Species Rhizophora Research Articles

AN INVESTIGATION OF SOME PHENOLOGICAL EVENTS IN THREE MANGROVE GENERA WITH REFERENCE TO SELECTED CLIMATIC FACTORS IN NEGOMBO LAGOON

Mangroves consist of ICw tree species which are adapted to grow under tidal conditions.Studies on the phenology of mangroves is scarce. The main objective of this research wasto study major phenological cycles of some overexploited species and to compare thesewith previous observations on the same species samples from three other lagoons.Phenological cycles of leafing. flowering and fruiting of R hizophora apiculata, R.Mucronata, Bru.guicra gvmnorhi:a. B. Sexangula and Ccriops taga! were studies for aperiod of 24 months at selected sites in Negombo lagoon which is located in the wet zoneof Sri Lanka. Phenological cycles were followed and phenological indices were calculated.Thcse d;lla were compared with monthly variations in rain fall. temperature and humidityof the study area.Leal production showed two distinct maxima per year in all species. Rainfall seemed toexert a great influence on leaf rcflushing. Peaks of leaf rcflushing coincided with lulls ofIluwcriru; and fruiting. Annual bimodality was observed for flowering fruiting in allspecies. These species showed unimodal pattern of some of these events when they weregrowing in dry zonePhenological cycles constructed using data obtained show no intraspecific variation in thetime required to complete a single flowering-fruiting cycle, Similarly. intragcncricvariation was absent in the life time of leafing cyclesIn Rh izophora species. leaf bud jut emerged took I - 1,5 yrs to complete a single cyclewhere as in Bruguicra species this period was 2 - 2,5 yrs, In CeriOI)S tagal, it was 1,5 - 2yrs. Similarly. a flower bud of Rhizophora species took 1,5 - 2.5 yrs, Brugcciera species Iyr and C tagu! about 1,5 yrs to form a mature hypocotyl.A comparison of these observations with findings of the previous study proves thatphenological cycles in studies species are environmentally dependent and not speciesspecific,Unimodality of floral phenology in dry zone species may he due to the seasonal variation inground water salinity,

A simple and inexpensive molecular assay for species identification of Indo-West Pacific Rhizophora mangroves for conservation and management

Mangrove species of the genus Rhizophora are predominant and highly sought-after for the reforestation of mangrove areas in Southeast Asia. Of the three Rhizophora species occurring in the Indo-West Pacific (IWP) region, R. mucronata and R. stylosa have similar morphological features, making species identification difficult. Their respective hybrids with R. apiculata are also difficult to tell apart morphologically. Based on DNA sequence alignment of the partial nuclear starch-branching enzyme II (SBE2) gene obtained in a recent study, we designed species-specific primers for a multiplex PCR assay for rapid species identification, allowing us to differentiate among samples of R. apiculata, R. mucronata, R. stylosa, and their respective hybrids. The method described here makes use of simple molecular techniques; we envision that this simple and inexpensive method will improve the efficiency of efforts to conserve and manage IWP Rhizophora populations.

Molecular identification of natural mangrove hybrids of Rhizophora in Peninsular Malaysia

Natural hybridization is common in plants. Very often, the identity of a putative hybrid is inferred based on the observation of morphological features intermediate between two possible parental species occurring in a specific location. However, due to plasticity of morphological features and the co-occurrence of more than two possible parental species, molecular markers would be most useful to establish the origin of a putative hybrid. In mangroves, three Rhizophora species (Rhizophora apiculata, Rhizophora mucronata, and Rhizophora stylosa) and two putative hybrids (Rhizophora × lamarckii and Rhizophora × annamalayana) are distributed in the Indo-West Pacific region. Leaf samples of Rhizophora were obtained from two locations in Peninsular Malaysia, namely, Bagan Lalang and Pulau Burung, where all three species grow in sympatry. We analyzed sequences of one chloroplast and six nuclear DNA regions. Our results confirmed earlier claims that the morphologically identified putative hybrids growing in Pulau Burung are R. × lamarckii, a cross between R. apiculata and R. stylosa. Our data also pointed to the possible discovery of a new Rhizophora hybrid—a cross between R. mucronata and R. stylosa—the identification of which would have been difficult based on morphological features alone. The directions and the stages of hybridization are also discussed.

