Webber Bruce L, Woodrow Ian E
School of Botany, The University of Melbourne, Parkville, Vic. 3010, Australia. Corresponding author; email:
School of Botany, The University of Melbourne, Parkville, Vic. 3010, Australia.
Funct Plant Biol. 2004 Jun;31(5):505-516. doi: 10.1071/FP03214.
The rare Australian rainforest tree Ryparosa sp. nov. 1 aff. javanica (sensu Webber & Curtis, BW-017; Achariaceae) has large fleshy fruits that undergo a distinctive colour change during ripening. Fruit seem highly suited to frugivore interactions with large ground-dwelling avian or marsupial frugivores, a role primarily filled by the endangered cassowary. We found that fruits had chemical defence traits that closely paralleled morphological ripening signals. Young fruit seeds had amongst the highest concentrations of plant tissue cyanogens ever recorded (some in excess of 12 mg g dw), yet the flesh of ripe fruits had negligible cyanogen defence. A seed treatment trial found that cassowary gut passage significantly improved germination from 4% to 92%, and we were not able to replicate this result with simulated treatments. While high levels of fruit fly larval infestation accounted for reduced seed viability, this predation was apparently reduced by cassowary gut passage. Post-germination seedling traits such as haustorial cryptocotylar cotyledons and epigeal germination may increase the chance of survival for establishing seedlings. We conclude that the range of traits seen in Ryparosa recruitment is particularly suited to interactions with frugivores and survival in a rainforest ecosystem.
澳大利亚稀有的雨林树种新种Ryparosa sp. nov. 1近爪哇树（按照韦伯和柯蒂斯的分类，BW - 017；毒鼠子科）结出大型肉质果实，这些果实在成熟过程中会经历独特的颜色变化。果实似乎非常适合与大型地栖鸟类或有袋类食果动物进行食果互动，这一角色主要由濒危的食火鸡承担。我们发现，果实具有与形态成熟信号密切平行的化学防御特征。幼果种子中的植物组织氰化物浓度是有记录以来最高的（有些超过12毫克/克干重），然而成熟果实的果肉中氰化物防御含量可忽略不计。一项种子处理试验发现，食火鸡肠道处理显著提高了发芽率，从4%提高到92%，而我们无法通过模拟处理重现这一结果。虽然高水平的果蝇幼虫侵染导致种子活力下降，但食火鸡肠道处理显然减少了这种捕食现象。发芽后幼苗的特征，如具吸器的隐子叶子叶和出土萌发，可能会增加幼苗定植存活的机会。我们得出结论，Ryparosa种子萌发过程中表现出的一系列特征特别适合与食果动物互动以及在雨林生态系统中生存。
