Although salinas occur frequently in 

 Florida, they are rarely extensive in 

 area. For example, between Rookery Bay 

 and Marco Island (south of Naples, 

 Florida) there are a series of salinas in 

 the black mangrove-dominated zone on the 

 upland side of the mangrove swamps. These 

 hypersaline lagoons occur where the normal 

 flow of fresh water from upland sources 

 has been diverted, presumably resulting in 

 elevated soil salinities during the dry 

 winter months. 



In summary, salinity is a problem for 

 mangroves only under extreme hypersaline 

 conditions. These conditions occur natu- 

 rally in Florida in irregularly flooded 

 areas of the "high swamp" above the normal 

 high tide mark and are accompanied by high 

 soil salinities. Florida mangroves, 

 listed in order of increasing salinity 

 tolerance, appear to be red, white, and 

 black. 



2.3 REPRODUCTIVE STRATEGIES 



As pointed out by Rabinowitz (1978a), 

 virtually all mangroves share two common 

 reproductive strategies: dispersal by 

 means of water (van der Pijl 1972) and 

 vivipary (Macnae 1968; Gill and Tomlinson 

 1969). Vivipary means that the embryo 

 develops continuously while attached to 

 the parent tree and during dispersal. 

 Since there is uninterrupted development 

 from zygote through the embryo to seedling 

 without any intermediate resting stages, 

 the word "seed" is inappropriate for 

 viviparous species such as mangroves; the 

 term "propagule" is generally used in its 

 place. 



While the phenology of black and 

 white mangroves remains sketchy, Gill and 

 Tomlinson (1971) thoroughly described the 

 sequence of flowering in the red mangrove. 

 Flowering in this species may take place 

 at any time of the year, at least in 

 extreme south Florida, but reaches a maxi- 

 mum in the late spring and summer. The 

 flowers open approximately 1 to 2 months 

 after the appearance of buds. The flower 

 remains intact only 1 to 2 days; this 



probably accounts for the low fertiliza- 

 tion rate, estimated by Gill and Tomlinson 

 at 0% to 7.2%. Propagule development is 

 slow, ranging from 8 to 13 months. Savage 

 (1972) mentions that on the Florida gulf 

 coast, red mangrove propagules mature and 

 fall from the tree from July to September. 

 Within the Everglades National Park, black 

 mangroves flower from May until July and 

 bear fruit from August until November 

 while white mangroves flower from May to 

 August and bear fruit from July to October 

 (Loope 1980). 



The propagules of the three species 

 of Florida mangroves are easy to differen- 

 tiate. The following descriptions all 

 come from Rabinowitz (1978a). White man- 

 grove propagules are small and flattened, 

 weigh less than a gram, are about 2 cm 

 long, are pea-green when they fall from 

 the parent tree, and turn mud-brown in two 

 days or so. The pericarp (wall of the 

 ripened propagule) serves as a float and 

 is not shed until the seedling is estab- 

 lished. During dispersal the radicle 

 (embryonic root) emerges from the propa- 

 gule. This germination during dispersal 

 has led Savage (1972) to refer to the 

 white mangrove as "semi-viviparous". 



The propagules of the black mangrove 

 when dropped from the tree are oblong- 

 elliptical (resemble a flattened olive), 

 weigh about 1 g and are about 2 cm long. 

 The pericarp is lost within a few days 

 after dropping from the tree; at this 

 point the cotyledons (primary leaves) 

 unfold and the propagule resembles two 

 butterflies on top of one another. 



Propagules of the red mangrove under- 

 go extensive vivipary while on the tree. 

 When propagules fall from the tree they 

 resemble large green beans. They are rod- 

 shaped with pointed ends, about 20 cm 

 long, and weigh an average of 15 g. 



Propagules of all three species float 

 and remain viable for extended periods of 

 time. Apparently, there is an obligate 

 dispersal time for all Florida mangroves, 

 i.e., a certain period of time must elapse 

 during dispersal for germination to be 



14 



