<i>Tapeinodasya</i> Weber-van Bosse (Ceramiales, Rhodophyta): redescription of an enigmatic genus of the Dasyaceae

Abstract

The genus &lt;i&gt;Tapeinodasya&lt;/i&gt;, originally described by Weber-van Bosse (1904) from Indonesia and the Sulu Archipelago (Philippines), has remained one of the least known genera of the Dasyaceae. Based on recent collections from the East African coast, vegetative and tetrasporangial structures are described in detail for the first time and the placement of genus &lt;i&gt;Tapeinodasya&lt;/i&gt; in the Dasyaceae based on cellulosympodial growth is confirmed. The genus is separated from all other genera of the Dasyaceae by a distinctive cauliflower-like habit, complete absence of monosiphonous filaments, extensively corticated tetrasporangial stichidia and the presence of both pre- and postsporangial cover cells. genus &lt;i&gt;Tapeinodasya&lt;/i&gt; appears to be related to the &lt;i&gt;Heterosiphonia&lt;/i&gt;-like genera, based on an alternate sequence of periaxial cell formation, a primary alternate- distichous arrangement of holoblastic branches, and branches separated from one another by one or more unbranched segments. Placement of genus &lt;i&gt;Tapeinodasya&lt;/i&gt; in a clade with &lt;i&gt;Thuretia&lt;/i&gt; and &lt;i&gt;Dictyurus&lt;/i&gt; as recently hypothesized is verified by the recognition of a clockwise mode of alternate periaxial cell formation and a primary bilateral organisation. Comparison of the East African specimens with the type collections of the other known species, shows that the Tanzanian specimens belong to the Indonesian &lt;i&gt;Tapeinodasya bornetii&lt;/i&gt; rather than to &lt;i&gt;T. etheliae&lt;/i&gt; which was described from the Amirante Islands. The presence of &lt;i&gt;T. bornetii&lt;/i&gt; in Tanzania represents a substantial range extension and a new record for the Indian Ocean.