Dispersal potential in two restricted and five wide-ranging Senecio (Asteraceae) taxa from central eastern New South Wales, Australia

Knowledge on how life history traits affect distribution in range-restricted and endemic plants is paramount for conservation and management, particularly for threatened species. Traits relating to dispersal ability are important in the ongoing persistence of range restricted species and may present a pathway to extinction or invasion. This is evident in the highly diverse and cosmopolitan genus Senecio (Asteraceae), where both threatened and invasive species occur within Australia. In this study, propagule geometry, settling velocity and dispersal potential for two range-restricted and threatened native taxa (S. linearifolious var. dangarensis Belcher ex I.Thomps., S. spathulatus var. attenuatus I.Thomps.) are contrasted with four native taxa that occupy wider ranges (S. amygdalifolius F.Muell., S. l. var. arachnoideus I.Thomps., S. l. var. macrodontus (DC.) I.Thomps., S. pinnatifolius A.Rich. var. pinnatifolius) and one introduced, wide-ranging species (S. madagascariensis Poir.). Differences were found in settling velocity and propagule morphology across all taxa. Based on propagule morphology, S. amygdalifolius has the greatest dispersal potential, S. spathulatus var. attenuatus the smallest, whereas all other taxa were similar. Although useful, dispersal potential alone does not fully explain distributional differences between all range-restricted and widespread taxa, and close assessment of habitat attributes may be required to further elucidate dispersal limitations in some taxa.

Download Full-text

A decline in the abundance and condition of a native bivalve associated with Caulerpa taxifolia invasion

Marine and Freshwater Research ◽

10.1071/mf06150 ◽

2007 ◽

Vol 58 (3) ◽

pp. 263 ◽

Cited By ~ 23

Author(s):

Jeffrey T. Wright ◽

Louise A. McKenzie ◽

Paul E. Gribben

Keyword(s):

Life History ◽

Life History Traits ◽

New South ◽

Caulerpa Taxifolia ◽

Shell Weight ◽

Tissue Weight ◽

Invasive Seaweed ◽

South Wales ◽

Fast Spreading ◽

Infaunal Bivalve

Caulerpa taxifolia is a fast-spreading invasive seaweed that threatens biodiversity in temperate Australian estuaries. To date, little is known about its effects on infauna. In the present study, we describe variation in demographic and life-history traits of the abundant infaunal bivalve, Anadara trapezia, in C. taxifolia and uninvaded habitats (seagrass and unvegetated sediments) at multiple sites across three estuaries in south-eastern New South Wales. Densities of A. trapezia were always lower in C. taxifolia than on unvegetated sediment, and lower in C. taxifolia than in seagrass at three out of four sites where they were compared. Dry tissue weight of A. trapezia was also lower in C. taxifolia than on unvegetated sediment at most sites, but was only lower in C. taxifolia than in seagrass at one of four sites. Populations were dominated by larger individuals (>45 mm length), but smaller individuals (35–45 mm length) were more common in C. taxifolia and seagrass. A. trapezia shell weight and morphology was variable and appeared weakly affected by invasion. Generally, our findings are consistent with the hypothesis that A. trapezia is negatively affected by C. taxifolia. However, C. taxifolia invasion appears complex and, at some places, its effects may not differ from those of native seagrass. There is a need for manipulative studies to understand the mechanisms underlying the effects of C. taxifolia on infauna.

Download Full-text