Center for Bottomland Hardwoods Research

Slide 9 of 28

Presentation: Stream Crayfish in Mississippi: Who's Where and Why
Author(s): Dr. Susan Adams

Slide Notes...

Co-occurrence

Stone and Roberts’ C-score is sig. larger than expected by chance. This score measures the avg number of “checkerboard units” between all possible pairs of species. In a competitively structured community, the C-score should be sig. larger than expected by chance.

# of checkerboard species pairs was not sig. larger than expected by chance. tabulates the number of species pairs that NEVER co-occur at any site. This suggests that completely allopatric species distributions is not what is driving the C-score. (In a competitively structured community, there should be more checkerboard pairs of spp. than expected by chance.)

# of unique species combinations was significantly smaller than expected by chance, as one would predict for a competitively structured community. (Counts number of unique species combinations that are represented in different sites. In a competitively structured community, there should be fewer species combinations than expected by chance.)