Basic Study of Chemical Constituents in Rhizophora Species

Rhizophora apiculata and Rhizophora mucronata are the mangrove plants of the genus Rhizophora. The chemical constituents of leaf samples for both species were analyzed by using Gas Chromatography-Mass Spectrometry (GC-MS). The analysis of chemical constituents of Rhizophora apiculata was found to be rich in 2-(2- ethoxyethoxy)ethanol (26.45%) and Kaur-16-ene (3.37%). Benzophenone (16.09%) and 2-(2-ethoxyethoxy)ethanol (7.82%) were the predominant constituents in Rhizophora mucronata.

Prediction of recovery pathways of cyclone-disturbed mangroves in the mega delta of Myanmar

Mangroves in the Ayeyarwady Mega Delta of Myanmar are crucial for the ecology, society and economy of this country. At the beginning of May 2008, a severe cyclonic storm, Cyclone Nargis, struck the Ayeyarwady mangroves. Since that time, the present long-term study has been exploring the dynamics of post-cyclone mangrove vegetation. Every year since the 2008 cyclone, a census has been taken of 60 permanent plots (each measuring 10m×10m) in six mangrove communities in order to predict trends in their long-term recovery. Each selected mangrove community was dominated by either Avicennia officinalis, Bruguiera sexangula, Excoecaria agallocha, Heritiera fomes, Rhizophora apiculata, or Sonneratia caseolaris. Mortality among the Rhizophoraceae group, including B. sexangula and R. apiculata adult individuals, was more than 90%, whereas for other species belonging to the non-Rhizophoraceae group, it was less than 20%. Based on the 5-year assessment, the mangroves showed considerable resilience after the catastrophic cyclone disturbance. However, the recovery potential of specific species varied. In particular, communities where R. apiculata dominated demonstrated slow recovery processes. The reasons for the vulnerability of this species of Rhizophora to cyclone disturbance is assumed to be the result of three indirect post-cyclone consequences: high mortality caused by limited sprouting ability after wind-induced disturbance; erosion that occurred in the stressful habitat on riverbank mud flats with frequent tidal inundation; and delayed phenology after the catastrophic disturbance. The attempt to generalise the recovery rate of mangroves based on the crown closure of the six dominant mangrove communities explored in this study showed a recovery rate of 61.06% during the 4years after Cyclone Nargis. The demonstration of these patterns and processes among the most dominant mangrove species after the cyclone disturbance should therefore provide reliable information to forest managers, ecologists and local people, helping them make management decisions regarding measures for mangrove restoration.

Basic Study of Chemical Constituents in Rhizophora Species

Basic Study of Chemical Constituents in Rhizophora Species

The Mechanism of Mangrove Tree in Wave Energy Propagation

The role of mangrove trees in reducing the tsunami waves during the tragedy of Andaman tsunami occurred on December 26, 2004, has been credited and these indirectly raise awareness about the role of mangroves forest as a natural breakwater on the beach. This paper will focus on the mangrove trees from Avicennia and Rhizophora species in order to identify the methods of breaking wave energy that has been carried out by the mangrove roots and stems. Analysis of the mangrove roots coordination pattern had been conducted by gathering data at study site located at Kemaman, Terengganu and the data had been plotted in Gambit software for simulation purpose in Fluent Inc software. Hence, the simulation result showed that the ratio of wave height and velocity reduction may vary depending on factors such as the species of the mangrove trees and density of the roots that grow around the tree. Consequently, the study will be examining the waveform that is mitigated by the both species Avicennia and Rhizophora using turbulent flow and experiment will be conducted to validate the data obtained by the simulation.

Isolation and characterization of 14 microsatellite markers for Rhizophora mucronata (Rhizophoraceae) and their potential use in range-wide population studies

A set of 14 new microsatellite markers was developed for mangrove species Rhizophora mucronata (Rhizophoraceae) by using pyrosequencing. Fifty-six samples from 9 populations of R. mucronata in the Indo-West Pacific region were genotyped; all loci were polymorphic, with the number of alleles ranging from 2 to 9. The mean expected heterozygosity per locus was 0.16 in a population from Sabah, no significant linkage disequilibrium was found among loci, and significant deviation from Hardy–Weinberg equilibrium was found in 3 loci. The polymorphic microsatellite markers with samples covering most of the species’ distribution range can be applied in genetic diversity studies covering a broad geographical range of the species.

