Native Habitats Of Cryptocorynes
Our knowledge about the native habitats of Cryptocorynes has expanded considerably over the last couple of years. Among the many publications, those compiled by Schulze (1971b, 1978), Horst (1983, 1986), Jacobsen (1976, 1980, 1982, 1985a, 1986, 1991) and Jacobsen and Bogner (1986, 1987) deserve special mention. These studies show that Cryptocorynes, which probably all go back to a single common source (monophy-letic), have, in the course of time, adopted rather different habitats during their evolution. Most will have only a very limited area of endemic distribution. Their habitats are
Natural habitat of Cryptocoryne bogneri in Sri Lanka.
generally more or less fast-flowing waters, their banks and edges, as well as pools that have remained after flooding, which may periodically dry out (temporary waters). Some Cryptocorynes exist in rivers which are subject to tidal influence by their proximity to oceans.
Among the most important ecological factors influencing the existence of Cryptocorynes are water chemistry, as well as the composition of the soil or substrate.
Published water analyses of native habitats distinctly show that water composition, especially the pH-value and hardness, are of very special importance for plant growth. Whereas the Cryptocorynes in Sri Lanka are usually found in waters featuring a weak acid to slightly alkaline pH-value, as well as predominantly medium-hard to hard water, the Cryptocoryne biotopes on Borneo and the Malay Peninsula are largely characterized by a very soft, extremely acid environment. It is thus hardly surprising that species from Sri Lanka (with the exception of C. bogneri, C. thwaitesii, C. alba) are better suited for aquarium cultivation than Cryptocorynes originating from typical black water biotopes on Borneo or the Malay Peninsula.
The condition of the substrate, too, is a vital ecological factor to which many Cryptocoryne species are highly tuned and adapted. Therefore, they often have only a limited tolerance for even minimal deviations from their optimum conditions. In their native habitats Cryptocorynes grow in very different soils. Species from streams and rivers in tropical rainforests exist in boggy and loamy, iron-holding soil, which displays a high degree of humic matter due to decaying foliage and rot. As regularly documented, the pH-values of the substrate are thus located in the strongly acid range. In contrast, in fast-flowing streams and rivers with a sandy-gravelly substrate, a usually weak acid reaction was recorded.
Apart from the individual factors of water chemistry and substrate, there is another es sential environmental factor, namely light intensity. Most Cryptocorynes from the Malay Peninsula (from Borneo and Sumatra) exist in semishaded to totally shaded locations; biotopes exposed to full sunlight are only occasionally found for Cryptocorynes from Sri Lanka.
The native habitats of Cryptocorynes are exceptionally different in their makeup, which is why generalizations are questionable because they lead to wrong perceptions and conclusions. A differentiating approach, therefore, which takes into consideration the ecological conditions of each and every Cryptocoryne species, is most important. It is for this reason that the native habitats of this highly specialized genus receive special attention in the descriptions of the individual species, taking into account all currently available information.
- Seedlings of Cryptocoryne ciliata.
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