Invasion, isolation and evolution shape population genetic structure in Campanula rotundifolia

The distribution and genetic structure of most plant species in Britain and Ireland bear the imprint of the last ice age. These patterns were largely shaped by random processes during recolonization but, in angiosperms, whole-genome duplication may also have been important. We investigate the distribution of cytotypes of Campanula rotundifolia, considering DNA variation, postglacial colonization, environmental partitioning and reproductive barriers. Cytotypes and genome size variation from across the species’ range were determined by flow cytometry and genetic variation was assessed using cpDNA markers. A common garden study examined growth and flowering phenology of tetraploid, pentaploid and hexaploid cytotypes and simulated a contact zone for investigation of reproductive barriers. Irish populations were entirely hexaploid. In Britain, hexaploids occurred mostly in western coastal populations which were allopatric with tetraploids, and in occasional sympatric inland populations. Chloroplast markers resolved distinct genetic groups, related to cytotype and geographically segregated; allopatric hexaploids were distinct from tetraploids, whereas sympatric hexaploids were not. Genome downsizing occurred between cytotypes. Progeny of open-pollinated clones from the contact zone showed that maternal tetraploids rarely produced progeny of other cytotypes, whereas the progeny of maternal hexaploids varied, with frequent pentaploids and aneuploids. The presence of distinctive hexaploid chloroplast types in Ireland, Scottish islands and western mainland Britain indicates that its establishment preceded separation of these land masses by sea-level rise c. 16 000 years BP. This group did not originate from British tetraploids and probably diverged before postglacial invasion from mainland Europe. The combination of cytotype, molecular, contact zone and common garden data shows an overall pattern reflecting postglacial colonization events, now maintained by geographic separation, together with more recent occasional local in situ polyploidisation. Reproductive barriers favour the persistence of the tetraploid to the detriment of the hexaploid.

Native Forb Response to Aminocyclopyrachlor

Native forbs are an essential component in the functioning and diversity of prairie communities. Aminocyclopyrachlor (AMCP) will effectively control many noxious weeds that invade prairie communities; however, its efficacy on desirable broadleaf plants is relatively unknown. Few field studies have been reported, and locating adequate populations of native forbs for evaluation of tolerance to herbicides is difficult. The susceptibility of 10 prairie forb species to AMCP was evaluated in the greenhouse. Species were chosen to correlate with a field study of AMCP and a previous greenhouse experiment. AMCP was applied at 0, 35, 70, and 105 g ha−1 with a methylated seed oil (MSO) plus silicone-based non-ionic surfactant (NIS) blend at 0.25% v/v when plants reached the growth stage simulating a spring treatment for weed control. Blueflag iris (Iris versicolor L.) and harebell (Campanula rotundifolia L.) were relatively tolerant and would likely be unharmed following an application of AMCP in the field. Wild licorice (Glycyrrhiza lepidota Pursh), prairie wild rose (Rosa arkansana Porter), purple prairie clover (Dalea purpurea Vent.), and wild bergamot (Monarda fistulosa L.) were moderately susceptible to AMCP; however, plants might regrow in the field, since some survived at the highest AMCP application rate (105 g ha−1) evaluated. Skyblue aster [Symphyotrichum oolentangiense (Riddell) G. L. Nesom], Canada goldenrod (Solidago canadensis L.), blue cardinal-flower (Lobelia siphilitica L.), and blacksamson echinacea (Echinacea angustifolia DC.) were susceptible to AMCP even when applied at 35 g ha−1. The susceptibility of greenhouse-grown forbs to AMCP was the same or similar to species evaluated in the field and can be used to predict native forb tolerance in the field.

Reappraisal of Campanula rotundifolia var. bulgarica Nejceff—a neglected taxon from Central Stara Planina Mountain, Bulgaria

Campanula rotundifolia var. bulgarica Nejceff, a neglected taxon in the Bulgarian flora with currently uncertain status, was collected and studied at its locus classicus in the Sokolna (Koru Dere) Reserve of Central Stara Planina Mountain. A detailed morphological analysis of Nejceff’s original material and other related species clearly indicates that this is a distinct taxonomic entity worthy of species rank. Campanula nejceffii, stat. nov. is distinguished by a combination of its pubescent habit, ovoid to elliptic-lanceolate cauline leaves, clearly spreading to reflexed narrowly triangular-lanceolate calyx teeth, erect buds and flowers. Complete species description and comparison with selected species in the C. rotundifolia group are given. The lectotypes of two taxa—C. rotundifolia var. bulgarica Nejceff and C. rotundifolia subsp. neicevii f. pirinica Stoj. & Acht. are designated by the authors.