Pachira aquatica, as indicator of mangrove limit?

Pachira aquatica has historically been regarded as a companion to the American mangroves Rhizophora mangle, Avicennia germinans and Laguncularia racemosa. This species has floating seeds with large cotyledons and is cryptoviviparous. On the stem it develops buttresses and aerial roots. It supports interstitial water salinities of 8.4 ups and superficial water of 18.7 ups. In the coastal plains where salinity is low it is mixed with elements of the floodplain forest and where the salinity is greater it appears with mangrove species. The seeds germinate in salt concentrations between 0 and 9.2 ups. Hydroperiod was determined in sites where the species is present, and ranges from 1.5 to -1 m with a flooding period of 8-12 months. Soil redox potential is from 490 to -47 mV. Maps were produced for 2 coastal lagoons and an estuary showing the distribution of mangroves and forested wetlands of P. aquatica around them. Based on the information generated, we propose P. aquatica should be considered as a high tide mangrove species and used as the distribution limit of mangroves. It is suggested that it should be considered and protected under Mexican law as one species of mangrove.