NewJames_Worth_PhD_Thesis_for_library.pdf (5.08 MB)
Range-wide chloroplast DNA phylogeographies of three widespread Australian cool temperate rainforest plants
thesisposted on 2023-05-26, 04:33 authored by Worth, JRP
How temperate plants and animals survived hostile climates during past glacial periods is critical to understanding modern ecological communities. Species may have survived in macro-refugia, and migrated large distances to reach their current range since climates recovered 10-12,000 years ago, or may have survived in many micro-refugia. The cool temperate rainforest of southeastern Australia provides opportunities to better understand how these processes have shaped the current biota. This thesis investigates the range-wide chloroplast DNA phylogeographies of three widespread Australian cool temperate rainforest plants. In the gravity-dispersed tree, Nothofagus cunninghamii (Nothofagaceae), 23 haplotypes were identified by PCR-RFLP and sequencing of 2164 base pairs of chloroplast DNA from 342 individuals. Deep haplotype divergence occurred, with the haplotype of N. moorei nested among those of N. cunninghamii. Western Tasmania was the stronghold of haplotype diversity, with evidence for multiple glacial refugia in coastal and inland locations. Three haplotypes endemic to the Victorian Central Highlands corroborate pollen evidence for last glacial maximum survival. In eastern Tasmania, an endemic and deeply diverged haplotype suggests long-term occupation within this region. In the bird-dispersed shrub Tasmannia lanceolata (Winteraceae) 30 haplotypes were identified by sequencing of 3190 base pairs of chloroplast DNA from 244 individuals. Strong phylogeographic structuring, with eight clades with predominantly non-overlapping geographic distributions, provided evidence for multiple glacial refugia, including within the driest parts of the species' range. This strong structure may be the result of the lack of vectors for effective long-distance dispersal, such as migratory birds. However, other factors limiting establishment at long distances, such as dioecy, competition, or selection may have contributed. Sequences of 3295 base pairs from 142 samples of the wind-dispersed tree, Atherosperma moschatum (Atherospermataceae), revealed low chloroplast variation (six haplotypes). The apparently ancestral haplotype was widespread across Tasmania. A single haplotype was found across all Victorian populations, while the most diverged haplotypes were observed near the northern limit of the species' range in New South Wales. The deep phylogeographic patterns in N. cunninghamii and T. lanceolata are the result of probable long-term survival in multiple regions, indicating the resilience of these species in apparently hostile last glacial climates. Differing dispersal traits have not affected the limited mobility of these species in response to past climatic changes. This contrasts with the extensive continent wide migrations of temperate species in the northern hemisphere. However, the very low diversity in A. moschatum may indicate a divergent history of this species.
Rights statementCopyright 2009 the author Chapter 2 appears to be the equivalent of the peer reviewed version of the following article: Worth, J. R. P., Jordan, G. J., McKinnon, G. E., Vaillancourt, R. E., 2009. The major Australian cool temperate rainforest tree Nothofagus cunninghamii withstood Pleistocene glacial aridity within multiple regions: evidence from the chloroplast, New phytologist 182(2), 519-532, which has been published in final form at https://doi.org/10.1111/j.1469-8137.2008.02761.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions