Plant sampling

Duke, N. C. & Kudo, H., 2018, Bruguiera × dungarra, a new hybrid between mangrove species B. exaristata and B. gymnorhiza (Rhizophoraceae) recently discovered in north-east Australia, Blumea 63 (3), pp. 279-285 : 279-280

Plant sampling

This study is based upon field observations, underpinned by reference to herbarium material at the Australian Tropical Herbarium (CNS) and the Queensland Herbarium (BRI). Plant material was collected mostly at locations selected according to a sampling program designed to investigate the occurrence and likely relationship between the sympatric taxa Bruguiera exaristata and B. gymnorhiza , and the new taxon B. × dungarra . Reference voucher collections of B. × dungarra were made for Machans Beach and Holloways Beach. The species and hybrids sampled (with numbers of samples for each shown in brackets; see Table 1), included: B. × dungarra (7), B. exaristata (10), B. gymnorhiza (9) and B. parviflora (3). The latter species was included as the outlier in the numerical analyses, and its occurrences were not necessarily sympatric with the other three. In all, 29 mature individual trees were assessed using a standardised set of morphological attributes, including numeric and discrete non-numeric multistate (descriptive) states. Measurements of foliage, floral parts and fruits are based on fresh material.

Further Bruguiera taxa were not considered in these particular analyses because this study focused on the specific relationships between populations of the taxa in sympatry ( B. × dungarra , B. exaristata and B. gymnorhiza ). Other species, like B. sexangula and B. × rhynchopetala , were mostly not locally present. Two key factors explain their absence:

1. the recorded southern latitudinal limit of B. sexangula and B. × rhynchopetala is the Herbert River (S18°31') on Australia’s east coast – this study specifically included one sample location much further south in Shoalwater Bay (S22°21'); and

2. the almost exclusive restriction of B. sexangula and B. × rhynchopetala to areas of notable riverine influence and relatively high rainfall ( Duke et al. 1998) – this study se- lectively sampled downstream estuarine sites, mostly away from riverine influence.

This does not imply that B. × dungarra was not found in wetter locations – the collection from the Johnstone River estuary validates its occurrence in such a riverine situation. But, for the purpose of this study, collections were mostly restricted to locations where other Bruguiera taxa were locally absent.