Roseapetra

Nelson, Wendy A., Neill, Kate F., Twist, Brenton A. & Sutherland, Judy E., 2021, A new genus and species in the Sporolithales (Corallinophycidae, Rhodophyta) from northern New Zealand: Roseapetra farriae sp. nov., Phytotaxa 490 (1), pp. 35-46 : 37-40

Roseapetra W.A. Nelson, Twist & K.F.Neill ( Figures 2 –12) gen. nov.

Type species: Roseapetra farriae sp. nov. W. A. Nelson, Twist & K. F.Neill

Etymology: Named for the pink/purple calcified growth on rocky substrata (Greek: Rosa = pink; petra = rock).

Diagnosis: Non-geniculate, crustose, smooth surface; flared epithallial cells; secondary pit connections and cell fusions; gametophytic phase with uniporate conceptacles; sporophytic phase with individual compartments grouped in sori, tetrasporangia cruciately divided; 3 stalk cells. This genus is recognised as distinct on the basis of sequence data.

Roseapetra farriae W. A. Nelson, Twist & K. F.Neill sp. nov.

Holotype (designated here): WELT A029120 ( NZC2438 ), W. Nelson, 8 Sep 2006, GenBank FJ361655 (psb A). (Figures 6–8)

Type Locality: Little Bay , Waikawau , Coromandel, North Island, New Zealand., (-36.6011333, 175.5490833) .

Additional material examined: New Zealand, North Island : Kapowairua (-34.4208333, 172.85625), K . Neill & T . Farr, 20 Mar 2007, WELT A029118 ( NZC2541 ), GenBank FJ361702 (psb A); Henderson Point (-34.7407167, 173.118), K . Neill & T . Farr, 19 Mar 2007, WELT A029117 ( NZC2521 ), GenBank FJ361698 (psb A); Ahipara, south end of 90 Mile Beach , (-35.1748833, 173.1173), K . Neill & T . Farr, 18 Mar 2007, WELT A029115 ( NZC2497 ) GenBank FJ361682 (psb A); Auckland west coast, Te Henga (-36.88745, 174.43735), W . Nelson, T . Farr & K . Neill, 22 Jul 2005, WELT A029119 ( NZC2014 ) GenBank FJ361360 (nSSU), KM 369120 (rbc L) , KM 369064 (psa A) , FJ361382 (psb A).

Etymology: the species epithet acknowledges the work of our colleague Tracy Farr, and her very significant contributions to the study of coralline algae in New Zealand.

Description:

Habit and vegetative morphology: Smooth, encrusting non-geniculate coralline alga growing on rocks and cobbles ( Fig. 2 ). Crusts dark purple to deep pink; 5–30 mm thick, up to at least ca 100 mm across. Thallus construction monomerous; flared epithallial cells ( Fig. 4 ); cell fusions common, often extending across several adjacent cell filaments (Figs 5, 9); secondary pit connections not observed.

Reproduction: Tetrasporangial compartments aggregated into loose sori, (36) 40–45 × 72–80 µm in diameter (Figs 3, 6–8), with apical plugs (Figs 6, 7); tetrasporangia divided cruciately and surrounded by elongated cells forming an involucre (Figs 7, 8). Sori slough at senescence with continued growth of cortex (Fig. 9). Carposporangial conceptacles uniporate, flask-shaped, (61) 65–75 (80) × 89–99 µm ( Fig 10 ). Gametangial conceptacles not shed but become buried in the thallus with secondary meristematic activity producing lens-like areas of regrowth (Figs 11,12).

Habitat and distribution: On rocky reefs, found under large brown algae (e.g. Carpophyllum spp. ) in low intertidal to upper subtidal zones. Known from the northern North Island of New Zealand.

Comments. Roseapetra farriae has been collected infrequently, with only five collections confirmed with sequence data. This species was found to be co-occurring with the much more commonly collected Heydrichia homalopasta . These two species are superficially similar although R. farriae has smaller tetrasporangial compartments (ca 43 × 76 µm vs 70 × 130 µm). To date all collections of R. farriae have been from the low intertidal/upper subtidal zone whereas H. homalopasta has also been found subtidally to depths of 18 metres.

Phylogenetic analyses. The concatenated dataset consisted of 2209 characters (850 psb A and 1359 rbc L) and 38 taxa ( Table 1), and the results of the phylogenetic analysis are shown in Figure 13 . The order Sporolithales was recovered as monophyletic with strong support (99.8 alrt, 99% Bootstrap support ( BS) and 1.0 posterior probability ( PP). The genus Sporolithon was weakly supported as monophyletic (87/59/0.95), however Heydrichia was not recovered as a monophyletic group. In both Bayesian and ML analyses, Heydrichia woelkerlingii and H. homalopasta were associated with strong support (99.3/100/1.0), but the association of H. cerasina Maneveldt & van der Merwe with these two received no significant support. In addition, the position of Roseapetra farriae in relation to the two well supported clades within Sporolithon , recognised by Richards et al. (2017) as clades A and B, and other Heydrichia taxa, received no significant support.

Under each of the RELL-BP, KH, SH, ELW and AU tests the differences in -ln-likelihood between unconstrained trees and trees in which the clade Heydrichia + Roseapetra was constrained to be monophyletic were not significant, indicating no significant evidence in our dataset for or against the inclusion of Roseapetra within Heydrichia .

FIGURE 5. Cross section showing cell fusions (arrows) and primary pit connections (dots) ( WELT A 029118). Scale bar = 20 µm.

FIGURE 6. Cross section of thallus with sorus of calcified tetrasporangial compartments (WELT A029120). Scale bar = 100 µm.

FIGURE 7. Tetrasporangial compartment with tetrasporangium, three stalk cells (numbered and arrows), apical plug (star), and narrow elongated cells forming involucre on either side of compartment (WELT A029120). Scale bar = 20 µm.

FIGURE 8. Tetrasporangial compartment with tetrasporangium, surrounded by narrow elongated cells of involucre, three stalk cells (numbered and arrows), first of cruciate divisions (star) (WELT A029120). Scale bar = 20 µm.

FIGURE 9. Post-release tetrasporangium (star) showing enlarged involucral cells (arrows) and shedding cortical layers (upper arrow). Lower arrows indicating some of the cell fusions between files of cells (WELT A029119). Scale bar = 20 µm.

FIGURE 12. Lens like regrowth (arrows) around remains of gametangial conceptacle (WELT A029118). Scale bar = 20 µm.

Figures

FIGURE 2. Roseapetra farriae growing on a rocky reef in the low intertidal zone at Kapowairua (WELT A029118). Scale bar = 1 cm. FIGURE 3. Surface of tetrasporangial sorus (WELT A029119). Scale bar = 1mm.

FIGURE 4. Cross section of upper cortex showing flared epithallial cells (arrows) (WELT A029118). Scale bar = 20 µm.

FIGURE 10. Carposporangial conceptacle with arrow pointing to rectangular carpospore (WELT A029118). Scale bar = 20 µm. FIGURE 11. Buried gametangial conceptacle (arrow) (WELT A029118). Scale bar = 50 µm.

FIGURE 13. Maximum likelihood phylogram of Sporolithales taxa estimated from concatenated psbA and rbcL sequence data. Support values are shown on each branch: approximate Likelihood Ratio Test (aLRT, %) and ML bootstrap (%) values above, and Bayesian PP values below. With the exception of support for Heydrichia, and support for the association of Roseapetra farriae with Sporolithon, only values greater than 0.8 (aLRT), 80% (bootstrap) and 0.9 (PP) are shown; all support values are shown if two support methods for a clade reach the cutoff value.