Fourth NAWQA Taxonomy Workshop on Harmonization of Algal Taxonomy October 2000

Transcription

1 Fourth NAWQA Taxonomy Workshop on Harmonization of Algal Taxonomy October 2000 Report No F The Patrick Center for Environmental Research held October 2000 at The Academy of Natural Sciences 1900 Benjamin Franklin Parkway Philadelphia, PA Prepared by Eduardo A. Morales February 7, 2001

2 INTRODUCTION The Fourth NAWQA Diatom Taxonomy Workshop was held at the Academy of Natural Sciences of Philadelphia (ANSP) on October Specialists participating in the workshop were: Dr. R. Jan Stevenson and Kalina Manoylova from Michigan State University; Dr. Rex L. Lowe from Bowling Green State University; Dr. Sophia I. Passy from the U.S.G.S Ecological Survey and the New York State Department of Environmental Conservation; William R. Cody, environmental consultant based in Ohio; Dr. Loren L. Bahls, environmental consultant based in Helena, Montana; Todd A. Clason, environmental consultant based in Seattle, Washington; and from the Patrick Center for Environmental Research s Phycology Section at the Academy of Natural Sciences of Philadelphia, Dr. Marina Potapova, Dr. Eduardo A. Morales, Dr. Donald F. Charles, Diane M. Winter, Karin C. Ponader and Frank W. Acker. The three previous NAWQA Taxonomy Workshops had the overall objectives of harmonizing taxa names used in the ANSP and University of Louisville/University of Michigan laboratories, identifying reference images for each taxon, and agreeing on up-to-date nomenclature to use when analyzing NAWQA 1997-start samples (see ANSP, 1999; 2000a,b). The fourth NAWQA Diatom Taxonomy Workshop focused on issues concerning the taxonomy of problematic Navicula and Gomphonema species. Taxa that received most attention during the workshop occur commonly in NAWQA material and are often difficult to identify during routine light microscopy. Future workshops will focus in a similar way on other genera. Dr. Potapova selected taxa in need of further taxonomic investigation based on her review of existing NAWQA data. During her preparation of data sets for ecological analyses, she had many sample counts in which some taxa seemed to have been either misidentified or lumped under a single name. On the other hand, she reviewed many slides containing type material and found that several taxa listed in NAWQA counts were in fact misidentified. Based on these observations, she compiled a list of problematic taxa within Navicula and Gomphonema. In most of the cases, problematic taxa corresponded to groups of species that may be easily confused with each other because they have similar diagnostic characteristics. Such problematic taxa were arranged into units referred to as complexes : Complex 1 - Navicula tripunctata - N. tripunctata var. schizonemoides - N. recens - N. sp. 5 ANS WRC - N. margalithii - N. erifuga - N. cari - Bill Cody s N. sp. 5 THE ACADEMY OF NATURAL SCIENCES 1 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

3 Complex 2 - Navicula cryptotenella - N. menisculus - N. radiosa var. tenella - N. cincta var. rostrata Complex 3 - Navicula notha - N. leptostriata - N. heimansioides Complex 4 - Navicula luzonensis - N. biconica - N. subminuscula Complex 5 - Gomphonema pumilum spp. Complex 6 - Gomphonema minutum - G. kobayasii An electronic version of the above list was sent to non-ansp workshop participants, and they were asked to prepare plates with photographs of specimens that they believed were difficult to determine and fell within one of the complexes listed above. These plates were distributed electronically among participants so they could raise hypotheses as to the identity of depicted taxa. Each participant was also asked to prepare a short presentation on any one of the complexes. Presentations were to incorporate the historical background of the taxa covered in that complex, different views in the literature as to their taxonomic position, affinities with closely related taxa, features used for identification, and relevant ecological information that might be helpful in the characterization of the taxon in question. Each presentation was to last 15 minutes and be followed by brief discussions. During the workshop, laboratory sessions were held following each one or two presentations and concentrated on examination of type slides from the Diatom Herbarium at ANSP and/or permanent slides from NAWQA study units. During laboratory sessions, intensive discussion and literature search led, in many cases, to the application of correct names to problematic taxa or to the conclusion that more research was needed in order to be confident about the identity of certain species and their varieties. During observation of type slides and laboratory discussions, Dr. Charles W. Reimer s participation was often crucial in reaching a THE ACADEMY OF NATURAL SCIENCES 2 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

