Appendix
Crustose Coralline Algae Species Studied
Most Caribbean algae are relatively easy to identify due to the existing taxonomic literature and
guides (e.g., Littler and Littler 2000). Tropical non-geniculate coralline algae, or “crustose coralline
algae” (CCA), are different. Coralline taxonomy has been in flux almost since its modern inception in the
late 1800s. Since the 1970s two schools developed with very different taxonomic schemes. In the 1980s
many taxa were synonomized based on their original descriptions (e.g., Woelkerling 1988). However, the
most recent revisions using molecular genetics (Bittner et al. 2011; Kato et al. 2011) revealed that some
important genera that had been synonomized are in fact phylogenetically distinct and thus should be
reinstated. One conspicuous example was the genus Porolithon that had been synonomized with
Hydrolithon. Molecular genetic studies determined them to be distinct, and thus, reinstated Porolithon
(Bittner et al 2011). Several biogeographically disparate species have also been synonomized, such as
Neogoniolithon solubile (type location Jamaica in the Caribbean), Neogoniolithon fosleii (type location
Mediterranean Egypt) and Neogoniolithon brassica-florida (type location southern most (temperate)
region of South Africa). This synonomy suggests a coralline flora that is without thermogeographic or
biogeographic limits, despite coralline literature to the contrary (Adey and Adey 1973; Adey and Steneck
2001). Molecular studies on N. brassica-florida concluded that this taxa appears “to be polyphyletic,
suggesting the presence of several cryptic species…” (Kato et al. 2011). To avoid including such cryptic
species, we followed Adey’s taxonomic schemes (Adey 1970; Adey et al. 1982) and follow many of the
original descriptions because they conform well with recent studies that use genetic data (Bittner et al.
2011; Kato et al. 2011). Accordingly, we use currently under-valued characteristics such as branching
propensity and morphology, thallus surface features, arrangements of unique cells (e.g., trichocytes,
described below), anatomical characteristics of epithallial, perithallial (cortical) and hypothallial (medulla
or basal) cell layers.
A specialized anatomical character that has received little attention in recent decades is the size
and arrangement of trichocyte cells. These were described by Foslie in the early 1900s and were recently
used for coralline taxonomy in Guam and the Hawaiian islands (Gordon et al 1976; Adey et al 1982,
respectively) where they were called “heterocysts”. “Heterocysts” is a term used for cyanobacteria and
since these are hair cells, “trichocyte” is a better descriptor (e.g., Woelkerling 1988). The arrangement of
trichocyte fields is a taxonomic characteristic that corresponds well with recent molecular-based
phylogenies. Porolithon’s distinctive tightly packed horizontal trichocyte fields make this genus easy to
identify. The closely related taxon Pneophyllum conicum was originally described as the genus
Paragoniolithon, which had loosely grouped horizontal trichocyte fields. The more distantly related
Hydrolithon (sensu Adey 1970) has widely spaced trichocytes. Thus, within the mastophoroids, there
exists a gradient of trichocyte arrangement that corresponds well with genetically based phylogenetic
trees.
Nongeniculate coralline algae are characterized by three distinct cell layers. The outer most layer
is the epithallus that is usually one cell layer thick but can be multilayered in some taxa. The cells
typically shed from the thallus taking epibionts with them (with one notable exception described below).
Epithallial cells are produced by the region of growth called the meristem (or subepithallial initials). The
meristem also produces cells that comprise the majority of the crust’s thickness in a layer called
“perithallus” but is roughly homologous with the cortex of typical erect fleshy macroalgae. The basal
layer of CCA is called the “hypothallus”, which is homologous with the medulla of typical erect fleshy
algae. Each of these tissue layers are composed with different arrangements of cells that can be
characteristic of taxonomic affinities. Beyond the anatomy we just described are several morphological
characters such as propensity to form protuberances (i.e., “branches”), thallus thickness, degree of
adherence to hard substrates and reproductive characters such as size, shape and pore characteristics of
the reproductive structured called conceptacles. Specifically the size and shape of asexual
(tetrasporangial) conceptacle pores used to release spores are often diagnostic for CCA taxa.
It is well beyond the scope of this paper to resolve taxonomic confusion surrounding CCA since
the taxonomic literature relevant for the Caribbean corallines is lacking or in need of a revision (Taylor
1960). Littler and Littler (2000) is a good field guide with excellent photographs, but it does not use the
diagnostic taxonomic characters necessary to reliably determine coralline species. For our study, we
define taxa on multiple independent characters that relate to regionally relevant described species. For
this reason, we provide the species names and descriptions of key anatomical and morphological
characteristics we used to identify the species used for the larval settlement and metamorphosis assays.
