COMPARISON OF ISOZYMES AMONG TYPHA SPECIES IN THE EASTERN UNITED STATES

Biochemical phenotsypes of four taxa of Typha from the eastern United States were determined by starch gel electrophoresis. The isozyme banding patterns of T. latifolia, T. angustifolia and T. domingensis are distinct and allow unambiguous species identification when morphological characters are inadequate or unsuitable. The fourth form, T. glauca, is not an F₁ hybrid, but it does appear to be intermediate between T. latifolia and T. angustifolia. The status of T. glauca and evolutionary relationships among the four forms may now be clarified by additional sampling because of the distinct and relatively invariant isozyme banding patterns which are described.     

Regional differences in the abundance of native, introduced, and hybrid Typha spp. in northeastern North America influence wetland invasions

In northeastern North America, an important wetland invader is the cattail Typha × glauca, a hybrid of native Typha latifolia and introduced Typha angustifolia. Although intensively studied in localized wetlands around the Great Lakes, the distributions of the hybrid and its parental species across broad spatial scales are poorly known. We obtained genotypes from plants collected from 61 sites spanning two geographical regions. The first region, near the Great Lakes and St. Lawrence Seaway (GLSL), has experienced substantial Typha increases over the last century, whereas more modest increases have occurred in the second region across Nova Scotia, New Brunswick, and Maine (NSNB). We found that hybrids predominate in the GLSL region, thriving in both disturbed and undisturbed habitats, and are expanding at the expense of both parental species. In contrast, the native T. latifolia is by far the most common of the three taxa across all habitat types in the NSNB region. We found no evidence that the formation of backcrossed and advanced-generation hybrids is limited by the reproductive barriers that are evident in F₁ hybrids. However, although backcrossed individuals arise in both regions, they are much less common than F₁ hybrids, which may explain why the parental species boundary remains. We conclude that F₁ hybrids are playing a key role in the invasion of wetlands in the GLSL region, whereas their low frequency in the NSNB region may explain why Typha appears to be much less invasive further east. An improved understanding of these contrasting patterns of distribution is necessary before we can accurately predict future wetland invasions.     

Typha glauca Godron and its parental plants in Poland: taxonomic characteristics

Natural interspecific hybridization between Typha latifolia L. and Typha angustifolia L. was analyzed by morpho-anatomical and molecular methods to determine whether the hybrid Typha glauca Godr. is present in Poland and to identify the best diagnostic traits for its identification. Eighty-three samples of the Typha species were collected. Nine random amplified polymorphic DNA (RAPD) primers provided 12 fragments specific for T. angustifolia and eight fragments specific for T. latifolia. DNA of all sampled individuals was analyzed with 20 diagnostic RAPD markers. The morpho-anatomical variability of T. glauca F₁ was found to be quite similar to that observed in parental plants. All of the 41 traits examined in the hybrids overlapped with those observed in the parents, however, the hybrids were visibly closer to T. angustifolia than to T. latifolia. The most discriminate characteristics were the length and pedicel width, as well as the epidermal cell thickness located above vascular bundles in leaf blades. Moreover, preliminary observations of seed sculpture showed that the length of testa cells could also be used to identify T. glauca. Clusters and the hybrid index (for molecular and morphological data) were highly coincident and support the hybridization hypothesis.     

Effects of experimental harvesting of an invasive hybrid cattail on wetland structure and function

