GERMINATION ECOPHYSIOLOGY OF HYDROPHYLLUM APPENDICULATUM,A MESIC FOREST BIENNIAL

In north central Kentucky, seeds of the mesic forest biennial Hydrophyllum appendiculatum Michx., are innately dormant at maturity in June. Under natural and simulated seasonal temperature changes, dormancy break occurred in two stages. Root dormancy was broken by high summer temperatures, and shoot dormancy was broken by low winter temperatures. Consequently, roots emerged from seeds during autumn, and cotyledons emerged the following spring. A 90-day warm (30/15 C) stratification treatment broke root dormancy, but the roots emerged only after transfer to lower temperatures. After the warm stratification treatment, roots emerged from 93, 73, 6 and 9% of the seeds incubated at 5, 15/6, 20/10 and 30/15 C (12/12 hr), respectively. Zero, 28, 56 and 84 days of cold (5 C) stratification of seeds with emerged roots resulted in 9, 21, 49 and 82% cotyledon emergence, respectively, at 20/10 C. Thus, H. appendiculatum exhibits a type of morpho-physiological dormancy known as epicotyl dormancy. Although many seeds germinate the first year, others remain dormant and germinate in successive years until the fourth season after ripening.     

NEW GENERA AND SPECIES OF CERAMIACEAE (RHODOPHYTA) FROM THE SOUTHEASTERN UNITED STATES1

Five Ceramiaceae (Rhodophyta) are reported from the offshore waters of the southeastern, warm temperate coast of the United States. These include two new monotypic genera, Calliclavula trifurcate Schneider in the Griffithsieae and Nwynea grandispora Searles in the Sphondylothamnieae, and three new species, Callithamniella silvae Searles, Ptilothamnion occidentale Searles, and Lejolisia exposita Schneider et Searles.     

PHYSIOLOGICAL CHARACTERIZATION OF SIX LIPID-PRODUCING DIATOMS FROM THE SOUTHEASTERN UNITED STATES1

Six strains of diatoms from intertidal waters were isolated as part of the SERI Aquatic Species Program collection and screening effort: Amphiprora hyalina Greville, Cyclotella cryptica Reimann, Lewin & Guillard, Navicula acceptata Hustedt (two strains, NAVIC6 and NAVIC8), Navicula saprophila Lange-Bertalot & Bonik, and Nitzschia dissipata (Kütz.) Grunow. Among numerous algal strains isolated as part of this collection effort, these six strains showed rapid growth and elevated lipid content in preliminary screening experiments and were chosen for further physiological characterization. N. dissipata grew most rapidly at 25°C, whereas the other five strains grew best at 30–35°C. Salinity tolerance varied among strains, with maximal growth occurring at the following conductivities: 10–60 mS.cm^?1 (A. hyalina and N. acceptata NAVIC8), 10–35 mS.cm^?1 (C. cryptica), 20–45 mS.cm^?1 (N. acceptata NAVIC6), 10 mS.cm^?1 (N. saprophila), and 20–35 mS.cm^?1 (N. dissipata). The diatoms also differed in their utilization of nitrogen sources with A. hyalina growing optimally with either nitrate or urea; N. acceptata NAVIC6, with either nitrate or ammonium; C. cryptica, N. acceptata NAVIC8, and N. dissipata, with nitrate; and N. saprophila, with urea. Under optimal conditions, A. hyalina grew at 2.0 doublings. day^?1; C. cryptica grew at 3.0 doublings. day^?1. Each Navicula strain had a growth rate of 3.8 doublings. day^?1, and N. dissipata grew at 2.6 doublings.day^?1. All six strains had lipid contents in excess of 37% ashfree dry weight (AFDW) under nutrient-limited conditions, with N. saprophila having the highest lipid content at 48% AFDW.     

SEED GERMINATION ECOPHYSIOLOGY OF JEFFERSONIA DIPHYLLA,A PERENNIAL HERB OF MESIC DECIDUOUS FORESTS

Freshly-matured seeds of the mesic deciduous woodland herb Jeffersonia diphylla (L.) Pers. (Berberidaceae) have underdeveloped (ca. 0.6 mm in length) embryos and exhibit deep, simple morphophysiological dormancy (MPD). For rapid growth of the embryos at October (20/10) and November (15/6 C) temperatures in October and November, seeds must first be exposed to high (30/15 C) summer temperatures. If embryo growth is not completed in autumn, it continues during winter. However, even after 10–12 weeks at summer temperatures, embryos grew very little at 5 C, unless growth already had begun at autumn temperatures. After embryo growth has been completed, or after it has been initiated, seeds require cold stratification (5 C) to overcome dormancy. Embryos must attain a minimum length of about 1 mm before seed dormancy can be broken by cold stratification. Gibberellic acid increased the rate of embryo growth in seeds kept at 20 C, but only 1–9% of them germinated. Thus, GA substitutes for warm but not cold stratification. High summer temperatures, as well as the traditionally-used autumn and winter temperatures, should be used in germinating seeds with deep, simple MPD.     

