American Journal of Plant Sciences
Vol.06 No.15(2015), Article ID:60112,10 pages

Two New Species of the Genus Dictyota (Phaeophyceae: Dictyotales) from the Mexican Caribbean

Jorge G. Lozano-Orozco1,2, Abel Sentíes2*, Olivier De Clerck3, Kurt M. Dreckmann2, Jhoana Díaz-Larrea2

1Doctorado en Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana, Iztapalapa, México

2Departamento de Hidrobiología, Universidad Autónoma Metropolitana, Iztapalapa, México

3Phycology Research Group and Centre for Molecular Phylogenetics and Evolution, Ghent University, Ghent, Belgium

Email: *

Copyright © 2015 by authors and Scientific Research Publishing Inc.

This work is licensed under the Creative Commons Attribution International License (CC BY).

Received 28 July 2015; accepted 27 September 2015; published 30 September 2015


During a molecular characterization of the genus Dictyota J. V. Lamouroux (Phaeophyceae, Dictyotales) along the Mexican coasts of the Gulf of Mexico and the Mexican Caribbean, using psbA and cox1 genes, it was found that two particular collections did not match with the sequences published for a total of 39 species of Dictyota. For each gene, both collections diverged in high-uncor- rected “p” distance values with respect to other related species. This high genetic divergence was corroborated by morphological analysis. Hence, we proposed Dictyota mayae J. Lozano-Orozco & Sentíes and Dictyota pedrochei J. Lozano-Orozco & Sentíes as new species.


Mexican Caribbean, Dictyota mayae sp. nov., Dictyota pedrochei sp. nov., Molecular Phylogeny, Taxonomy

1. Introduction

Floristic identification of species belong to the genus Dictyota J. V. Lamouroux (Phaeophyceae, Dictyotales), it has been a controversial issue among the community of Dictyotales specialists for at least the past two decades [1] - [3] . This scenario was the consequence of that nineteenth-century phycological school which saw the least minimal morphological difference as a diagnostic feature (the classical algorithm for that is: if one cell, then species A; if two, then species B), which in turn was the consequence of a very low morphological variability and phenotypic plasticity, both intra and inter species. Today, 77 specific names are recognized within the genus worldwide [4] . For the American Atlantic, for example, we recognize 15 species [5] , and 11 for the Mexican Caribbean alone [6] - [9] . Fortunately, methods of modern molecular phylogenetics have allowed us to solve the problems resulting from the lack of reliable morphological characters. As an instance for genus Dictyota, molecular characters have been used in order to redefine intraspecific and interspecific taxonomy [10] - [16] . Recently, several authors studied the taxonomic relationships of Dictyota species at the interspecific level, combining mor- phological and molecular data [3] [17] - [20] . As a result of these studies, new species had been described within Dictyota [3] [18] [20] . Because of the above, we started a molecular characterization of genus Dictyota along the Mexican coasts of the Gulf of Mexico and the Mexican Caribbean. During the research, however, it was found that two particular sample collections did not match the sequences published for a total of 39 species of Dictyota. A high genetic divergence, together with morphological analyses, convinced us of the presence of two new species, which here we formally described.

2. Materials and Methods

The specimens studied in the present study were collected at Punta Brava and Puerto Morelos, Quintana Roo, in March 2012, by J.G. Lozano-Orozco and A. Sentíes. Voucher samples were fixed in 4% formalin solution for morphological analysis.

The specimens were examined using a Leica stereomicroscope (Leica MZ 12.5, Wetzlar, Germany). Transverse hand sections in the apical, middle and basal regions of the thallus were made with a stainless steel razor blade under a dissecting scope. Photomicrographs were taken with an Olympus Vg-160 digital camera (Tokyo, Japan) coupled to a Nikon Eclipse E200 microscope (Tokyo, Japan). Voucher specimens were deposited at UAMIZ Herbarium (UAMIZ1231, UAMIZ1232, UAMIZ1233 and UAMIZ1234).

