C. Barre Hellquist

Cryptic species in an endangered pondweed community (Potamogeton, Potamogetonaceae) revealed by AFLP markers

Cryptic species are morphologically indistinguishable, yet reproductively isolated. Morphological boundaries between species can also be obscured by hybridization and clonality. Determining the roles of reproductive isolation, hybridization, and clonality in morphologically indistinguishable taxa is essential to determining appropriate species-level taxonomic rankings for conservation purposes. The taxonomic status of the endangered Little Aguja pondweed of west Texas, Potamogeton clystocarpus, is uncertain due to a lack of fixed morphological differences between it and two sympatric congeners. Morphology, amplified fragment length polymorphisms (AFLPs), and sequences of the internal transcribed spacer (ITS) region and trnL-F intron and spacer were used to determine the degree of genetic distinctiveness, hybridization and clonality for this rare species. AFLPs indicate that P. clystocarpus is a genetically distinct lineage compared to P. pusillus and P. foliosus. No hybrids involving P. clystocarpus were detected, but two putative hybrids involving P. pusillus and P. foliosus were identified. Clonal growth was only detected in P. pusillus. A combination of morphological and molecular markers was successful in determining the genetic distinctiveness of an endangered cryptic species, Potamogeton clystocarpus. Further sampling in this and adjacent drainages is necessary to assess the degree of endemism of P. clystocarpus and confidently rule out hybridization and clonality in this taxon.

Nuclear and plastid DNA sequences reveal complex reticulate patterns in Australian water-lilies (Nymphaea subgenus Anecphya, Nymphaeaceae)

Thisstudyrepresentsthe firstcomprehensiveanalysisofphylogeneticrelationshipswithintheAustralianwater- lilies,Nymphaeasubg.Anecphya.Our51-accessiondatasetcoversall10speciesofthesubgenus,exceptthenewlydescribed N. alexii, and includes information from the nuclear ITS as well as from thechloroplasttrnTtrnFregion. The results show that molecular data are consistent with morphology, because the subdivision of subg. Anecphya into two major clades, a large-seeded and a small-seeded group, could be confirmed. Within the large-seeded group, Nymphaea atrans and N.immutabilisseemtoformoneclade,whereassamplesofN.gigantea,N.georginae,N.macrospermaandN.carpentariae form another. Relationships within the small-seeded group, containing all samples of N. violacea, N. elleniae and N. hastifolia, are less clear, since the trees obtained from the chloroplast and the nuclear marker are incongruent. The samplesofN.violaceadonotformamonophyleticgroupineachofthetrees,but—atleastintheITStree—groupwitheither N. elleniae or N. hastifolia/Ondinea, respectively. Polymorphisms among ITS paralogues, i.e. substitutions at single nucleotidepositionsandlengthpolymorphisms,havebeenobservedinsomesamplesofN.violacea.Thisfactaswellasthe incongruent phylogenetic signal obtained from the chloroplast and the nuclear genomes point to recent hybridisation or introgression in this group. Remarkably, Ondinea purpureais resolved within the small-seeded group by both markers and seems to have a close relationship to N. hastifolia. Although incomplete lineage sorting cannot be fully excluded to explain high variability in N. violacea, molecular data potentially hint to a case of still imperfect taxonomy.

Taxonomic Considerations in Aquatic Vegetation Assessments

ABSTRACT Correct identification of vascular aquatic plants is extremely important when studying waters for various management policies. The plants should be thoroughly examined by a person familiar with aquatic flora who is able to interpret technical botanical keys, because many taxa are similar in appearance. Misidentification often leads to possible eradication of an important or rare species from a body of water. Voucher specimens should be collected from the area studied. These specimens must be recorded in field notes, pressed as soon as possible, and then properly identified. Complete data should include such things as associated plants, water characteristics, and a detailed location description. A good library of various field manuals and the use of a herbarium are very helpful in making correct identifications. Specimens should be placed in a herbarium collection at a location that is easily accessible, such as a university or state agency. Voucher sheets serve as valuable documentation that may ...

Xylem of early angiosperms: Nuphar (Nymphaeaceae) has novel tracheid microstructure1

SEM studies of xylem of stems of Nuphar reveal a novel feature, not previously reported for any angiosperm. Pit membranes of tracheid end walls are composed of coarse fibrils, densest on the distal (outside surface, facing the pit of an adjacent cell) surface of the pit membrane of a tracheid, thinner, and disposed at various levels on the lumen side of a pit membrane. The fibrils tend to be randomly oriented on the distal face of the pit membrane; the innermost fibrils facing the lumen take the form of longitudinally oriented strands. Where most abundantly present, the fibrils tend to be disposed in a spongiform, three-dimensional pattern. Pores that interconnect tracheids are present within the fibrillar meshwork. Pit membranes on lateral walls of stem tracheids bear variously diminished versions of this pattern. Pits of root tracheids are unlike those of stems in that the lumen side of pit membranes bears a reticulum revealed on the outer surface of the tracheid after most of the thickness of a pit membrane is shaved away by the sectioning process. No fibrillar texturing is visible on the root tracheid pits when they are viewed from the inside of a tracheid. Tracheid end walls of roots do contain pores of various sizes in pit membranes. These root and stem patterns were seen in six species representing the two sections of Nuphar, plus one intersectional hybrid, as well as in one collection of Nymphaea, included for purposes of comparison. Differences between root and stem tracheids with respect to microstructure are consistent in all species studied. Microstructural patterns reported here for stem tracheid pits of Nymphaeaceae are not like those of Chloranthaceae, Illiciaceae, or other basal angiosperms. They are not referable to any of the patterns reported for early vascular plants. The adaptational nature of the pit membrane structure in these tracheids is not apparent; microstructure of pit membranes in basal angiosperms is more diverse than thought prior to study with SEM.