We describe the CCA in sufficient detail so others could arrive at the same determination using a
dissecting microscope and when genetic studies have been completed, revisions can be made of these
taxa. To be conservative, we only describe taxa whose type locality is relevant to the tropical western
Atlantic. Our approach in effect resurrects some taxa that have been synonomized based on relatively few
currently accepted taxonomic characters. While it is correct that many characters used in past coralline
taxonomic studies are variable, when several characters are considered simultaneously, the likelihood of
identifying either genetically unique or remarkably convergent taxa increase.
Family: Peyssonneliaceae
Species: Peyssonnelia sp. (Decaisne 1841)
Distinguishing characteristics are described in Littler and Littler (2000).
Order Corallinales
Family: Corallinaceae
Subfamily Lithophylloideae (tetrasporangial conceptacles single pored, secondary pits between adjacent
cells; recent molecular genetic study found the articulated coralline Amphiroa is a lithophylloid
and so it is included here (Bittner et al 2001))
Species Amphiroa tribulus (J. Ellis & Solander)
Distinguishing characteristics are described in Littler and Littler (2000).
Species Titanoderma prototypum (Foslie) Woelkerling, Y.M.Chamberlain & P.C.Silva.
Distinguishing characteristics: Pink to red coloration with a thin overgrowing thallus in which
overall thickness is achieved by single layered vertical (“palisade”) hypothallus
repeatedly overgrows itself usually showing distinct arcuate pattern over overgrowth
(called “aplanate branching”). Epithallial cells are uniquely retained and are visible in
cross section under overgrowing portion of the thallus. Another much rarer Titanoderma
species (T. bermudense) has a distinct white margin on its very regular overgrowing
thallus and it does not retain epithallial cells. T. prototypum has single pored
tetrasporangial conceptacles that are raised with an outside diameter ranging between 400
– 600 µm. Type locality: St. Croix, U.S. Virgin Islands. It is important to note this name
is for the Caribbean species, but has been applied to an undescribed, morphologically
similar species found in the Pacific Ocean.
Subfamily Mastophoroideae (Tetrasporangial conceptacles single pored, vegetative cell fusions between
adjacent cells)
Species Neogoniolithon affine (Foslie & Howe) Setchell and Mason
Distinguishing characteristics: Irregular relatively thin dark red-brown thallus, coaxial (acruate
and aligned cells) hypothallus, raised tetrasporangial conceptacles 500 – 600 µm OD.
Trichocytes are small and often not visible with dissecting microscope. Type locality:
Culebra, Puerto Rico
Species Neogoniolithon mamillare (Harvey) Setchell and Mason
Distinguishing characteristics: Smooth yellow-brown-pink crust that develops irregular
mammalate (wider than they are high protuberances) thallus that often has conspicuous
curved sloughing or flaking of epithallial cells. Strongly raised large conceptacles 800 –
1800 µm OD. Hypothallus parallel. Large trichocytes with a scattered distribution are
very distinct with a dissecting microscope. Type locality: Brazil
Species Neogoniolithon munitum (Foslie & Howe) Adey
Distinguishing characteristics: Red-brown or yellow brown, rugulose (irregular, rough surface
with no pattern), subtesslate (distinct raised surface patches, “subtesselate” refers to less
distinct tessellations), medium thickness (ca 500µm) crust with a growing margin that
may be nonadherent (“leafy”), tetrasporangial conceptacles raised dome (very abundant)
conceptacles 275 – 475 µm OD. Trichocytes are small and inconspicuous when using
dissecting microscope.
Species Hydrolithon boergesenii (Foslie) Foslie
Distinguishing characteristics: Purple coloration, strongly tessellated surface texture with an
adherent thallus margin that is not white. Tetrasporangial conceptacles abundant,
distinctly raised, rounded dome-shaped 300 – 400 µm OD. Single layered hypothallus is
rarely visible with dissecting microscope.
Species Paragoniolithon solubile (Foslie & Howe in Foslie) Adey, Townsend and Boykins
Distinguishing characteristics: Expansive and often moderately thick crust > 500 µm. The
hypothallus is strongly coaxial. The conceptacles are readily visible with dissecting
microscopes, strongly raised and large 900 – 1800 µm. Type locality: Jamaica
Species Porolithon pachydermum (Foslie) Foslie
Distinguishing characteristics: Blue to purple coloration, smooth surface texture, chalky very
thick thallus that usually grows on upper facing convex hard substrates in shallow zones
< 10 m deep. Conceptacles slightly raised or flush and small, 100 – 200 µm OD.
Hypothallus parallel and moderately thin (50 – 200 µm) which is sometimes visible with
dissecting microscopes.
Species Lithoporella atlantica (Foslie) Foslie
Distinguishing characteristics: Pink to red coloration with thin leafy over-growing thallus with
conspicuous fan-like arrangement of the cells. The hypothallus is single layered with a
vertical (palisade) orientation, and the conceptacles are raised (500 – 800 µm OD).