4 decision regarding the application of a name. He also provided references, material, and translations from German for many of the taxa covered during the workshop. At the end of the final day of the workshop, all participants met to discuss the format and contents of the workshop report, names to be applied to specimens depicted on plates prepared prior to the event, changes to be made to NAWQA counts in light of the evidence generated during the discussion sessions, and the possible topics of future diatom taxonomic workshops. This report includes the outcomes of discussions arranged by complex and plates to support decisions made during such discussions. These plates should be used by NAWQA taxonomists as a reference for future identification of depicted taxa. Plates include images presented before the workshop and during presentations, images scanned from bibliographical references, and images taken during and after the workshop. Morphological terminology used in this report follows Barber and Haworth (1981) and Cox (1996). THE ACADEMY OF NATURAL SCIENCES 3 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

5 WORKSHOP OUTCOMES Complex 1 - Navicula tripunctata - N. tripunctata var. schizonemoides - N. recens - N. sp. 5 ANS WRC - N. margalithii - N. erifuga - N. cari The main reasons for considering these taxa were that, in many instances, each name listed had been applied to more than one morphological group, and/or a single morphological group had been identified using more than one of these names. For example, at least two different morphological groups were identified as N. tripunctata var. schizonemoides herein referred to as Groups I and II. Group I (Plate 1, Figs. 1-19) resembles material presented by Krammer and Lange-Bertalot (1986) as N. recens. The latter is a second name used by some NAWQA taxonomists to refer to this Group I. Additionally, a third name Navicula sp. 5 ANS WRC- was applied to this same group. Group II (Plate 2, Figs. 1-9) also received three different names: N. tripunctata var. schizonemoides, N. heufleri var. leptocephala, and N. erifuga. The taxonomic status of N. tripunctata var. schizonemoides is largely unclear in the literature. Specimens depicted in Plate 1 have been traditionally considered by taxonomists based in the U.S. to belong to this taxon (e.g., Patrick and Reimer, 1966). The combination N. tripunctata var. schizonemoides was erected by Patrick (1959) based on specimens identified by Van Heurck ( , Text, p. 83; Atlas, plate VII, Figs. 9 and 10) as N. gracilis var. schizonemoides. Van Heurck considered Schizonema neglectum (Thwaites, 1848) to be the basyonym of N. gracilis var. schizonemoides. However, observations made by Lange-Bertalot (pers. comm.) on type material of Schizonema neglectum led him to conclude that the latter taxon is simply a synonym of N. tripunctata (nominate variety). Hence, the synonymy established by Van Heurck, and thus Patrick s combination, might be incorrect. Since only drawings of Schizonema neglectum are available in the literature at this time, the true identity of this taxon remains unresolved and merits further research. On the other hand, European workers have often included specimens resembling those presented in Plate 1 (Figs. 1-19) in N. recens (Krammer and Lange-Bertalot, 1986; Lange- Bertalot, 1980). Frustule dimensions and characteristics of NAWQA specimens depicted in Plate 1 fit the description of N. recens. However, N. recens is also a species that needs further revision as pointed out by its own author (Lange-Bertalot in Krammer and Lange-Bertalot [1986]). Many diagnostic features are shared with other taxa and the only character that seems unique; i.e., the THE ACADEMY OF NATURAL SCIENCES 4 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

