Infraspecific genetic variation in Biscutella laevigata (Brassicaceae): new focus on Irene Manton's hypothesis

 Genetic variation in 42 populations throughout the range of Biscutella laevigata L. (Brassicaceae), a morphologically variable central European species, has been investigated by enzyme electrophoresis with three loci (Amy1, Amy2, and Gpi2). Genetic identities and the Fitch-Margoliash tree suggest differentiation into four regional groups: 1) a northwestern diploid group (northern France and northern Germany), 2) a northeastern diploid group (southern Germany, Upper Austria, northern Lower Austria, Poland, and Romania), 3) a central diploid group in southern Lower Austria corresponding to subspecies austriaca, and 4) a southern tetraploid group in Alpine areas of France, Germany, Switzerland, Austria, Italy, and Slovenia corresponding to subspecies laevigata. Geographically isolated diploid relic populations that are genetically depauperate are found in the NW and NE diploid groups. On the other hand, the diploid relic subspecies austriaca from the NE Prealps and Alps is highly variable. Subspecies laevigata appears to be a genetical autotetraploid with multiple origins involving several diploid progenitors (the NW diploids, subspecies austriaca and B. prealpina). Received April 6, 2001; accepted March 6, 2002 Published online: October 14, 2002 Addresses of the authors: Karin Tremetsberger (e-mail: k.tremetsberger@gmx.net), Christiane K?nig, Rosabelle Samuel, Tod F. Stuessy, Department of Higher Plant Systematics and Evolution, Institute of Botany, University of Vienna, Rennweg 14, A-1030 Vienna, Austria. Wilhelm Pinsker, Institute of Medical Biology, University of Vienna, Waehringerstra?e 10, A-1090 Vienna, Austria.     

Phylogeographic patterns in Hypochaeris section Hypochaeris (Asteraceae, Lactuceae) of the western Mediterranean

Aim  To analyse phylogeographic patterns in the four species of Hypochaeris sect. Hypochaeris , evaluating possible areas of origin and the microevolutionary processes that have shaped their morphology, genetics and distribution.
Location  Western Mediterranean area.
Methods  We applied amplified fragment length polymorphism (AFLP) markers to a total of 494 individuals belonging to 82 populations of Hypochaeris arachnoidea , H. glabra , H. radicata and H. salzmanniana to determine population structure.
Results  Populations with the largest proportion of private and rare AFLP fragments were found in Morocco. This region was consequently inferred to be the ancestral area for H. arachnoidea , H. glabra , H. radicata and H. salzmanniana . The Guadalquivir River (southern Spain) was inferred to be an effective dispersal barrier for H. glabra and H. radicata. The Strait of Gibraltar was inferred to be a somewhat weaker barrier than the Guadalquivir River for H. radicata and a much weaker barrier for H. glabra . The main barrier for H. salzmanniana coincides with the extension of the Rif Mountains to the Atlantic coast in Morocco, and the Strait of Gibraltar is a much weaker barrier for this species. Hypochaeris arachnoidea appears to have originated in the Atlas Mountains.
Main conclusions  The highest levels of genetic variation in La Mamora forest ( H. glabra and H. salzmanniana ) or the adjacent central Middle Atlas ( H. arachnoidea and H. radicata ) in Morocco suggest that these areas were a centre of origin of Hypochaeris sect. Hypochaeris . All three potential barriers – the Guadalquivir River, the Strait of Gibraltar, and the Rif Mountains – have been important in shaping genetic diversity in species of section Hypochaeris .     

A revision of Moonia (Compositae,Heliantheae, Coreopsidinae)

The genusMoonia of India and Ceylon, traditionally placed in the subtribe Melampodiinae, is shown to have closer affinities withDahlia andHidalgoa of the subtribe Coreopsidinae. Several morphologically heterogeneous taxa are excluded fromMoonia, and the remaining species,M. heterophylla, is described and illustrated.     

FLAVONOID EVOLUTION IN DENDROSERIS (COMPOSITAE,LACTUCEAE) FROM THE JUAN FERNANDEZ ISLANDS,CHILE

Leaf flavonoid chemistry was examined from the three subgenera and 11 species of the endemic genus Dendroseris (Compositae, Lactuceae) of the Juan Fernandez Islands, Chile. Eight of the species are restricted to the older island (Masatierra, ca. 4 million years old), which is also closer to the mainland. Three species, one from each subgenus, are restricted to Masafuera, which is younger geologically (1–2 million years old) and 145 km further west of Masatierra. A total of 16 compounds was identified, with the 7-0-glucosides of the flavones apigenin and luteolin accounting for 12 of the constituents. Two glucosides of the flavonol quercetin were detected. Despite considerable interpopulation variation within species, six of the taxa have distinctive flavonoid profiles. Although there are few absolute differences among the subgenera, they can be distinguished chemically. Subgenus Rea contains the greatest number of compounds, and a previous cladistic analysis based on morphological features suggested this subgenus as most primitive. Subgenus Phoenicoseris is considered highly derived morphologically, and it has a reduced flavonoid chemistry. Very little reduction in flavonoid diversity was seen in the morphologically specialized subg. Dendroseris as compared to subg. Rea. A trend in reduction of numbers of compounds was seen for two of the three species on the younger island of Masafuera when compared to their presumed ancestors on Masatierra. Flavonoids of selected species of Hieracium and Hypochaeris, presumptive mainland progenitors of Dendroseris, reveal a close chemical affinity with the former genus.     

