Rainwater in cupulate bracts repels seed herbivores in a bumblebee-pollinated subalpine flower

Persistent calyces increase floral longevity and female fitness in Salvia miltiorrhiza (Lamiaceae)

The evolution of persistent calyces may be an adaptation to ensure reproductive success of certain flowering plants. However, experimental evidence of the functions of persistent calyces during flowering and seed development remains scarce. We explored the possible functions of persistent calyces in Salvia miltiorrhiza, a perennial herb with campanulate calyx. We conducted calyx manipulation experiments to examine whether persistent calyces affect visitation rates of nectar robbers and pollinators, individual flower longevity, fruit set, seed set and seed mass. Our findings suggested that shortening of the calyx significantly decreased individual flower longevity, fruit set and seed mass, but did not affect visitation of pollinators and nectar robbers. In addition, the seed set of control flowers and the flowers with calyx shortened at the beginning of fruiting stage (CSF flowers) did not significantly differ, but both were higher than that of the flowers with calyx shortened at the beginning of blooming stage (CSB flowers). The seed set and fruit set of CSB flowers were limited by pollination due to the reduction in floral longevity. We conclude that persistent calyces of S. miltiorrhiza may represent adaptive strategies to maintain floral longevity and increase plant fitness. Persistent calyces may provide protection for the growth of flowers and contribute resources to the development of fruits and seeds.

Geographic consistency and variation in conflicting selection generated by pollinators and seed predators

BACKGROUNDS AND AIMS

Floral traits that attract pollinators may also attract seed predators, which, in turn, may generate conflicting natural selection on such traits. Although such selection trade-offs are expected to vary geographically, few studies have investigated selection mediated by pollinators and seed predators across a geographic mosaic of environments and floral variation.

METHODS

Floral traits were investigated in 14 populations of the bumble-bee-pollinated herb, Pedicularis rex, in which tubular flowers are subtended by cupular bracts holding rain water. To study potentially conflicting selection on floral traits generated by pollinators and florivores, stigmatic pollen loads, initial seed set, pre-dispersal seed predation and final viable seed production were measured in 12-14 populations in the field.

KEY RESULTS

Generalized Linear Model (GLM) analyses indicated that the pollen load on stigmas was positively related to the exsertion of the corolla beyond the cupular bracts and size of the lower corolla lip, but so too was the rate of seed predation, creating conflicting selection on both floral traits. A geographic mosaic of selection mediated by seed predators, but not pollinators, was indicated by significant variation in levels of seed predation and the inclusion of two-, three- and four-way interaction terms between population and seed predation in the best model [lowest corrected Akaike Information Criterion (AICc)] explaining final seed production.

CONCLUSIONS

These results indicate opposing selection in operation: pollinators generated selection for greater floral exsertion beyond the bracts, but seed predators generated selection for reduced exsertion above the protective pools of water, although the strength of the latter varied across populations.

Towards a comprehensive phylogeny of the large temperate genus Pedicularis (Orobanchaceae), with an emphasis on species from the Himalaya-Hengduan Mountains

BACKGROUND

Striking interspecific variations in floral traits of the large temperate genus Pedicularis have given rise to controversies concerning infra-generic classifications. To date, phylogenetic relationships within the genus have not been well resolved. The main goal of this study is to construct a backbone phylogeny of Pedicularis, with extensive sampling of species from the Himalaya-Hengduan Mountains. Phylogenetic analyses included 257 species, representing all 13 informal groups and 104 out of 130 series in the classification system of Tsoong, using sequences of the nuclear ribosomal internal transcribed spacer (nrITS) and three plastid regions (matK, rbcL and trnL-F). Bayesian inference and maximum likelihood methods were applied in separate and combined analyses of these datasets.

RESULTS

Thirteen major clades are resolved with strong support, although the backbone of the tree is poorly resolved. There is little consensus between the phylogenetic tree and Tsoong's classification of Pedicularis. Only two of the 13 groups (15.4 %), and 19 of the 56 series (33.9 %) with more than one sampled species were found to be strictly monophyletic. Most opposite-/whorled-leaved species fall into a single clade, i.e. clade 1, while alternate leaves species occur in the remaining 12 clades. Excluding the widespread P. verticillata in clade 1, species from Europe and North America fall into clades 6-8.

CONCLUSIONS

Our results suggest that combinations of morphological and geographic characters associated with strongly supported clades are needed to elucidate a comprehensive global phylogeny of Pedicularis. Alternate leaves are inferred to be plesiomorphic in Pedicularis, with multiple transitions to opposite/whorled phyllotaxy. Alternate-leaved species show high diversity in plant habit and floral forms. In the Himalaya-Hengduan Mountains, geographical barriers may have facilitated diversification of species with long corolla tubes, and the reproductive advantages of beakless galeas in opposite-/whorled-leaved species may boost speciation at high altitude.