Invasive plants, such as the hybrid cattail Typha × glauca, can reduce biodiversity and alter the ability of wetlands to provide critical ecosystem services, including nutrient cycling and carbon storage. Several approaches have been used to reduce Typha dominance and restore invaded wetlands, but long‐term studies assessing benefits of these restoration efforts are limited. A previous study demonstrated that aboveground harvesting of Typha × glauca stems and litter reduced Typha dominance 2 years post‐treatment in a Great Lakes coastal wetland. In the current study, we extended monitoring of experimental aboveground Typha harvest to 4 years post‐treatment and added assessments of treatment effects on soil nutrients, carbon emissions, and microbial community composition. Aboveground harvest treatment resulted in a dramatic reduction in Typha litter cover that persisted for 4 years, increased soil temperature, and increased abundance of the native plant genus Carex. However, aboveground harvest treatment did not significantly reduce Typha abundance, nor did it have significant effects on soil nutrient concentrations, carbon fluxes, or the taxonomic composition of soil microbial communities. We did observe differences in bacterial community composition between plots based on time since Typha invasion, which may indicate some legacy effects of Typha invasion. At the scale of this experiment (4 × 4 m plots), our results indicate that a single aboveground removal of Typha × glauca is not sufficient to restore a heavily invaded freshwater wetland ecosystem, and that periodic harvesting of Typha stems and litter may be required to maintain native plant abundance.     

Intercontinental dispersal of Typha angustifolia and T. latifolia between Europe and North America has implications for Typha invasions

The full effects of biological invasions may be underestimated in many areas because of cryptogenic species, which are those that can be identified as neither native nor introduced. In North America, the cattails Typha latifolia, T. angustifolia, and their hybrid T. × glauca are increasingly aggressive invaders of wetlands. There is a widespread belief that T. latifolia is native to North America and T. angustifolia was introduced from Europe, although there has so far been little empirical support for the latter claim. We used microsatellite data and chloroplast DNA sequences to compare T. latifolia and T. angustifolia genotypes from eastern North America and Europe. In both species, our data revealed a high level of genetic similarity between North American and European populations that is indicative of relatively recent intercontinental dispersal. More specifically, the most likely scenario suggested by Approximate Bayesian Computation was an introduction of T. angustifolia from Europe to North America. We discuss the potential importance of our findings in the context of hybridization, novel genomes, and increasingly invasive behaviour in North American Typha spp.     

Molecular genetic data reveal hybridization between Typha angustifolia and Typha latifolia across a broad spatial scale in eastern North America

A recent increase in the abundance of cattails (Typha spp.) in North American wetlands has been anecdotally linked with hybridization between Typha latifolia and Typha angustifolia. In this study, we used molecular genetic markers (microsatellites) to investigate whether the hybrid lineage (Typha × glauca) is restricted to The Great Lakes region, or exists across a much broader spatial scale. We also investigated the possibility of backcrossing and genetic introgression in natural populations. Parental species could be distinguished from one another based on the distribution of alleles at six microsatellite loci. Species identification based on genetic data corresponded well with species identifications based on leaf width, a key morphological trait that can distinguish the two parental species. We found that hybrids occur in Ontario, Quebec, New Brunswick, and Nova Scotia, but we did not detect hybrids in Maine. F₁s are more abundant than backcrossed or intercrossed hybrids, although we also found evidence of backcrossing, particularly in Ontario. This indicates that hybrids are fertile, and are therefore potential conduits of gene flow between the parental species. Further work is needed to determine whether T. × glauca is particularly successful in the Great Lakes region relative to other areas in which the two parental species co-exist, and to assess whether introgression may lead to increased invasiveness in the species complex.     

Gas chromatography mass spectrometry based profiling of alkyl coumarates and ferulates in two species of cattail (Typha domingensis P., and Typha latifolia L.)

Several long-chain n-alkyl coumarates and ferulates were identified in cattails (Typha domingensis and Typha latifolia) from the Florida Everglades. Characterization of these compounds was achieved based on the interpretation of mass spectra obtained by GCMS as their trimethylsilyl ether derivatives, comparison with published mass spectra and available standards. Both n-alkyl p-coumarates and n-alkyl ferulates were identified in roots and leaves of both Typha species, featuring unique distribution patterns and differences between leaf and root biomass. For both Typha species, roots have higher concentrations and a much greater diversity of n-alkyl p-coumarates and ferulates but with different side chain carbon numbers ranging from C₁₄ to C₂₈. Typha domingensis leaves only contained n-alkyl ferulates with traces of n-alkyl p-coumarates, while both types of compounds were present in Typha latifolia leaf material. These chemicals were not found in the other dominant wetland vegetation, which suggests their potential for application as phytochemical tracers of fresh cattail-derived organic matter in the Everglades ecosystem.     

