Gene variation and gene flow inOrchis morio (Orchidaceae) from Italy

Data are presented on genetic variation at 27 enzyme loci of the Green-Winged orchid,Orchis morio, in 18 population samples from Italy. The existence in Italy of two subspecies, i.e. subspp.morio andpicta, is not supported by allozyme data. No genetic heterogeneity was found betweenmorio-like andpicta-like samples and specimens. Moreover, morphological transition between the two forms was observed in different Italian populations. The parameters of genetic variability estimated forO. morio populations are consistent with those found among monocotyledon plants, and among those outcrossing, animal-pollinated and with wind-dispersed seeds. Genetic diversity of ItalianO. morio is mostly within populations. Correspondingly, low values of interpopulational genetic distance were found. This appears to be due to high levels of gene flow, which were estimated with different methods. The lack ofO. longicornu from Italian samples, as well as of any hybrid withO. morio (F₁, backcrossed or recombinant individuals) is demonstrated on the basis of genetic data. It is concluded that recurrent reports ofO. longicornu from Italy are due to confusion withO. morio or with otherOrchis species.     

Evidence of chloroplast capture in South American Nothofagus (subgenus Nothofagus,Nothofagaceae)

Subgenus Nothofagus, although geographically restricted at present to temperate areas of South America, has captured much attention in discussions of plant biogeography due to its widespread distribution through Gondwanan continents during the Tertiary. However, phylogenetic relationships within the subgenus Nothofagus have not yet been resolved. We examined geographic patterns of intraspecific and interspecific genetic variation to detect whether incongruences in nuclear or plastid DNA phylogenies occur, in order to better understand the evolutionary history of the subgenus Nothofagus. We conducted spatially-explicit sampling at 10 distinct locations throughout the range of austral South American forests and sampled all present Nothofagus species. We used ITS and chloroplast DNA sequences to estimate phylogenetic relationships. A phylogeny constructed from nuclear genes resolved the subgenus Nothofagus as monophyletic. We found that N. antarctica was a sister to a clade of evergreen species (N. betuloides, N. dombeyi, and N. nitida), while N. pumilio likely diverged earlier. Nine cpDNA haplotypes were distinguished in the subgenus Nothofagus which were associated to geographic locations rather than to taxonomic relationships. This species-independent cpDNA phylogeographic structures within the subgenus Nothofagus may be related to repeated chloroplast capture events over geological time in Patagonia.     

Carbohydrate storage,survival, and growth of two evergreen <Emphasis Type="Italic">Nothofagus</Emphasis> species in two contrasting light environments

A number of traits have been attributed important roles in tolerance of shade by plants. Some explanations emphasize traits enhancing net carbon gain; others emphasize energy conservation traits such as storage of non-structural carbohydrates (NSC). To date, cross-species studies have provided mixed support for the role of NSC storage in low-light survival. We examined NSC status, survival, biomass, and growth of large seedlings of two evergreen species of differing shade tolerance (Nothofagus nitida and N. dombeyi) grown in deep shade and 50% light for two growing seasons. We expected to find higher NSC concentration in the more shade-tolerant N. nitida and since allocation to storage involves sacrificing growth, higher growth rate in the shade-intolerant N. dombeyi. NSC concentration of both species was >twofold higher in 50% light than in deep shade, and in roots and stems did not differ significantly between species in either environment. NSC contents per plant were also similar between dead and living plants in deep shade. N. dombeyi outgrew N. nitida in 50% light, while this pattern was reversed in deep shade. Survival in deep shade was not correlated with NSC concentration. Leaf mass fraction was similar between species in 50% light, but lower in N. dombeyi in deep shade. Results provide little evidence of a link between carbohydrate storage and low-light survival in Nothofagus species, and support the view that understorey survival is primarily a function of net carbon gain. Patterns of variation in NSC concentration of the temperate species we studied are likely dominated by more important influences than adaptation to shade, such as limitation of growth or adaptation to cold stress.     

Retracing the evolutionary history of Nothofagus in its geo‐climatic context: new developments in the emerging field of phylogeology

Phylogeographic studies have made a significant contribution to the interpretation of genetic lineage distribution in response to climate changes, such as during glaciation events of the Neogene. However, the effects of ancient landscapes associated with global sea level rises, tectonic processes, and climatology driving lineage evolution have been largely overlooked. These effects can be tested in widespread lineages of cold‐tolerant species that have endured cooling, and thus, phylogeographic patterns may reflect large‐scale processes that were not reset by the ice ages. We hereby combine geological evidence from marine sedimentary basins, Andean orogeny, and climatology with molecular dating and statistical phylogeography to infer how geological and climatic processes affected the distribution of lineages in cold‐tolerant Nothofagus species during the Cenozoic. A total of 239 populations along the entire range of all species within the genus Nothofagus (N. antarctica, N. betuloides, N. dombeyi, N. nitida, and N. pumilio) were sampled and analyzed by sequencing three non‐coding regions of the chloroplast. We found 30 chloroplast DNA haplotypes that were geographically structured. Molecular dating calibrated with fossils revealed that ancestral lineages appeared in Eocene/Oligocene, whereas most divergences took place during the Miocene; in turn, Bayesian skyline plots showed that population expansion occurred in the Early Pleistocene (1.5–1 million years ago). Lineage divergence from all wide‐ranging Nothofagus was spatially and temporally concordant with episodic marine transgressions and warmer times in Patagonia during Eocene/Miocene Epochs. Long‐lasting stable raised areas preserved haplotype diversity throughout Patagonia, from where cold‐tolerant taxa expanded their ranges during pre‐Quaternary times. The detailed study of such ancient divergences is novel and allows us to infer the effects of geological processes on distribution patterns of ancient lineages, that is, phylogeology.     

Response of photosynthesis and respiration to temperature under water deficit in two evergreen Nothofagus species

Respiration and photosynthesis were studied in two Nothofagus species with different drought tolerance in order to evaluate the effect of water deficit on foliar carbon balance and the possible role of the alternative pathway on respiratory adjustment. We propose that under severe water deficit the more drought‐tolerant species N. dombeyi is able to decrease its respiration more than the less drought‐tolerant species N. nitida, thus carbon gain could be maintained when photosynthesis is suppressed by drought. Dark respiration (R_d) and carbon assimilation under saturating light (A_sat) were evaluated under seasonal field conditions and during drying and re‐watering cycles under glasshouse. In addition, respiratory pathway changes were evaluated by oxygen isotope fractionation. In the field, N. dombeyi displayed greater light‐saturated photosynthetic capacity than N. nitida, but R_d did not differ between species during summer. In the glasshouse, N. dombeyi displayed an unchanged rate of R_d and increased carbon loss under severe water deficit. Nothofagus nitida displayed a more flexible respiratory response to water deficit, with a lower thermal sensitivity of respiration (decrease in Q₁₀) and a decrease in R_d. This contributed to maintaining leaf carbon balance during the water deficit period. Respiratory electron flow was mainly via the cytochrome pathway for both species and under all treatments, indicating no strong participation of alternative respiration. Our results suggest that under severe water stress, N. dombeyi could be more injured than N. nitida and that the lack of control in the carbon loss under prolonged periods of drought could be limiting for its survival.     

Magellanic woodpecker ( Campephilus magellanicus) abundance and foraging in Tierra del Fuego, Chile

The Magellanic woodpecker (Campephilus magellanicus) is a vulnerable and poorly studied bird in the sub-antarctic deciduous and evergreen beech (Nothofagus) forests of South America. On Tierra del Fuego island (Chile), we compared Magellanic woodpecker abundance and its foraging habitat in two forest types: pure N. pumilio and mixed forests composed by N. pumilio and N. betuloides, including managed and non managed stands. At a regional scale, abundance of woodpeckers was greater in landscapes including both forest types than in pure N. pumilio landscapes. When both forest types occurred together, woodpecker abundance did not differ between them. The number of trees with foraging signs was correlated with Magellanic woodpecker abundance and was also associated with N. betuloides and snag densities, but was not affected by forest management. Occurrence of pecking on foraging trees was greater in mixed Nothofagus than pure N. pumilio stands. Woodpeckers foraged disproportionately more on larger diameter and more decayed trees. Moreover, trees used for foraging were positively correlated with canopy cover and snag density and were negatively correlated with distance to nearby peatlands and beaver ponds. Direct observation revealed that the flying distance between trees was negatively correlated with proportion of trees with foraging signs. Woodpeckers chose trees that were visited before, suggesting a pattern of tree recognition within foraging territories.Communicated by F. Bairlein     