Growth of the mangrove species Rhizophora stylosa Griff. at its southern latitudinal limit in eastern Australia

A study on the growth of Rhizophora stylosa Griff. was undertaken in three estuaries spanning the southernmost 265km of its range at its latitudinal limit in eastern Australia. A shoot tracking methodology was devised to follow vegetative phenological patterns and branching and to derive indices of relative growth between trees. Despite an apparent expansionary phase in distribution and a recent increased trend in mean temperature, comparisons of growth in the three estuaries do not suggest a latitudinal cline. The phenologies of leaf gain and leaf loss are generally comparable between R. stylosa in New South Wales and elsewhere, as is the rate of growth assessed by leaf initiation. However, leaf longevity and the number of leaves held on the shoot appears to be overall greater in NSW than in lower latitudes, perhaps as an adaptive response to lower levels of assimilation. This study suggests that R. stylosa is not close to physiological limits at the end of its range, supporting a contention that its current known southern limit is not at an absolute thermal boundary.

Insulin-like antigen of mangrove leaves and its anti-diabetic activity in alloxan-induced diabetic rats

The objective of this study was to evaluate the anti-diabetic potential of three mangrove plants, Rhizophora mucronata, Rhizophora apiculata and Rhizophora annamalayana, and to detect the presence of their insulin-like protein. The in vivo anti-diabetic experiment was done on male albino Wister rats. Oral administration of 60 mg kg−1 leaf powder extract of the three different mangrove plants for 30 days modulated the parameters such as blood glucose, plasma insulin, body weight, total haemoglobin, glycosylated haemoglobin, liver glycogen, plasma and tissue lipids, cholesterol, triglycerides, free fatty acids and phospholipids to normal levels in the alloxan-induced diabetic rats. The anti-diabetic activity of R. apiculata was more pronounced than that of the other mangrove extracts, but it was on a par with the commercial drug glibenclamide. The presence of an insulin-like protein in the mangrove extracts was detected by SDS-PAGE analysis and confirmed through ELISA. Hence, the anti-diabetic activity and the presence of an insulin-like protein in Rhizophora species were proved scientifically.

Hybridization and introgression in New World red mangroves,Rhizophora(Rhizophoraceae)

Hybridization is common in both animals and plants and can lead to a diverse array of outcomes ranging from the generation of new ecotypes or species to the breakdown of morphological differences. Here, we explore the extent of hybridization in the three currently recognized New World Rhizophora species-R. mangle, R. racemosa, and the putative hybrid species R. harrisonii. • We assayed variation across the three recognized Rhizophora species using two noncoding chloroplast (cpDNA), two flanking microsatellite regions (FMRs), and six microsatellite loci. • Gene genealogies of cpDNA and FMRs showed a strong phylogeographic break across the Central American Isthmus, but little relationship to recognized species boundaries. Instead, individuals collected in the same ocean basin and classified as R. mangle and R. racemosa by morphological characteristics were more closely related to each other than with similar looking individuals collected in the other ocean basin. Nonetheless, there were low, yet significant differences at microsatellite loci among co-occurring populations of R. mangle and R. racemosa in both ocean basins, suggesting that two taxonomic groups coexist. However, we found no genetic evidence that R. harrisonii was a hybrid species. Rather, R. harrisonii appears to represent a morphotype produced by ongoing hybridization and backcrossing between R. mangle and R. racemosa. • Our data support ancient and persistent introgressive hybridization among new world Rhizophora and argue for a full revision of the systematic relationships of the group based on much finer morphological, ecological, and genetic analyses.

