Pollination ecology of Isoglossa woodii, a long‐lived, synchronously monocarpic herb from coastal forests in South Africa

Abstract

Synchronous monocarpy in long‐lived plants is often associated with pollination by wind, in part because infrequent mass flowering may satiate pollinators. Selfing in synchronous monocarps may provide reproductive assurance but conflict with the benefits of outcrossing, a key evolutionary driver of synchrony. We predicted that animal‐pollinated species with synchronous flowering would have unspecialised flowers and attract abundant generalised pollinators, but predictions for selfing and outcrossing frequencies were not obvious. We examined the pollination biology of Isoglossa woodii (Acanthaceae), an insect‐pollinated, monocarpic herb that flowers synchronously at 4–7‐year intervals. The most frequent visitor to I. woodii flowers was the African honeybee, Apis mellifera adansonii. Hand‐pollination failed to enhance seed production, indicating that the pollinators were not saturated. No seed was set in the absence of pollinators. Seed set was similar among selfed and outcrossed flowers, demonstrating a geitonogamous mixed‐mating strategy with no direct evidence of preferential outcrossing. Flowers contained four ovules, but most fruits only developed one seed, raising the possibility that preferential outcrossing occurs by post‐pollination processes. We argue that a number of the theoretical concerns about geitonogamous selfing as a form of reproductive assurance do not apply to a long‐lived synchronous monocarp such as I. woodii.

Ecological filtering by a dominant herb selects for shade tolerance in the tree seedling community of coastal dune forest

“…Isoglossa woodii may have caused a dichotomy in the light response of tree species, but because of its dominance and relatively long maturation time of up to 7 years (GriYths et al 2010), the shaded micro-environment at the forest Xoor has selected against light-demanding tree species, which have consequently been lost from the seeding community over time, while relatively shade-tolerant species have been favoured. This scenario explains: (1) the lack of an apparent trade-oV between LCP and A max in the extant group of species, and (2) the comparatively low LCPs recorded from all the tree species tested from Cape Vidal.…”

“…The understorey is dominated by Isoglossa woodii, a semi-woody herb endemic to Indian Ocean coastal dune forest in eastern South Africa and southeastern Mozambique (Tinley 1985), where it covers from 65 to 95% of the forest Xoor ). This monocarpic herb Xowers synchronously at 4-to 7-year intervals (GriYths et al 2010). It grows to a height of 1-3 m at stem densities of 15-30 stems per m 2 during the vegetative phase ( Fig.…”

Predator satiation and recruitment in a mast fruiting monocarpic forest herb

“…1) covering at least 65 % of the forest floor (Griffiths et al, 2007). The species exhibits synchronous reproduction and mortality events on a 4 -7 year cycle (Griffiths et al, 2010). Following flowering and seed dispersal, I. woodii dies back and the population regenerates from seed.…”

Sistema reprodutivo e polinização de Lepidagathis sessilifolia (Pohl) Kameyama ex Wassh. & J.R.I. Wood (Acanthaceae), em remanescente florestal da região sudoeste de Mato Grosso, Brasil

“…Pesquisas em Lamiales-Scrophulariales sensu amplo registraram a ocorrência de uma diversidade de sistemas reprodutivos, desde a polinização cruzada obrigatória até autogamia (Endress 1994 (Griffiths et al 2010), obtiveram percentuais similares na formação desses frutos, confirmando a autocompatibilidade na família Acanthaceae. Por outro lado, alta frequência de autofecundação, via geitonogamia, autogamia, agamospermia ou autopolinização biparental, pode acarretar em depressão endogâmica, na presença de genes deletérios na população (Richards 1997).…”

“…Dentre as três espécies de Ruellia, duas eram cleistógamas e floresceram durante todo o ano, a presença de reprodução sexuada e assexuada também foi registrada para essas espécies (Lima e Vieira 2006). Morcegos (Vogel et al 2004), beija-flores (Sigrist e Sazima 2002;Lima e Vieira 2006), abelhas (Lima e Vieira 2006;Döll et al 2007;Griffiths et al 2010) …”