Total DNA was extracted from silica gel-preserved material using a Dneasy Mini Kit (Qiagen, Valencia, CA, USA) following the manufacturers’ instructions. A total of 956 bp from the psbA gene were amplified using the psbA F and psbA R primers [16] , and 672 bp were amplified for cox1 with Gaz1R and Gaz1F primers (adapted from [21] ), using the AmpliTaq kit of the Applied Biosystems (Lincoln Ventre Drive Foster City, CA, USA). All PCR products were checked for their correct length by electrophoresis on 1% agarose gel. The PCR products were sent to Macrogen (Gasan-dong, Seoul, Korea) to be purified and sequenced. Alignments for psbA and cox1 sequences were constructed using MEGA version 5 [22] . Collection sites and GenBank Accession Numbers of the specimens used in the phylogenetic analysis are provided in Table 1.

Phylogenetic relationships were inferred using a concatenated matrix (1703 nt) of two genes from 39 taxa (psbA = 1031 bp; cox1 = 672 bp; Table 1). Canistrocarpus crispatus (J. V. Lamouroux) De Paula & De Clerck, Dictyopteris polypodioides (A. P. De Candolle) J. V. Lamouroux, Rugulopteryx okamurae (E. Y. Dawson) I. K. Hwang, W. J. Lee & H. S. Kim and Scoresbyella profunda Womersley were included as outgroup taxa based on previous results obtained by [23] . The intraspecific and interspecific divergence values obtained for psbA and cox1 were calculated using uncorrected “p” distances implemented in MEGA version 5 [22] . The Bayesian phylogenetic analysis was inferred with MrBayes v.3.0 beta 4 software [24] using the general time-reversible model of nucleotide substitution with invariant sites and Gamma-distributed rates for the variables sites (GTR + I + G). This model was selected based on Maximum Likelihood (ML) ratio test implemented by the software ModelTest 0.1.1 [25] . For the Bayesian analysis, five chains of the Markov chain Monte Carlo (one hot and four cold) were run, sampling one tree every 1000 generations for 5 × 106 generations starting with a random tree. Maximum likelihood analysis was performed using TOPALI v2 software [26] with the GTR + I + G model. The ML bootstrap analyses were conducted with 100 replicates. Support values [27] were computed, as implemented in TOPALI v2.

3. Results

3.1. Morphological Analysis

Dictyota mayae: J. Lozano-Orozco & Sentíes sp. nov. (Figures 1(A)-(H)).

Table 1. Taxa used in this study for phylogenetic analysis.

Figure 1. Dictyota mayae J. Lozano-Orozco & Sentíes sp. nov. (1) Habit of sporophyte, Puerto Morelos, Quintana Roo, designated as holotype (UAMIZ1231). Scale bar = 2 cm; (2) Sporophyte (UAMIZ1232). Scale bar = 2 cm; (3) Detail of dichotomous branching (UAMIZ1231). Scale bar = 5 mm; (4) Note sporangial zone on the surface of the thallus (UAMIZ1231). Scale bar = 500 μm; (5) Detail of the apical cells UAMIZ1231. Scale bar = 500 μm; (6) Antheridial zone of the thallus (UAMIZ1233). Scale bar = 300 μm; (7) Cross section of the middle portion of a branch (UAMIZ1233). Scale bar = 100 μm; (8) Cross section of the thallus, note spermatangia (UAMIZ1233). Scale bar = 100 μm.

Description: Thalli 22 - 40 mm long, erect, attached to the substrate by rhizoids. Sympodial and stricly dichotomous branching. Color in situ brown with iridescence, obtuse apices, smooth margins. Solitary or grouped sporangia in the middle of thalli. The width of the axes is uniform throughout the thalli 3 - 4 mm, apical cell protruding. Cortex unilayered, cells 40 - 43 mm long, 17 - 19 mm wide. Medulla unilayered, cells 190 - 200 mm long, 78 - 83 mm wide. Sporangia scattered singly on both thallus surfaces, dark brown. 95 - 100 mm in diameter, borne on a single stalk cells 15 - 18 mm high. Antheridia grouped in elipsoidal sori 360 - 380 mm long and 220 - 240 mm wide. The antheridia 60 - 65 mm high borne on a single stalk cell 9 - 10 mm high.