CHROMOSOME NUMBERS AND PHYLOGENY IN MELAMPODIUM (COMPOSITAE)

The haplord chromosome numbers of n = 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species of Melampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series of x2 = 9, 10, 11, and 12. Of these four groups of species, the x = 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base in Melampodium. A comparison of morphological and cytological data from the closely related genera, Acanthospermum and Lecocarpus, indicates that the latter are probably on a common base of x = 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.     

Systematic relationships in the white-rayed species of Melampodium (Compositae)

The white-rayed species complex ofMelampodium has been treated by various authors as containing one, two, or three species. A re-evaluation of the taxa in this complex by use of Chromatographic profiles of methanolic leaf extracts from numerous populations over the range of the group has revealed three distinct patterns which, along with morphological and ecological data, provide support for the recognition of three species within the group. Distributional analysis of previously and newly reported chromosome counts of 157 plants in 99 populations shows tetraploid races ofn = 20 in bothM. leucanthum var.leucanthum andM. cinereum var.cinereum to be located primarily in central and south central Texas but locally intermixed with diploid races. Interpretation of morphology, meiotic configurations, and chemical profiles confirms that these cytotypes are autopolyploid in origin and should not be given formal recognition. All data are used to interpret evolutionary relationships, and it is believed thatM. leucanthum var.argopkyllum may closely resemble the progenitor of the entire complex.     

Genetic races associated with the genera and sections of host species in the holoparasitic plant Cytinus (Cytinaceae) in the Western Mediterranean basin

* Speciation via race formation is an important evolutionary process in parasites, producing changes that favour their development on particular host species. Here, the holoparasitic plant Cytinus, which has diverse host species in the family Cistaceae, has been used to study the occurrence of such races. * Amplified fragment length polymorphism (AFLP) analyses were performed on 174 individuals of 22 populations parasitizing 10 Cistaceae species in the Western Mediterranean basin. * Neighbour-joining, multivariate ordination analyses, and individual-based Bayesian analyses, clustered Cytinus populations into five well-characterized genetic races that, overall, agreed with the taxonomic sections of their hosts. In the AMOVA, among-races differences accounted for almost 50% of the genetic variation. The isolation-by-distance model was not supported by a Mantel test among Cytinus populations (r = 0.012; P = 0.456). All races showed low within-population genetic diversity, probably as a result of restricted pollen flow aggravated by flowering asynchrony, restricted seed dispersion, or stochastic processes. * The genetic differentiation among the five races of Cytinus is congruent with the view that these races are well-characterized lineages that have evolved independently as a result of selective pressures imposed by their hosts. This pattern, with genetically distinctive groups associated with the infrageneric sections of the host species, has not been reported previously for parasitic angiosperms.     

Rooting and dating maples (Acer) with an uncorrelated-rates molecular clock: implications for north American/Asian disjunctions

Simulations suggest that molecular clock analyses can correctly identify the root of a tree even when the clock assumption is severely violated. Clock-based rooting of phylogenies may be particularly useful when outgroup rooting is problematic. Here, we explore relaxed-clock rooting in the Acer/Dipteronia clade of Sapindaceae, which comprises genera of highly uneven species richness and problematic mutual monophyly. Using an approach that does not presuppose rate autocorrelation between ancestral and descendant branches and hence does not require a rooted a priori topology, we analyzed data from up to seven chloroplast loci for some 50 ingroup species. For comparison, we used midpoint and outgroup rooting and dating methods that rely on rooted input trees, namely penalized likelihood, a Bayesian autocorrelated-rates model, and a strict clock. The chloroplast sequences used here reject a single global substitution rate, and the assumption of autocorrelated rates was also rejected. The root was placed between Acer and Dipteronia by all three rooting methods, albeit with low statistical support. Analyses of Acer diversification with a lineage-through-time plot and different survival models, although sensitive to missing data, suggest a gradual decrease in the average diversification rate. The nine North American species of Acer diverged from their nearest relatives at widely different times: eastern American Acer diverged in the Oligocene and Late Miocene; western American species in the Late Eocene and Mid Miocene; and the Acer core clade, including A. saccharum, dates to the Miocene. Recent diversification in North America is strikingly rare compared to diversification in eastern Asia.     

Patterns of genetic diversity in colonizing plant species: Nassauvia lagascae var. lanata (Asteraceae: Mutisieae) on Volcan Lonquimay, Chile

The effect of colonization on the distribution of genetic diversity within and among populations in relation to species characteristics remains an open empirical question. The objective of this study was to contrast genetic diversity within and among established and colonizing populations of Nassauvia lagascae var. lanata on Volcán Lonquimay (Araucanía Region, Chile), which erupted on 25 December 1988, and relate genetic diversity to biological characteristics of the populations. We analyzed a total of 240 individuals from 15 populations distributed along the Andes Cordillera using AFLP and obtained a total of 307 AFLP bands, of which 97.7% are polymorphic. Values of population differentiation (F(ST)) did not differ significantly among established and colonizing populations, but colonizing populations did have reduced levels of genetic divergence (as indicated by private and rare bands) and genetic variation (e.g., Shannon index). We conclude that a founder effect through limited numbers of founding propagules derived from nearby source populations has not yet been compensated for by subsequent population growth and migration. Low rates of secondary dispersal via running water, kin-structure within populations, and slow population growth seem to contribute to the slow recovery of genetic diversity.