About Me

Evolution of Communities on Remote Islands

(see here for videos of spiders)

I have been examining how communities are assembled through speciation. These studies make use of the chronological arrangement of the Hawaiian Islands to visualize snapshots of evolutionary history. Within this context, we can study the spiders' adaptive radiations over time in a natural time-series laboratory of evolution. We have found that, (1) species assembly is not random; (2) within any community, similar sets of distinct ecological types, or ecomorphs ("green" which sits on leaves; "maroon," which is mostly on moss; "small brown," among twigs; and "large brown," on tree bark) arise through both dispersal and evolution; and (3) species assembly is dynami
c with maximum species numbers in communities of intermediate age. The similar dynamics of species accumulation through evolutionary (species accumulate through evolutionary adaptation) and ecological (species accumulate through immigration) processes suggests universal principles may underlie community assembly. Web-building species also show convergence: similar web types have evolved independently in different species, suggesting convergence in web-building behaviors between quite disparate species on different islands.
 

Clockwise from top: T. brevignatha, T. restricta, T. anuenue, T. quaimodo

T. quasimodo

Spiny leg Tetragnatha

Photos: D. Liittschwagger & S. Middleton

T. kauaiensis