ECOTYPIC VARIATION IN CYSTOCLONIUM PURPUREUM (RHODOPHYTA) SYNCHRONIZES LIFE HISTORY EVENTS IN DIFFERENT REGIONS1

Temperature and daylength responses were determined in culture for isolates of the red alga Cystoclonium purpureum (Hudson) Batters from Nova Scotia (NS, Canada), Helgoland (HE, Germany), and Roscoff (RO, France). Most isolates survived temperatures of –1.5°/–2° to 23°C, whereas 25°C was lethal. Only the RO-gametophytes died at 23°C. Optimal growth conditions were 10°–20°C in both long and short days for the NS isolates and 8°–15°C and 8°–18°C at daylengths of >12 h for the RO and HE isolates, respectively. Tetrasporophytes and gametophytes of the NS isolate reproduced at 10°–20°C in long and short days within 5 months. At lower temperatures reproduction was limited or slow. The European isolates formed tetrasporangia at 10°–20°C (HE) or 5°–l8°C(RO), spermatangia at 5°–15°C (HE) or 5°–20°C (RO), and carpospores at 5°–15°C(HE) or 10°–15°C (RO). Short days either blocked or delayed reproduction of the European isolates. The phenology of C. purpureum was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. In early spring, growth was rapid and plants started to form reproductive structures. In summer, tetra-and carpospores were shed followed by degeneration of the upright axes while branched holdfasts persisted. New upright axes and juvenile plants were formed in autumn, but these remained small during the winter months. Published data indicate that the seasonal pattern at Nova Scotia is similar, although the onset of growth and reproduction is delayed until the end of spring. These observations correspond well with the results of the experiments. The life history of C. purpureum is regulated by temperature and daylength. In the eastern Atlantic, the limiting effect of short days confines growth and reproduction to spring and summer. In the western Atlantic, low winter temperatures alone bring about the same seasonal pattern. After plants have reproduced, uprights degenerate in spite of continuing favorable conditions.     

ECOTYPIC DIVERGENCE IN ALPINE POLEMONIUM VISCOSUM: GENETIC STRUCTURE,QUANTITATIVE VARIATION,AND LOCAL ADAPTATION

Polemonium viscosum has a continuous distribution from 3,500 m in the krummholz to 4,025 m on the summit ridges of Pennsylvania Mountain, Colorado. Seeds produced by plants at opposite ends of this cline, 1.5 km apart, differed significantly at allozyme loci in two consecutive breeding seasons. Mean multilocus F_st values for both years (0.015 and 0.069) were significantly different from zero, indicating restricted gene exchange between subpopulations. Average allele frequencies at two individual loci also differed significantly between families comprising krummholz and summit subpopulations. Progeny of plants growing on the summit had higher leaf production rates, more densely packed leaflets, and lower resistance to aphids than progeny of plants growing in the krummholz site, when tested under greenhouse conditions. These differences probably reflect the restricted opportunities for growth and severe exposure at high elevations, and the increased risk from herbivores near timberline. The two subpopulations did not differ in leaf length (stature), leaf width, or pubescence. Reciprocal transplanting of seedlings between krummholz and summit sites confirmed that the differences were adaptive, since progeny from each subpopulation performed significantly better in their parent's habitat. Coordinated studies of genetic structure, quantitative variation, and local adaptation across the elevational range of P. viscosum provide a comprehensive view of ecotypic divergence in this widespread alpine plant.     

