Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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    Ploidy variation in Rhododendron subsection Maddenia and its implications for conservation.
    (Oxford University Press on behalf of the Annals of Botany Company, 2023-06-01) Hu L; Tate JA; Gardiner SE; MacKay M; Loureiro J
    Polyploidy, which is common in plants, can confound taxon recognition and hence conservation assessments. In the taxonomically complex genus Rhododendron, 25 % of the over 1,300 taxa are considered under threat and 27 % Near Threatened or Data Deficient, with their taxonomy needing to be resolved urgently. Although ploidy levels of Rhododendron taxa range from diploid (2x) to dodecaploid (12x) according to previous reports, the extent of polyploidy across the genus has not been examined. We first summarized the taxonomic distribution of polyploids in the genus based on the literature. Then as a case study, we estimated ploidy levels of 47 taxa in subsection Maddenia (subgenus Rhododendron, section Rhododendron) using flow cytometry, together with verification of meiotic chromosome counts for representative taxa. The summary of reported ploidy in Rhododendron indicates that polyploidy is most common in subgenera Pentanthera and Rhododendron. In subsection Maddenia, all examined taxa are diploids except for the R. maddenii complex that shows a high ploidy variation (2-8x, 12x). We investigated ploidy level of 12 taxa in subsection Maddenia for the first time, and estimated genome sizes of two Rhododendron species. Knowledge of ploidy levels will inform phylogenetic analysis of unresolved species complexes. Overall, our study of subsection Maddenia provides a model for examining multiple issues including taxonomic complexity, ploidy variation and geographic distribution in relation to biodiversity conservation.
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    Predictors of tree damage and survival in agroforests after major cyclone disturbance in Fiji
    (Springer Nature, 2024-03-12) McGuigan A; Tora M; Tikonavuli V; Ticktin T
    This study explores the resilience and damage dynamics of agroforests, a critically important yet understudied agroecological system, in the aftermath of Category-5 Cyclone Winston in Fiji. As agroforestry gains prominence globally as a versatile production system able to support agrobiodiversity and food security for climate resilience, understanding the characteristics that contribute to its resistance and resilience to disturbance becomes increasingly important. Here we examine the effects of individual and species-specific traits, and management (planted and fallow vs forest areas) on the probability of tree stem survival and damage, and discuss the resistant and resilient qualities of trees and management actions in these systems. We found that the probability of post-cyclone survival increased as a function of wood density, irrespective of management type. Damage severity increased with tree size (diameter at breast height). Some of the species with the highest wood density were native trees, emphasizing the role of native species in agroforests, and the value of agroforests to conservation. Overall, agroforest trees experienced relatively low stem mortality (12.2%), suggesting that these agroforests may resist extreme disturbances despite their potential vulnerabilities such as landscape edge effects and altered species compositions. Our study provides insight into the potential of agroforests as resilient agroecological systems capable of withstanding escalating cyclone intensities, and the role of effective management strategies for fostering resilience amid a rapidly changing climate.