Breeding system and thrips (Thysanoptera) pollination in the endangered tree Ocotea porosa (Lauraceae): implications for conservation

Abstract

Ocotea porosa has been extensively exploited over the past few decades because of the quality of its wood. Today, populations are reduced and the species is now included in the Red List of threatened species by the International Union for Nature Conservation. For conservation and management purposes, it is extremely important that we understand its reproductive ecology. Floral morphology was described based on field and scanning electron microscopic examination. The reproductive system was determined through experimentally controlled pollination along with observations of pollen tube growth. Pollinators were identified through field observations. Flowers of O. porosa are small, shallow, inconspicuous, asynchronous and grouped in inflorescences. This species presented self-compatibility, but did not reproduce through apomixy and spontaneous selfpollination was very rare (5%). Despite being monoclinal, flowers were protogynic, and the gynoecium was receptive after the first day of anthesis when the anthers were closed. Spontaneous self-pollination was avoided by the extrorse position of the anthers of the internal stamens. Frankliniella gardeniae (Thysanoptera) was the only pollinating species observed and, after visiting several asynchronous flowers in the same inflorescence, favors geitonogamy. Together the small distance supposedly achieved by thrips in flight and the small population density of O. porosa can reduce the chances of cross-pollination in this species. If so, conservation measures must include preservation of the current population and possibly planting to increase population density. This would reduce the distance between individuals and increase genetic variability. Thrips as pollinators must be included in conservation planning for O. porosa.

Reproductive ecology ofOcotea catharinensis, an endangered tree species

“…Furthermore, flowers produced nectar and scent, which are attractive to insects (Fægri & van der Pijl ). Flowers also presented barriers to self‐fertilisation, such as protogyny, already described for other Lauraceae species (Kubitzki & Kurz ; Danieli‐Silva & Varassin ), and herkogamy. Nevertheless, none of these traits was efficient in completely preventing self‐fertilisation, as evidenced by the significant estimated selfing rate.…”

“…), Diptera (Nóbrega et al . ), Hemiptera (Souza & Moscheta ) and Thysanoptera (Danieli‐Silva & Varassin ). Nevertheless, hymenopterans seem to be the more frequent and diverse floral visitors to Lauraceae species.…”

“…Dick et al . ; Danieli‐Silva & Varassin ). Mating system studies, in turn, examine how individuals from a given species cross to form the progeny.…”

“…). Furthermore, pollination vectors can alert researchers to the need for conservation efforts, especially for species with few, or even single, pollinators, such as figs (Janzen ) or Ocotea porosa (Danieli‐Silva & Varassin ).…”

How many species of arthropods visit flowers?

“…Although they are no longer considered the major pollinators of many south-east Asian dipterocarps (Momose et al 1998), they are still acknowledged as the major pollinators of a number of tropical tree species in Australia (Hansman 2001), Africa (Frame and Durou 2001), south-east Asia (Kato et al 2008), and the Neotropics (Gottsberger et al 1980;Bawa et al 1985;Danieli-Silva and Varassin 2013) (Table 1). Thrips can certainly reach extremely high densities on flowers (Wardhaugh et al 2014), to the point where Charles Darwin himself complained that high abundances of thrips were interfering with his pollination research (Mound 2009).…”