Characterization of cork warts and aerenchyma in leaves of Rhizophora mangle and Rhizophora racemosa

Mangroves are a diverse group of plants that inhabit tidal zones in the tropics and sub-tropics. Some mangrove species occupy the lower tidal zone in which the substrate is anoxic for long time periods while some mangroves inhabit the upper tidal zone in which the substrate should be less anoxic. Recent research has shown that about 12 species of mangroves from the Americas and from Australia transport air internally from openings in leaves called cork warts, as air enters leaves it collects within leaf aerenchyma (special air spaces within leaves) where the air expands when heated by sunlight. Aerenchyma in leaves is connected to aerenchyma in stems and stilt roots that lead to small roots in the substrate. Eventually, youngest root tissues are aerated while they grow within the anoxic substrate. Data of this study show that cork warts and leaf aerenchyma develop during leaf initiation in both shoot terminals of branches as well as in viviparous seedlings. The number of cork warts per leaf is similar for leaf primordia and for fully enlarged leaves for both Rhizophora species. Tissue sections of leaves of less than 30 mm2 area show an area of more translucent cells. Leaves with a surface area of 200 mm2 show a distinct aerenchyma tissue in which cells have no contents. For such leaves the depth of aerenchyma was 54 µm with a total leaf depth of 230 µm. Fully enlarged leaves had an aerenchyma depth of about 81 µm while the total leaf thickness was about 660 µm. For all leaves above 30 mm2, aerenchyma comprised 25% of total leaf volume. Densities of cork warts were the same for emerging leaf primordia as for fully enlarged leaves. The results of this study show that cork warts and aerenchyma develop in leaf primordia of both terminal buds and viviparous seedlings. Aerenchyma and cork warts become active once they emerge from their stipular coverings.

Intertidal substrate modification as a result of mangrove planting: Impacts of introduced mangrove species on sediment microfacies characteristics

A programme of mangrove planting has been undertaken around the island of Rodrigues (SW Indian Ocean) since the mid-1980’s involving the introduction of the species Rhizophora mucronata. We examined three coastal embayment sites (Baie Diamant, Anse Goeland and Anse Pansia) in which planting has been undertaken over different time periods within the past 20 years. Planting has met with variable success in the different sites, probably due to variations in fluvial and groundwater influence. At two sites (Baie Diamant – first planted in 1990, and Anse Pansia – first planted in 1995) ecological data indicates that the mangroves are becoming well-established, and sedimentary evidence suggests that relatively rapid modification of intertidal substrates has occurred. This is evident in the form of significant increases in sediment organic-matter content (especially fibrous organic-matter) and an increase in the accumulation of sediment fines inside the mangroves. A strong correlation exists between the magnitude and depth of substrate modification and mangrove forest density, especially root and sapling density. At the third site, Anse Goeland (first planted in 2001), mangrove establishment has not been successful, many of the seedlings have died and no secondary colonisation has occurred. Sediment substrates show no deviation from background levels in terms of organic content or weight % fines content, and we find no evidence for mangrove planting influencing sediment substrates. Despite evidence for the development of a distinctive mangrove facies at Baie Diamant and Anse Pansia there is, however, no evidence as yet for a marked change in substrate geochemistry such as would be demonstrated by evidence of active bioclast dissolution – a common process in many natural (mature) mangrove substrates. We infer this to be a function of the present relative immaturity of the still developing mangrove substrates, but may also be a function of the apparent paucity of burrowing crabs which play an important role in nutrient cycling and sediment geochemistry. Thus whilst the mangroves in some of the study sites are reaching a stage where they are producing distinctive sedimentary facies, the systems appear to be in a state of progressive sedimentary and diagenetic modification as the floral and infaunal components of the mangroves continue to develop.

Isolation and characterization of microsatellite loci in the red mangrove Rhizophora mangle (Rhizophoraceae) and its related species

Fourteen microsatellite markers were isolated from the red mangrove Rhizophora mangle (Rhizophoraceae), a widely distributed mangrove plant in the New World and West Africa. The range of expected heterozygosity of these markers was 0.000–0.672 in the two populations of R. mangle. Cross-species testing was examined for five other species of Rhizophora, and Kandelia candel and Bruguiera gymnorrhiza. All 14 markers could be amplified in R. samoensis, thirteen in R. racemosa, and six markers in all other species of Rhizophora. Our findings greatly increase the utility of these markers.

