Schenk, J. J., Rowe, K. C., & Steppan, S. J. 2013. Ecological Opportunity and Incumbency in the Diversification of Repeated Continental Colonizations by Muroid Rodents. Systematic Biology, DOI:10.1093/sysbio/syt050.
This paper explores the question of whether primary colonizers of continents experience increased diversification rates and higher carrying capacities compared to later secondary colonizers. Theoretically, the “incumbents” would have access to a greater number and variety of niches, and those showing up late to the party would have fewer resources to exploit. Makes sense. However, rodents don’t appear to follow some of the general predictions of ecological opportunity when they colonize continents (and they’ve colonized and recolonized continents plenty of times). Under ecological opportunity, diversification is expected occur rapidly and early until the source of available niches are spent. One of of the hallmark signals of EO on molecular phylogenies is an early burst pattern of diversification with a later slowdown as niches are filled and speciation slows down. Only South American rodents fit the predictions of the incumbency model, while the remaining rodents leave lots of open questions to explore. One major concern is whether or not sampling only 20% (297 of 1,517 species) of the clade is responsible for the idiosyncratic results for different continents, and this issue overshadows the attempts to accurately measure diversification parameters using different methods with various types of phylogenies. The manuscript offers plenty of systematics and biogeography of rodents for all of the rat lovers out there. [UW phylogenetics seminar, 9/26/2013, A. Leaché]