Etymology: The specific epithet honors the Mayans, a well known ethnic group in the history of southeastern Mexico and Central America.

Holotype: Voucher POK80, housed at UAMIZ under the code 1231. Material collected by J. Lozano and A. Sentíes, 12-03-2012, sporophyte.

Type locality: Puerto Morelos (18˚36'22'' N, 103˚30'05'' W), Quintana Roo, Mexican Caribbean.

Isotypes: UAMIZ1232 and UAMIZ1233.

Distribution and habitat: The species is known only from the type locality. Usually growing on coral or sand in shallow water (1 - 2 m at low tide).

Dictyota pedrochei: J. Lozano-Orozco & Sentíes sp. nov. (Figures 2(A)-(F)).

Description: Thalli 40 - 50 mm long, erect, attached to the substrate by rhizoids. Sympodial and dichotomous branching to irregular. Color in situ dark brown. Iridescence absent, obtuse apices, smooth margins, with surface proliferations in middle segments. The width of the axes is uniform throughout the thallus 3 - 4 mm, apical cell protruding. The sporangia common on middle parts of the thallus. Cortex unilayered, cells 19 - 20 mm long, 9 - 10 mm wide. Medulla unilayered, cells 98 - 103 mm long, 55 - 60 mm wide. Sporangia scattered singly on both thallus surfaces, dark brown. 90 - 95 mm in diameter, borne on a multiple stalk cells 40 - 45 mm high.

Figure 2. Dictyota pedrochei J. Lozano-Orozco & Sentíes sp. nov. (9) Image of sporophyte from Punta Brava, Quintana Roo, designated as holotype (UAMIZ1234). Scale bar = 1 cm; (10) Specimen from Punta Brava, Quintana Roo. Detail of dichotomy (UAMIZ1235). Scale bar = 1 mm; (11) Apical portion of thallus (UAMIZ1235). Scale bar = 150 μm; (12) Note proliferations on the thallus and monosporangia (black arrows and red arrow, respectively; UAMIZ1235). Scale bars = 400 μm; (13) Detail of the monosporangia. (UAMIZ1235). Scale bar = 70 μm; (14) Monosporangia on the cortical cells in transverse sections (UAMIZ1235). Scale bar = 50 μm.

Etymology: The specific epithet honors the Mexican phycologist Francisco F. Pedroche.

Holotype: Voucher POK82, housed at UAMIZ under the code 1234. Material collected on by J. Lozano- Orozco and A. Sentíes, 11-03-2012, sporophytic.

Type locality: Punta Brava (18˚36'22'' N, 103˚30'05'' W), Quintana Roo, Mexican Caribbean.

Isotype: UAMIZ1234.

Distribution and habitat: The species is known only from the type locality, growing epilithically at this locality exposed in the shallow sublittoral.

3.2. Molecular Analysis

A total of 39 sequences were analyzed (Table 1). The Maximum Likelihood and Bayesian trees obtained for each marker were similar (not shown). Additionally, a phylogenetic analysis was carried out combining the partial sequences of psbA and cox1 genes of the 39 correspondent taxa, analysis of ML and IB produced highly congruent trees, differing in some positions that had poor support clades, but where the two new species are located, both analyses produced excellent support clades (Figure 3). Both new species diverged in high-uncorrected p distances values from the rest of the Dictyota representatives (>0.8% psbA and >11% cox1), confirming that these two samples constitute new taxonomic entities, or evolutionary independent lineages.

