The reproductive biology of boreal forest herbs. I. Breeding systems and pollination

Abstract

Detailed observations and experimental studies of the reproductive biology of 12 boreal forest herbs were conducted over a 3-year period (1978–1980) in spruce–fir forests of central New Brunswick. The species examined were Aralia nudicaulis, Chimaphila umbellata, Clintonia borealis, Cornus canadensis, Cypripedium acaule, Linnaea borealis, Maianthemum canadense, Medeola virginiana, Oxalis montana, Pyrola secunda, Trientalis borealis, and Trillium undulatum. All taxa are insectpollinated perennials and most exhibit clonal growth. Floral syndromes of the understory community are relatively unspecialized with many species possessing small white or green flowers. A total of 103 taxa of insects were collected from flowers during the 1979 season. Bombus spp. are the major pollinators of 5 of the 12 species. Syrphid flies, bee flies, and halictid and andrenid bees were also commonly observed. Controlled pollinations were undertaken to determine the breeding systems of herbs. Bagged, self-, cross- and open-pollinated treatments were used to investigate the capacity for self-pollination, compatibility status, and factors influencing fecundity in each species. A diversity of reproductive systems was revealed. Six species are completely dependent on insects for pollination, four species are weakly autogamous, one is strongly autogamous, and one appears to be apomictic. Comparisons of fruit-set and seed set from controlled self- and cross-pollinations indicate that four species are strongly self-compatible, one is dioecious, and the remainder display varying degrees of self-incompatibility. Despite this variation, outbreeding appears to be the most common reproductive mode. In several species there is evidence that low pollinator service limits fruit-set.

Interaction of pollinators and herbivores on plant fitness suggests a pathway for correlated evolution of mutualism- and antagonism-related traits

“…Pollination studies have often compared seed production of plants exposed to natural pollination with those subject to pollinator exclusion or augmented pollination (33)(34)(35)(36). Herbivory studies, on their part, have frequently revealed extensive herbivory on flowers or developing fruits, a situation particularly frequent among perennial herbs such as H. foetidus (37)(38)(39)(40)(41).…”

Mating patterns and genetic diversity in the wild Daffodil Narcissus longispathus (Amaryllidaceae)

“…Species that bloom in early spring when unfavourable weather conditions often prevail are susceptible to unpredictable pollinator service. Probably as a response to uncertain pollination environments many early blooming herbs possess floral traits, such as extended floral longevities and selfcompatibility, which reduce the likelihood of reproductive failure (Schemske et al, 1978;Barrett and Helenurm, 1987;Herrera, 1995). However, self-compatible species with long floral lifespans may be vulnerable to unpredictable pollinator service, which can potentially result in increased self-fertilization.…”

Features of grass and subshrub reproduction in forest phytocoenoses

“…About 40 % of the species of forest grasses of forest ecosystems of the temperate zones have autogamy [4]. But, basically, the researchers record pollination deficitinforestgrassesasoneofthekeyreasonsforthelowleveloffruiting.…”