Year

2023

Degree Name

Bachelor of Conservation Biology (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Natalie Rosser

Abstract

An essential factor in assessing the success of woodland restorations is understanding whether gene flow and connectivity between restored and remnant populations has been re-established. Without pollinator services, isolated populations can further subdivide and face concerns of inbreeding depression, which is not the target of restoration projects. Within the ‘Central Valley’ of the Warrumbungle National Park, a series of restoration plantings were performed between the 1980s and 1990s to restore the previously abundant Box-Gum Grassy Woodlands, in particular White Box Gum trees (Eucalyptus albens). Extensive land clearing meant that these populations became extremely fragmented within the agricultural matrix, with only a few remaining extant remnant trees. This restoration was discovered to use locally sourced genetic material for plantations within the park, which is known to cause issues with inbreeding depression and lower genetic variability. Extending upon previous studies, I analysed relictual (historic scattered trees), natural (leftover extant populations), planted (restored trees) and sapling/seedling populations (juveniles grown in situ and ex situ) of E. albens trees for the genetic diversity and population structure by extracting genomic DNA and genotyping of SNP presence and absence conducted using DArTseq microarray developed for Eucalypt species. For the first time for this species, a high-confidence paternity analysis of seedlings and a parent pair analysis of saplings were conducted from a range of populations and were used to quantify pollen-mediated gene flow respectively to analyse connectivity between populations. By combining all analyses, I assessed the genetic success of this mature restoration project, with a focus on determining whether planted populations of E. albens displayed comparable genetic diversity levels and population structure to those of their remnant cohorts and whether there was evidence of gene flow between these groups. Analysis of genetic diversity and differentiation in dartR yielded no significant difference in genetic diversity between all groups, and most populations were relatively homogenous (especially natural stands) in structure, except for two planted populations, that were sourced externally from the valley. Seedlings planted in situ had lower inbreeding levels, suggesting that there was further outcrossing between stands between generations. Parentage analysis revealed that planted and natural populations were outcrossing, suggesting successful gene flow and genetic compatibility. Overall, there was little negative effect of local provenance sourcing, and the restoration was actively producing many viable saplings ameliorating inbreeding issues.

FoR codes (2020)

410204 Ecosystem services (incl. pollination), 410402 Environmental assessment and monitoring, 410405 Environmental rehabilitation and restoration

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.