Helen J. Michaels

Monophyly of the Asteridae and Identification of Their Major Lineages Inferred From DNA Sequences of rbcL

A parsimony analysis of 57 angiosperm rbcL sequences was conducted to test the monophyly of the Asteridae and to identify major lineages within the Asteridae. Three major clades, the Caryophyllidae, the Rosidae plus Dilleniidae, and the Asteridae sensu lato, emerge from an unresolved radiation in the «higher» dicots. The Asteridae sens. lat. include the Ericales, Cornales, and Apiales in addition to the Asteridae sens. str. Two major lineages within the Asteridae sens. lat. are identified: the Dipsacales, Apiales, Asterales, and Campanulales in one, and the Gentianales, Scrophulariales, Lamiales, Boraginales, and Solanales in the other (...)

Phylogeny and character evolution in the Asteraceae based on chloroplast DNA restriction site mapping

Phylogenetic relationships among species representing 57 genera from 15 currently recognized tribes of Asteraceae were assessed by chloroplast DNA restriction site mapping. Phy- logenetic analyses of 328 informative restriction site mutations were performed using both Dollo and Wagner parsimony and the bootstrap method. The results provide strong support for the monophyly of the subfam. Asteroideae, which includes the nine tribes Astereae, Anthemideae, Inuleae, Senecioneae, Calenduleae, Eupatorieae, Heliantheae, Coreopsideae, and Tageteae. The monophyly of the Lactucoideae (excluding the Barnadesiinae) is less strongly supported and this subfamily consists of the six tribes Mutisieae, Cardueae, Vernonieae, Liabeae, Lactuceae, and Arc- toteae. The molecular phylogeny indicates that 13 of 15 tribes are monophyletic, with the Helian- theae and Tageteae being paraphyletic. Several groups of tribes are shown to be closely related, including the Liabeae and Vernonieae, and the Tageteae, Coreopsideae, Heliantheae, and Eupato- rieae, but relationships among the other tribes remain unclear. Tribal placement of five morpho- logically anomalous genera (Blennosperma, Cotula, Echinops, Stokesia, and Ursinia) is also clarified. The chloroplast DNA phylogeny shows almost complete congruence with the less explicit phyletic scheme proposed by Thorne but differs markedly from the cladistically-based phylogeny of Bremer. The availability of a molecular phylogeny for the Asteraceae allows for an independent assessment of the patterns of morphological, chemical, and chromosomal evolution in the family. A much higher incidence of parallelism occurs in secondary chemistry than in morphological characters. The subfam. Asteroideae has a number of evolutionarily derived floral features and it exhibits a much more diverse and biosynthetically complex secondary chemistry.

Phylogenetic implications of rbcL sequence variation in the Asteraceae

Complete nucleotide sequences of the rbcL gene were obtained for 25 species of Asteraceae representing 15 of the currently recognized tribes and three outgroup families. A total of 345 variable nucleotide positions was identified, 170 of which were phylogenetically informative. Phylogenetic analyses of the rbcL data generated eight equally parsimonious trees with a consistency index of 0.47. Three major monophyletic clades that correspond to the subfamilies Barnadesioideae, Cichorioideae, and Asteroideae were identified in the most parsimonious cladograms; however, support for these groups was not strong (...)

Phylogenetic analysis of chloroplast DNA restriction site data at higher taxonomic levels: an example from the Asteraceae

Chloroplast DNA variation was examined among 57 genera of Asteraceae representing 15 currently recognized tribes. Complete cleavage maps were constructed for 11 six‐base pair restriction enzymes, and a total of 927 cleavage site differences was detected, 328 of which are phylogenetically informative. The data were used to construct phylogenetic trees using both Wagner and Dollo parsimony and the resulting monophyletic groups were evaluated statistically using the bootstrap method. The level of homoplasy in the restriction site data is 54–56% (excluding autapomorphies), most of which is due to parallel site losses. The most parsimonious trees generated by both parsimony methods have nearly identical topologies at lower taxonomic levels, but differ in subfamilial circumscriptions and tribal groupings. Dollo parsimony provides support for the monophyly of two subfamilies, the Lactucoideae (excluding the Barnadesiinae) and Asteroideae, but Wagner parsimony supports the monophyly of the Asteroideae only. This incongruence is due to different assumptions of the two parsimony methods about relative rates of parallel site gains and losses. After eliminating the six most rapidly changing restriction sites or performing successive approximation, Wagner parsimony produces trees with the same subfamilial groupings as the Dollo trees. We conclude that the Dollo tree with two monophyletic subfamilies is the best estimate of phylogenetic relationships in the Asteraceae because this method more accurately reflects the evolution of restriction sites. We also demonstrate that in spite of high levels of homoplasy in chloroplast DNA restriction site data at these higher taxonomic levels, it is possible to make statistically supported estimates of phylogenetic relationships.

Chloroplast DNA Variation in the Asteraceae: Phylogenetic and Evolutionary Implications

The sunflower family (Asteraceae) is one of the largest families of flowering plants, consisting of approximately 1,100 genera and 25,000 species (Jeffrey, 1978). The family has been variously divided into two or three subfamilies and 10 to 17 tribes (reviewed in Jansen et al., 1991a; Bremer, 1987). In addition to the disagreement concerning intrafamilial relationships, the phylogenetic affinities of the Asteraceae to other angiosperm families have been the topic of considerable debate (Cronquist, 1955,Cronquist, 1977, 1981; Carlquist, 1976; Wagenitz, 1976; Stebbins, 1977; Turner, 1977a; Jeffrey, 1977; Bremer, 1987). Until recently, systematic studies in the family relied on more traditional taxonomic characters and less rigorous phylogenetic methods. During the past five years we have been examining chloroplast DNA (cpDNA) variation in the Asteraceae to evaluate phylogenetic relationships at a wide range of taxonomic levels using several cladistic methods. We have accumulated restriction site data for approximately 250 genera in the family from all currently recognized tribes. In addition, we have sequenced the gene encoding the large subunit of ribulose-l,5-bisphosphate carboxylase (rbcL) from representative species in the Asteraceae and putatively related families. Our studies, which have produced the largest molecular data set for any plant family, have allowed us to perform phylogenetic comparisons from the intraspecific to the interfamilial levels.

Interfamilial relationships of the Asteraceae: insights from rbcL sequence variation

Nucleotide sequences of the chloroplast gene rbcL were analyzed to examine relationships among the large, distinctive family Asteraceae and eight putatively closely related families. Phylogenetic analysis of a total of 24 sequences of rbcL identified a lineage consisting of two families, the Goodeniaceae and Calyceraceae, as the sister group to the Asteraceae. In addition, a strongly supported major monophyletic clade consisting of Asteraceae, Goodeniaceae, Calyceraceae, Corokia (Cornaceae sensu Cronquist), Menyanthaceae, Lobeliaceae, and Campanulaceae was found. These results clearly distance from the Asteraceae certain groups previously considered closely related; moreover, the results support alternative hypotheses of affinity that were based upon floral and inflorescence morphology, biogeography, pollen morphology, chemistry, and pollen-presentation mechanisms

Logging and Edaphic Factors in the Invasion of an Asian Woody Vine in a Mesic North American Forest

Factors contributing to an invasion of the Asian woody vine Celastrus orbiculatus in a mesic forested Massachusetts (USA) sanctuary were investigated. Planting germinated C. orbiculatus seeds in the field revealed that, although they tolerate a wide range of conditions, seedlings grow largest in moist circumneutral soil under high irradiance. A study of naturally occurring vines in a logged forest suggested that C. orbiculatus invaded two years after harvest, and invasion may have been triggered by logging disturbance. Vine stems were more abundant on former logging roads than in surrounding selectively logged areas. Former logging roads had a significantly higher soil pH than surrounding areas and, due to the direction of construction, a significantly more southerly aspect. Fourteen years after harvest, logging roads continued to provide this aggressive exotic with superior habitat for establishment and growth.

Seed size and sex ratio in spinach: application of the Trivers- Willard hypothesis to plants

AbstractPlants germinating from large spinach seeds have a significantly male-biased sex ratio while small seeds yield a female-biased sex ratio, as predicted by the Trivers-Willard hypothesis. This male-biased sex ratio is not due to differential germination or survivorship, nor is it the result of sexual lability. Seeds yielding males are not more likely to occur at lower nodes, or to be the first seed initiated at a node or to have fewer siblings at a node than females. Seeds yielding males acquire a disproportionate share of resources. Interestingly, the gender, but not the size of previously initiated seeds had a profound effect on the size of subsequent seeds and on the likelihood that these seeds would germinate. Males following females were much larger than females following males. If all of the previous seeds initiated at a node were of the same gender, the likelihood that subsequent seeds would fail to germinate was more than four times greater than if the previously initiated seeds were not of ...

Effects of pollination limitation and seed predation on female reproductive success of a deceptive orchid.

This research examines the contribution of plant height, number of flowers, number of stems, as well the joint impacts of mutualists and antagonists on the pollination biology and seed production of the imperiled, deceptive orchid, Cypripedium candidum. We found flowering stem height to be the only morphological feature significant in reproduction, with taller flowering stems simultaneously receiving increased pollination and decreased seed predation. Furthermore we found decreased seed mass in individuals subjected to hand-self pollination treatments. Our results may help explain the factors limiting seed production in other Cypripedium and further emphasize the importance of management in orchid conservation.

When it pays to cheat: Examining how generalized food deception increases male and female fitness in a terrestrial orchid

Background Experimental manipulations of floral nectar in food deceptive species can reveal insights into the evolutionary consequences of the deceptive strategy. When coupled to pollen tracking, the effects of the deceptive pollination syndrome on both male and female reproductive success may be quantified. Attraction of pollinators in deceit-pollinated species often relies on producing a conspicuous floral display which may increase visibility to pollinators, but in-turn may increase within plant selfing. Methodology To understand the role of deception in Orchidaceae reproduction we studied Cypripedium candidum. All species of the Cypripedium genus employ a generalized food deceptive pollination strategy and have been suggested as a model system for the study of pollinator deception. We conducted a nectar addition experiment that randomly assigned the four plants closest to a transect point to receive one of four histochemical dyes. Two individuals selected for nectar addition in each of altogether 25 blocks received 2μl of 25% sucrose solution in the labellum of each flower, while two others received no artificial nectar. Number of fruits produced, fruit mass and fruit abortion were scored at the end of the four-month experiment. Results Nectar addition increased (p<0.0001) self-pollination and pollen discounting by nearly 3x, while plants not receiving nectar had greater (p<0.0001) numbers of non-self pollinia deposited and lower rates of pollen discounting. There was a non-significant (p = 0.0645) trend for deceptive plants to set more fruit, while presence of nectar did not affect pollen export. Conclusions This study demonstrates the adaptive advantages of food deception by showing a concurrent reduction in particular male and female functions when a food reward is restored to a deceptive flower. We found generalized food deception to not only decrease inbreeding depression in the system, but concurrently have no effect on pollinator attraction and fruit set when compared with rewarding flowers.