Seed ecology of Captain Cook tree [Cascabela thevetia (L.) Lippold] - germination and longevity

Bebawi, Faiz F., Campbell, Shane D. and Mayer, Robert J. (2017) Seed ecology of Captain Cook tree [Cascabela thevetia (L.) Lippold] - germination and longevity. Rangeland Journal, 39 4: 307-316. doi:10.1071/RJ17025

Author Bebawi, Faiz F.
Campbell, Shane D.
Mayer, Robert J.
Title Seed ecology of Captain Cook tree [Cascabela thevetia (L.) Lippold] - germination and longevity
Formatted title
Seed ecology of Captain Cook tree [Cascabela thevetia (L.) Lippold] - germination and longevity
Journal name Rangeland Journal   Check publisher's open access policy
ISSN 1036-9872
Publication date 2017-01-01
Year available 2017
Sub-type Article (original research)
DOI 10.1071/RJ17025
Open Access Status Not yet assessed
Volume 39
Issue 4
Start page 307
End page 316
Total pages 10
Place of publication Clayton, VIC, Australia
Publisher C S I R O Publishing
Language eng
Formatted abstract
Cascabela thevetia (L.) Lippold (Apocynaceae), commonly known as Captain Cook tree or yellow oleander, has established large infestations in riparian areas along several creeks and rivers in northern Queensland. To better understand the ecology of C. thevetia and the implications for its spread and management, this study reports seven experiments related to the seed ecology of its yellow and peach biotypes. We quantified its germination response to ambient (Experiment 1a and 1b), alternating and constant temperature (Experiment 2a and 2b) regimes and exposure to different light conditions (Experiment 3). Seed longevity under two soil types, two levels of pasture cover and three burial depths was also determined (Experiment 4a and 4b).

Both loose seeds and seeds still within pods (kernels) of the two biotypes of C. thevetia were able to germinate in all months of the year in northern Queensland, irrespective of the large differences in monthly ambient temperatures experienced at the Charters Towers study site. Both biotypes also germinated across a wide range of alternating day/night temperatures from 16/12°C to 47/37°C and constant temperatures from 17°C to 44.0°C. Germination of the two biotypes was significantly greater (4-fold) and faster (7 days earlier) under shade than under natural light conditions. Over all biotypes, soil types, levels of pasture cover and burial depths, no seeds of C. thevetia remained viable after 2 years: longevity was much less in many circumstances.

The results demonstrate that C. thevetia seeds can germinate over a wide temperature range, whereas the ability of seed to remain viable at low temperatures highlights the potential for expansion of its current potential distribution towards southern latitudes of the Australian continent. Across all experimental conditions, the yellow biotype displayed superior seed germination and viability traits compared with the peach biotype. Seed banks of the peach and yellow biotypes of C. thevetia are short-lived (2 years), which may be exploited when developing management strategies to reduce its impacts.

Keyword Biotypes
Burial depth
Temperature requirements
Yellow oleander
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
School of Agriculture and Food Sciences
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Created: Fri, 04 May 2018, 17:03:47 EST by Shane Campbell on behalf of Learning and Research Services (UQ Library)