Growth of three cattail (<Emphasis Type="Italic">Typha</Emphasis>) taxa in response to elevated CO<Subscript>2</Subscript>

The establishment of non-native species and the increase in atmospheric CO₂, in combination, have the ability to alter current ecosystems. Previous studies have shown that invasive species tend to respond more strongly to CO₂ than natives, but these comparisons have been of different and unrelated species. To assess how response to CO₂ might be related to invasiveness per se, we compared a native (Typha latifolia) with a congeneric invasive (Typha angustifolia), as well as their hybrid (T. × glauca). All three taxa are common components of wetland vegetation, often occurring in near monocultures. An open-top chamber experiment was used to examine the effects of elevated and ambient CO₂ concentrations on the three taxa. All three increased rhizome biomass by 40% in elevated CO₂. Although the absolute increase did not differ among taxa, the invasive T. angustifolia had a much higher proportional response in biomass and photosynthetic rate (45 and 40% respectively). The weaker response of the two larger taxa native T. latifolia (16 and 2%) and hybrid T. × glauca (−4% and −1%) was possibly driven by soil nutrient deficiency, such that they were not able to benefit from increased CO₂. However, under low nutrients the smaller species T. angustifolia may become more a problematic invader in the future.     

Analysis of pollen proteins of Typha species in relation to identification of hybrids

Hybridization studies have been carried out with Typha angustifolia, T. latifolia, T. shuttleworthii and T. minima. All combinations, except those with T. minima, were successful. The hybrid $\text{T. latifolia (♀) × T. angustifolia (♂)}$ has been obtained after 5 attempts involving hundreds of pollinations. The pollen proteins of the parental as well as the F₁ generation have been examined by isoelectrofocusing (IEF). The proteins from each species and each hybrid form displayed a distinct and constant pattern. The pollen protein profile thus represents a new, quite easily accessible character by which F₁ hybrids between the species studied can be unequivocally identified, whereas the morphological criteria described in the literature to distinguish intermediate forms is insufficient for this purpose.     

Effects of nickel toxicity on morphological and physiological aspects of osmoregulation in <Emphasis Type="Italic">Typha domingensis</Emphasis> (<Emphasis Type="Italic">Typhaceae</Emphasis>) populations

The present work examined morphological and physiological aspects of osmoregulation in some differently adapted populations of Typha domingensis. Six populations of T. domingensis were grown in waterlogged conditions under four levels of nickel (0, 50, 100 and 1500 mg/kg of Ni). The Ni tolerance was explored on the basis of different characteristics of shoots. Along with the increasing level of Ni stress, all populations showed an increment of proline and glycinebetaine content, low photosynthetic and transpiration rates and decreased chlorophyll content. Analyzed morphological parameters revealed possible adaptations to deal with Ni stress. The less tolerant Sahianwala population produced more aerenchyma, less accumulation of osmolytes and reduced shoot fresh weight under Ni stress than the tolerant ones. Our results suggested that T. domingensis has the capacity to survive under Ni stress and could be used for the absorption of toxic metal ions from industrially polluted water.     

MORPHOLOGICAL ABERRATIONS IN TYPHA POPULATIONS IN A POST-THERMAL AQUATIC HABITAT

Morphological aberrations in Typha populations inhabiting a once thermally stressed aquatic system on the Savannah River Plant in South Carolina were investigated by using both morphological and enzymatic procedures. No evidence of hybridization or introgression between T. latifolia and T. domingensis was found. Exposures of these populations to postthermal conditions and low levels of radiocesium were judged insignificant in contributing to the morphological differences observed. Both genotypic flexibility and plasticity appear to be critical factors in the adaptation of Typha to varied environments.     

