Kenneth R. Robertson

Phylogeny and classification of Rosaceae

Phylogenetic relationships among 88 genera of Rosaceae were investigated using nucleotide sequence data from six nuclear (18S, gbssi1, gbssi2, ITS, pgip, and ppo) and four chloroplast (matK, ndhF, rbcL, and trnL-trnF) regions, separately and in various combinations, with parsimony and likelihood-based Bayesian approaches. The results were used to examine evolution of non-molecular characters and to develop a new phylogenetically based infrafamilial classification. As in previous molecular phylogenetic analyses of the family, we found strong support for monophyly of groups corresponding closely to many previously recognized tribes and subfamilies, but no previous classification was entirely supported, and relationships among the strongly supported clades were weakly resolved and/or conflicted between some data sets. We recognize three subfamilies in Rosaceae: Rosoideae, including Filipendula, Rubus, Rosa, and three tribes; Dryadoideae, comprising the four actinorhizal genera; and Spiraeoideae, comprising Lyonothamnus and seven tribes. All genera previously assigned to Amygdaloideae and Maloideae are included in Spiraeoideae. Three supertribes, one in Rosoideae and two in Spiraeoideae, are recognized.

A synopsis of genera in Maloideae (Rosaceae)

The number of genera recognized in subfam. Maloideae by different authors has varied greatly; a historical summary is presented here. We have evaluated generic limits based on our own observations of a suite of morphological characters for about 200 species chosen to represent the taxonomic and geographic diversity of the approximately 940 species of Maloideae. A narrow circumscription of genera is generally adopted, with 28 genera recognized. Hesperomeles is considered distinct from Osteomeles; Eriolobus and Docyniopsis from Malus; and Aria, Chamaemespilus, Cormus, and Torminalis from Sorbus. Micromeles is included within Aria and Stranvaesia and Aronia within Photinia. The genera are either relatively small or relatively large: 19 genera have 11 or fewer species, seven between 26 and 97 species, and only two contain more than 100 species. The traditional division of Maloideae into two tribes is unwarranted and does not reflect relationships of the genera. The extensive hybridization between genera and subgeneric groups seems to reflect weak overall barriers to hybridization in the subfamily rather than indicate evolutionary relationships. Diagnoses are presented for each genus as well as a table comparing morphological characters for all genera. The following new combinations are made: Chamaemespilus alpina, Photinia floribunda, P. melan- ocarpa, P. pyrifolia, Malus subg. Sorbomalus, Torminalis clusii, and T. orientalis.

Origins and evolution of subfam. Maloideae (Rosaceae)

Subfam. Maloideae (x = 17) has been held to be tetraploid since 1931 while later, Sax elaborated by Stebbins, specifically implicated subfam. Spiraeoideae (x = 9) and Amygdaloideae (x = 8) in an allotetraploid ancestry. The allotetraploid theory has gained considerable credibility with many workers on Rosaceae but, although support for it is not unanimous, and it is sometimes ignored, there has never been any attempt at refutation. To date, the theory has depended mainly on chromosome constitution, and, in a rather general way, on the morphological characteristics of the respective taxa. In this paper we review the allotetraploid hypothesis and generally verify it by an extensive character analysis of the Maloideae, Amygdaloideae, and Spiraeoideae. Since no specifically rosoid or quillajoid characters exist in the Maloideae, no candidate near-ancestral genera in subfam. Rosoideae or tribe Quillajeae can be pinpointed. The autapomorphic fruit of the Maloideae-the pome-is derivable from spiraeoid or proto-amygdaloid characters. In a parsimony analysis of a 96 taxa x 36 variable data matrix the phenetic genera were, for the most part, returned as clades, but their placement was to a significant extent, peculiar. The consistency index was extremely low. Furthermore, the addition of only three OTUs resulted in major relocations of some of the genera. We concluded that, in this type of situation, parsimony analysis is not robust, and sought other explanations for the relationships suggested. We favour the idea that several clades of Maloideae originated independently in a highly reticulate system existing shortly after the original allotetraploid cross. This notion of polychotomous early evolution alone, we feel, makes sense of the general correspondence of phenetic genera to cladistic genera, remarkably low consistency index, great instability of the cladogram with respect to changing only a few OTUs, and the manifestly great ability of most maloidean genera to hybridize. Thus, the precise phylogeny of the Maloideae must remain quite unknown until a very different kind of investigation has been successfully conducted. The present paper is one of a series by the authors reviewing generic limits and examining evolutionary pathways in the subfam. Maloideae. We develop the Sax-Stebbins hypothesis on the allotetraploid origin of the Maloideae and seek to define more clearly the characteristics of the original maloid in order to inform the search for evolutionary pathways. The Maloideae are an important group of woody plants containing close to 1000 species and 20-30 genera dependent on circumscription (Phipps et al. 1990). As one of the four subfamilies of the Rosaceae, which is often considered quite pivotal in dicotyledonous evolution, Maloideae have received a great deal of taxonomic and revisionary attention since the time of their first formal recognition by de Jussieu in 1791. However, little of this attention has been explicitly cladistic. Subfamily Maloideae constitutes a natural group of plants, with synapomorphic pome fruit, base chromosome number of x = 17 and an autapomorphic suite of rust parasites (Savile 1979). The widespread occurrence of gameto-

