Paula S. Williamson

Floral development in the Nymphaeales

Numerous phylogenetic analyses and recent paleobotanical findings continue to support the inclusion of Nymphaeales as basal or near‐basal extant angiosperms. The distinctive differences in floral morphology and habit between non‐Nymphaealian taxa of the ANITA grade compared with water lilies, nevertheless, remain perplexing. In this investigation, scanning electron microscope observations on Brasenia (Cabombaceae), Nuphar, Nymphaea, Ondinea, Victoria, and Euryale (Nymphaeaceae) are added to the observations of earlier investigations to enhance our understanding of early floral evolution and shifts in floral ontogeny and to contribute new data for improved cladistic analyses. The enlargement of flowers and amplification of floral parts distinctive in Nymphaeaceae is based on continuing surface area enlargement of the floral apex, allowing numerous organs to be produced acropetally in distinctive parastichies, compared with the ring meristem found in some primitive eudicots (Nelumbonaceae, Papaveraceae) that increase floral organ number but in dense pulses or clusters without clear order. The smaller flowers of the Cabombaceae and their lower number of floral organs are now regarded as more typical of the ancestral angiosperm flower. One may conclude that changes in the size of the floral apex and its geometric conformation alter flower size, number of parts, and phyllotaxy. The ebracteate condition and herbaceous, aquatic habit of Nymphaeales when compared with Archaefructus, a recently discovered herbaceous aquatic angiosperm from the Upper Jurassic/Lower Cretaceous that is proposed as a new basal angiosperm family, continue to question the relationship of early angiosperms to the aquatic habitat. Is the ebracteate state significant, and how did the shift to aquatic habitats impact floral form of early angiosperms?

Levels and patterns of genetic variation in the endangered species Abronia macrocarpa (Nyctaginaceae)

Genetic variation was evaluated in the federally endangered species Abronia macrocarpa (large-fruited sand-verbena), an herbaceous perennial restricted to deep sandy soils and endemic to three counties of east-central Texas. Seven of the ten known populations were sampled and analyzed using starch gel electrophoresis of eight enzymes coded by 18 interpretable loci. Duplicate gene expression was observed for four loci, suggesting polyploid ancestry for the lineage that includes A. macrocarpa. Values for estimators of genetic polymorphism within populations (ranges: P = 38.9%-61.1%, A = 1.7-2.1, H = 0.122-0.279) exceeded average values for seed plants (P = 34.2%, A = 1.53, H = 0.113). Genotype proportions at most loci in most populations were in Hardy-Weinberg equilibrium, consistent with obligate outcrossing previously documented for this species; exceptions could be attributed to population substructure. Values of F(ST) tended to be high, ranging from 0.021 to 0.481 for individual loci (mean F(ST) = 0.272), indicating substantial divergence and limited gene flow among populations, despite their close geographic proximity. Pairwise values of Neis genetic identity between populations ranged from 0.799 to 0.975 and tended to be influenced by geographic proximity of population pairs. Collectively, these data suggest a long history of isolation among populations that have not been subjected to bottlenecks. Isolation of A. macrocarpa populations apparently results from the disjunct occurrence of suitable habitat and perhaps has been accentuated by human disturbance.

Phylogenetic interpretations from selected floral vasculature characters in the Nymphaeaceae sensu lato

Abstract The Nymphaeales are assigned a key, basal, pivotal evolutionary position in nearly every old and modern system of classification. Over the past three decades many of the studies on this plant group have focused on floral aspects, especially vasculature and developmental studies. In this investigation, literature on the floral vasculature of the taxon has been reviewed with 12 characters selected for cladistic analysis. Results of phylogenetic analysis of floral vascular features are in agreement with other sets of data (e.g. morphological, biochemical, molecular) in retaining the Nelumbonales as a separate order from the Nymphaeales. Floral vasculature features offer less resolution, however, of relationships within the Nymphaeales.

BREEDING SYSTEM OF ASTROPHYTUM ASTERIAS: AN ENDANGERED CACTUS

Abstract Astrophytum asterias is an endangered cactus occurring in southern Texas and northeastern Mexico. The purpose of this study was to provide fundamental information about the reproductive biology of the species. Breeding-system experiments were conducted in Starr County, Texas. Pollination treatments were applied to explore whether the species is self-compatible or self-incompatible and whether plants are experiencing pollinator limitation. Treated (bagged) flowers were self-pollinated or outcrossed by hand, or allowed to naturally self-pollinate. Control flowers were unbagged and unmanipulated (open-pollinated). In each treatment and controls, we calculated mean fruit set and mean seed set per plant. Controls had 18.3% fruit set, with a mean seed set of 13.3 ± 14.7 seeds. The outcross treatment resulted in 88.6% fruit set, with a mean seed set of 95.8 ± 5.9 seeds. Median mean fruit and seed set in the outcross treatment were 1 and 92.7, respectively. Although some controls set fruit and seed, median mean fruit and seed set was 0. No fruit or seed was set in self-pollinated treatments. These results showed that the species is an obligate outcrosser. Reproductive success is, therefore, dependent on a vector to transfer pollen. The fact that fruit set and seed set were higher in hand-outcrossed flowers than in open-pollinated flowers suggests that A. asterias might be experiencing reproductive constraints in terms of availability or effectiveness of pollinators.