Effects of invasive Typha × glauca on wetland nutrient pools,denitrification, and bacterial communities are influenced by time since invasion

Invasive plants dramatically shift the structure of native wetland communities. However, less is known about how they affect belowground soil properties, and how those effects can vary depending on time since invasion. We hypothesized that invasion of a wetland by a widespread invasive plant (Typha × glauca) would result in changes in soil nutrients, denitrification, and bacterial communities, and that these effects would increase with time since invasion. We tested these hypotheses by sampling Typha-invaded sites of different ages (~40, 20, and 13 years), a Typha-free, native vegetation site, and a restored site (previously invaded ~30–40 years ago) but that had Typha return within 2 years of the restoration. At each site, we measured Typha stem density, plant species richness, soil nutrients, denitrification rates, and the abundance and composition of bacterial denitrifier communities. All Typha-dominated sites had the least plant species richness regardless of time since invasion. Additionally, sites that were invaded the longest exhibited significantly higher concentrations of soil organic matter, nitrate, and ammonium than the native site. In contrast, denitrification was higher in sites invaded more recently. Denitrifier diversity for the nirS gene was also significantly different, with highest nirS diversity in sites invaded the longest. Interestingly, the denitrifier communities within the restored site were most similar to the ones in T. × glauca sites, suggesting a legacy effect. Our study suggests this invader can alter important ecosystem properties, such as native species richness, nutrient pools, and transformations, as well as bacterial community composition depending on time since invasion.     

Fibre cables in the lacunae of Typha leaves contribute to a tensegrity structure

Background and Aims

Cables composed of long, non-lignified fibre cells enclosed in a cover of much shorter thin-walled, crystal-containing cells traverse the air chambers (lacunae) in leaves of the taller species of Typha. The non-lignified fibre cables are anchored in diaphragms composed of stellate cells of aerenchyma tissue that segment the long air chambers into smaller compartments. Although the fibre cables are easily observed and can be pulled free from the porous-to-air diaphragms, their structure and function have been ignored or misinterpreted.

Methods

Leaves of various species of Typha were dissected and fibre cables were pulled free and observed with a microscope using bright-field and polarizing optics. Maximal tensile strength of freshly removed cables was measured by hanging weights from fibre cables, and Instron analysis was used to produce curves of load versus extension until cables broke.

Key Results and Conclusions

Polarized light microscopy revealed that the cellulose microfibrils that make up the walls of the cable fibres are oriented parallel to the long axis of the fibres. This orientation ensures that the fibre cables are mechanically stiff and strong under tension. Accordingly, the measured stiffness and tensile strength of the fibre cables were in the gigapascal range. In combination with the dorsal and ventral leaf surfaces and partitions that contain lignified fibre bundles and vascular strands that are strong in compression, the very fine fibre cables that are strong under tension form a tensegrity structure. The tensegrity structure creates multiple load paths through which stresses are redistributed throughout the 1–3 m tall upright leaves of Typha angustifolia, T. latifolia, T. × glauca, T. domingensis and T. shuttleworthii. The length of the fibre cables relative to the length of the leaf blades is reduced in the last-formed leaves of flowering individuals. Fibre cables are absent in the shorter leaves of Typha minima and, if present, only extend for a few centimetres from the sheath into the leaf blade of Typha laxmannii. The advantage of the structure of the Typha leaf blade, which enables stiffness to give way to flexibility under windy conditions, is discussed for both vegetative and flowering plants.     

THERMAL SENSITIVITIES OF MALATE DEHYDROGENASE ISOZYMES IN TYPHA

Two species of cattail. Typha latifolia L. and T. domingensis Pers., occur naturally along the shoreline of Par Pond, an 1,128 ha impoundment subjected to intermittent thermal stress at the Savannah River Plant in South Carolina. T. domingensis is not tolerant of the stresses imposed at the hottest section of this lake. Typha latifolia is established throughout the lake but at the hottest section displays an altered morphology compared with stands from ambient areas. Both T. latifolia and T. domingensis are electrophoretically monomorphic, and no variation in isozyme expression in ten enzyme systems was recorded in populations from Par Pond. The malate dehydrogenase (MDH) isozyme patterns for T. latifolia and T. domingensis are identical, but their thermal sensitivities differ sharply. All six major T. domingensis MDH isozymes are denatured by heating at 50 C; whereas, T. latifolia has three isozymes which are stable at 50 C and three isozymes which are denatured at this temperature. Tests of thermal stability are more useful than measurements of electrophoretic mobility in detecting enzyme differences and a possible biochemical basis for differences in thermal tolerance in these natural populations.     

Genetic relationship and genetic diversity among Typha taxa from East Asia based on AFLP markers

The genetic relationship and diversity among four Typha taxa in East Asia were evaluated using amplified fragment length polymorphism (AFLP) markers. Three AFLP selective primer combinations generated a total of 707 amplification products, of which 704 (99.6%) were polymorphic. The unweighted pair-group method with arithmetic mean (UPGMA) dendrogram and principal component analysis (PCA) plot confirmed the taxonomic status of four separate species. East Asian Typha taxa separated into two groups: the first with Typha angustifolia and the second with T. orientalis, T. laxmanni, and T. latifolia with a high bootstrap value for UPGMA (93%) and a low first score for PCA (25%). The two clusters corresponded with two sections based on the bracteoles in the female flower: section Bracteolatae and section Ebracteolatae. T. angustifolia showed the highest genetic diversity among the four Typha taxa (percentage of polymorphic loci [PPL] = 71%, H_o = 0.157), whereas T. latifolia had the lowest genetic diversity (PPL = 40%, H_o = 0.117). Genetic diversity was related to the presence of the gap between male and female inflorescences. A positive correlation between genetic distance and geographic distance was clearly found in the two species with continuous inflorescences (T. latifolia and T. orientalis). This positive correlation was not observed in the other species with discontinuous spikes (T. angustifolia and T. laxmanni).     

Habitat preferences of cattail species and hybrids (Typha spp.) in eastern Canada

Interspecific hybridization is widespread in plants and is an important evolutionary process. Hybrids may be fitter than their parental species, at least under some environmental conditions, and this may lead to partitioning of taxa by habitat. In eastern Canada, two cattail species (Typha latifolia and Typha angustifolia) and their hybrid (Typha x glauca) are known to have become increasingly widespread in recent decades, although their habitat preferences and patterns of co-existence at the local scale are not well known. We quantified the occurrence of these three taxa in three different habitat types (high traffic, low traffic, and ‘natural’) at 40 different sites along a sampling route of approximately 2000 km in eastern Canada. There were no significant overall associations between habitat type and taxon, although intraspecific comparisons among sites showed that the hybrid was most likely to grow in high traffic (highly disturbed) sites. In addition, pairwise comparisons revealed significant independence of T. latifolia and T. angustifolia, although the hybrid was equally likely to co-exist with either of its parental species. The presence of the three taxa in several habitats, including highly disturbed roadside areas, is consistent with their increasingly invasive tendencies.     

Typha × glauca dominance and extended hydroperiod constrain restoration of wetland diversity

Urban wetlands typically have few plant species. In wetlands designed to improve water quality, nutrient-rich water and highly variable water levels often favor aggressive, flood-tolerant plants, such as Typha × glauca (hybrid cattail). At Des Plaines River Wetlands Demonstration Site (Lake Co., IL), we assessed T. × glauca dominance and plant community composition under varying hydroperiods in a complex of eight constructed wetlands. Plots flooded for more than 5 weeks during the growing season tended to be dominated by T. × glauca, while plots flooded fewer days did not. Plots with high cover of T. × glauca had low species richness (negative correlation, R² = 0.72, p < 0.001). However, overall species richness of the wetland complex was high (94 species), indicating that wetlands in urbanizing landscapes can support many plant species where T. × glauca is not dominant. T. × glauca-dominated areas resisted the establishment of a native plant community. Removing T. × glauca and introducing native species increased diversity initially, but did not prevent re-invasion. Although 12 of the 24 species we seeded became established in our cleared plots, T. × glauca rapidly re-invaded. In year 1, T. × glauca regained an average of 11 ramets m⁻², and its density doubled in year 2. The likelihood of planted species surviving decreased as duration of inundation increased, and in both seeded and planted plots, graminoids had greater survivorship through year 2 than forbs across a range of water levels. Within 4 years, however, T. × glauca was the most common plant, present in 92% of the cleared plots. Simply removing T. × glauca and adding propagules to an urban wetland is not sufficient to increase diversity.     

