Funding for this research was provided by:
National Science Foundation (EAR1212754, EAR1250449, EAR0707861)
Received: 22 May 2018
Accepted: 13 August 2018
First Online: 1 September 2018
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.