6 convergence of the striae at the valve ends, might be a state of either a purely genetically determined or an environmentally induced character. The literature contains no reference to the relationship between N. tripunctata var. schizonemoides and N. recens. Production of mucilage tubes by N. tripunctata var. schizonemoides has been reported (Patrick, 1959; Patrick and Reimer, 1966). Evidently, this was a key feature in separating this variety from N. tripunctata var. tripunctata (also mentioned by Cox [1979]). However, Lange-Bertalot (pers. comm.) states that the nominate variety of N. tripunctata is also able to produce mucilaginous tubes under certain environmental circumstances. Hence, the usefulness of mucilaginous-tube production as a character for classification of this group remains unclear. It is not known at this stage whether mucilaginous tubes are simply a facultative feature produced when organisms are subjected to changing environmental conditions. Culture studies may prove useful in solving this matter (Patrick, 2000 pers. comm.). NAWQA specimens from Groups I and II differ from N. gracilis var. schizonemoides (A- V.H. 234) (Plate 3, Figs. 1-6). Specimens in the mentioned slide are larger in size, have slightly lower density of striae and areolae, and there are also slight differences in valve shape and striae pattern at the central area. Thwaites drawings of S. neglectum (Plate 3, Fig. 11) bear even less resemblance to organisms in NAWQA samples. These drawings depict valves with parallel striae and lacking the somewhat acute-angled subfacia (due to shorter striae) characteristic of NAWQA specimens. Krammer and Lange-Bertalot s illustrations of N. recens (Plate 3, Figs. 7-10) are very similar to NAWQA specimens allocated in Group I (Plate 1). For the time being, and since the relationship between N. recens and N. tripunctata var. schizonemoides needs clarification, both names will be maintained in NAWQA counts. As for the name Navicula sp. 5 ANS WRC, this taxon should be transferred to N. recens, as agreed by workshop participants. As stated before, Group II, referred to as N. tripunctata var. schizonemoides, also received the names N. erifuga and N. heufleri var. leptocephala in NAWQA counts. It was clear to Workshop participants that for this Group II none of the taxonomic names discussed for the first group could be applied. A literature search for N. erifuga and N. heufleri var. leptocephala revealed that these two taxa are synonyms. In 1986, Krammer and Lange-Bertalot concluded that N. heufleri var. leptocephala was in fact a separate entity since transitional forms between this and the nominate variety of N. heufleri could not be found. These authors then raised N. heufleri var. leptocephala to the species level under the name N. erifuga. Workshop participants agreed to use the name N. erifuga for Group II (Plate 2, Figs. 1-9). In NAWQA counts, the name N. heufleri var. leptocephala was also applied to a group that, in reality, belongs to N. libonesis. Workshop participants agreed that the latter should be applied to organisms such as those depicted on Plate 2, Figs THE ACADEMY OF NATURAL SCIENCES 5 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

7 Although N. tripunctata (nominate variety) was not discussed in depth during the workshop, none of the participants considered it to be a problematic taxon. It is easily distinguished from the var. schizonemoides and from N. recens by the straight nature of the striae and by the symmetry of the subfacies (central area). Dr. Potapova noted that the taxon illustrated in Plate 4, Figures 1-5 has been misidentified as N. tripuncata. This taxon has an asymmetric central area, proximal raphe ends bent unilaterally toward the primary side of the valve, and only superficially resembles N. tripunctata in valve outline and striae pattern. This taxon should be kept separate from N. tripunctata, but a name for it has not been found in the literature. For now, the name Navicula sp. 5 SCTX MP should be used. K. Manoylova found a taxon (Plate 4, Figs. 6-8) that also resembles taxa in Complex 1 and is probably closely related to the N. recens-tripunctata var. schizonemoides group. This taxon is distinguishable from all the above taxa by a number of characteristics. Valve outline is clearly lanceolate and the width of the valve is narrower. Valve ends are cuneate and although the striae have similar patterns of orientation and distribution similar to N. recens and N. tripunctata var. schizonemoides, they are finer due to smaller-sized lineolae. This taxon could not be found in the literature and may also correspond to a new species. For the time being, it should be kept separate from the rest of the species in this complex under the name: Navicula sp. 1 ACAD NAWQA (NADED ID ). N. margalithii was not discussed during the workshop. Its morphology closely resembles that of N. tripunctata (nominate variety), but N. margalithii differs, among other features, in its preference for brackish to marine habitats. Navicula cari, although not discussed in depth, is sufficiently distinct and does not pose difficulties. Both N. margalithii and N. cari can be identified using Krammer and Lange-Bertalot (1991, 1986). Complex 2 Navicula cryptotenella N. menisculus N. radiosa var. tenella N. cincta var. rostrata Many inconsistencies were found in NAWQA counts regarding species in this complex. Such inconsistencies may have had their origin in the apparent existence of transitional forms among these species. This is illustrated by the case of N. cryptotenella and N. menisculusculus, in which smaller varieties of the latter species (i.e., grunowii, obtusa, and upsaliensis; see below) can resemble N. cryptotenella in both the valve outline and diagnostic valve ornamentation. THE ACADEMY OF NATURAL SCIENCES 6 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

