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Conspecificity of two morphologically distinct calcified red algae from the northwest Pacific Ocean: Galaxaura pacifica and G. filamentosa (Galaxauraceae, Rhodophyta)

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ABSTRACT

Background: Members of the calcified red algal genus, Galaxaura, are distributed predominantly in warm temperate, subtropical, and tropical regions worldwide. The capacity of these algae to form calcified thalli could play a critical role in the carbon cycle of these ecosystems. Previous studies have suggested that the reported species diversity of Galaxaura may be exaggerated due to a lack of knowledge regarding external morphological differences between gametophytic and tetrasporophytic plants (or among different life stages) of a single species.

Results: To examine this issue, this study collected specimens of two morphologically distinct Galaxaura from Taiwan and the Philippines. These specimens were initially identified as two species (G. pacifica Tanaka and G. filamentosa Chou ex Taylor) based on their morphological features. Our molecular analyses, however, unexpectedly showed that these two specimens shared 100% identical rbc L sequences, indicating that they represented a single species comprising two distinct external morphologies. Furthermore, our extensive observations and molecular analyses on several specimens from different locations in southern Taiwan has revealed that these morphological differences could be due to seasonal variation.

Conclusions: This study proposes that G. “filamentosa” from the Philippines could represent the remnants of the lower villous part of older gametophytic plants of G. pacifica after senescence of the upper smooth part of the thallus. As such we propose that these two previously distinct algal species from the northwest Pacific Ocean as a single species, G. pacifica. This study shows that the biodiversity of the calcified red algae Galaxaura could be overestimated without the assistance of molecular tools. Additionally, this study provides insights into the biodiversity and unique biology of the calcified red algae Galaxaura.

Electronic supplementary material: The online version of this article (doi:10.1186/1999-3110-54-1) contains supplementary material, which is available to authorized users.

No MeSH data available.


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Drawings of carpogonial branches ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Type I carpogonial branch pattern showing that the carpogonial branch initiation replaces one of cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h), and the basal cell (b); (B) Type II carpogonial branch pattern showing that the carpogonial branch initiation arises between cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowhead), and the basal cell (b); (C) Type III carpogonial branch showing a mixture of type I and type II carpogonial branch pattern. The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowheads), and the basal cell (b) bearing several sterile filaments (arrows); (D) Developed type I carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and two basal cells (b1, b2) producing many sterile filaments (arrows); (E) Developed type III carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and the basal cell (b) producing many sterile filaments (arrows).
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Fig9: Drawings of carpogonial branches ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Type I carpogonial branch pattern showing that the carpogonial branch initiation replaces one of cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h), and the basal cell (b); (B) Type II carpogonial branch pattern showing that the carpogonial branch initiation arises between cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowhead), and the basal cell (b); (C) Type III carpogonial branch showing a mixture of type I and type II carpogonial branch pattern. The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowheads), and the basal cell (b) bearing several sterile filaments (arrows); (D) Developed type I carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and two basal cells (b1, b2) producing many sterile filaments (arrows); (E) Developed type III carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and the basal cell (b) producing many sterile filaments (arrows).

Mentions: (FiguresĀ 5A-5N, 6A-6E, 7A-7C, 8A-8H, 9A-9E and 10A-10G).Figure 6


Conspecificity of two morphologically distinct calcified red algae from the northwest Pacific Ocean: Galaxaura pacifica and G. filamentosa (Galaxauraceae, Rhodophyta)
Drawings of carpogonial branches ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Type I carpogonial branch pattern showing that the carpogonial branch initiation replaces one of cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h), and the basal cell (b); (B) Type II carpogonial branch pattern showing that the carpogonial branch initiation arises between cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowhead), and the basal cell (b); (C) Type III carpogonial branch showing a mixture of type I and type II carpogonial branch pattern. The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowheads), and the basal cell (b) bearing several sterile filaments (arrows); (D) Developed type I carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and two basal cells (b1, b2) producing many sterile filaments (arrows); (E) Developed type III carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and the basal cell (b) producing many sterile filaments (arrows).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383922&req=5

Fig9: Drawings of carpogonial branches ofGalaxaura pacificaTanaka from Small Port, KNP, southern Taiwan.(A) Type I carpogonial branch pattern showing that the carpogonial branch initiation replaces one of cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h), and the basal cell (b); (B) Type II carpogonial branch pattern showing that the carpogonial branch initiation arises between cortical filaments (co). The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowhead), and the basal cell (b); (C) Type III carpogonial branch showing a mixture of type I and type II carpogonial branch pattern. The carpogonial branch consists of the carpogonium (c) with the trichogyne (t), the hypogynous cell (h) bearing the sterile cell (arrowheads), and the basal cell (b) bearing several sterile filaments (arrows); (D) Developed type I carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and two basal cells (b1, b2) producing many sterile filaments (arrows); (E) Developed type III carpogonial branch showing the carpogonium (c) with trichogyne (t), the hypogynous cell (h) bearing several sterile cells (arrowheads), and the basal cell (b) producing many sterile filaments (arrows).
Mentions: (FiguresĀ 5A-5N, 6A-6E, 7A-7C, 8A-8H, 9A-9E and 10A-10G).Figure 6

View Article: PubMed Central

ABSTRACT

Background: Members of the calcified red algal genus, Galaxaura, are distributed predominantly in warm temperate, subtropical, and tropical regions worldwide. The capacity of these algae to form calcified thalli could play a critical role in the carbon cycle of these ecosystems. Previous studies have suggested that the reported species diversity of Galaxaura may be exaggerated due to a lack of knowledge regarding external morphological differences between gametophytic and tetrasporophytic plants (or among different life stages) of a single species.

Results: To examine this issue, this study collected specimens of two morphologically distinct Galaxaura from Taiwan and the Philippines. These specimens were initially identified as two species (G. pacifica Tanaka and G. filamentosa Chou ex Taylor) based on their morphological features. Our molecular analyses, however, unexpectedly showed that these two specimens shared 100% identical rbc L sequences, indicating that they represented a single species comprising two distinct external morphologies. Furthermore, our extensive observations and molecular analyses on several specimens from different locations in southern Taiwan has revealed that these morphological differences could be due to seasonal variation.

Conclusions: This study proposes that G. “filamentosa” from the Philippines could represent the remnants of the lower villous part of older gametophytic plants of G. pacifica after senescence of the upper smooth part of the thallus. As such we propose that these two previously distinct algal species from the northwest Pacific Ocean as a single species, G. pacifica. This study shows that the biodiversity of the calcified red algae Galaxaura could be overestimated without the assistance of molecular tools. Additionally, this study provides insights into the biodiversity and unique biology of the calcified red algae Galaxaura.

Electronic supplementary material: The online version of this article (doi:10.1186/1999-3110-54-1) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus