Long-term studies on phenology are rarely reported from arctic and alpine areas, but are essential for understanding biotic and abiotic controls on flowering. We monitored first flowering day (FFD) for 144 species in a subarctic-alpine area in Swedish Lapland over a period of 10 yr (1992-2001). Temperature and global radiation were monitored continuously, and snowcover duration was observed. Thawing degree-days and snowcover duration (exposure) were the dominant environmental controls on phenology. We introduce a lability index (LI) to describe the interannual variability in FFD among species. The temporal sequence of species is very constant among years, although a few species are more labile. The species were also classified into the catagories "Functional type," "Raunkiær's life form," and "Sørensen's wintering floral type." The last two reflected the environmental data best, and together with "Exposure" they were combined into a phenology index (PI). The index was subsequently used in a triangular ordination together with FFD. The ordination illustrates whether species flower earlier or later than expected from their preconditions. We hypothesize that species having a delayed flowering respond more readily to global warming than species having an already optimized flowering.

Several naturally occurring hybrids in Potentilla (Rosaceae) have been reported, but no molecular evidence has so far been available to test these hypotheses of hybridization. We have compared a nuclear and a chloroplast gene tree to identify topological incongruences that may indicate hybridization events in the genus. Furthermore, the monophyly and phylogenetic position of the proposed segregated genera Argentina, Ivesia and Horkelia have been tested. The systematic signal from the two morphological characters, style- and anther shape, has also been investigated by ancestral state reconstruction, to elucidate how well these characters concur with the results of the molecular phylogenies. Six major clades, Anserina, Alba, Fragarioides, Reptans, ivesioid and Argentea, have been identified within genus Potentilla. Horkelia, Ivesia and Horkeliella (the ivesioid clade), form a monophyletic group nested within Potentilla. Furthermore, the origin of the proposed segregated genus Argentina (the Anserina clade) is uncertain but not in conflict with a new generic status of the group. We also found style morphology to be an informative character that reflects the phylogenetic relationships within Potentilla. Five well-supported incongruences were found between the nuclear and the chloroplast phylogenies, and three of these involved polyploid taxa. However, further investigations, using low copy molecular markers, are required to infer the phylogeny of these species and to test the hypothesis of hybrid origin.

A northern Swedish population of Bartsia alpina, an arctic-alpine perennial herb, was found to suffer high levels of predispersal seed predation by larvae of two insect species, both specialists on rhinanthoid Scrophulariaceae hosts. The primary predator is Aethes deutschiana (Lepidoptera-Tortricidae), the host of which was previously unknown. The other predator is Gimnomera dorsata (Diptera-Scatophagidae), which is basically a Pedicularis specialist. Both predators are attacked by larvae of Scambus brevicorais (Hymenoptera-Parasitica-Ichneumonidae). Total predation pressure was more or less constant during 1985-1987, but in 1988 the level was doubled, the possible reasons of which are discussed. Large inflorescences of B. alpina suffer significantly higher predation pressures than small ones. It is shown that predation is most intense in the middle of the inflorescences. The same floral nodes are known to produce more selfed seeds than distal and basal nodes. Seed predation in B. alpina thus results in an increased proportion of outcrossed seeds entering the seed pool. Selection pressures on host plant and predator fauna are discussed.

No abstract

Species in the ivesioid clade of Potentilla (Rosaceae) are endemic to western North America, an area that underwent widespread aridification during the global temperature decrease following the Mid-Miocene Climatic Optimum. Several morphological features interpreted as adaptations to drought are found in the clade, and many species occupy extremely dry habitats. Recent phylogenetic analyses have shown that the sister group of this clade is Potentilla section Rivales, a group with distinct moist habitat preferences. This has led to the hypothesis that the ivesioids (genera Ivesia, Horkelia and Horkeliella) diversified in response to the late Tertiary aridification of western North America. We used phyloclimatic modeling and a fossil-calibrated dated phylogeny of the family Rosaceae to investigate the evolution of the ivesioid clade. We have combined occurrence- and climate data from extant species, and used ancestral state reconstruction to model past climate preferences. These models have been projected into paleo-climatic scenarios in order to identify areas where the ivesioids may have occurred. Our analysis suggests a split between the ivesioids and Potentilla sect. Rivales around Late Oligocene/Early Miocene (∼23 million years ago, Ma), and that the ivesioids then diversified at a time when summer drought started to appear in the region. The clade is inferred to have originated on the western slopes of the Rocky Mountains from where a westward range expansion to the Sierra Nevada and the coast of California took place between ∼12-2 Ma. Our results support the idea that climatic changes in southwestern North America have played an important role in the evolution of the local flora, by means of in situ adaptation followed by diversification.