8 NAWQA records show that names mentioned above have been used interchangeably and that, in many instances, more than one morphologically distinct group has received the same name. Krammer and Lange-Bertalot (1986) studied populations of N. radiosa var. tenella and concluded that there are no transitional forms between this and the nominate variety. Hence, they raised the variety tenella to the species level naming it N. cryptotenella. NAWQA taxonomists will follow Krammer and Lange-Bertalot s study and use the name N. cryptotenella. This taxon (Plate 5) is characterized by narrower valves (when compared to N. menisculus and its varieties), a very narrow central nodule, and radiate striae becoming parallel toward the valve ends. Characteristically, a longer stria flanked by two smaller ones is present on at least one side of the central area. Although in smaller specimens this feature may be distorted, it may be observed in the majority of the specimens encountered during routine counts. However, and as pointed out by W. Cody in his presentation of this complex, similar taxa share this diagnostic feature, but frequently differ from each other in a number of other characteristics. These include differences in valve outline, thickness of striae (hence, stria number per 10 :m), raphe structure, etc. N. cryptotenella and associated taxa can be found in plates presented by Krammer and Lange- Bertalot (1991, 1986) and they should be used as sources of identification. Plate 5 illustrates specimens found in NAWQA material and a SEM photograph from the Thames River Estuary, CT. N. menisculus (nominate variety) is a much more robust taxon than N. cryptotenella (Plate 6, Figs. 1-4). Striae in the former taxon are very conspicuous and lineolae are often visible during routine analyses. The shape of the valves is broadly lanceolate with frequently perfectly cuneate ends. Axial area is narrow, but more visible than that of N. cryptotenella. Striae are radiate and sometimes somewhat curved at the central portion of the valve due to the fact that the raphe lies on a depression (ridge) that runs along the axial area of the valve. The striae are slightly radiate to parallel at the valve ends. Although this taxon may occasionally have a short stria flanked by smaller ones at one side of the central area (e.g., Plate 6. Fig. 1), the reverse is usually true; i.e., a smaller stria is surrounded by two longer ones. N. menisculus var. upsaliensis (Plate 6, Figs. 5 and 6) differs from the nominate variety in that the valves possess slightly rostrate ends. Striae are strongly radiate and a higher number of shorter striae are present in the central axial area. A further difference between this and the nominate variety is that the striae at the poles tend to vary from parallel to slightly convergent in the var. upsaliensis. Drawings presented by Patrick and Reimer (1966) for this taxon (Plate 6, Figs. 7 and 8) were based on A-V. H. 190 (a specimen from this latter slide is presented in Plate 6, Fig. 2). However, Van Heurck s specimens differ substantially from valves in the type material of N. menisculus var. upsaliensis (Krammer and Lange-Bertalot, 1986) (Plate 6, Figs. 5 and 6). The latter possess extremely radiate and sigmoid striae in the central area and the striae at the apices might vary from parallel to slightly convergent. In contrast, specimens in A-V. H. 190 are, in general, more robust and have radiate and slightly curved striae in the central area. Striae at the apices are slightly radiate to parallel, though in a few instances they might be slightly convergent. This is to say that specimens in A-V. H. 190 bear more resemblance to the nominate variety of N. menisculus than to the variety upsaliensis (compare Fig. 2 with Figs. 1, 3, and 4 and THE ACADEMY OF NATURAL SCIENCES 7 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

9 then with Figs. 5 and 6 in Plate 6). Hence, identification of drawings in Patrick and Reimer (1966) as N. menisculus var. upsaliensis might be incorrect. N. menisculus var. grunowii is a much smaller taxon than the nominate and the upsaliensis varieties (Plate 6, Figs. 9-15). The ends of the valve vary from slightly cuneate to broadly rounded. Striae are much finer, radiate in the middle portion to parallel toward the end of the valves. The central axial area presents shorter striae which vary in number from one to four. The axial area is much narrower than in the nominate and the upsaliensis varieties. N. menisculus var. obtusa incorporates organisms with elliptical valves. Apices of the valves are rounded or slightly cuneate. Striae are parallel and end at the same level at the axial area throughout the length of the valve, although in rare cases a smaller stria can be observed at the central axial portion of the valve. Lineolae are much longer than in the grunowii variety, hence, striae are much wider in N. menisculus var. obtusa. A plate for this taxon can be found in Simonsen (1987; Plate 329, Figs. 25 and 26). In NAWQA counts, N. menisculus var. menisculus has been sometimes misidentified as N. menisculus var. upsaliensis. Many other records of N. menisculus var. upsaliensis should be changed to N. menisculus var. grunowii as revealed by observations of NAWQA material made by Dr. Potapova. Future identification of the upsaliensis variety should not be based on diagrams presented in Patrick and Reimer (1966). Apparently, the occurrence of this variety is more restricted in U.S. rivers than that of the variety grunowii. Similarly, the abundance of N. menisculus var. obtusa in these ecosystems is yet to be determined. Currently, NAWQA counts contain a few records of this taxon, but further research is needed to verify its identity. We mention it here to avoid its misidentification in the future. Type material for N. cincta var. rostrata was analyzed during the workshop (Plate 7, Figs. 1-8). This taxon seems to be sufficiently different from other taxa to support its maintenance as a separate taxon. In NAWQA counts, this name has been misapplied and in all cases records of N. cincta var. rostrata should be changed to N. veneta. The latter taxon can be identified based on Krammer and Lange-Bertalot (1986, Plate 32, Figs. 1-4, p. 505). Complex 3 Navicula notha N. leptostriata N. heimansioides The NAWQA database contains records of these species. However, the fact that all three taxa are very closely related at the morphological level made it difficult to separate them into distinct groups. Additionally, past differences among NAWQA taxonomists about the identity of THE ACADEMY OF NATURAL SCIENCES 8 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

10 N. notha and N. leptostriata made it clear that a review of the taxonomy of these taxa was needed. Examination of plates and discussion presented by Krammer and Lange-Bertalot (1986) for N. heimansioides and by Wallace (1960) for N. notha led to the conclusion that these two taxa actually represent morphological variations of a single species. The only basis used by Krammer and Lange-Bertalot for separation of these two taxa is the larger size of the frustules of N. heimansioides. Examination of the type material of N. notha (Plate 7, Figs. 9-17) revealed that the range of length given by Wallace was much shorter than many of the valves present in his permanent slide (A. G. C. 4613b). Larger specimens in such material are morphologically similar to smaller representatives of the same population, and thus, cannot be separated from specimens diagrammed by Wallace (compare Figs with Figs in Plate 7). Previous changes made in NAWQA counts from N. notha to N. leptostriata seem therefore not to be correct. An example of the occurrence of N. notha in NAWQA material is given in Plate 7, Figs N. leptostriata and N. notha can be distinguished from each other based on a number of characteristics. N. leptostriata is much less silicified, the endings of the raphe at the central nodule are closer to each other, striae are much finer (due to smaller lineolae), and the central area is much wider (Krammer and Lange-Bertalot, 1991, Plate 70, Figs. 9-14, p. 388). The extent of the occurrence of N. leptostriata in NAWQA material is yet to be determined. Available data suggest that this taxon is not common in U.S. rivers. Van Dam and Kooyman (1982) described N. heimansii, but it was later determined by Krammer and Lange-Bertalot (1986) that this taxon should be a synonym of N. leptostriata. Complex 4 Navicula biconica N. luzonensis N. subminuscula Dr. Potapova found that the names N. luzonensis and N. biconica were applied to a single morphological group. Also, the names N. luzonensis and N. subminuscula were used interchangeably to identify the morphological group illustrated in Plate 8, Figs The confusion between N. luzonensis and N. biconica seems to have had its origin in the drawing presented by Patrick and Reimer (1966) for the latter taxon (Plate 8, Fig. 12). This drawing depicts a much wider valve and much coarser striae than the type specimen (Plate 8, Fig. 13), characteristics that resemble more those of N. luzonensis (compare Figs with in Plate 8). THE ACADEMY OF NATURAL SCIENCES 9 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

11 In the specific case of the Central Nebraska study unit (Figs. in Plate 8, except Figs. 12 and 13), both N. luzonensis and N. biconica are present. In many samples from this study unit, however, counts of N. biconica should reflect lower percentages than those recorded by NAWQA taxonomists. An additional observation of specimens of N. biconica in the Central Nebraska study unit is that they seem to represent transitional forms between the type specimen of N. biconica (Plate 8, Fig. 13) and representatives of N. molestiformis, as presented in Krammer and Lange-Bertalot (1986, Plate 45, Figures 1-9, p. 531). Thus, the relationship between these latter taxa should be reviewed. As demonstrated by Krammer and Lange-Bertalot (1986), N. luzonesis (Hustedt 1942) is a synonym of N. subminuscula (Manguin, 1941). Therefore, future NAWQA counts should refer to specimens such as those presented in Plate 8, Figs as N. subminuscula. Workshop participants agreed that most records of N. biconica should be changed to N. subminuscula, and that all records of N. luzonensis should be changed to N. subminuscula. As for records of N. biconica in the Central Nebraska study unit, they should be kept as they are for now until the relationship of this population and N. molestiformis is clarified. Complex 5 Gomphonema pumilum spp. The taxonomic position of this taxon was not discussed in depth and should be considered as a topic for a future workshop. Although this taxon is sufficiently distinct from closely related taxa, NAWQA taxonomists have either confused it with other closely related gomphonemoid taxa or have applied the name G. pumilum to different morphological groups. In light of these problems, correcting the taxonomy of this taxon will be a difficult endeavor. For now, most records for G. pumilum will be left as they are. In the future, however, NAWQA taxonomists must differentiate this species from other taxa using Kociolek and Kingston (1999), Kociolek and Stoermer (1990, 1991), and Reichardt (1997). Complex 6 Gomphonema minutum G. kobayasii Many NAWQA counts contain records of these two taxa. In many cases these two names have been used to refer to a single morphological group. However, these two species are easily THE ACADEMY OF NATURAL SCIENCES 10 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