AreAltica carduorumandAltica cirsicola(Coleoptera: Chrysomelidae) Different Species? Implications for the Release ofA. cirsicolafor the Biocontrol of Canada Thistle in Canada

Altica carduorumandAltica cirsicolaare two species of leaf-feeding beetle (Coleoptera: Chrysomelidae) which appear to be morphologically indistinguishable and reportedly hybridize in the laboratory. A European population ofA. carduorumwas previously screened for host-plant specificity and released in North America for the control of Canada thistle,Cirsium arvense.A population ofA. cirsicolafrom China is currently being considered as a biocontrol agent forC. arvenseand, as a different beetle species, must be screened using host-specificity tests similar to those used forA. carduorum.IfA. carduorumandA. cirsicolaare, in fact, one species, the screening requirements forA. cirsicolacould be significantly reduced. Hence, we investigated the taxonomic relationship betweenA. carduorumandA. cirsicolausing morphometric analyses, hybridization experiments, and DNA fingerprinting using random amplified polymorphic DNA (RAPD) analysis. Discriminant function analyses indicate thatA. carduorumandA. cirsicolacannot be reliably distinguished by their morphologies, and interspecific matings produce fertile F₁offspring. However, because interspecific matings produce significantly fewer offspring than intraspecific matings, and because of clear differences in their DNA profiles, we conclude thatA. carduorumandA. cirsicolaare separate species. This study serves to highlight the value of genetic analyses in taxonomic studies and their role in biological control programs.     

Structure and tree-fall gap dynamics of old-growth Nothofagus forests in Tierra del Fuego,Argentina

Abstract. Tree size and age structure, tree-fall and gap characteristics, and regeneration in gaps were studied in Nothofagus-dominated old-growth forests in Tierra del Fuego, Argentina. Gap-phase regeneration has resulted in all-aged populations for N. pumilio, N. betuloides, and Drimys winteri, and regeneration in gaps appears to be maintaining coexistence between species in mixed stands. N. betuloides fills many gaps via advance regeneration and some individuals persist for > 150 yr in the understory. Multiple periods of release and suppression indicate that N. betuloides may take advantage of several gap events to reach the main canopy. Likewise, Drimys grows well under closed canopy and can rapidly respond to gap formation, sometimes impeding the regeneration of N. betuloides. In contrast, N. pumilio regenerates in gaps mainly from seed or from advance regeneration of small, ephemeral seedlings. Gap turnover times in Fuegian forests were estimated at 300 - 500 yr, although gap formation was highly episodic and possibly associated with regionally extensive windstorms, earthquakes, and stand-level dieback. 92 % of gaps involved multiple tree-falls, and at least 53 % involved secondary expansion. Gap and tree-fall characteristics in Tierra del Fuego were similar to results from northern Patagonia, Chile, and New Zealand; however, we emphasize that regeneration of Nothofagus spp. and Drimys winteri in gaps depends on associated vegetation and varies along both local and regional environmental gradients.     

Age structure and dynamics of Patagonian beech forests in Torres del Paine National Park,Chile

This study documents the stem size and age-structure in forests dominated by different species of Nothofagus in Torres del Paine National Park (51° S), in the Chilean Patagonian region. We also explored the relationship between the various types of Nothofagus forest and postglacial succession. Pioneer stands on moraine fields 1–2 km of the glacier front are dominated by Nothofagus betuloides and Nothofagus antarctica. Moraines appear to be first colonized by the evergreen N. betuloides, followed within 5–7 years by deciduous N. antarctica. Nothofagus antarctica may replace the former species and develop monospecific stands on glacial valleys. Most trees in the N. antarctica stand studied were older than 40 years and floods may cause a significant mortality of young trees. Recruitment from seed seems to be infrequent. Old-growth stands dominated by deciduous Nothofagus pumilio occupy more stable substrates, and probably represent the last stage of postglacial succession. This long-lived tree species had recorded ages over 200 years. The canopy of N. pumilio forests appears to be a mosaic of even-aged, old-growth patches. We propose that regeneration episodes follow the blowdown of a large portion of the canopy, with long intervals with little or no regeneration. Windstorms may be an important force influencing the regeneration of N. pumilio. Exogenous disturbances, such as floods and windstorms, are an integral part of the forest cycle in the Patagonian region.     

