Functional Traits of Terrestrial Plants in the Intertidal: A Review on Mangrove Trees.

AbstractTrue mangroves are vascular plants (Tracheophyta) that evolved into inhabiting the mid and upper intertidal zone of tropical and subtropical soft-sediment coasts around the world. While several dozens of species are known from the Indo-West Pacific region, the Atlantic-East Pacific region is home to only a mere dozen of true mangrove species, most of which are rare. Mangrove trees can form dense monospecific or multispecies stands that provide numerous ecosystem services. Despite their eminent socioecological and socioeconomic relevance and the plethora of studies on mangroves, many details of the ecology of mangrove ecosystems remain unknown; and our knowledge about general ecological principles in mangrove ecosystems is scarce. For instance, the functional trait concept has hardly been applied to mangroves. Here we provide an inventory of 28 quantitative and 8 qualitative functional traits of true mangrove species and stipulate some insight into how these traits may drive ecosystem structure and processes. The differentiation between true mangroves and mangrove associates, which can dwell inside as well as outside mangrove forests, is reflected by a number of leaf traits. Thus, true mangroves exhibit lower specific leaf area, lower leaf N content, and lower K∶Na ratio, and higher leaf succulence, higher Na and Cl content, and higher osmolality than mangrove associates. True mangrove species that form pure stands produce larger leaves and exhibit higher N content per leaf area, higher leaf K and Ca content, greater maximum plant height, longer propagules, and lower root porosity than more sporadic species. The species-specific expression of most traits does not reflect the species' position along intertidal gradients, suggesting that adaptation to tidal inundation does not explain these traits. Rather, many of the traits studied herein exhibit strong phylogenetic signals in true mangroves. Thus, wood density is high in most species of the Rhizophoraceae, irrespective of their habitat or maximum height. On the other hand, species of the genus Sonneratia exhibit low wood density and do not grow taller than 20 m. Some leaf traits of true mangroves are more like those of plants from drier environments, reflecting the perception that a saline environment creates physiological drought stress. Along the same line, most true mangrove species exhibit sclerophyllous leaf traits. The few major mangrove tree species of the Atlantic-East Pacific are as distinct from each other, with regard to some traits, as are the many mangrove species of the Indo-West Pacific. We hypothesize that this phenomenon explains the similarly high biomass of mangrove forests in both the species-rich Indo-West Pacific and the species-poor Atlantic-East Pacific.

Introducing the Mangrove Microbiome Initiative: Identifying Microbial Research Priorities and Approaches To Better Understand, Protect, and Rehabilitate Mangrove Ecosystems.

Mangrove ecosystems provide important ecological benefits and ecosystem services, including carbon storage and coastline stabilization, but they also suffer great anthropogenic pressures. Microorganisms associated with mangrove sediments and the rhizosphere play key roles in this ecosystem and make essential contributions to its productivity and carbon budget. Understanding this nexus and moving from descriptive studies of microbial taxonomy to hypothesis-driven field and lab studies will facilitate a mechanistic understanding of mangrove ecosystem interaction webs and open opportunities for microorganism-mediated approaches to mangrove protection and rehabilitation. Such an effort calls for a multidisciplinary and collaborative approach, involving chemists, ecologists, evolutionary biologists, microbiologists, oceanographers, plant scientists, conservation biologists, and stakeholders, and it requires standardized methods to support reproducible experiments. Here, we outline the Mangrove Microbiome Initiative, which is focused around three urgent priorities and three approaches for advancing mangrove microbiome research.

Nuclear and mitochondrial multilocus phylogeny and survey of alkaloid content in true salamanders of the genus Salamandra (Salamandridae).

The genus Salamandra represents a clade of six species of Palearctic salamanders of either contrasted black-yellow, or uniformly black coloration, known to contain steroidal alkaloid toxins in high concentrations in their skin secretions. This study reconstructs the phylogeny of the genus Salamandra based on DNA sequences of segments of 10 mitochondrial and 13 nuclear genes from 31 individual samples representing all Salamandra species and most of the commonly recognized subspecies. The concatenated analysis of the complete dataset produced a fully resolved tree with most nodes strongly supported, suggesting that a clade composed of the Alpine salamander (S. atra) and the Corsican fire salamander (S. corsica) is the sister taxon to a clade containing the remaining species, among which S. algira and S. salamandra are sister species. Separate analyses of mitochondrial and nuclear data partitions disagreed regarding basal nodes and in the position of the root but concordantly recovered the S. atra/S. corsica as well as the S. salamandra/S. algira relationship. A species-tree analysis suggested almost simultaneous temporal splits between these pairs of species, which we hypothesize was caused by vicariance events after the Messinian salinity crisis (from late Miocene to early Pliocene). A survey of toxins with combined gas chromatography/mass spectroscopy confirmed the presence of samandarine and/or samandarone steroidal alkaloids in all species of Salamandra as well as in representatives of their sister group, Lyciasalamandra. Samandarone was also detected in lower concentrations in other salamandrids including Calotriton, Euproctus, Lissotriton, and Triturus, suggesting that the presence and possible biosynthesis of this alkaloid is plesiomorphic within the Salamandridae.