Reproductive biology of an endangered lithophytic shrub and implications for its conservation

Abstract

Background Plants in cliff habitats may evolve specific reproductive strategies to cope with harsh environments, and unraveling these reproductive characteristics can improve our understanding of survival strategies and lithophyte evolution. This understanding is especially important for efforts to protect rare and endemic plants. Here, we investigated the reproductive biology of Lonicera oblata, an endangered lithophytic shrub that is scattered in highly fragmented and isolated cliff habitats of the Taihang and Yan mountains in North China. Results Flowers of L. oblata are herkogamous and protandrous, characteristics that can prevent autogamy at the single-flower level, and insects are necessary for pollination. The outcrossing index, pollen/ovule ratio, and the results of hand pollination were measured and all revealed a mixed mating system for L. oblata, that combines cross-fertilization and partial self-fertilization. The floral traits of L. oblata of zygomorphic and brightly yellowish corolla, heavy fragrance, and rich nectar, suggest an entomophilous pollination system. Sweat bees were observed as the most effective pollinators but their visiting frequencies were not high. Pollen limitation may limit the reproductive success of L. oblata. Conclusions We determined the reproductive characteristics of L. oblata, a critically endangered species endemic to cliffs in North China, providing insight into its endangerment and suggesting conservation strategies. L. oblata has highly pollinator-dependent self-fertilization as part of a mixed mating system. Floral features such as low-flowering synchrony, asynchronous anthers dehiscence, and high duration of stigma receptivity, improve pollination efficiency in the case of low pollinator service. Our work provides reference information to understand the survival strategies and conservation of L. oblata and other lithophytes.

Reproductive Biology and Breeding Systems of Two Opisthopappus Endemic and Endangered Species on the Taihang Mountains

“…Floral syndromes comprise sets of integrated floral traits (e.g., morphology, color, and scent) [ 4 , 25 , 28 ]. For the two species of Opisthopappus , the floral syndromes were similar ( Figure 1 ) except for the capitulum size and the number of ligules and florets ( Table 1 ).…”

“…Reproduction is not only the most important and relatively fragile step in the life cycles of plants but also the core of their evolutionary process [ 1 , 2 , 3 , 4 ]. Meanwhile, pollination biology is a critical parameter in the life history of flowering plants that determines the success of sexual reproduction [ 5 , 6 , 7 ].…”

“…Cliff habitats are sensitive to climate change, which can disrupt the overlap in seasonal timing of flower production and pollinator activity, which further reduces pollination [ 11 , 12 , 13 ]. Thus, the reproductive success of these lithophytes may be reduced by both uncertain pollinator services and low pollen outputs [ 4 , 14 ]. Studies of the reproductive characteristics of these lithophytes can improve our understanding of their evolutionary processes and survival strategies, yet there have been few corresponding investigations to date [ 3 , 6 , 7 , 15 ].…”

Genomic Data Reveals Profound Genetic Structure and Multiple Glacial Refugia in Lonicera oblata (Caprifoliaceae), a Threatened Montane Shrub Endemic to North China

“…(ii) The combined side effect of its reproductive system and fruit dispersal characteristics. A mixed mating system of biased outcross and partial self-fertilization is observed in L. oblata , and insects are necessary for pollination ( Wu et al, 2022 ), while pollen limitation occurs during its flowering period. The harsh climate conditions during its flowering period (strong wind, sudden drop in temperature, snow, and/or dusty wind in the early spring) greatly interfere with the activities of effective pollinators and the pollination success of L. oblata .…”

“…Its limestone-specific habitat may greatly restrict its expansion, and the limited populations are highly fragmented and affected by human activities (e.g., agriculture, tourism, and logging). Furthermore, pollen limitation and harsh climate conditions during its flowering period restrain its survival and reproduction ( Wu et al, 2022 ). Our results reveal a low genetic diversity and high genetic differentiation, which may suggest a reduction in the species fitness.…”