Copyright (c) 2009 All rights reserved. http://works.bepress.com/rebecca_dolan Recent documents in Rebecca W. Dolan en-us Sun, 31 May 2009 10:41:50 PDT 3600 http://works.bepress.com/rebecca_dolan/20 http://works.bepress.com/rebecca_dolan/20 Mon, 13 Apr 2009 12:45:24 PDT Disturbances such as fire have the potential to remove genetic variation, but seed banks may counter this loss by restoring alleles through a reservoir effect. We used allozyme analysis to characterize genetic change in two populations of the perennial Hypericum cumulicola, an endemic of the fire-prone Florida scrub. We assessed genetic variation before and one, two, and three years after fire that killed nearly all aboveground plants. Populations increased in size following fire, with most seedlings likely recruited from a persistent seed bank. Four of five loci were variable. Most alleles were present in low frequencies, but our large sample sizes allowed detection of significant trends. Expected heterozygosity increased, and allele presence and allele frequencies showed marked shifts following fire. The post-fire seedling cohort contained new alleles to the study and one new allele to the species. Population differentiation between the two study sites did not change. Our study is the first to directly documents genetic changes following fire, a dominant ecological disturbance worldwide, and is also one of the few to consider shifts in a naturally recruiting post-disturbance seedling cohort. We demonstrate the potential of seed banks to restore genetic variation lost between disturbances. Our study demonstrates that rapid genetic change can occur with disturbance and that fire can have positive effects on the genetics of rare species. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/19 http://works.bepress.com/rebecca_dolan/19 Wed, 08 Apr 2009 10:41:24 PDT The Streptanthus morrisonii complex is a six-taxon group of closely related serpentine rock outcrop endemics from Lake, Napa, and Sonoma counties of California, USA. Two new subspecies (S. morrisonii subsp. kruckebergii and S. brachia/us subsp. hoffmanii) from Lake County, California, are described. The relationship of these taxa to others in the section is reviewed and descriptions and a key are provided. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/18 http://works.bepress.com/rebecca_dolan/18 Wed, 08 Apr 2009 10:40:40 PDT Streptanlhus vernalis is a newly described species inhabiting serpentine rock outcrops in the Three Peaks area in Lake County, California. Morphological and allozyme data indicate that this taxon is related to the S. morrisonit complex. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/17 http://works.bepress.com/rebecca_dolan/17 Thu, 12 Mar 2009 12:32:00 PDT Seed size is normally distributed for many annual species, while mature plant size is frequently positively skewed. A study was conducted to determine the influence of seed size and the role of genetic differences in determining relative seedling size for Ludwigia leptocarpa. Seed size had a significant effect on percentage germination and time of seed germination but no effect on dry weight or leaf area of seedlings. Seed size and spacing had a significant effect on seedling dry weight for plants grown under competition, while relative day of emergence had no effect. Familial (genetic) differences were found in average seed weight between maternal plants, but not in average number of days to germination, average weight of seeds which germinated, or shoot dry weight. It is concluded that neither seed size alone nor genetic differences between plants are directly responsible for the development of size hierarchies in Ludwigia leptocarpa populations. Large seed size does convey an advantage in growth when plants from seeds of differing initial size interact. Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/16 http://works.bepress.com/rebecca_dolan/16 Thu, 12 Mar 2009 12:30:00 PDT (1) Germination cohorts of Ludwigia leptocarpa, a semi aquatic annual plant were marked in the field at time of establishment and followed through the 1981 and 1982 growing seasons at a site in southern South Carolina. (2) Data from each cohort were pooled to determine demographic characteristics of the population as a whole, then analysed separately to determine the effect of time of germination on survivorship, relative growth rate, and adult size. (3) Changes in numbers of L leptocarpa fit a Deevey Type II survivorship curve. This and other characteristics of the species classify it as 'r-selected'. Aspects of the life history may reflect a 'bet-hedging' strategem that ensures establishment. (4) Differences in the time of germination are not responsible for differences in adult size, even when early germinating plants have as many as 35 days more for growth than late germmators. This, and the fact that differences occur even within single cohorts, implies that factors other than time of germination must influence plant size. Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/15 http://works.bepress.com/rebecca_dolan/15 Thu, 12 Mar 2009 12:25:12 PDT To compare adjacent post oak flatwoods and barrens communities in south-western Indiana, we used vegetational, environmental and fire history data in multivariate analyses. Barrens had greater dominance by post oak and lower tree species richness, but variation in tree species composition was not strongly related to soil moisture, litter depth or other environmental gradients measured. Tree growth has been slow and variable, with little difference between the barrens and flatwoods. Barrens and flatwoods differ in herb species composition, but with considerable overlap. In the barrens, herbaceous vegetation composition was correlated with tree basal area, litter depth and soil moisture; in the flatwoods, it was correlated with soil moisture and microelevation. The barrens and flatwoods differed only slightly but significantly in environment: barrens soils were drier in June 1986 than flatwoods soils. Data from fire-scarred trees show no clear evidence of differences in frequency or extent of fire between the flatwoods and barrens. Multistemmed post oaks in the barrens indicate that past cutting may have contributed to these openings within the closed canopy flatwoods matrix. Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/14 http://works.bepress.com/rebecca_dolan/14 Thu, 12 Mar 2009 12:20:43 PDT The Friesner Herbarium (But) of Butler University is a collection of over 100,000 specimens built from the personal herbarium of Ray C. Friesner. He and other botanists at Butler amassed one of the largest and most complete collections of Indiana plants. Active exchange from the 1920's through the 1940's increased the holdings of plants from other states. Although the collection does not contain many type specimens, it is rich in vouchers from floristic and ecological studies conducted in the first half of the 20th century and published in the scientific journal, Butler University Botanical Studies. Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/13 http://works.bepress.com/rebecca_dolan/13 Thu, 12 Mar 2009 12:18:41 PDT No abstract available. Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/12 http://works.bepress.com/rebecca_dolan/12 Thu, 12 Mar 2009 12:10:40 PDT The distribution of genetic variation within and among plant populations is influenced by both contemporary and historical factors. I used isozyme analysis of band phenotypes to examine genetic structure in the rare prairie forb Silene regia. Relationships between current-day population size, isolation, and phenotypic variation were assessed for 18 populations in two regions with differing postglacial history. Western populations from unglaciated southern Missouri and Arkansas were more genetically diverse based on the Shannon-Weaver index (H) and a polymorphic index than were more eastern populations. These differences may be due to loss of variation with repeated founding of new populations in previously glaciated sites in Indiana and Ohio. Within the western region, population size was not significantly correlated with genetic variation. In the east, size was correlated with Shannon-Weaver diversity. There was no relationship between variation and isolation in either region, but eastern populations were slightly more differentiated. Greater among-population differentiation and the demonstrated connection between population size and variation in the eastern sites may reflect lower levels of interpopulation gene flow in the fragmented remnant prairies of Indiana and Ohio. Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Rebecca W. Dolan http://works.bepress.com/rebecca_dolan/11 http://works.bepress.com/rebecca_dolan/11 Thu, 12 Mar 2009 12:08:01 PDT We studied the demographic viability of populations of a long-lived iteroparous prairie perennial, Silene regia, in relation to management regimes, population sizes, geographical region (Ohio and Indiana vs. Missouri and Arkansas), degree of isolation and amount of genetic variation. Demographic data were collected from 16 populations for up to 7 years. This species has high survivorship, slow growth, frequent flowering and episodic seedling recruitment. Matrix projection methods were used to summarize population performance with and without recruitment. Median finite rates of increase by population varied from 0.57 to 1.82 and from 0.44 to 0.99, respectively. Populations with the highest rates of increase had been burned. Six of eight populations, for which stochastic modelling predicted persistence for 1000 years, included fire in their management. None of the five populations with predicted 100-year extinction probabilities of 100% was managed for conservation or burned. An intermediate group of three populations with at least 10% probability of extinction between 100 and 1000 years was not managed, but was none the less kept open by mowing and herbicide application. Analysis of composite elasticities showed that growth and fecundity terms were higher for growing (vs. declining) populations and that growth elasticity was higher in burned than unburned populations. Lack of burning shifts the elasticity spectrum from that typical of open habitat herbs (higher growth and fecundity elasticities) to values usually found for closed habitat herbs (higher survival elasticities). In multivariate analyses predicting finite rates of increase (with and without recruitment), fire management and region were the strongest predictors, followed by genetic variation, population size, isolation and interactions of population size and fire, and region and fire. Populations with the highest rates... Note: Link is to the article in a subscription database available to users affiliated with Butler University. Appropriate login information will be required for access. Users not affiliated with Butler University should contact their local librarian for assistance in locating a copy of this article. Eric S. Menges