and Cumilla positioned nearby while Dinajpur showed maximum genetic distance with that of Cumilla. Mantel test showed significant (p=0.05) correlation between genetic and geographic distances indicating “Isolation by Distance”. Data of the present study indicated higher genetic polymorphism (68.87%) in the Sal population of Madhupur tract compared to other two populations. Small population size of Sal of Dinajpur forest might be related with its low genetic diversity. Data of the present study suggest immediate attention for the conservation of Sal forests in Bangladesh before further genetic erosion occurs. Bangladesh J. Bot. 50(2): 405-412, 2021 (June)

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Light-dependent calcification in Red Sea giant clam <i>Tridacna maxima</i>

Biogeosciences ◽

10.5194/bg-16-2635-2019 ◽

2019 ◽

Vol 16 (13) ◽

pp. 2635-2650 ◽

Cited By ~ 8

Author(s):

Susann Rossbach ◽

Vincent Saderne ◽

Andrea Anton ◽

Carlos M. Duarte

Keyword(s):

Primary Production ◽

Red Sea ◽

Gross Primary Production ◽

Dry Mass ◽

Giant Clam ◽

Light Levels ◽

Unicellular Algae ◽

Giant Clams ◽

Intermediate Size ◽

Tridacna Maxima

Abstract. Tropical giant clams of the subfamily Tridacninae, including the species Tridacna maxima, are unique among bivalves as they live in a symbiotic relationship with unicellular algae and generally function as net photoautotrophs. Light is therefore crucial for these species to thrive. Here we examine the light dependency of calcification rates of T. maxima in the central Red Sea as well as the patterns of its abundance with depth in the field. Red Sea T. maxima show the highest densities at a depth of 3 m with 0.82±0.21 and 0.11±0.03 individuals m−2 (mean ± SE) at sheltered and exposed sites, respectively. Experimental assessment of net calcification (µmol CaCO3 cm−2 h−1) and gross primary production (µmol O2 cm−2 h−1) under seven light levels (1061, 959, 561, 530, 358, 244, and 197 µmol quanta m−2 s−1) showed net calcification rates to be significantly enhanced under light intensities corresponding to a water depth of 4 m (0.65±0.03 µmol CaCO3 cm−2 h−1; mean ± SE), while gross primary production was 2.06±0.24 µmol O2 cm−2 h−1 (mean ± SE). We found a quadratic relationship between net calcification and tissue dry mass (DM in gram), with clams of an intermediate size (about 15 g DM) showing the highest calcification. Our results show that the Red Sea giant clam T. maxima stands out among bivalves as a remarkable calcifier, displaying calcification rates comparable to other tropical photosymbiotic reef organisms such as corals.

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Low genetic diversity and inbreeding depression in Queensland Koalas

Wildlife Research ◽

10.1071/wr9930177 ◽

1993 ◽

Vol 20 (2) ◽

pp. 177 ◽

Cited By ~ 29

Author(s):

JMW Wilmer ◽

A Melzer ◽

F Carrick ◽

C Moritz

Keyword(s):

Genetic Diversity ◽

Mitochondrial Dna ◽

Inbreeding Depression ◽

Natural Populations ◽

Small Population ◽

Phascolarctos Cinereus ◽

Low Genetic Diversity ◽

History Of ◽

Biased Sex Ratio ◽

Two Populations

The amount of genetic variation in two natural populations of Queensland koalas (Phascolarctos cinereus adustus) was assessed by analysis of mitochondrial DNA. Levels and any adverse effects of inbreeding (inbreeding depression) were estimated from the pedigree of a well-characterised captive colony. Genetic diversity of mitochondrial DNA was found to be exceedingly low both within and between the two populations, but the variation detected was found to be strongly structured geographically. Inbreeding levels in the captive colony were moderate to high yet the only apparent evidence of inbreeding depression was a male-biased sex ratio. There was no evidence for decreased juvenile survivorship or growth rate with inbreeding. Because of the limited data it would be premature to conclude that koalas are relatively resistant to the effects of inbreeding. However, we suggest the hypothesis that koalas have a history of small population size, resulting in reduced susceptibility to inbreeding depression.

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