12 distinguished from each other in both their valve and girdle views. In G. minutum (Plate 9, Figs. 1-19) valves are broadly clavate, striae are much coarser due to the existence of double rows of poroids (SEM), and the arching of the striae at the central nodule is very conspicuous. In girdle view, this taxon is distinctly wedge-shaped and a single row of poroids on the valvocopulae can be seen easily (Krammer and Lange-Bertalot, 1991, Tafel 81, Fig. 4, pg. 411). NAWQA counts of this taxon also include an entity that is closer to G. tenellum, as presented in Patrick and Reimer (1975). The latter presents an incipient capitate head pole that is broader than that of G. minutum. For now, these two morphs will be kept together, but further studies should be conducted to elucidate their true identity. In G. kobayasii valve contours are not broadly clavate, but lanceolate (Plate 10, Figs. 1-11). Striae are parallel to slightly radiate in arrangement; striae on the opposite side of the stigma are distinctly disordered and irregular. The striae are much more sparse than in G. minutum and they are also less conspicuous (composed of lineolae as revealed by SEM). The axial area is broader than in G. minutum. Girdle views of G. kobayasii have the shape of rectangular boxes and also show distinct, but much coarser, rows of poroids on the valvocopulae. Plates for G. minutum and G. kobayasii are presented here (Plates 9 and 10), but also refer to Kociolek and Kingston (1999) for further details on these taxa. Although not in this complex, the taxonomic position of Gomphoneis herculeana and G. minuta was discussed (Plate 11, Figs. 1-7). Valve dimensions and striae number for both of these taxa are similar to each other and the only basis for their separation at this point are the more linear valve outline and the absence of an inflated portion in the valves of G. minuta (Kociolek and Stoermer, 1988) (compare Figs. 1 and 3 with 2 and 4 in Plate 11). More information on the morphology of these two entities, as well as their ecology, should be investigated to establish whether there is a clear separation between them. Additionally, gomphonemoid diatoms without stigmata from the Arcadian-Pontchartrain study unit were presented by K. Manoylova (Plate 11, Figs. 8-12). Her specimens closely resemble Gomphonema patrickii (Kociolek et al., 1995), and as such should be inserted in the NAWQA database. THE ACADEMY OF NATURAL SCIENCES 11 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