The Tallgrass Prairie Mosaic

Grasslands are biological communities in which the landscape is dominated by herbaceous vegetation, especially grasses: they contain few trees or shrubs. An estimated 16 to 40% of the world’s land surface is, or was, covered by grasslands (Singh et al. 1983, Burton et al. 1988, Groombridge 1992). Area estimates of current savanna and temperate grasslands are from 16.1% to 23.7% of the world’s land area (Groombridge 1992). Notable examples include prairies of North America, llanos of northern South America, cerrados and campos of Brazil, pampas of Argentina, steppes of central Asia, veldt and savannas of Africa, and grasslands of Australia. Grasslands are the largest vegetational unit in North America, covering approximately 20% of the land area, and prairies are the most abundant type of grassland on the continent (Kuchler 1964, Risser et al. 1981, Burton et al. 1988). Prior to European settlement, prairies occupied a more or less continuous (except at the fringes), roughly triangular shaped area covering 3.6 million square km. The base extended for 3,900 km along the foothills of the Rocky Mountains from the Canadian provinces of Saskatchewan and Manitoba southward through New Mexico into Texas (Figure 3.1). The apex of the triangle, the prairie peninsula (Transeau 1935), extended 1,600 km eastward into the Midwest and included the prairies of Illinois, Iowa, Indiana, Minnesota, Missouri, and Wisconsin, with scattered outliers in southern Michigan, Ohio, southwestern Ontario, and Kentucky (Risser et al. 1981; Madson 1982; Farney 1980; Weaver 1954, 1968; Whitney and Steiger 1985) (Figure 3.1). This chapter focuses on this eastward projection of tallgrass prairie around what is known as the prairie peninsula (Transeau 1935).

Chloroplast Biogenesis 77: Two Novel Monovinyl and Divinyl Light‐Dark Greening Groups of Plants and Their Relationship to the Chlorophyll a Biosynthetic Heterogeneity of Green Plants

Abstract— On the basis of the steady‐state accumulation of divinyl (DV) or monovinyl (MV) protochlorophyllide (Pchlide) a in darkness (D) or in the light (L), green plants have been classified into three different greening groups namely dark divinyl‐light divinyl (DDV‐LDV), dark monovinyl‐light divinyl (DMV‐LDV) and dark monovinyl‐light monovinyl (DMV‐LMV) (Ionannides et al., Biochem. Syst. Ecol. 22, 211‐220,1994). Interruption of the L phase of the photoperiod by a brief period of darkness (LD condition) revealed a predominance of different chlorophyll (Chl) a biosynthetic routes, depending upon the greening group affiliation of the plant species. For example, in DMV‐LDV and DMV‐LMV plants, the predominant Chl a biosynthetic routes under the LD condition appear to be the MV Chi a biosynthetic route and/or a mixed DV‐MV Chi a biosynthetic route that bifurcates at the level of DV Pchlide a. On the basis of DV and MV Pchlide a accumulation rates after re‐darkening, this greening group is designated as a light‐dark MV (LDMV) subgroup. In DDV‐LDV plants, the predominant LD Chi a biosynthetic routes appear to be the DV Chi a biosynthetic route and/or a mixed DV‐MV Chi a biosynthetic route that bifurcates at the level of DV Chlide a. This greening group is designated as a light‐dark DV (LDDV) subgroup. It is proposed that upon inhibiting the conversion of Pchlide a to Chi a by interruption of the L phase of the photoperiod by a brief period of D, the rates of DV and MV Pchlide a regeneration may reflect the carryover rates of DV and MV Pchlide a biosynthesis in L instead of reflecting a differential use of DV and MV carboxylic biosynthetic rates in D. It is also shown that in LDMV plants, MV Chlide a and MV Chi a are formed without the participation of [4‐vinyl] Chlide a reductase. On the basis of recently published evidence, it is also argued that Pchlide oxidoreductase‐A (POR‐A) may be active in LDDV plants, while POR‐B may predominate in LDMV plant species. The evolutionary significance of the LDDV and LDMV greening subgroups is discussed.

