For their field project on the effects of competition a pair of ecology students studied two species of bivalve-eating starfish, the Newman Star, Stricklandia soileauae (Hale, 1991) and O'Pry's Star, Inderkummenia mcdadei Meyer and Hoffman, 2012. They collected data on mean starfish mouth size from a number of sites.
Site Mean mouth size
The Aguinaga Hills
Stricklandia soileauae 4.0 cm
Inderkummenia mcdadei 2.6 cm
Wacko Warren's Tours
Stricklandia soileauae 4.1 cm
Inderkummenia mcdadei 2.5 cm
The Blay Locks
Stricklandia soileauae 3.9 cm
Inderkummenia mcdadei 2.5 cm
Urban Renewal Zone
Inderkummenia mcdadei 3.2 cm
Boyett City
Stricklandia soileauae 3.2 cm
Sarah's Booth
Stricklandia soileauae 4.2 cm
Inderkummenia mcdadei 2.4 cm
Messy Nick's Emporium
Stricklandia soileauae 4.2 cm
Inderkummenia mcdadei 2.4 cm
Young's Madhouse
Stricklandia soileauae 3.2 cm
The Clay Pits
Stricklandia soileauae 3.9 cm
Inderkummenia mcdadei 2.2 cm
Breauville
Stricklandia soileauae 3.2 cm
Kacietown
Stricklandia soileauae 3.1 cm
New Sydney
Stricklandia soileauae 3.1 cm
Victory Land
Inderkummenia mcdadei 3.0 cm
Crystal River
Inderkummenia mcdadei 3.1 cm
Cooley Creek
Inderkummenia mcdadei 4.0 cm
Stricklandia soileauae 2.3 cm
The Davis Coast
Inderkummenia mcdadei 3.2 cm
Tailor Shop
Stricklandia soileauae 3.9 cm
Inderkummenia mcdadei 2.1 cm
Eakin's Bacon
Inderkummenia mcdadei 3.3 cm
Port Landry
Stricklandia soileauae 3.3 cm
Johnson City
Stricklandia soileauae 4.1 cm
Inderkummenia mcdadei 2.5 cm
Nick's Pass
Stricklandia soileauae 3.2 cm
Kellar's Cellar
Inderkummenia mcdadei 3.3 cm
The students claimed that their data suggest that the two species might be competitors. Why? Their professor agreed with them, but pointed out that they had not yet proven that these two species are competitors. Why? What should they do to prove the two species are competitors?