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Citation for Study 1718

About Citation title: "The role of biotic and abiotic factors in the evolution of ant-dispersal in the milkwort family (Polygalaceae)".
About This study was previously identified under the legacy study ID S1681 (Status: Published).


Forest F., Chase M., Persson C., Crane P., & Hawkins J. 2007. The role of biotic and abiotic factors in the evolution of ant-dispersal in the milkwort family (Polygalaceae). Evolution, null.


  • Forest F.
  • Chase M.
  • Persson C.
  • Crane P.
  • Hawkins J.


A phylogenetic approach was taken to investigate the evolutionary history of seed appendages in the plant family Polygalaceae (Fabales) and determine which factors might be associated with evolution of the elaiosome through comparisons to abiotic (climate) and biotic (ant species number and abundance) timelines. Molecular data sets from three plastid regions representing 160 species were used to reconstruct a phylogenetic tree of the order Fabales, focusing on Polygalaceae. Bayesian dating methods were used to estimate the appearance in Polygalaceae of ant-dispersed elaiosomes, shown by likelihood optimizations to have a single origin in the family. Topology-based tests indicated a diversification rate shift associated with appearance of caruncular elaiosomes. We show that evolution of the caruncular elaiosome type currently associated with ant dispersal occurred 54.0-50.5 Ma. This is long after an estimated increase in ant lineages in the Late Cretaceous based on molecular studies, but broadly concomitant with increasing global temperatures culminating in the Late Paleocene-Early Eocene thermal maxima. These data suggest that although most ant major clades were present when elaiosomes appeared, the environmental significance of elaiosomes may have been an important factor in success of elaiosome-bearing lineages. Ecological abundance of ants is perhaps more important than lineage numbers in determining significance of ant dispersal. Thus, our observation that elaiosomes pre-date increased ecological abundance of ants inferred from amber deposits could be indicative of an initial abiotic environmental function.

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