Pollination ecology of the Australian cycad Lepidozamia peroffskyana (Zamiaceae)

Abstract

Abstract. Experiments carried out to investigate the reproductive ecology of the Australian cycad Lepidozamia peroffskyana (Regal, Bull. Soc. Imp. Nat. Mosc. 1857, 1: 184) revealed that this species is pollinated exclusively by host-specific Tranes weevils (Pascoe 1875). The weevils carry out their life cycle within the tissues of the male cones but also visit the female cones in large numbers. Female cones from which insects (but not wind) were excluded had a pollination rate that was essentially zero. In contrast, female cones from which wind (but not insects) were excluded had a pollination rate comparable with naturally pollinated cones. Assessment of Tranes weevil pollen load indicated that they are effective pollen-carriers. No other potential insect pollinators were observed on cones of L. peroffskyana. Sampling of airborne loads of cycad pollen indicated that wind-dispersed grains were not consistently recorded beyond a 2-m radius surrounding pollen-shedding male cones. The airborne load of cycad pollen in the vicinity of pollination-receptive female cones was minimal, and the spatial distribution of the coning population indicated that receptive female cones did not usually occur close enough to pollen-shedding male cones for airborne transfer of pollen to explain observed natural rates of seed set. These multiple lines of evidence suggest that wind-once considered the only pollination vector for cycads and other gymnosperms-plays only a minimal role in the pollination of L. peroffskyana, if any at all. The global diversity of insects associated with cycads suggests that some lineages of pollinating beetles may have been associated with cycad cones since Mesozoic times.

Molecular and Morphological Phylogenetic Analyses of New World Cycad Beetles: What They Reveal about Cycad Evolution in the New World

“…[6][7][8]. Similar experiments and observations on other continents indicate the same for other genera of cycads [9][10][11][12][13][14][15][16][17][18][19]. In a recent seminal work on guidelines for cycad classification, insect symbionts of cycads were identified as having a potentially important impact on cycad classification: "Insects appear to be the primary vectors for pollination [ .…”

The Pollination of Mid Mesozoic Seed Plants and the Early History of Long-proboscid Insects1,2,3

“…Insects are involved in the pollination of the most plesiomorphic, extant cycad taxon, Cycas L. of the Cycadaceae (Ornduff, 1991;Yang et al, 1999;Kono & Tobe, 2007). Extant Zamiaceae and Stangeriaceae, whose earliest occurrences are Jurassic, are obligately insect pollinated by a spectrum of beetle pollinators, such as Boganiidae, Erotylidae, Belidae, and Curculionidae (Norstog, 1987;Norstog & Fawcett, 1989;Crowson, 1991;Donaldson, 1992;Forster et al, 1994;Norstog et al, 1995;Tang, 1997;Wilson, 2002;Hall et al, 2004;Oberprieler, 2004), and also by the aeolothripid thrips Cycadothrips (Okajima, 2000;Mound & Terry, 2001;Terry et al, 2005). It has been suggested that most of these associations are ancient and mid Mesozoic in origin.…”

Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism

“…The pollination system of cycads typically involves broodsite mutualisms in which the pollinators are insect herbivores whose larvae feed on male cone tissues and female cones are pollinated when visited by mistake [25][26][27][28][29]. Pollination in these dioecious gymnosperms is mediated by specific cone volatile compounds [30].…”