396 Wetlands Ecosystems Figure Alligator in pool at Everglades National Park, southern Florida, USA Figure Acidic peatland, coastal Maine, USA Most of the carnivorous species in the world occur in wetlands and other oligotrophic habitats The relationships between insect capture, mineral nutrition (particularly nitrogen and phosphorus), and plant growth and reproduction have been investigated for numerous species The relatively large diversity of organisms that can survive in the ‘‘pitchers’’ of some carnivorous plants also has been studied (Figure 9) Although benefits to carnivorous plants have been demonstrated, there is limited evidence that carnivory is necessary for most species to survive Evergreen, sclerophyllous shrubs that generally belong to the Ericaceae (heath family) are characteristic of nutrient-poor peatlands The role of this foliage type in wetlands is uncertain, but it has been suggested that plant species with evergreen leaves may be more efficient in using nutrients than species with deciduous leaves These leaves, which persist for up to four years, extend the period that the plant can photosynthesize, which conserves energy in the plant because all of the leaves not have to be renewed each year Furthermore, evergreen species tend to resorb more nutrients from senescing leaves than other species, thus increasing nutrient use efficiency High nutrient resorption and long retention of nutrients in evergreen sclerophyllous leaves may be especially important in phosphorus-poor habitats such as bogs One of the most important groups of plants in colder, generally acidic wetlands of the world are Sphagnum mosses, a Figure Yellow pitcher plants in pocosin, South Carolina, USA Figure 10 Acidic peatland in the Adirondacks, New York, USA large genus consisting of more than 135 species (Figure 10) These mosses can thrive in conditions highly stressful to most plants (e.g., low pH, low nutrient availability, and saturated soils) They are the primary peat producers worldwide and have the capacity to modify the environment in ways that favor their own growth Once established, Sphagnum mosses can further acidify their environment through cation exchange processes and by excretion of polygalacturonic acids They