13 ADDITIONAL TAXA CONSIDERED DURING THE WORKSHOP In addition to the species above, the taxonomic status of several other taxa was considered. These taxa were included in discussions due to their resemblance to some of the taxa originally included in the six complexes presented above. In the case of N. symmetrica, workshop participants agreed not to follow the grouping proposed by Krammer and Lange-Bertalot (1991) in which N. symmetrica is placed as a variety in N. schroeteri. N. symmetrica is distinct from N. schroeteri and associated taxa and should stand on its own. As for the rest of the varieties in N. schroeteri presented by Krammer and Lange-Bertalot (1991), i.e., the varieties schroeteri and escambia, NAWQA taxonomists will follow the mentioned authors taxonomy. The retention of the name N. symmetrica will not cause inconsistencies in existing NAWQA data because all taxonomists distinguished this taxon from N. schroeteri in the past. N. lanceolata was also discussed during the workshop. This taxon had been discussed during the third workshop, but Dr. Bahls suggested a re-consideration of its taxonomic position. Participants examined type material from the Agardh Collection in the ANSP Diatom Herbarium and concluded that Krammer and Lange-Bertalot s decision to synonymize Frustulia lanceolata Agardh with N. lanceolata (Agardh) Ehrenberg is in fact correct (Krammer and Lange-Bertalot, 1986). Also, the same authors were correct in synonymizing N. lanceolata (Agardh) Kützing with N. trivialis Lange-Bertalot. For NAWQA purposes, the name N. viridula var. avenacea will be changed to N. lanceolata (Agardh) Ehrenberg and analysts will continue using the name N. trivialis. The use of the name N. vandamii (Krammer and Lange-Bertalot, 1991) should be avoided and N. canalis is preferred in its place. The reason for this is that N. canalis (Patrick, 1944) has priority in time over N. vandamii (Schoeman and Archibald, 1986). Examination of the type slide of N. canalis from the ANSP Diatom Herbarium (Plate 12, Figs. 1 to 4)) led to the conclusion that both of these names have been applied to a single species. Additionally, K. Manoylova presented specimens which she originally had identified as Navicula sp. 1 0B UL NAWQA 96 KM, but now should be changed to N. canalis (Plate 12, Figs. 5 and 6). All records of N. vandamii in the NAWQA database should be changed to N. canalis. N. veneta, N. exilis, and N. reichardtiana were also considered during the workshop. In NAWQA counts N. reichardtiana was commonly grouped together with N. veneta and/or N. cryptocephala var. veneta, whereas N. exilis was often included in N. veneta. N. veneta, N. exilis, and N. reichardtiana are distinct entities and should be kept separate in NAWQA counts. Thus, appropriate changes should be made and future identification of all these taxa should be based on plates presented by Krammer and Lange-Bertalot (1991, 1986). Krammer and Lange-Bertalot (1986) raised N. cryptocephala var. veneta to the species level THE ACADEMY OF NATURAL SCIENCES 12 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

14 under the name N. veneta. This decision was based on the absence of transitional forms between N. cryptocephala var. veneta and the nominate variety of N. cryptocephala. Such a decision will be adopted by NAWQA taxonomists. Workshop participants adopted the decision made by Germain (1981) indicating that N. salinarum var. intermedia is not a variety of closely related taxa such as N. salinarum or N. cryptocephala. For this reason, it should be considered as a different species and the name N. capitatoradiata should be used to refer to it. Finally, the case of N. secreta var. apiculata and N. gregaria was also considered during the Workshop. These two taxa were determined to be sufficiently different as to maintain their current status. N. secreta var. apiculata is a much more robust taxon and its pattern of striation is different from that of N. gregaria (compare Figs. 7 and 8 with Figs. 9 and 10 in Plate 12). In both taxa the striae are composed of lineolae, but in N. secreta var. apiculata these structures are larger, and therefore, the striae are more conspicuous and their density is lower (Plate 12, Figs. 7 and 8). There are also, differences in the structure of the raphe. In N. gregaria, the raphe lies on a ridge and the ends of this structure at the central nodule bend unilaterally (Plate 12, Figs. 9 and 10). Although the raphe also lies on a ridge in N. secreta var. apiculata, the proximal raphe ends are directly opposite to each other and do not bend to the sides. Both taxa should continue to be kept separate during analyses of NAWQA material and their identification should be based on photographs presented herein. Navicula gregaria has been observed to be far more common in NAWQA samples than N. secreta var. apiculata. THE ACADEMY OF NATURAL SCIENCES 13 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

