Ecology and evolution of Devonian trees in New York, USA

In a survey of 1992 to 1994, mangrove forests withfour species of true mangroves, Kandelia candel(L.) Druce, Avicennia marina(Forsk.) Vierh.,Rhizophora stylosaGriff., and Lumnitzera racemosaWilld., were found at 22locations in the west coast of Taiwan. The northernrange of their distribution was at Tanshui Estuary(Latitude 25°11′N) and the southern range atTapen Bay (22°28′N). The total area wasestimated to be 286.95 ha. There was an obvious changein species composition and a decrease in speciesnumber of true mangroves from south to north: the fourspecies dominated by A. marinain thesouth and K. candelas thesole species in the north. Air temperature associatedwith sea surface temperature and oceanic currents inwinter, but not soil property, was found to be theprimary environmental factor, affecting the diversityand distribution of true mangroves in Taiwan as wellas in the northeast region of Asia.

Diversity and distribution of the mangrove forests in Taiwan.

The litter production and decomposition of a mangrove forest at Ohura Bay, Okinawa were studied with the use of littertraps and litterbags. The litter production of the Kandelia candel community (PI), the Kandelia candel and Bruguiera gymnorrhiza com­ munity (P2) and the Bruguiera gymnorrhiza community (P3) was 8.72,10.74 and 7.73 ton/hal year, respectively. Litterfall rates were seasonal in the three communities. The first peak of litterfall in PI and P2 was in May (spring) as a result of the K. candel mature fruit fall, while that in P3 was in February as a result of the B. gymnorrhiza leaf fall. Due to typhoons, remarkable increases occurred during July and August (summer) and all com­ munities showed great peaks at that time. Afterward, the amount of litterfall in the three communities decreased greatly. Leaves of K. candel decomposed slightly faster than those of B. gymnorrhiza. In both species, the early decomposition (after 1 and 2 months) was great, followed by a slower decrease in dry mass for the remaining period of the experiment. The dry mass of twigs showed a much slower decrease compared with that of the leaves. The decrease in twig mass of the two species was almost entirely the result of bark loss which flaked from the wood. After 6 months decomposition, the woody materials remained generally firm and hard without obvious signs of breakdown.

Litter Production and Decomposition of a Mangrove Forest at Ohura Bay, Okinawa

The littorinid gastropod Littoraria flammea has been widely quoted as one of only three or four marine molluscs believed to have become extinct in historic times. It is easily recognized by its delicate, elongate, striped shell. We review the literature and available museum material to show that its only recorded locality was Shanghai and that it has not been collected since about 1855. We report the rediscovery of this species in salt marshes near Shanghai, where the habitat is under threat from invasive Spartina. For the first time we describe the penis, pallial oviduct and radula. These are the same as those of L. melanostoma, previously recorded only from Fujian province and southwards, where its shell is different from that of L. flammea. We now report a population of L. aff. melanostoma from between Fujian and Shanghai, with shells of intermediate form and colour. Analyses of sequences of COI, 12S and 28S genes do not support separation of these two Littoraria species, in terms of either reciprocal monophyly or genetic distance. Present evidence suggests that L. flammea could be only a distinctive morphological form or extreme of a cline, at the northern limit of the range of L. melanostoma.

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Rediscovery of one of the very few ‘unequivocally extinct’ species of marine molluscs: Littoraria flammea (Philippi, 1847) lost, found—and lost again?

Mangrove trees planted for restoration or rehabilitation often fail to show satisfactory survivals. Although it is generally assumed that barnacle fouling is a factor in mangrove mortality, the sub-lethal response of mangroves to this fouling is not known. In the present study, we compare the leaf morphology (stomata density, leaf thickness, percentage thickness of palisade layer and number of hypodermal layers), lenticel density and the plant fitness (number of flowers or droppers per tree) between mangroves fouled by the acorn barnacle Fistulobalanus albicostatus (the fouled group, number of barnacles ~ 120 individuals per tree) and non-fouled mangroves (the control group). We observed 55 Kandelia obovata from three locations, two in Hong Kong (n = 35, fouled 25 and control 10) and one location in Taiwan (n = 20, fouled 10 and control 10). Aegiceras corniculatum (n = 45) was observed from two sites in Hong Kong, one on the east coast (n = 20, 10/10) and one on the west coast (n = 25, 10/15). In seedlings (K. obovata
n = 10, 5/5), fouling density did not affect leaf morphology. In mature trees, however, leaves from fouled trees had significantly higher density of stomata and stem lenticel, a lower percentage thickness of leaf palisade layer and more layers of lower hypodermis in the leaves, probably for compensating the impeded gaseous exchange functions of the lenticels. The number of droppers and flowers on fouled mangroves was significantly lower. It is possible that after compensating for respiratory stress, the plant had less energy available for reproduction. Although there was no obvious barnacle-induced mortality in this study, barnacles appear to be related to a reduction in plant fitness. This may induce sufficient stress that over time fouled mangroves cannot sustain viable populations.

Adaptations to barnacle fouling in the mangroves Kandelia obovata and Aegiceras corniculatum

Funjian Province, in the subtropical zone of China, has six mangrove species: Bruguiera gymnorrhiza, Kandelia candel, Excoecaria agallocha, Acanthus ilicifolius, Aegiceras corniculatum, and Avicennia marina. Along the southern coastal portion of Fujian all six species and several associations occur; in the middle region four species and fewer associations are found; and in the northern region only Kandelia candel occurs. The northern region at 27° 20′ is the northern most extent of mangroves on the China coast.

Peng Lin

Papers

Ecological notes on the mangroves of Fujian, China