ECOTYPIC VARIATION IN PHYLLOPHORA PSEUDOCERANOIDES (RHODOPHYTA) ENSURES WINTER REPRODUCTION THROUGHOUT ITS GEOGRAPHIC RANGE1

Responses to temperature and daylength were determined in laboratory culture for isolates of the red alga Phyllophora pseudoceranoides (Gmelin) Newroth et A.R.A. Taylor from Nova Scotia, Iceland, Roscoff (France), and Helgoland (Germany). All isolates grew from 3° to 25° C and survived from -2° or 0° C to 27° C but not 30° C. Reproductive requirements differed between life history phases and isolates. Isolates from Helgoland and Roscoff formed sporangial sori at 3°-20° C, tetraspores at 3°-12° C, and procarps at 10°-20° C, irrespective of daylength. Spermatangia developed at 10°-23° C but only in long days. As the other European isolates, the isolate from Iceland formed tetrasporangia at 3°-12° C, but it had an additional requirement for short days. The Nova Scotian isolate formed sori at 10°-20° C and sporulated at 10°-18° C. When grown plants were transferred from noninductive to inductive conditions, sori were formed after 4 months and tetraspores developed and were shed (1-)3 months later. Procarps formed 1(-3) months after transfer. The phenology of P. pseudoceranoides was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. Plants were perennial, forming new blades from October to June, which degenerated between August and February. In June, reproductive structures (sori, spermatangia, and procarps) started to appear on the new blades. From October to April, mature cystocarps were found. Mature tetrasporangia were observed only in February. The life history of P. pseudoceranoides is regulated by temperature and daylength. Differential effects on the different life history phases all serve to confine the production of spores (both carpospores and tetraspores) to the winter season. Differences in response between isolates from different geographic regions bring about the same effect: spores are shed only in winter. The nature of the geographic boundaries of P. pseudoceranoides is discussed.     

ECOTYPIC DIFFERENTIATION WITHIN FOUR NORTH AMERICAN PRAIRIE GRASSES. III. CHROMATOGRAPHIC VARIATION

Four widespread grasses, Andropogon scoparius Michx., A. gerardi Vitman, Sorghastrum nutans (Nash) Hitchc. and Panicum virgatum L., have been studied behaviorally and morphologically. In the present comparison characteristic flavonoid patterns were shown whereby the four grass taxa can be separated at the generic and specific level. The greatest similarity was shown by the two Andropogon species. Panicum was most dissimilar. Although intrapopulational and interpopulational variation was demonstrated within each of the four taxa, both in transplanted material and in native plants of the original transplant site, there was no decisive correlation of biochemical variation with geographic origin, vegetative characteristics or maturity pattern. Early-flowering clones with short flowering culms and glabrous leaves, originating in northern and western areas, were essentially similar biochemically to later-flowering clones with tall flowering culms and extremely pubescent leaves, originating in southeastern areas. Blade samples collected in late fall, 1963, and in early spring, 1964, from the same transplanted clones were similar in flavonoid pattern. In P. virgatum. individual clonal patterns were characteristic of ramets grown under various day-length-thermoperiod conditions. Although biochemical markers for ecotypes would be useful êological tools, partially replacing their cultivation in transplant gardens, geographically correlated patterns were not revealed in this study. However, this study supports the present systematic position of the various morphologically and behaviorally diverse populations within the four taxa.     

防风悬浮培养中的体细胞胚发生

将防风（Ｓａｐｏｓｈｎｉｋｏｖｉａ ｄｉｖａｒｉｃａｔａ （Ｔｕｒｃｚ．） Ｓｃｈｉｓｃｈｋ．）试管苗幼根接种在含０．５ ｍ ｇ／Ｌ ２,４－Ｄ 的ＭＳ培养基上诱导出愈伤组织,继而在含１０％ 椰子乳和０．５ ｍ ｇ／Ｌ ２,４－Ｄ的ＭＳ液体培养基中振荡分散建立了细胞悬浮物。至胚性细胞团产生后转至无激素培养基中形成体细胞胚。观察了从单细胞直到球形胚发生的显微及超微结构的变化。在胚性细胞团阶段细胞内出现周质内质网,它的出现可能与细胞团向原胚过渡时的特殊代谢相联系。从单细胞至原胚各阶段细胞内均含有圆球体,到原胚时数量大增,而且其中央电子致密的基质变小变浅,周边部分扩大并更加透明,暗示圆球体在胚胎发生早期起着贮藏蛋白或脂蛋白的作用,后来消耗于原胚的建成而衍生为脂滴。球形胚阶段,在很多细胞的液泡中出现团块状的液泡蛋白。此外还观察到,悬浮培养时单细胞的聚集能促进体细胞胚的发生     

