Notes on the marine algae of the Bermudas. 15. Dichotomaria huismanii (Galaxauraceae, Rhodophyta), a new species in the D. marginata complex from the western Atlantic

Abstract

Notes on the marine algae of the Bermudas. 15. Dichotomaria huismanii (Galaxauraceae, Rhodophyta), a new species in the D. marginata complex from the western Atlantic DOI 10.1515/bot-2015-0068 Received 19 August, 2015 accepted 7 January, 2016; online first 4 February, 2016 Abstract: Using plastid-encoded rbcL and mitochondrial COI-5P sequence data, the species in Bermuda formerly recognized as Dichotomaria marginata was found to be a cryptic species in a wide complex of species all falling under the morphologically broad species concept for this supposed pantropical species. The new species, Dichotomaria huismanii, shows subtle anatomical and morphological differences when compared to D. marginata, and at present is only known from Bermuda. Bermuda specimens were compared with our isolates of D. marginata from St. Croix (Virgin Is.), as well as rbcL sequenced specimens with those from Guadeloupe and Puerto Rico in GenBank as D. marginata. Morphological and molecular characterization of D. marginata is provided along with the new species.

Seaweed diversification driven by Taiwan’s emergence and the Kuroshio Current: insights from the cryptic diversity and phylogeography of Dichotomaria (Galaxauraceae, Rhodophyta)

“…Red algal species are morphologically differentiated by the gross morphology of the thallus, including overall in situ appearance, thallus size, and branch length, as well as the characteristics of the sporophyte cortex, such as the size and shape of the different layers of cells composing the cortex. Previous studies comparing the morphology of Dichotomaria species have also relied on these traits (Tanaka, 1935;Kurihara et al, 2005;Wang et al, 2005;Liu et al, 2013;Wiriyadamrikul et al, 2014;Schneider et al, 2016). Building upon these diagnostic traits used for red algae, we have expanded the existing original account of D. elegans and D. latifolia (Tanaka, 1935) by providing newly generated morphological descriptions, micromorphology plates, and corresponding molecular data.…”

“…Morphological examinations of thalli of both tetrasporophytic and gametophytic plants were carried out for the three species within the D. marginata complex found in Taiwan: D. "marginata", "D. latifolia", and "D. elegans". We selected the following traits: gross morphology, color, habitat preference, external branch width, as well as specific characteristics of the gametophyte (epidermal cells and spine cells width and height) and tetrasporophyte (stalk cells height, outer cortical cells width and height, and the presence of apiculate tips), based on their established taxonomic relevance in previous Dichotomaria studies (Tanaka, 1935;Kurihara et al, 2005;Wang et al, 2005;Liu et al, 2013;Wiriyadamrikul et al, 2014;Schneider et al, 2016). The majority of stalk cells of the tetrasporophyte were dichotomous, attached to two outer cortical cells; therefore, to avoid bias, we only measured their height.…”

“…Dichotomaria marginata (J.Ellis & Solander) Lamarck, 1816, a tropical and sub-tropical species with a flattened gross morphology (Huisman and Borowitzka, 1990), was historically grouped with several other species forming the D. marginata complex (Huisman and Borowitzka, 1990;Huisman et al, 2004b). However, subsequent molecular and morphological analyses (Schneider et al, 2016;Santos et al, 2020) have identified distinct species within this complex. Hence, the D. marginata complex species diversity is not well characterized, with new species continually being discovered (Sherwood et al, 2010;Liu et al, 2013;Wiriyadamrikul et al, 2014;Schneider et al, 2016;Santos et al, 2020).…”

“…However, subsequent molecular and morphological analyses (Schneider et al, 2016;Santos et al, 2020) have identified distinct species within this complex. Hence, the D. marginata complex species diversity is not well characterized, with new species continually being discovered (Sherwood et al, 2010;Liu et al, 2013;Wiriyadamrikul et al, 2014;Schneider et al, 2016;Santos et al, 2020). In addition, regionally endemic lineages have been observed, including D. tenera (Kjellman) Huisman et al in South Africa and D. viridis G.N.Santos et al in Brazil (Huisman et al, 2004b;Santos et al, 2020).…”

Could marine animal conservation laws be responsible for the decline or extirpation of macroalgal populations in Bermuda over the past century?

“…Despite its impregnation with calcium carbonate, the tips of specimens recently collected are nearly always truncated with a regrowth of medullary filaments emerging, clear evidence of prior herbivore grazing (Schneider et al 2016, figures 8, 9). Today's plants are half the size of mature 19th century plants (Schneider et al 2016, figure 7), sparsely branched, and rarely found, and only then as isolated individuals.…”