Genetic structure of the red mangrove (Rhizophora mangle L.) on the Colombian Pacific detected by microsatellite molecular markers

Rhizophora mangle, one of the five species of the genus Rhizophora, is found widely distributed along the American and West African coasts. This species is one of the principal constituents of the mangrove ecosystem in Colombia and is also found within the most important economic activities for the communities that inhabit the littoral. In order to assess the degree of genetic diversity of R. mangle in five populations of the Colombian Pacific, nuclear microsatellite molecular markers were used. In 92 individuals sampled, it was found that 100% of the loci were polymorphic \( (\overline H _0 = 0.494) \), and no private alleles were detected. The population structure of R. mangle in the Colombian Pacific, was highly significant (P < 0.001); however, the greatest differentiation was detected at the within-population level (94.62%). For the populations of La Plata, Virudo and Charambira, the tendency toward panmixia could be the cause of the low differentiation among these three locations. Within populations, the genetic diversity revealed a deviation from Hardy–Weinberg equilibrium with high significance in Virudo and Tumaco, where it appears the intense anthropogenic activity has exercised strong pressure on the red mangrove, resulting in the possible fragmentation of the local landscape and therefore an increase in the rate of endogamy within these populations. Despite this situation, our study―one of the first developed in genetics of the red mangrove in Colombia―did not show evidence of recent bottleneck effects or deterioration in its genetic composition, which could be exploited to propose management and restoration programs for the zones where the forests of this species are degraded.

Influence of a Salinity Gradient on the Vessel Characters of the Mangrove Species Rhizophora mucronata

Although mangroves have been extensively studied, little is known about their ecological wood anatomy. This investigation examined the potential use of vessel density as a proxy for soil water salinity in the mangrove species Rhizophora mucronata (Rhizophoraceae) from Kenya. In a time-standardized approach, 50 wood discs from trees growing in six salinity categories were investigated. Vessel densities, and tangential and radial diameters of rainy and dry season wood of one distinct year, at three positions on the stem discs, were measured. A repeated-measures ANOVA with the prevailing salinity was performed. Vessel density showed a significant increase with salinity, supporting its use as a prospective measure of salinity. Interestingly, the negative salinity response of the radial diameter of vessels was less striking, and tangential diameter was constant under the varying environmental conditions. An effect of age or growth rate or the presence of vessel dimorphism could be excluded as the cause of the absence of any ecological trend. The clear trend in vessel density with salinity, together with the absence of a growth rate and age effect, validates the potential of vessel density as an environmental proxy. However, it can only be used as a relative measure of salinity given that other environmental variables such as inundation frequency have an additional influence on vessel density. With view to a reliable, absolute proxy, future research should focus on finding wood anatomical features correlated exclusively with soil water salinity or inundation frequency. The plasticity in vessel density with differing salinity suggests a role in the establishment of a safe water transport system. To confirm this hypothesis, the role of inter-vessel pits, their relationship to the rather constant vessel diameter and the underlying physiology and cell biology needs to be examined.

Common allometric equations for estimating the tree weight of mangroves

Inventory data on tree weights of 104 individual trees representing 10 mangrove species were collected from mangrove forests in South-East Asia to establish common allometric equations for the trunk, leaf, above-ground and root weight. We used the measurable tree dimensions, such as dbh (trunk diameter at breast height), DR0.3 (trunk diameter at 30 cm above the highest prop root of Rhizophora species), DB (trunk diameter at lowest living branch), and H (tree height) for the independent variable of equations. Among the mangrove species studied, the trunk shape was statistically identical regardless of site and species. However, ρ (wood density of tree trunk) differed significantly among the species. A common allometric equation for trunk weight was derived, when dbh2H or DR0.32H was selected as the independent variable and wood density was taken into account. The common allometric equations for the leaf and the above-ground weight were also derived according to Shinozaki's pipe model and its extended theory. The common allometric relationships for these weights were attained with given ρ of each species, when DB2 or dbh2 or DR0.32 was selected as the independent variable. For the root weight, the common equation was derived from the allometric relationship between root weight and above-ground weight, since these two partial weights significantly correlated with each other. Based on these physical and biological parameters, we have proposed four common allometric equations for estimating the mangrove tree weight of trunk, leaf, above-ground part and root.

