Kurt M. Dreckmann

Genetically recognizable but not morphologically: the cryptic nature of Hydropuntia cornea and H. usneoides (Gracilariales, Rhodophyta) in the Yucatan Peninsula

Abstract: Species recognition in algae is often extremely difficult due to the paucity of morphological characters and high environmental plasticity. If environment is important to morphology, then related species growing in sympatry are good candidates to discover diagnostic characters. We studied algae collected in sympatric populations in tropical Atlantic Mexico. Hydropuntia cornea and H. usneoides have high morphological variation and have been difficult to diagnose morphologically. We used four molecular markers (RuBisCo spacer, cox2–3 spacer, rbcL and COI) to investigate the genetic relationship between samples that correspond to either H. cornea or H. usneoides; in addition, we determined if molecular-characterized groups were morphologically distinguishable. RuBisCo and cox2–3 spacers revealed low genetic variation but showed two genetic groups: groups I and II. rbcL and COI phylogenies also showed a separation into two groups, corresponding with cox2–3 spacer groups I and II. Group I matched sequences in GenBank of H. usneoides and group II with H. cornea. Populations were mixed for these genetic groups, with group I prominent in Quintana Roo populations. Morphological analysis of samples in both genetic clades showed that they are not distinguishable. As the difference between the two groups is only genetic, they are, consequently, cryptic species. While the extremes of morphology in allopatric populations may be distinguishable, we do not feel that in most cases these species can be recognized. Therefore, we propose that these two ‘species’ should be designated as a species complex (the Hydropuntia cornea/H. usneoides complex).

Meristotheca cylindrica sp. nov. (Solieriaceae, Rhodophyta) from the southern Gulf of Mexico

Abstract: Meristotheca cylindrica sp. nov. from the Gulf of Mexico is described on the basis of morphological and molecular evidence. Previously, all known species of Meristotheca were described as flattened or peltate in habit; the diagnostic character for M. cylindrica sp. nov. is a thallus with a cylindrical (or terete) axis and branches. rbcL sequences indicate an independent monophyletic group within the genus.

Tepoztequiella rhizoidea gen. et sp. nov. (Solieriaceae, Rhodophyta) from the Yucatan Peninsula, Mexico

Abstract: Molecular methods have greatly aided in discovering new diversity in many cryptic algal groups. Molecular-assisted species discovery has focused morphological analyses on previously overlooked taxa, leading to a better understanding of diversity and evolutionary patterns. The Yucatan Peninsula, as a junction of North and South American Atlantic floras, is very diverse and, while a well-explored area, continues to reveal new species. Our studies in this area have revealed a new cylindrical member of the Solieriaceae. Based on COI-5P, rbcL and RuBisCo spacer sequences, we show that this entity is phylogenetically unique. Its position in phylogenetic analyses, combined with morphological characters and the genetic divergence from other species and genera within the family, strongly supports the establishment of Tepoztequiella rhizoidea gen. & sp. nov. The diagnostic character of T. rhizoidea is the presence of many rhizoids arising from medullary filaments and from the cells of the inner cortex.

Phylogeography of Hydropuntia cornea/Hydropuntia usneoides complex (Gracilariales, Rhodophyta) in the Yucatan Peninsula

Abstract: Phylogeographic studies can contribute to our understanding of the evolutionary forces acting on the patterns of genetic variation and the evolutionary history of species. The Hydropuntia cornea/Hydropuntia usneoides species complex consists of two common species of red algae in the Gulf of Mexico and Caribbean Sea. Both species exhibit high phenotypic plasticity and total overlap in morphological characters and are only distinguished genetically (group GI, assigned to H. usneoides and group GII, assigned to H. cornea). In the Yucatan Peninsula, where they are abundant, they have a sympatric distribution. In order to understand the historical events and their influence on the current distribution patterns of these species around the Yucatan Peninsula and compare them with some populations from Venezuela and Brazil, we analyzed variation in the plastid-encoded RuBisCo spacer. A total of 133 individuals collected from 14 sites were sequenced. The analyses revealed 12 haplotypes (R1–R12). The haplotype network revealed two major groups (GI and GII) separated by three mutational steps. Group I was found in almost all sampled sites (n = 13), while GII was found in six sites but was absent from the Gulf of Mexico (Campeche). Haplotype R1 was the most abundant in GI, and haplotype R4 was dominant in GII. Genetic variation was higher in GI than in GII. Mismatch distribution suggests that GI may be in a period of demographic equilibrium, and GII experienced a recent demographic expansion and may have come from the south when the northern portion of the peninsula emerged (2.8 million years ago). Our results revealed that the Yucatan Peninsula is a mix of southern and northern floristic influences, which can be explained by the geological events in the area.

Solieria incurvata (Solieriaceae, Rhodophyta), a new species from Venezuela based on morpho-anatomical and molecular evidence

Abstract Solieria incurvata from Puerto Escondido, Estado Falcon, Venezuela, is described as a new species based on morpho-anatomical and molecular data. Morphologically S. incurvata differs from other Solieria species, with which it shares its distributional range, by its narrow branches that become gradually constricted toward their bases, by possessing acute and incurved apices, and by its branching pattern and anatomical morphometrics. On the basis of COI-5P and rbcL sequences, the new species forms an independent lineage that clearly belongs in the Solieria clade of the Solieriaceae.

Gracilaria microcarpa sp. nov. (Gracilariaceae, Rhodophyta) from the southwestern Gulf of Mexico

Abstract Although the genus Gracilaria is well represented on the Mexican coasts, there are few studies focused on the taxonomic aspects and the clarification of the relationships between species. The high morphological plasticity exhibited by several of its representatives could underestimate the true species richness. In the present study, a group of cylindrical specimens of Gracilaria from the southeastern Gulf of Mexico, previously identified as G. cornea, was collected. Based on COI-5P and rbcL sequences, these samples formed an independent group closely related to G. ferox, a flat species. Morphologically, our specimens differed from G. ferox and the other species of Gracilaria by the presence of very small cystocarps and a thick pericarp composed of many layers of cells. We propose Gracilaria microcarpa sp. nov. as the name for this group of cylindrical specimens from the Yucatan Peninsula of Mexico.

Variación genética en Meristotheca cylindrica (Solieriaceae, Rhodophyta) en Campeche, México

RESUMEN Antecedentes . Los estudios enfocados en la variacion genetica son fundamentales para evidenciar procesos de radiacion adaptativa y especiacion. En este sentido, los marcadores moleculares han jugado un papel protagonico durante las pasadas tres decadas. Objetivos . Meristotheca cylindrica es una especie comun en las costas de Campeche, importante economicamente por la presencia de carragenanos en su pared celular; sin embargo, despliega un espectro de variabilidad morfologica que la confunde con especies pertenecientes a categorias taxonomicas diferentes, razon que la hace un buen ejemplo para analizar la probable variacion genetica al interior de sus poblaciones. Metodos . Utilizando secuencias de ADN plastidial de la region espaciadora de laRuBisCo, y ADN mitocondrial de la region espaciadora cox 2-3,fue posible determinarla variacion genetica en 45 individuos de M. cylindrica procedentesde cinco poblaciones registradaspara Campeche. Resultados. La region espaciadora de la RuBisCo arrojo cuatro haplotipos (R1-R4), de los cuales R1 fue el mas abundante; la diversidad haplotipica fue similar en las poblaciones (Hd<0.4) y la red haplotipica revelomoderada divergencia entre las poblaciones. La region espaciadora cox 2-3nos permitio encontrar nueve haplotipos (C1-C9); la poblacion con la mayor diversidad haplotipica fue Sabancuy (Hd=0.7), en contraste con Bahia Tortuga, en la que solo se presento un haplotipo (por tanto Hd=0). La red haplotipica con la region espaciadora cox 2-3 revelo estructura total. Conclusiones. La distribucion de los haplotipos con ambos genes, y la estructura mostrada en las redes haplotipicas, sugieren un evento de especiacion para estos grupos. Finalmente, discutimos el aislamiento geografico del suroeste del Golfo de Mexico como un escenario evolutivo plausible. Abstract Backgrounds . Studies centered on genetic variation are nuclear to show processes such as adaptive radiation, and speciation. In this sense, the current molecular protocols have proved to be a very useful tool for at least three decades. Objectives. Meristotheca cylindrica is a common species along the coast of Campeche, at the south western Gulf of Mexico, it is, also, an economically important resource because the carrageenans present in its cell walls. However, it displays a spectrum of morphological variation close to taxa not taxonomically related. This feature alone, makes M. cylindrica a perfect system to analyze a probable genetic variation within its known populations. Methods. Using DNA plastidial sequences of the spacer region of RuBisCo, and the spacer mitochondrial region cox2 -3, it was possible to show genetic variation in 45 individuals of M. cylindrica from five populations. Results. RuBisCo produced four haplotypes (R1-R4), R1 being dominant. Haplotypic diversity was similar through the populations (Hd=~0.2, ~0.38), but the haplotypic net reflected moderated divergence between populations. The cox 2-3 spacer analysis, otherwise, shows up nine haplotypes (C1-C9). The population with the higher haplotypic diversity was Sabancuy (Hd=0.7), in contrast with Bahia Tortuga, in which we found just one haplotype (so,Hd=0). Conclusions. The haplotypic network, through the spacer region cox 2-3 analysisrevealsa totalgenetic structure. Haplotypic distribution (sustained with both genes), and the genetic structure evidenced by the haplotypic net, suggest an event of speciation in course. We discuss the geographical isolation of the South Western Gulf of Mexico as an evolutionary scenario..