The genetic consequences of emus as a vector for the long distance dispersal of seed in Leucopogon nutans

Dispersal is a primary function of most living organisms and is vital for reproduction and population growth. Aiding in population persistence as well as gene flow within a population and also between metapopulations, dispersal is vital for ensuring biodiversity and the conservation of populations and species. This study demonstrated for the first time the use of genetic tools on seeds dispersed by emus. Through the use of microsatellite markers, this study assessed the genetic diversity and structure of plant populations of Leucopogon nutans (a fire-killed perennial shrub) in two SW Australian jarrah forest areas that differed in disperser (emu) abundance; an area with high emu abundance (Avon Valley; AV), and one with low emu abundance (Sawyers Valley; SV). Seeds were also sourced from emu scats in the high abundance (Avon Valley) area. 37 scats were analysed and contained a mean of 255±140 fruits per scat, with a total of 11000 fruit collected overall. Seed fill in scats was low, with 2% of fruit containing seeds. All three sampled groups (plants at AV and SV, scats at SV) showed high levels of heterozygosity (He ≥0.50). Most importantly, seeds sourced from emu scats showed a relatively high level of population differentiation (mean FST= 0.052±0.036) and when compared to adult plants at the same site showed an even higher level of differentiation (mean FST=0.066±0.021). The area with low emu abundance (SV) showed the lowest level of population differentiation between plant samples (0.014±0.01). The high level of differentiation between seeds sourced from scats and adult plants at Avon Valley suggests that a portion of the seeds in scats originated outside of the adult plant sample region. This suggests that there is greater genetic structuring 1) within scats, compared to adults over the same area and 2) in areas with high emu abundance. These results reflect emu foraging habits, suggesting that emus graze within small patches of genetically similar adult plants before moving some distance (up to several kilometres) to other grazing hotspots. They support the, up to now largely circumstantial, evidence of emus as long distance dispersal vectors, with evidence suggesting that a portion of the potentially viable seeds found in scats originated greater the 3km away