Comparative analysis of the pattern of population genetic diversity in three Indo-West Pacific Rhizophora mangrove species

Rhizophora species are the most widely distributed mangrove trees in the Indo-West Pacific (IWP) region. Comparative studies of these species with shared life history traits can help identify evolutionary factors that have played most important roles in determining genetic diversity within and between populations in ocean-current dispersed mangrove tree species. We sampled 935 individuals from 54 natural populations for genotyping with 13 microsatellite markers to investigate the level of genetic variation, population structure, and gene flow on a broad geographic scale in Rhizophora apiculata, Rhizophora mucronata, and Rhizophora stylosa across the IWP region. In contrast to the pattern expected of long-lived woody plants with predominant wind-pollination, water-dispersed seeds and wide geographic range, genetic variation within populations was generally low in all the three species, especially in those peripheral populations from geographic range limits. Although the large water-buoyant propagules of Rhizophora have capacity for long distance dispersal, such events might be rare in reality, as reflected by the low level of gene flow and high genetic differentiation between most of population pairs within each species. Phylogeographic separation of Australian and Pacific island populations from SE Asian lineages previously revealed with DNA sequence data was still detectable in R. apiculata based on genetic distances, but this pattern of disjunction was not always evident in R. mucronata and R. stylosa, suggesting that fast-evolving molecular markers could be more suitable for detecting contemporary genetic structure but not deep evolutionary divergence caused by historical vicariance. Given that mangrove species generally have small effective population sizes, we conclude that genetic drift coupled with limited gene flow have played a dominant role in producing the current pattern of population genetic diversity in the IWP Rhizophora species, overshadowing the effects of their life history traits. Recent population fragmentation and disturbances arising from human activities could further endanger genetic diversity in mangrove trees

Mangroves of South-East Australia

[Extract] The mangroves of south-east Australia have special features beyond the defining characteristics of this unique plant group, and in keeping with a transitional temperate climate for the region (Duke et al. 1998a; Duke 2006). In general, mangroves are intertidal halophytes with a capacity to grow taller than 1-2 metres in height, often around 3-5 metres - and sometimes up to 50 metres in equatorial places. Like tidal saltmarsh plants, mangroves routinely deal with salt and saturated soils. Their success in meeting these challenges is measured, in part, by the number of species occupying in these habitats worldwide, and the number of specialised adaptations in morphology, anatomy, life history and physiology. Mangroves are surprisingly well-represented in south-east Australia, given their location in relatively high latitudes. In general, this unique group of chiefly tropical halophytes comprises a wide diversity of 21 plant families, made-up of angiosperms predominantly, plus a gymnosperm. In south-east Australia, the diversity of mangroves is relatively low, with the gymnosperm, Acrostichum - the Mangrove Fern, and four flowering plant families, Rhizophoraceae, Euphorbiaceae, Myrsinaceae and Avicenniaceae (or Acanthaceae). In this diverse group, there are six mangrove species found in the south-east, south of the Queensland border

Monitoring mangrove threats across the Torres Straits using remote-sensing

Given the expansiveness of mangroves across the Torres Straits, we suggest that a long-term monitoring program utilise satellite remote sensing to capture monthly and annual changes that are also coupled with in-field shoreline surveys that are repeated on a 5-10 year cycle. The remote sensing data indicators could then alert where management actions/interventions are required to assess and potentially remedy any areas of concern (or “alert to action”). This monitoring program would involve training rangers and support them in making more informed management decision

Pioneering mangrove monitoring program partners experts with the community

Australia’s first community ‘watch’ program for mangroves that addresses both scientific and environmental management needs is underway. Such a monitoring system has never before been conducted by a partnership between community members and scientists

MangroveWatch Burnett Mary region is one year old! Outcomes and lessons learned

MangroveWatch Burnett Mary Region has successfully completed its first year and established itself as a powerful community driven environmental monitoring method with outcomes relevant to our scientific understanding, improved management of tidal wetlands, and climate change adaptation. Here we outline the role of MangroveWatch, how it works, and why it works

Mangrove ecosystem services and the potential for carbon revenue programmes in Solomon Islands

Mangroves are an imperilled biome whose protection and restoration through payments for ecosystem services (PES) can contribute to improved livelihoods, climate mitigation and adaptation. Interviews with resource users in three Solomon Islands villages suggest a strong reliance upon mangrove goods for subsistence and cash, particularly for firewood, food and building materials. Village-derived economic data indicates a minimum annual subsistence value from mangroves of US$ 345–1501 per household. Fish and nursery habitat and storm protection were widely recognized and highly valued mangrove ecosystem services. All villagers agreed that mangroves were under threat, with firewood overharvesting considered the primary cause. Multivariate analyses revealed village affiliation and religious denomination as the most important factors determining the use and importance of mangrove goods. These factors, together with gender, affected users' awareness of ecosystem services. The importance placed on mangrove services did not differ significantly by village, religious denomination, gender, age, income, education or occupation. Mangrove ecosystem surveys are useful as tools for raising community awareness and input prior to design of PES systems. Land tenure and marine property rights, and how this complexity may both complicate and facilitate potential carbon credit programmes in the Pacific, are discussed