GENUS-LEVEL DIVERSIFICATION IN THE ROSALES RESULTS FROM A THREE-WAY INTERACTION BETWEEN ANIMAL DISPERSAL, LARGE GEOGRAPHIC RANGE SIZE, AND WITHIN-GENUS SPECIES RICHNESS

The origin – and demise – of biological diversity is a question that interests biologists and paleontologists alike. Many recent studies focus on systematic comparisons, although ecological comparison is still common and the fossil record remains the best source of information on past diversity available. Relationships between geographic range, diversity, and taxon survivorship are demonstrated in paleontological studies as well as in extant populations, but mechanisms that link the ecological traits of a species with its geographic range are not well understood. Here I use the Rosales, a diverse group of flowering plants possessing a wide range of life history traits and dispersal modes, as well as a good fossil record, in order to quantify the relationships between different modes of dispersal, life history traits, and geographic range using herbarium specimens and museum collection databases. Uniting modern phylogenetic methods with a paleobotanical prospective, this study also compares the three-way relationship between seed dispersal, geographic range size, and lineage selection and diversification together possibly for the first time. Phylogenetic correlation is controlled for using the MuSSE method in order to elucidate differences between character state proliferation resultant from differential net diversification rates (lineage selection) as distinguished from selection at the individual level (character state change). Phylogenies used are APG III and Potter et al.’s (2007) phylogeny of the Rosaceae, with Rosaceae sequences acquired from Potter et al and other Rosales augmented via GenBank. Morphological data was taken from museum collections. The dominant effect is a three-way interaction by which within-genus species richness, large genus-level geographic range size, and animal dispersal, together, drive positive net diversification rates at the genus level. Genera without these three characteristics break even (if herbaceous), or preferentially become extinct (if woody). These results suggest that megayear-term survival of plant lineages at least in the current global climate regime is dependent upon colonization ability, including the ability to reach a prospective new habitat (dispersal), and then to establish (the other terms of the interaction).