Fine-scale environmental variation contributes to introgression in a three-species spruce hybrid complex

Hybridization is common for many forest trees, where weak barriers to reproduction obscure species boundaries. We characterized the genomic structure of Picea populations comprising three species spanning two well-known contact zones, the Picea sitchensis?×?Picea glauca and the P. engelmannii?×?P. glauca hybrid zones, using a set of 71 candidate-gene single nucleotide polymorphisms. The genetic structure of populations suggests a complex genomic architecture shaped by interspecific gene flow and strong environmental selection, with increased genetic diversity in hybrids. The presence of admixture among all three species suggests that three-way hybrids with mixed ancestry occur where species ranges overlap in transitional environments. Significant clinal variation and associations with climatic variables (including continentality, temperature, and precipitation) differ between hybrid zones, indicating that individual species and their hybrids are adapted to distinct environmental niches. Allele–environmental association analysis revealed that most of the candidate genes with evidence of selection were unique to either the Sitka?×?white or the Engelmann?×?white hybrid zones, with few shared between these zones. Management of these widespread and diverse gene pools will be best served through development of climate-based seed transfer, with recommended seed sources informed by a combination of genetic and climatic information for future climates.     

Anomalies of broad-leaved cattail (<Emphasis Type="Italic">Typha</Emphasis> L., Typhaceae) in a small anthropogenic pond of the Upper Volga basin

An increased anthropogenic impact on the hydrophilic ecosystems of technogenic ponds of the Volga–Caspian basin has enhanced the migration of Typha latifolia L. and closely related species. Due to backcrossings and anomalies among bractless sections of the genus Typha, new morphological traits have been formed in T. latifolia via the stage of a nonspecific form development. Morphological anomalies revealed in an association of Typhetum latifoliae Soó 1927 of a small anthropogenic pond in the Yaroslavl region have been studied.     

Emergent macrophytes in phosphorus limited marshes: do phosphorus usage strategies change after nutrient addition?

Two strategies for phosphorus (P) economy in P-limiting environment are conservation of use and enhanced acquisition. Using two wetland macrophytes as an example, we show how these strategies change when the P-limitation is removed. Phosphorus resorption and activities of root phosphatases were evaluated over 4 years in Eleocharis cellulosa Torr. and Typha domingensis Pers. from nutrient addition experiment (P, N, N&P, control) established in 15 P limited marshes of Belize. We hypothesized that after P addition both species will increase tissue P content and decrease P resorption efficiency and root phosphatase activity. Initially high phosphorus resorption efficiency, PRE, significantly decreased in Eleocharis 2 years after the first nutrient addition, while no significant decrease was recorded for Typha. Even more dramatic was 5- to 6-fold increase in P in senescent tissues of Eleocharis as compared to less than 2-fold increase in Typha. Root phosphatase activity was high for both species from control plots. After P addition, Eleocharis showed 35% to 70% decrease in enzyme activity correlated to availability of inorganic P in sediments. Eleocharis and Typha employ the “conservation of use” strategy when growing in P limited oligotrophic marshes. In addition, Eleocharis is also using the “enhanced acquisition” strategy. These strategies change when the P limitation is removed but the response varies between the two species and thus changes in the proportion of these two species in a community may result in differences in ecosystem processes such as decomposition.