Figure 3. Phylogenetic relationship of Dictyota representatives based on concatenated Bayesian analysis of psbA and cox1 DNA sequences. The GTR + I + G evolutionary model was used in the Bayesian Analysis, selected by a maximum-like- lihood radio test. Bayesian posterior probability (right) and ML bootstrap (left) values are indicated at the node. The localities are from the psbA sequences (right) and cox1 (left); other dates are shown in Table 1.

Table 2.Morphological comparison of D. mayae and D. pedrochei with other Dictyota species reported for Mexican Atlantic.

4. Discussion

4.1. Phylogenetic Analysis

Considering the problems with the identification from the majority of Dictyota species based solely on morphological, anatomical or reproductive characters, we performed a phylogenetic analysis based on psbA and cox1 partial sequences. Two clades representing two undescribed species become apparent. These taxa, Dictyota mayae and D. pedrochei, are clearly delineated by long and highly supported branches. The divergence of psbA and cox1 sequences within the new species and the other Dictyota species was high (>0.8% psbA and >11% cox1). We determine that are new taxonomic entities because the divergence values obtained in the psbA gene are within intraspecific (<1%) and interspecific limits (<7%) previously reported in the literature for Dictyotales [18] [29] .

4.2. Morphological Comparison and Distribution

Table 2 shows character distribution for species previously reported, plus the two new species here proposed. The morphological comparison between D. mayae and the other species phylogenetically related reveal striking differences. One of the main features is that D. mediterranea (Schiffner) G. Furnari and D. fasciola (Roth) J. V. Lamouroux have a multilayered medullary layer, with no iridescence in coloration, while D. mayae has a single medullary layer, color in situ is brown, with clear iridescence. In addition, D. fasciola and D. mediterranea are distributed in the European Atlantic and Mediterranean Sea. In the case of D. pedrochei, it also has several discrepancies with D. acutiloba J. Agardh, a phylogenetically related species that has a spiraling thallus, with a height to 20 cm, tufts of hairs in centrally located irregular rows on both surfaces, while D. pedrochei has a flattened thallus, a height to 5 cm and, surface proliferation in the middle of thallus without hairs. Primarily, D. acutiloba has a greater height than that of D. pedrochei, which is from Mexican Caribbean while D. acutiloba is strictly from the Pacific Ocean.

5. Conclusion

In this study, we perform morphological and molecular analyses on several species belonging to the genus Dictyota with special reference to the Mexican Caribbean. Analyses of thallus construction and a concatenated matrix of two phylogenetic markers have been found successful in supporting our conclusion that D. mayae and D. pedrochei are two evolutionarily independent lineages, and consquently two different species for the science. The application of morphological and molecular tools is improving our understanding of the biodiversity in the Mexican Caribbean, and in particular, to develop a model to have a better understanding of global diversity of Dictyota.


The first author thanks the postgraduate studies: Doctorado en Ciencias Biológicas y de la Salud of the Univer- sidad Autónoma Metropolitana and to R. Mondragon for editing the figures. This study was supported by the following projects: UAMI, Consejo de la Div. C.B.S., (Sesión 15.14-131014) and Secretaría de Educación Pública-PROMEP (UAMI-CA-117) and partially by a CONACyT fellowship to J. Lozano. This paper contains in part the results of a Doctoral dissertation of Jorge Gregorio Lozano-Orozco. The authors thank Dr. Juan Manuel López-Bautista from the University of Alabama, Tuscaloosa, for his useful suggestions to the text. To Dr. Michel J. Wynne for reading the manuscript and adding valuable suggestions for improvement.

Cite this paper

Jorge G. Lozano-Orozco,1 1,Abel Sentíes,Olivier De Clerck,Kurt M. Dreckmann,Jhoana Díaz-Larrea, (2015) Two New Species of the Genus Dictyota (Phaeophyceae: Dictyotales) from the Mexican Caribbean. American Journal of Plant Sciences,06,2492-2501. doi: 10.4236/ajps.2015.615251


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