ECOTYPIC DIFFERENTIATION WITHIN FOUR NORTH AMERICAN PRAIRIE GRASSES. I. MORPHOLOGICAL VARIATION WITHIN TRANSPLANTED COMMUNITY FRACTIONS

Ecological variation within transplanted community fractions, containing Andropogon scoparius Michx., A. gerardi Vitman, Panicum virgatum L. and Sorghastrum nutans (L.) Nash, included broad behavioral and morphological differentiation. In Austin, Texas, during 1958–1962, southern community fractions that contained early spring activity, late flowering and late fall dormancy included taller plants than early-flowering, northern community fractions. The tallest populations in all 4 species originated in Texas. In P. virgatum, size of leaves and panicles showed north-south trends similar to culm height values. Leaf pubescence and leaf glaucousness in all 4 species showed geographic patterning that was not correlated with north-south maturity gradients. Greatest pubescence was on clones in community fractions from pine woods in the Southeast. Glaucousness was concentrated in community fractions from central Texas northward to Nebraska.     

ECOTYPIC DIFFERENTIATION WITHIN FOUR NORTH AMERICAN PRAIRIE GRASSES. II. BEHAVIORAL VARIATION WITHIN TRANSPLANTED COMMUNITY FRACTIONS

Ecotypic differentiation in transplanted clones of Andropogon scoparius Michx., A. gerardi Vitman, Panicum virgatum L. and Sorghastrum nutans (L.) Nash showed north-south correlations. In Austin, Texas, during 1959–1962, southern populations had earliest spring activity, latest flowering and latest dormancy. Northern community fractions from Massachusetts to North Dakota showed early flowering and a short span separating initial anthesis among the species-populations. Community fractions from Virginia to Nebraska had initial anthesis over a longer period than in more northern or more southern samples. Community fractions from South Carolina to eastern Texas had late flowering over a short period. Western community fractions, latitudinally and altitudinally diverse, were behaviorally uniform. The length of the growing period and its recurrent selection have sorted out ecological variants in harmony with the habitat gradients. Whether they are of the predominant physiognomic types, as in the true prairie region, or understory plants in the pine forests, the 4 grass taxa are in the climax matrix.     

TRACHEID LENGTH AS AN ECOTYPIC CHARACTER IN ACER NEGUNDO L.

Laboratory germinated seedlings of Acer negundo grown under controlled environmental conditions showed patterns of decreasing cell length (tracheids) with decrease in length of growing season of parental tree's habitat. Populations tested represented a range in latitude of 15 degrees (Texas to Canada) and the results indicate populational response to shorter growing seasons being reflected in xylem development.     

VARIATION IN DEVELOPMENTAL CONSTRAINTS IN SIGMODON

Developmental constraints can be interpreted as factors of developmental origin responsible for covariation among measured variables. Several hypotheses have been proposed to link the possession of such constraints to subsequent evolution. Using confirmatory factor analysis, we compare developmental factors across selected taxa of cotton rats, genus Sigmodon. Three factors explain well the covariation among orofacial measurements: (1) responses to body size variation, (1) coordinated growth of traits of the occluding-tooth complex, and (3) responses to musculoskeletal interactions. Sigmodon taxa share these factors, but differ in the variance-covariance matrix of factors, and the unique variances of individual traits. Patterns of covariation among measurements of the neurocranial complex reflect responses to body size variation, and perhaps also responses to fetal brain growth. While there are no significant differences across taxa in factorpattern, variance-covariance matrix of factors, or unique variance of measured neurocranial variables, the neurocranium is only weakly constrained. We doubt that even the relatively stronger developmental constraints on the orofacial complex would prevent evolutionary divergence because differences in the variances and covariances of factors, and in levels of unique variance of individual traits can provide different opportunities for selection to act in different Sigmodon taxa.