GERMINATION ECOPHYSIOLOGY OF HERBACEOUS PLANT SPECIES IN A TEMPERATE REGION

Germination phenology data have been collected from 75 winter annuals, 49 summer annuals, 28 monocarpic perennials, and 122 polycarpic perennials, and experimental investigations of dormancy breaking and germination requirements have been conducted on 56 winter annuals, 32 summer annuals, 18 monocarpic perennials, and 73 polycarpic perennials. The purpose of these studies was to determine if there are correlations between the dormancy breaking and germination requirements of seeds and the germination phenology, life cycle type, habitat requirements, range of geographical distribution, and phylogenetic relationships of the species. Germination phenology is highly correlated with the responses of seeds to the yearly temperature cycle. Species with winter and summer annual life cycles have predictable germination characteristics, but monocarpic and polycarpic perennials do not. Several dormancy types may be found in a given habitat, and narrowly endemic and widely-distributed species in the same genus may have similar germination characteristics. Within some families there is a tendency for a particular type of seed-temperature response to be very important, but frequently this is related to the predominance of a given life cycle type in the family.     

HISTORICAL BIOGEOGRAPHY AND CONTEMPORARY PATTERNS OF MITOCHONDRIAL DNA VARIATION IN WHITE-TAILED DEER FROM THE SOUTHEASTERN UNITED STATES

Mitochondrial DNA (mtDNA) was used to characterize patterns of geographic variation among white-tailed deer (Odocoileus virginianus) populations in the southeastern United States. Fifteen restriction enzymes were employed to survey and map 99 restriction sites in 142 deer from 18 localities in five southeastern states. Phylogenetic analysis revealed three primary groups of haplotypes: (1) southern Florida and the Florida Keys, (2) the remainder of peninsular Florida northward to South Carolina, and (3) the Florida panhandle westward to Mississippi. Geographical heterogeneity in haplotype frequencies suggests that stochastic lineage sorting or isolation by distance are not important determinates of mtDNA differentiation among deer populations. The pattern of mtDNA variation in white-tailed deer is concordant spatially with those observed in unrelated taxa suggesting the common influence of historical biogeographic events. The data (1) support previous hypotheses that relate contemporary patterns of intraspecific phylogeography in northern Florida to the physiogeographic history of the region; and (2) suggest that genetic differentiation in southern Florida may be attributable to episodes of Pleistocene dispersal. Despite potentially high vagility and human intervention, ecological and demographic characteristics of deer have effectively preserved the historical pattern of intraspecific mtDNA differentiation.     

EFFECTS OF SULFIDE ON THE GROWTH OF THREE SALT MARSH HALOPHYTES OF THE SOUTHEASTERN UNITED STATES

A hydroponic culture experiment was performed to ascertain whether sediment soluble sulfide at in situ concentrations plays a role in the determination of height forms of Spartina alterniflora in salt marshes of the United States. Additional experiments were conducted for both Spartina cynosuroides and Borrichia frutescens to determine if sulfide also influences the overall distribution of these species in the marsh. In situ soluble sulfide concentrations ranged from 0.02 mm in creek bank sites up to 3.0 mm in the inner marsh. In culture treatments, both plant height and biomass production of S. alterniflora were inhibited at a sulfide concentration as low as 1.0 mm , strongly suggesting a role for sulfide in the determination of height forms in the marsh. Production of S. cynosuroides was inhibited at high sulfide concentrations. However, over a range of concentrations similar to in situ values, no significant reduction in growth was observed, indicating sulfide was not a primary determinant of growth in stands of S. cynosuroides on Sapelo Island, Georgia. A sulfide concentration of 0.5 mm inhibited production in B. frutescens. In situ sulfide concentrations as high as 0.5 mm were found only in mixed stands of Juncus roemerianus and B. frutescens.     

AGE AND POLYPHYLETIC ORIGINS OF HYBRID AND SPONTANEOUS PARTHENOGENETIC CAMPELOMA (GASTROPODA: VIVIPARIDAE) FROM THE SOUTHEASTERN UNITED STATES

We used mtDNA sequence variation to assess the origin, age, and spatial patterns of sequence divergence of triploid hybrid and diploid spontaneous parthenogens from southeastern United States populations of the freshwater snail Campeloma. There was strong support for multiple origins of both parthenogens using likelihood-ratio tests, and we argue that parthenogens are recently derived from sexuals. Atlantic coastal populations of C. limum or C. floridense were the maternal ancestors of Gulf Coast triploid hybrids in the Florida Panhandle. Sequence divergence within monophyletic groups of both parthenogens is similar to within-population divergence found in sympatric sexuals, and monophyletic clades of hybrid and spontaneous parthenogens are geographically widespread throughout the Atlantic and Gulf Coast rivers. These patterns are consistent with higher dispersal rates and recent range expansion of parthenogens, which should reduce the effects of mutation accumulation or parasitism. Range expansion may have occurred through interdrainage transfer during Pleistocene glacial periods.     

CHROMOSOME COUNTS OF COMPOSITAE FROM THE UNITED STATES AND MEXICO

Chromosome counts are reported for 126 taxa representing 122 species and 61 genera of Compositae. First reports include two genera, Stylocline (n = 14) and Chromolepis (n = 19), 17 species, two infraspecific taxa, and one interspecific hybrid. Five additional taxa have chromosome numbers differing from previously published accounts. Carminatia is reinstated to generic status.