The movement of the sea urchins into habitats already occupied by black-lipped abalone will most likely cause in the level of interspecific competition for resources. As a result of the range expansion of the sea urchins, the population size of black-lipped abalone , or both the sea urchin and black-lipped abalone could
Answers
Background
Global climate change has resulted in a southerly range expansion of the habitat modifying sea urchin Centrostephanus rodgersii to the east coast of Tasmania, Australia. Various studies have suggested that this urchin outcompetes black-lipped abalone (Haliotis rubra) for resources, but experiments elucidating the mechanisms are lacking.
Methodology/Principal Findings
We outline a new framework involving experimental manipulations and Markov chain and Pareto modelling to examine the effects of interspecific competition between urchins and abalone and the effect of intraspecific competition in abalone, assessed as effects on behaviour. Manipulations of abalone densities had no detectable effect on urchin behavioural transitions, movement patterns or resightability through time. In contrast, additions of urchins resulted in abalone shifting microhabitats from exposed to sheltered positions, an increase in the proportion of mobile abalone, and declines in abalone resightability through time relative to controls without the urchins. Our results support the hypothesis of asymmetrical competitive interactions between urchins and abalone.
Conclusions/Significance
The introduction of urchins to intact algal beds causes abalone to flee and seek shelter in cryptic microhabitat which will negatively impact both their accessibility to such microhabitats, and productivity of the abalone fishery, and will potentially affect their growth and survival, while the presence of the abalone has no detectable effect on the urchin. Our approach involving field-based experiments and modelling could be used to test the effects of other invasive species on native species behaviour.
Answer:
If the sea urchins will continue to expand, then the black lipped abalone would more likely lose the competition for resources and their population would slowly decrease. As a result of this continued competition, both species could evolve to adapt to the limited available resources by changing their diet or resources.