Transitions in Ancient Inland Freshwater Resource Management in Sri Lanka Affect Biota and Human Populations in and around Coastal Lagoons

The increasing anthropogenic pressure on natural environments results in impacts that affect tropical forest areas and their biodiversity. Adverse impacts on terrestrial and oceanic environments often compound in the intertidal area, where mangrove forest ecosystems thrive. In tropical coastal areas of many developing countries where people depend on wood and other mangrove forest products and services, forest degradation leads to socioeconomic problems. At the same time, increasing freshwater needs in these areas are expected to cause additional problems. On the basis of remote sensing and ground truthing complemented by colonial archival material from the Dutch East India Company (1602-1800), we report that changes to the historic system of inland freshwater management have increased dramatically in recent times. Hydrological changes, such as interbasin transfers, have resulted in a qualitative ecological and socioeconomic degradation in three coastal lagoons in southern Sri Lanka. Variations in river hydrology have caused changes in the areas suitable as mangrove habitat and, thus, have resulted in an altered distribution. However, increases in mangrove area can mask the degradation of the site in terms of floristic composition, significance of the species, and biodiversity (this effect is termed "cryptic ecological degradation"). It is important that such changes be carefully monitored to ensure biological and socioeconomic sustainability.

Sustained high levels of foliar herbivory of the mangrove Rhizophora stylosa by a moth larva Doratifera stenosa (Limacodidae) in north-eastern Australia

The moth larva, Doratifera stenosa (Lepidoptera: Limacodidae), was observed feeding voraciously in great numbers on mature leaves of Rhizophora stylosa in mangroves at Port Curtis in Central Queensland, NE Australia. This behaviour was considered unusual since mangroves, and the Rhizophora species in particular, reportedly harbour few herbivores and have relatively low levels of herbivory, less than 10%. During a two year period (1996–1998), larvae were observed consuming around 30–40% of leaves in the canopy each year, and the mangroves appeared able to sustain these high levels of herbivory. The impact on trees was assessed in conjunction with a study of the herbivore, its behaviour and life history, in an attempt to explain the occurrence. Larvae were 1–2 cm in length, bright green and gregarious, with numerous small, stinging hairs along their upper bodies. Feeding was in small cohort groups of 5–70 individuals that broke up immediately prior to each moult after which they regrouped in much larger numbers of mixed cohorts to form single-file processions across branches, stems and prop roots. In this way, they moved to neighbouring trees with less affected foliage. One of the outstanding characteristics of this herbivore was its ability to desist from killing host trees although it appeared quite capable of doing so had it remained on individual trees. By moving from tree to tree, the herbivore was able to heavily crop Rhizophora foliage in an apparently sustainable manner. These findings demonstrate the role and importance of foliar herbivory in severely affected forests and how such instances best not be ignored or treated as curiosities in future assessments of herbivory and forest turnover in mangrove ecosystems.

Cytogenetics and reproductive biology of mangroves in Rhizophoraceae

Three mangrove species, Bruguiera gymnorrhiza (L.) Lam., Rhizophora samoensis (Hochr.) Salvoza, Rhizophora stylosa Griff. and a putative hybrid Rhizophora ×selala (Salvoza) between the latter two species were studied for their cytogenetics and reproductive biology. Although chromosome numbers in all four taxa were confirmed as 2n = 36, the size of the chromosomes was slightly larger in genus Bruguiera. Regular chromosome pairing was observed in the three species; however, in the hybrid meiosis was very irregular. Pollen viability in all three species was very high (&gt;80%); however, in the hybrid pollen viability was &lt;10%. This could be due to non-homology in the chromosomes of the two parental species and irregular meiosis in the hybrid. Due to highly irregular meiosis in the hybrid and uneven distribution of chromosomes to the two poles, most of the pollen was non-viable. All three species were fully self-compatible. Between B. gymnorrhiza and the two Rhizophora species, pollen in crosses and reciprocal crosses failed to germinate, indicating cross-incompatibility between these two genera. Partial cross-compatibility was recorded between R. samoensis and R. stylosa. In many crosses, pollen tubes were observed growing freely up to the base of the style. This also accords with occasional crossing of these species in nature. However, due to only partial homology in the chromosomes of these two species, the hybrids produced are always sterile. Similarly, cross-compatibility between the hybrid and its two parental species was also partial. This could be attributed to allelic differences between the two species and their hybrid and also to physiological and/or chemical hindrance of the pollen-tube growth through the stylar tissue.