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Abstract Detail


Schenk, John J. [1], Jacobs, Sarah [2], Hufford, Larry [3].

Comparative Diversification Analyses of Hydrangeaceae and Loasaceae: The Role of Continental Dispersal in Generating Species Diversity.

Hydrangeaceae and Loasaceae are sister clades that likely originated in arid regions of Mesoamerica but subsequently experienced different biogeographic and speciation histories. Hydrangeaceae became particularly diverse in Asia, with additional centers of diversity in western and eastern North America. Loasaceae, in contrast, has two centers of diversity, one in western North America and a second in the South American Andes Mountains. We tested the hypothesis that these clades share a common origin in Mesoamerica, and then compared how they diversified along both biogeographic and phylogenetic axes. Because these lineages experienced different biogeographic transitions that expanded their ranges into novel continental areas, we were able to examine and compare the consequences of colonization to ecological opportunity. Under an ecological opportunity model, we predicted that clades will experience an increase in speciation rates following the first colonization of new continental areas. We constructed a time-calibrated, phylogenetic hypothesis consisting of approximately 64% of the species diversity, and then applied the phylogeny to diversification and historical biogeographic analyses. The Hydrangeaceae-Loasaceae split occurred at least 95.34–72.94 mybp. Speciation rates were approximately constant from that time until about 18 mybp, after which they sharply increased. Historical biogeographic analyses supported a Mesoamerican origin of Loasaceae and Hydrangeaceae, followed by numerous biogeographic transitions in both clades. Lineages of Hydrangeaceae diversified early into Asia from western North America, followed by eastern North America colonizations. A significant diversification rate increase was identified in the Philadelphus clade, associated with its initial colonization of Eurasia. A second increased diversification rate, unassociated with a geographic change, was identified in the Hydrangea-2 clade. Loasaceae experienced greater early lineage diversification in western North America than Hydrangeaceae, followed by a biogeographic transition into South America at the origin of Loasoideae. The latter range expansion into South America was not associated with a significant increased diversification rate; however, increased diversification was inferred in the Cajophora clade, a change likely tied to ecological opportunities created with the Andean uplift. Two increased shifts were associated within Mentzelia: one in Mentzelia section Trachyphytum and a second in Mentzelia section Bartonia. Neither of the two Mentzelia shifts were associated with continental-scale biogeographic transitions. We conclude that geographic range expansions have been important in generating species diversity in both families, but climate change, including aridification of the American West during the Miocene and glaciations during the Pleistocene, may have been equally important in accelerating cladogenesis in Mentzelia.

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1 - Georgia Southern University, Department of Biology, 4324 Old Register Road, Biological Sciences Building, Statesboro, GA, 30458, United States
2 - University of Idaho, Department of Biology, 875 Perimeter Drive MS 3051, Moscow, ID, 83844, USA
3 - Washington State University, SCHOOL OF BIOLOGICAL SCIENCES, 312 Abelson Hall, PULLMAN, WA, 99164-4236, USA

Adaptive radiation
Ecological opportunity

Presentation Type: Oral Paper
Session: 2, Macroevolution
Location: Fort Worth Ballroom 5/Omni Hotel
Date: Monday, June 26th, 2017
Time: 8:15 AM
Number: 2002
Abstract ID:82
Candidate for Awards:None

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