An evolutionary study of chlorophyll biosynthetic heterogeneity in green plants

Abstract Chlorophyll biosynthetic heterogeneity among plant species was investigated to determine the stability of a greening group within a species, the effects of age and treatment with chemical compounds on greening groups, and possible relationships of chlorophyll heterogeneity with existing classification schemes. Green plants exhibited one of three different greening groups, depending upon the chlorophyll biosynthetic route that is used to form monovinyl (MV) or divinyl (DV) protochlorophyllides. Algae, bryophytes, ferns, and gymnosperms belonged exclusively to the dark divinyl-light divinyl (DDV-LDV) greening group. Angiosperms exhibited all three greening groups. Most angiosperm species examined belonged to the dark monovinyl-light divinyl (DMV-LDV) greening group, and several belonged to the DDV-LDV group. The dark monovinyl-light monovinyl (DMV-LMV) greening group was rare and confined to derived groups in Cronquists classification scheme. On the basis of these results, it is proposed that the DDV-LDV greening group is ancestral in green plants, the DMV-LMV group derived, and the DMV-LDV group evolutionarily intermediate. However, within angiosperms, present data indicate that DMV-LDV is ancestra, DMV-LMV is advanced and DDV-LDV is secondarily derived.

Characterization of Waterhemp (Amaranthus tuberculatus) × Smooth Pigweed (A. hybridus) F1 Hybrids1

In the state of Illinois, waterhemp and smooth pigweed are among the worst agricultural weeds. Previous research shows high potential for hybridization between these two species. However, the actual occurrence of hybrids in natural settings is still uncertain. Morphological similarity between hybrids and waterhemp makes field surveys of hybrids difficult to conduct. The main purpose of this study was to characterize the morphology of waterhemp × smooth pigweed F1 hybrids, emphasizing evaluation of characters that may allow for hybrid discrimination in field Amaranthus communities. Concurrently, the study characterized hybrid reproductive fitness, chromosome number, and DNA content. To accomplish this, hybrids were obtained from field crosses. A species-specific polymorphism in the ALS gene was used to verify hybrid identity. Significant differences (α = 0.05) between hybrids and individuals of the parental species were observed for five staminate and five carpellate characters. Of these, five characters differentiated hybrids from waterhemp. However, clustering analyses using these characters indicated that morphological differences were not reliable enough, by themselves, for unambiguous hybrid identification. Also, hybrid homoploidy (2n = 32) with respect to parental species excluded chromosome counts in hybridity determinations. However, DNA content analysis may be used for such purpose. Hybrids had an average of 1.21 pg of DNA per 2C nucleus, a value intermediate to that of parental species. Hybrids produced 3.3 or 0.7% the seed output of parental and sibling waterhemp individuals, respectively. Percent micropollen in hybrids was 95-times greater than in parental species. Hybrid sterility appears to be the most reliable feature for hybrid discrimination when conducting field surveys. However, molecular and cytogenetic analyses as employed in this study may be desired for ultimate identity corroboration. Nomenclature: Common waterhemp, Amaranthus rudis Sauer #3 AMATA; smooth pigweed, Amaranthus hybridus L. # AMACH; tall waterhemp, Amaranthus tuberculatus (Moq.) Sauer # AMATU. Additional index words: Gene flow, evolution, herbicide resistance. Abbreviations: ALS, acetolactate synthase (EC 2.2.1.6); PCR, polymerase chain reaction.

The Biogeography of and Habitat Loss on Hill Prairies

According to Evers (1955) the term hill prairie was first used by A.G. Vestal in the 1940s during his ecology classes and seminars at the University of Illinois. Hill prairies, as defined by Vestal, are islandlike prairie openings occurring on steep slopes, typically river bluffs, that are (or were) otherwise forested. Hill prairies have also been called bluff prairies, goat prairies, and prairie openings (Robertson et al. 1995). The distribution of hill prairies extends from the upper Mississippi River Basin, in central Minnesota (Olson 1989) and Wisconsin (Shimek 1924), to southern Illinois (Evers 1955), and in Missouri (Steyermark 1963), Iowa (Cooper and Hunt 1982, White and Glenn-Lewin 1984), and parts of South Dakota (Novacek 1985) primarily along the Missouri River. Four basic types of hill prairies are recognized based on soil substrate: (1) loess, (2) sand, (3) glacial drift, and (4) gravel hill prairies. The research described here focuses on loess hill prairies within Illinois. Loess hill prairies are the most frequent type within Illinois and occur along the Mississippi River, the Illinois River from its junction with the Mississippi River to Putnam County, and along with the Sangamon River in Cass, Menard, and Mason Counties (Evers 1955, Kilburn and Warren 1963). Glacial drift hill prairies occur in Coles and Vermilion Counties of east central Illinois (Reeves et al. 1978, Ebinger 1981). Before European settlement, it is likely that hill prairies never formed large continuous segments in Illinois but were fragmented by ravines that dissect the river bluffs and slopes, and delimited on the upland sides by forest