Inbreeding depression, outbreeding depression and heterosis in rare species in the genus Schiedea (Caryophyllaceae) on Oʻahu

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2012-05
Authors
Weisenberger, Lauren Ann
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[Honolulu] : [University of Hawaii at Manoa], [May 2012]
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Abstract
The Hawaiian flora is rare, with approximately 10% extinct, 30% federally listed as endangered or threatened, and 89% endemic. Reintroductions are a tool for recovery efforts for species with few in situ individuals to establish healthy populations. Determining whether reintroductions should represent a single or multiple population(s) is based on factors including population demography and trends, gene flow, breeding and mating systems, inter-population and intra-population genetic variation, and variation in habitats between populations. Concerns about inbreeding depression and outbreeding depression were investigated in three critically endangered species of Schiedea (Caryophyllaceae). Ex situ living collections were hand-pollinated with pollen from the same plant, a plant from the same population, or a plant from another population. Progeny were propagated and outplanted into suitable habitat within the historic range of each species. One outplanting site was used for each species except S. kaalae, where two plantings were conducted because populations occurred in two mountain ranges with different forest types (wet vs. mesic). Early and later life stages were measured, including estimates for the number of flowers and seeds a plant produced, and cumulative and relative performance of cross treatments were calculated. Neither inbreeding depression nor outbreeding depression was detected in the relative performance of any stage for all three species. Heterosis was present in S. kaalae and S. obovata and progeny from crosses between populations were more relatively fit than progeny from crosses within populations (which had the same relative fitness as selfed progeny). Local adaptation to habitat differences may have been present in these two species due to the different forest types between the two mountain ranges (S. kaalae), and a rainfall gradient across the distribution of S. obovata. Plants of S. kaalae with maternal sources from the Waiʻanae Mountains had a lower chance of survival than expected at the Koʻolau Mountain outplanting site. Plants of S. obovata with maternal sources from the wetter end of the rainfall gradient produced less seeds than the plants with maternal sources from the drier end of the gradient, where the outplanting site was located. Management recommendations include outplanting heterotic individuals from all available populations.
Description
Ph.D. University of Hawaii at Manoa 2012.
Includes bibliographical references.
Keywords
botany, Schiedea (Caryophyllaceae), Hawaiian flora
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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Botany.
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