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Abstract Detail



Systematics Section/ASPT

Oliver, Margaret [1], Metzgar, Jordan [2], Ickert-Bond, Stefanie [3].

Morphologically diverse but with surprisingly little genetic structure: the evolutionary history of three closely related species of Therorhodion.

We looked at the phylogenetic relationships and morphology among dwarf rhododendron (Therorhodion camtschaticum Small, T. glandulosum Standley ex Small and T. redowskianum Hutch.) in the heath family (Ericaceae, subfamily Rhodoreae). Therorhodion was originally considered part of the genus Rhododendron but was described as its own genus by Small in 1914. Only recently has this distinction been more widely recognized and substantiated by genetic data. Therorhodion camtschaticum is restricted to southeast Alaska and the Aleutian chain extending into Kamtschatka and Japan, while T. glandulosum is today found only on the Seward Peninsula and lower Yukon in North America, but broadly distributed in the Russian Far East. The third species T. redowskianum is distinct morphologically from the former two and restricted to eastern Asia. When in sympatry the species are well marked morphologically. While Therorhodion camtschaticum and T. glandulosum are similar in size, T. redowskianum is smaller in stature and leaf size. All three species have ten stamens but T. camtschaticum and T. glandulosum both have five that are significantly longer than the rest. In T. camtschaticum the style exceeds the length of the stamens, while it is typically the same length in T. glandulosum, and shorter and reflexed in T. redowskianum. The corolla in T. camtschaticum has ciliate margins, while T. glandulosum and T. redowsianum both have glabrous corollas. We inferred phylogenetic relationships based on sequence data from five plastid loci (trnL, rbcL, matK, ndhF, trnS-G-G, psbA-trnH, and trnT-trnL) and two nuclear loci (ITS and GBSSI or waxy) to test four hypotheses: 1) there are three reciprocally monophyletic lineages of Therorhodion; 2) there are separate western and eastern Beringian clades in Therorhodion; 3) the eastern Beringian clade is younger than the western Beringian clade; and 4) two dispersal routes (across the Bering Land Bridge and across the Aleutians) led to current diversity in Western North America. Based on our preliminary analysis, tribe Rhodoreae is sister to the crowberry tribe Empetreae. Within tribe Rhodoreae a highly supported Therorhodion clade is sister to a highly supported clade of the remaining Rhododendron species sampled including Menziesia. Within Therorhodion two well-supported clades are recovered; one of the two accessions of T. redowskianum and another clade including T. glandulosum and T. camtschaticum. The observed biogeographic disjunction in Therorhodion supports the influence of the Bering Land Bridge in facilitating floristic exchange between eastern Asia and western North America.


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1 - University of Alaska Fairbanks, Biology and Wildlife, 907 Yukon Drive, Fairbanks, AK, 99775, USA
2 - University Of Alaska Fairbanks, Museum Of The North, 907 Yukon Drive, Fairbanks, AK, 99775, USA
3 - University Of Alaska Museum Of The North, Herbarium (ALA) And Dept. Of Biology And Wildlife, University Of Alaska Fairbanks, 907 Yukon Dr., Fairbanks, AK, 99775, USA

Keywords:
Therorhodion
Ericaceae
phylogenetics
Morphology
Biogeography.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PSY031
Abstract ID:275
Candidate for Awards:None


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