Potamogeton×haynesii (Potamogetonaceae), a new species from northeastern North America

Potamogeton×haynesii is described as a new species from northeastern North America. The nameP. longiligulatus has been misapplied to this plant. Following the study of type material,P. longiligulatus is placed in synonymy underP. strictifolius.

Microstructure of Tracheids of Nymphaea

Hand sections of root and stem xylem of diverse species of Nymphaea (including Ondinea) were studied with SEM in order to explore the diversity of wall structure within the genus. Lateral walls of root tracheary elements are untextured at the magnifications used, but end wall structure suggests that lysis of pit membranes leaves a cellulosic network with a large reticulum. Stem tracheids have lateral walls that are untextured or have a few prominent fibrils, but end walls have a dense accretion of coarse fibrils. These fibrils form a spongiform or compressed network overlying the pit membranes. In addition, on the lumen side of pit membranes, coarse fibrils cross the pits in an axial direction. These coarse fibrils are connected to pit borders, and they may extend onto wall surfaces of the tracheary elements. These fibrillar accretions are considered here to fulfill criteria as secondary‐wall components. Variation within the genus with respect to the fibrillar accretions may occur, but there may be more extensive diversity within any given sample than among species. Root tracheary elements could be considered to be vessel elements because of the extensive removal of wall material from the end‐wall pit membranes. Stem tracheary elements qualify as tracheids because, rather than showing lysis of pit‐membrane portions, end‐wall pit membranes bear fibrillar accretions that are only sparsely porose. The absence of coarse fibrillar accretions on lateral walls of stem tracheids (on tracheid‐to‐parenchyma interfaces) provides difficulty for any hypothesis that would relate wall thickenings to turgor pressure. The patterns of fibrillar accretion observed in Nymphaea include all patterns thus far reported from stem tracheids in the other genera of the family, and they must be considered to be a characteristic of Nymphaeaceae.

The endangered Florida pondweed (Potamogeton floridanus) is a hybrid: Why we need to understand biodiversity thoroughly

Thorough understanding of biodiversity is a fundamental prerequisite for biological research. A lack of taxonomic knowledge and species misidentifications are particularly critical for conservation. Here we present an example of Potamogeton floridanus, the Florida Pondweed, an endangered taxon endemic to a small area in the Florida panhandle, whose taxonomic status remained controversial for more than a century, and all previous attempts to elucidate its identity have failed. We applied molecular approaches to tackle the origin of the mysterious taxon and supplemented them with morphological and anatomical investigations of both historical herbarium collections and plants recently collected in the type area for a comprehensive taxonomic reassessment. Sequencing of two nuclear ribosomal markers and one chloroplast non-coding spacer resulted in the surprising discovery that P. floridanus is a hybrid of P. pulcher and P. oakesianus, with the former being the maternal parent. The hybrid colony is currently geographically isolated from the distribution range of P. oakesianus. We show that previous molecular analyses have failed to reveal its hybrid identity due to inadequate nuclear DNA sequence editing. This is an example how the uncritical use of automized sequence reads can hamper molecular species identifications and also affect phylogenetic tree construction and interpretation. This unique hybrid taxon, P. ×floridanus, adds another case study to the debate on hybrid protection; consequences for its conservation are discussed.

Distribution and Ecology of a New Species of Water-lily, Nymphaea loriana (Nymphaeaceae), in Western Canada

Nymphaea loriana Wiersema, Hellq. & Borsch (Lori’s Water-lily) is a newly described, Canadian endemic species that has been found in central Manitoba and east-central Saskatchewan. To assess the status of a species, data regarding its distribution, population size, habitat, and search effort are needed. The purpose of this paper is to document these factors for this species. The extent of occurrence of N. loriana is approximately 15 100 km 2 but the known area of occupancy is a mere 20 km 2 . The estimated population size of N. loriana is about 750 individual plants, although more may exist on poorly explored rivers and lakes within the extent of occurrence and possibly in northeastern Ontario. Nymphaea loriana occurs in fresh, stagnant, or slowly moving water in boreal lakes and rivers and is typically associated with N. leibergii (Dwarf Water-lily), Schoenoplectus tabernaemontani (Soft-stemmed Bulrush), Potamogeton natans (Floating-leaved Pondweed) and Nuphar variegata (Variegated Pondlily). Potential threats to the persistence of this species include low water quality resulting from mining, forestry, and agriculture, and changes to water flow because of dam construction and climate change. Monitoring known populations and searching for additional ones may be needed to assess the status of this species.