Effects of genetic and environmental host plant variation on the susceptibility of two noctuids toBacillus thuringiensis

TwoApium graveolens var.rapaceum (L.) cultivars that differ in their suitability for the survival and growth ofSpodoptera exigua (Hübner) andTrichoplusia ni (Hübner) were used to examine the effect of genetic and seasonal environmental variation in host plant suitability on the efficacy ofBacillus thuringiensis subsp.kurstaki (Berliner). The effects of host plant genotype andB. thuringiensis were generally independent, so thatB. thuringiensis efficacy was greatest on the resistant host plant cultivar. Host plant suitability varied within growing season for both insect species but, while host plant suitability decreased with increasing plant age forT. ni, the response ofS. exigua to plant age was not as clear. Within season variation in host plant suitability affectedB. thuringiensis efficacy and the interaction betweenB. thuringiensis and host plant cultivar forS. exigua but not forT. ni. Soluble protein and Folin-Denis phenolic concentrations of host plant tissue were not correlated with changes in host plant suitability to either insect species.     

Magellanic Woodpecker (Campephilus magellanicus) sap feeding and its role in the Tierra del Fuego forest bird assemblage

Several woodpecker species feed on phloem-sap flowing from pecked trees. We report sap consumption by the magellanic woodpecker (Campephilus magellanicus) inhabiting beech (Nothofagus) forests of Tierra del Fuego island (Chile). Magellanic woodpeckers drilled sap wells in N. betuloides trees close to their nests and also when they were moving in family groups. Three other bird species were observed foraging and competing for sap: the austral parakeet (Enicognathus ferrugineus) and two small passerines, the patagonian sierra-finch (Phrygilus patagonicus) and the white-crested elaenia (Elaenia albiceps). The abundance of these three bird species was greater in sites around sap wells than in other forest sites, suggesting that magellanic woodpecker is an important species in maintaining the Nothofagus forest bird assemblage.     

Mass loss and nutrient release from decomposing evergreen and deciduous Nothofagus litters from the Chilean Andes

Abstract Leaf litter decomposition experiments were conducted on two deciduous (Nothofagus obliqua (roble)) and Nothofagus pumilio (lenga)) and one evergreen (Nothofagus dombeyi) Nothofagus (Nothofagaceae) species from a single Chilean forest in order to understand how congeneric trees with differing leaf lifespans impact the soil in which they grow. Single‐species litter samples were decomposed in a mixed hardwood forest in Ohio and in a deciduous‐evergreen Nothofagus forest in Chile. In the Ohio forest, the two deciduous species’ litters decomposed at k ≈ 1.00 per year and the evergreen at k ≈ 0.75 per year. In Chile k ranged from k ≈ 0.06 (N. obliqua) to k ≈ 0.23 (N. pumilio) per year. In both experiments, N and P were released faster from the deciduous litters than from evergreen litter. In Ohio, evergreen litter immobilized more N and P for a longer time period than did deciduous litter. As N. dombeyi stands tend to have lower available soil N and P in this particular mixed Nothofagus forest, the increased time of N and P immobilization by N. dombeyi litter suggests a feedback role of the tree itself in perpetuating low N and P soil conditions.     

Dynamic management of genetic resources: maintenance of outcrossing in experimental metapopulations of a predominantly inbreeding species

Dynamic management of genetic resources inpredominantly inbreeding species requiresincreased levels of outcrossing to limit theloss of genetic variation due to smallereffective sizes and to favour the emergence ofnew genetic combinations. Here, we show thatoutcrossing rates can artificially bepermanently increased in experimental evolvingplant metapopulations, using Arabidopsisthaliana as a model. We introducedmale-sterility genes and used an adequatemanagement of the resulting female plants tomodify the outcrossing rates. As expected, theincrease in outcrossing resulted in lowerlevels of heterozygote deficiency (F _is) than observed in natural populationsof A. thaliana and therefore in themaintenance of potentially higher levels ofgenetic variation. An additional selectiveadvantage for females' offspring, due to theproduction of larger seeds by females and apossible heterosis effect, furthermore led tosmaller F _is than expected from therealized outcrossing rate. This selectiveadvantage also resulted in an increase infemale frequency, especially in metapopulationswith large population sizes, creating anon-causal negative correlation between femalefrequency and heterozygote deficiency.     

The inheritance of organogenic response in melon

Previous studies have demonstrated variation in organogenic competence among plants within a population ofCucumis melo. In order to determine if leaf explant response is under genetic control, we investigated the distribution of the shoot regeneration frequency in F₁ and F₂ generations from parents representing extreme values forin vitro organogenic response. Results suggest a genetic model with two genes, partial dominance, independent segregation and similar effects for both genes.     

Hybridization and evolution inCardamine (Brassicaceae) at Urnerboden, Central Switzerland: Biosystematic and molecular evidence

Hybridization between two diploid (2n = 2x = 16) species ofBrassicaceae, Cardamine rivularis andC. amara, at Urnerboden, Central Switzerland, resulted in the rather unusual triploid hybridC. insueta (2n = 3x = 24), and later on in the amphiploidC. schulzii (2n = 6x = 48). The hybrid and the neopolyploid species colonized successfully some man-made biotopes. Plants ofC. insueta are mostly functional females with non-dehiscent anthers, but true hermaphrodite individuals with partly sterile pollen grains also occur within the population. Analyses of cpDNA and nuclear DNA permitted to establish the parentage of the hybrid: the maternal parent which contributed unreduced egg cells proved to beC. rivularis whereas the normally reduced pollen originated fromC. amara. The pronounced genetic variability inC. insueta revealed by isozyme and RAPD analyses, at variance with the polarized segregation, heterogamy and strong vegetative reproduction of the hybrid, is possibly influenced by recurrent formation ofC. insueta which party results from backcrosses betweenC. insueta andC. rivularis but may also proceed by other pathways. The amphiploidCardamine schulzii has normally developed anthers but its pollen is sometimes highly sterile. The surprisingly uniform genetic make-up of the new amphiploid species might be related to its possible monotopic origin and/or young phylogenetic age but should be further assessed. Site management seems to be very important to a further development of hybridogenous populations and their parent species. In conclusion, the evolution at Urnerboden is discussed in the context of the traditional concept of multiple plant origins.     

Patterns of genetic differentiation in two annual bromegrasses,Bromus lanceolatus andB. hordeaceus (Poaceae)

Infraspecific genetic differentiation was analysed in two tetraploid annual bromegrasses,Bromus lanceolatus (from N Africa) andB. hordeaceus (from N Africa and France). Genetic analysis of populations was based on allozyme polymorphisms at 17 loci. Different fixed heterozygous phenotypes were scored in both species, according to their allopolyploid origin. In N Africa, more variation occurred among populations ofB. lanceolatus than ofB. hordeaceus. The variation was not randomly distributed among populations of both species. InB. lanceolatus, differentiation was correlated with climatic variables rather than with geographic distance between populations. Higher correlation of genetic differentiation with geographic distance occurred inB. hordeaceus, particularly at large geographic scale, between French and N African populations. Within each region, the populations appeared weakly genetically differentiated, even when belonging to different subspecies.     

