Seed size and the regeneration niches of one rare (Melaleuca deanei) and three common (Melaleuca styphelioides,Melaleuca thymifoliaandMelaleuca nodosa)Melaleuca(Myrtaceae) species of theSydney region

Abstract

Seed size and the regeneration niches of one rare (Melaleuca deanei) and three common (Melaleuca styphelioides, Melaleuca thymifolia and Melaleuca nodosa) Melaleuca (Myrtaceae) species of the Sydney region Abstract Melaleuca species occupy varied habitats across Australia with 16 members of the genus occurring in the Sydney district including the rare species Melaleuca deanei F. Muell. Little is known of their germination and recruitment requirements. This paper reports on experiments assessing the effects of temperature, water potential, fire cues, light and shade levels on germination in four species of Melaleuca native to the Sydney region. For the shade experiment, seedling survival at 12 months is also reported. The experiments tested the hypothesis that M. deanei, which exhibits few seedlings in the field, has limited seedling recruitment because of its particular requirements for germination and establishment. Further, that it differs in these requirements from three common congenerics: M. nodosa (Sol ex Gaertn.) Sm., M. thymifolia Sm. and M. styphelioides Sm. Results indicate that M. deanei has a substantially similar temperature and water potential range for germination to the common congeners from 15 to 35°C, and 0 to −0.65 ψ. Melaleuca nodosa displayed the broadest regeneration niche on all factors assessed. Germination of M. styphelioides was significantly reduced in the dark and M. styphelioides and M. deanei were most sensitive to shade in the seedling establishment/post-germination phase. Melaleuca deanei had significantly larger seed that was slower to germinate in all experiments. Germination of the four species was unaffected by the application of heat and smoke.The substantially similar germination parameters exhibited by the four species, despite differences in habitat, may reflect their close phylogenetic affinities. The effects of fire on stimulating seed release from the canopy, the high-light environment post-fire together with adequate follow-up rainfall may all be critical in seedling establishment for M. deanei.

Recruitment of Melaleuca quinquenervia (Myrtaceae) in the fringing forests of the Myall Lakes, NSW, Australia

“…Consistent with previous germination studies in M. quinquenervia (Rayachhetry et al 1998; Van et al 2005), and the genus more broadly (Robinson et al 2006;Hewitt et al 2015), this study showed little difference between germination figures and viability figures.…”

Genetic and environmental factors in the trade‐off between sexual and asexual reproduction of a rare clonal angiosperm

“…Fire also triggered seed release en masse in the field from a strongly serotinous canopy seed bank, with seed noted to then germinate readily within larger populations following rainfall. However, in all populations monitored, seedlings failed to survive longer than one year, with soil moisture adequate for germination and seedling survival apparently critical (Virtue ; Hewitt et al and and observations since).…”

“…Melaleuca deanei displayed similar germination parameters to four common congeners, despite its occurrence over relatively drier substrates (Hewitt et al ). The root suckering and paperbark covering of the roots of M. deanei appear also to be adaptations for the more periodically waterlogged environments that are believed to be ancestral to Melaleuca and in which many present‐day members of the genus occur (Lamont ; Barlow ; Brophy et al ; Edwards et al ).…”

“…Seed mass and viability among populations and the effects of temperature, water potential, shade levels, fire cues and light vs. dark on germination percentage and T 50 (speed of germination) were tested in controlled experiments over two years (Hewitt et al ).…”

Seed traits of species from South Brazilian grasslands with contrasting distribution

“…Studies have been investigating whether common species with broader distributions possesses patterns of seed traits and germination characteristics that favor their occurrence compared to more narrowly distributed close relatives (Lavergne et al 2004;Mattana et al 2010;Youssef et al 2011;Imbert et al 2012). For instance, Paulů et al (2017) found significant differences in seed mass, while other studies showed that rare species could possess either lighter or heavier seeds than their common congeners (Brown et al 2003;Hewitt et al 2015). There is no consensus about possible patterns of species distributions determined by seed features since patterns are largely species-specific (Paulů et al 2017).…”