15 REFERENCES Academy of Natural Sciences of Philadelphia (ANSP) First NAWQA Diatom Taxonomy Harmonization Workshop. Clason, T.A. and D.F. Charles. Patrick Center for Environmental Research. The Academy of Natural Sciences of Philadelphia. Report No a. Second NAWQA Diatom Taxonomy Harmonization Workshop. Clason, T.A. and D.F. Charles. Patrick Center for Environmental Research. The Academy of Natural Sciences of Philadelphia. Report No b. Third NAWQA Diatom Taxonomy Harmonization Workshop. E.A. Morales and M. Potapova. Patrick Center for Environmental Research. The Academy of Natural Sciences of Philadelphia. Report No Barber, H. G. and Haworth, E. Y A Guide to the Morphology of the Diatom Frustule. Freshwater Biological Association. Sci. Publ. No. 44. Titus Wilson & Son Ltd. England. 112 pp. Cox, E.J Taxonomic studies of the diatom genus Navicula Bory: The typification of the genus. Bacillaria 2: Identification of Freshwater Diatoms from Live Material. Chapman & Hall. England. 158 pp. Germain, H Flore des diatomées. Diatomophycées eaux douces et sumâtres du Massif Armoricain et des contrées voisines d Europe occidentale. Société Nouvelle des Éditions Boubée. Paris, France. 444 pp. Hustedt, F Süsswasser-Diatomeen del indomalayischen Archipiels und der Hawaii-Inseln. Internat. Rev. Hydrobiol. 42: Kociolek, J.P. and J.C. Kingston Taxonomy, ultrastructure, and distribution of some gomphonemoid diatoms (Bacillariophyceae: Gomphonemataceae) from rivers in the United States. Can. J. Bot. 77: Kociolek, J. P. & Stoermer, E. F Taxonomy, ultrastructure and distribution of Gomphoneis herculeana, G. eriense and closely related species (Naviculales: Gomphonemataceae). Proc. Acad. Nat. Sci. Phil. 140: Kociolek, J.P. and E.F. Stoermer A new, highly variable Gomphonema (Bacillariophyceae) species from Laurentian Great Lakes. Pages in M. Ricard THE ACADEMY OF NATURAL SCIENCES 14 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

16 and M. Coste, eds. Ouvrage dédié à la Mémorie du Professeur Henry Germain ( ). pp Koeltz Scientific Books, Germany Taxonomy and ultrastructure of some Gomphonema and Gomphoneis taxa from the upper Laurentian Great Lakes. Can. J. Bot. 169: Kociolek, J.P., E.F. Stoermer and M.A. Edlund Two new freshwater diatom species. Pages 9-19 in J.P. Kociolek and M.J. Sullivan, eds. A Century of Diatom Research in North America: A tribute to the Distinguished Careers of Charles W. Reimer and Ruth Patrick. Koeltz Scientific Books, Germany. Krammer, K. and Lange-Bertalot, H Bacillariophyceae. 1. Teil: Naviculaceae.In: H. Ettl, J. Gerloff, H. Heynig and D. Mollenhauer, eds. Süsswasserflora von Mitteleuropa. Vol. 2(1): Gustav Fisher Verlag, Germany Bacillariophyceae. 4. Teil: Achnanthaceae. Kritische Ergänzungen zu Navicula (Lineolatae) und Gomphonema. In: H. Ettl, J. Gerloff, G. Gärtner, H. Heynig and D. Mollenhauer, eds. Süsswasserflora von Mitteleuropa. Vol. 2(4): Gustav Fisher Verlag, Germany. Lange-Bertalot, H Zur taxonomischen Revision einiger ökologische wichtiger Naviculae lineolatae Cleve. Die Formenkreise um Navicula lanceolata, N. viridula, N. cari. Cryptogamie Algalogie 1: Manguin, E Contribution à la flore des diatomées d eau douce de Madagascar. Review Algologie 12: Patrick, R New changes and nomenclatural changes in the genus Navicula. Proc. Acad. Nat. Sci. Philadelphia 111: Patrick, R. and C.W. Reimer The Diatoms of the United States. Exclusive of Alaska and Hawaii. Vol. 1. Monographs of the Academy of Natural Sciences of Philadelphia pp The Diatoms of the United States. Exclusive of Alaska and Hawaii. Monographs of the Academy of Natural Sciences of Philadelphia 2(13): Reichardt, E Taxonomische revision des artenkomplexes um Gomphonema pumilum (Bacillariophyceae). Nova Hedwigia 65: THE ACADEMY OF NATURAL SCIENCES 15 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

17 Schoeman, F. R. & Archibald, R. E. M Navicula vandamii nom. nov. a new name for Navicula acephala Schoeman, and a consideration of its taxonomy. Nova Hedwigia 44: Simonsen, R Atlas and Catalogue of the Diatom Types of Friedrich Hustedt. Vols J. Crammer, Germany. Thwaites, G.H.K Further observations on the diatomaceae with descriptions of new genera and species. Ann. Mag. Nat. Hist. 1(2): Van Dam, H. and H. Kooyman A new diatom from Dutch moorland pools: Navicula heimansii. Acta Bot. Neerlandica 31:1-4. Wallace, J.H New and Variable Diatoms. Notulae Natura 331:1-8. THE ACADEMY OF NATURAL SCIENCES 16 PATRICK CENTER FOR ENVIRONMENTAL RESEARCH

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