Molecular phylogeny ofNothofagus (Nothofagaceae) based on theatpB-rbcL intergenic spacer of the chloroplast DNA

The genusNothofagus is distributed in the Southern Hemisphere from South America to Oceania, and its distribution has been assumed to be formed by continental drift by means of Gondwana break-up during the Mesozoic era. The phylogeny of the genus was elucidated by the sequences ofatpB-rbcL intergenic spacer of cpDNA for the better understanding of its evolution and biogeography. The phylogeny ofNothofagus corresponded completely to the pollen morphology which recognizes four pollen types in extant species, and agrees well with the taxonomic system of Hill and Read (1991) although there, the subgenusNothofagus showed in unresolved polytomy. The topology of the phylogenetic tree reveals that subgenusLophozonia was derived first, and thenFuscospora, Nothofagus andBrassospora. Species from South America and New Zealand were assigned to each cluster according to their pollen morphology. Therefore, diversification ofNothofagus should have already proceeded at the subgenus level before the completion of Gondwana break-up Tropical species distributed in New Guinea and New Caledonia whose evolutionary history has been controversial were revealed to be a derived group. All five New Caledonian species formed a monophyletic group with very few sequence divergences in the intergenic spacer of cpDNA, thus showing rapid adaptive radiation in the island. Evolutionary trends of several morphological traits ofNothofagus are discussed. The evolution of valve number of cupules, number of nuts per cupule, and habit of leaf-fall (evergreen or deciduous) which are diversified in the genus, were revealed as having occurred several times as the result of convergence.     

Isozyme variation inBulnesia retama,B. schickendantzii andB. foliosa (Zygophyllaceae)

The genetic variation between two allopatric populations ofBulnesia retama and that ofB. schickendantzii andB. foliosa was investigated. The Peruvian population ofB. retama showed low values of P (0.117) and He (0.057) compared to those in the Argentine population with P = 0.59 and He = 0.269;B. schickendantzii showed P = 0.54 andB. foliosa P = 0.17. Genetic identity between the latter was 0.836 and between the allopatric populations ofB. retama was 0.89; the Peruvian population had reduced allelic variation per locus (A = 1.176) in comparison to the Argentine population (A = 1.955). The values of A, P, He andWright's fixation indices suggest that the Peruvian population could have originated from a single or very few migrants from southern latitudes (founder effect).     

Allozyme diversity and systematics inAnnonaceae—a pilot project

Five species ofAnnona and one species fromArtabotrys, Cananga, Polyalthia, andRollinia were investigated in regard to 11 different allozyme loci. Preliminary studies on small population samples ofAnnona suggest genetic uniformity in three species and variability within and between populations in two other species. The allotetraploid origin ofA. glabra is clearly shown by its hybrid enzyme bands. The genetic distance between fiveAnnona species partly corresponds with their morphological relationships; onlyA. muricata appears more separated than is suggested by morphology. A comparison of the five genera demonstrates close relationship betweenAnnona andRollinia. Two enzyme loci are identical within all taxa investigated and possibly may serve as a genetic marker for the family.     

Patterns of allozyme diversity in several selected rare species in Korea and implications for conservation

Because some endemic plants appear to be adapted to a narrow setof environmental conditions with limited genetic diversity, an analysis ofpopulation genetic structure is necessary to fully evaluate the impact of rarityon genetic variation. Listed as endangered species in Korea, only fewpopulations of Abeliophyllum distichum, Leonticemicrorhyncha, Bupleurum euphorbioides, andBerchemia berchmiaefolia were found. A reduced level ofgenetic variation in B. berchemiaefolia is consistent withthe occurrence of a genetic bottleneck and inbreeding. Leonticemicrorhyncha differed dramatically from other taxa in its observed level of geneticvariation, probably due to its predominant selfing. The level ofallozyme variation maintained by A. distichum was high forendemic species. Compared to species with similar traits, A.distichum maintained a relatively higher genetic diversity, probably dueto floral heteromorphism and preferred outcrossing. Bupleurumeuphorbioides maintained a higher genetic diversity due to outcrossing,but at the individual locus, deficiency of heterozygosity prevailed. Probablyinbreeding between local neighborhoods was frequent because A.distichum and B. euphorbioides were pollinatedby small fly species which might be less effective as a pollen dispersal, andtheir visits were extremely scarce and controlled by the weather conditions.Since much of the species-to-species variation in genetic diversity is due tothe specific ecological and evolutionary history of a species, any managementplan developed should be based on historical changes in the population size anddistribution to better predict the amounts and patterns of genetic diversity.