Floral aspects of Barclaya (Nymphaeaceae): pollination, ontogeny and structure

Barclaya, endemic to Southeast Asia, includes four species: B. longifolia Wallich. B. motleyi Hooker f., B. kunstleri (King) Ridley, and B. rotundifolia Hotta. The genus has been traditionally assigned monotypic status in the family Barclayaceae or tribe Barclayeae primarily based on the occurrence of a hypogynous calyx, originally interpreted as an involucre in an otherwise epigynous flower, orthotropous ovules, lack of an aril, and inaperturate pollen. Cladistic and molecular studies support the association of Barclaya with Euryale, Victoria, Nymphaea, Ondinea, and Nuphar in the family Nymphaeaceae. Floral structure reveals (1) vasculature and developmental support for the hypothesis that the hypogynous appendages are sepals, (2) that pollen is zonasulculate, (3) that floral ontogeny is similar to that previously described for epigynous members of the Nymphaeaceae s. str., and (4) anatomical and morphological similarities with other Nymphaeaceae s. str. The cleistogamous and chasmogamous flowers are self-pollinating, the latter perhaps facilitated by flies in emergent flowers.

Effectiveness and Importance of Pollinators to the Star Cactus (Astrophytum asterias)

Abstract Astrophytum asterias (star cactus) is an obligate outcrosser that does not reproduce vegetatively, so all reproduction is the result of inter-plant transfer of pollen by insects. By measuring seed set resulting from single pollinator visits, we evaluated effectiveness (mean seed set per visit) and importance of pollinator (effectiveness times frequency of visitation) of insects visiting flowers of A. asterias. Results indicate that the most common visitor, Macrotera lobata, is a relatively ineffective pollinator, while the less common Diadasia rinconis is the most effective and important pollinator. Two behavioral variables (duration of visit, whether or not visitors landed on the stigma) were assessed as possible predictors of fruit set. While duration of visit was not predictive of fruit set, there was a positive correlation between fruit set and the proportion of visits a visitor landed on the stigma when entering the flower.

Germination of Seeds in the Endangered Abronia macrocarpa

Abstract Abronia macrocarpa is endemic to Texas and it is listed as endangered by federal and state agencies, but it is believed to have a high potential for recovery. Reintroduction is a potential option for recovery of this species and this could be accomplished using seeds planted in the field or transplanting individuals produced ex situ from seeds. We used a split-plot design to determine the percentage of seeds germinating in the field and to test effects of planting seeds in spring versus autumn. Season of planting significantly influenced percentage of germination. Seeds planted in spring (April 2005) exhibited 27.8% germination, while germination of seeds planted in autumn (November 2005) was only 0.8%. We also investigated the induction of seed germination in the laboratory. Difference in germination was 0–68.6% between the control and treatments. Combining scarification then warm stratification followed by cold stratification resulted in significantly higher germination than other treatments.

College Student Knowledge and Perceptions of Invasive Species

The purpose of this study was to determine college students’ understanding of invasive species and their support for plant and animal pest control and eradicationmethods. Surveys were administered at a university and community college in Texas in biology and agriculture departments. A total of 533 respondents participated in the study. Most students said they were not part of any type of environmental organization and felt they were not very informed about invasive species issues. More students reported learning about invasive species in high school than in college courses. The average score on knowledge questions related to invasive and native plants and animals was 32%. Most students underestimated the negative impact of invasive species but many were aware of costs to manage those species. Reliable reported sources of information included environmental organizations, college courses, and the Internet. Pearson product-moment correlations showed positive relationships between students who had college class instruction regarding invasive species and positive attitudes toward management of invasive species. Positive relationships were also found between instruction and an awareness of invasive plants or animals. Respondents whowere knowledgeable of invasive species in the community had more positive attitudes toward the management of invasive species. In demographic comparisons, differences were found with males, upperclassmen, and those identifying as Caucasian or other havingmore knowledge of invasive species and more positive attitudes toward their management.