ABSTRACT

The granite rock-holes (sometimes called gnammas) across northern Eyre Peninsula (EP), South Australia, are a unique but poorly studied ephemeral freshwater habitat containing a complex invertebrate community. Macroinvertebrate predator occurrence is often sporadic, both spatially and temporally. We aimed to determine if environmental conditions might predict predator occurrence in EP rock-holes. A total of 14 rock-holes were sampled across five granite outcrops along the Eyre Highway. Extensive dip-net sampling was undertaken and nymphs of three damselfly species were recorded from the rock-holes: Austrolestes annulosus (Lestidae), Ischnura aurora, and Xanthagrion erythroneurum (both Coenagrionidae), all in a single rock-hole at Pildappa Rock. This sole rock-hole contained a prominent floating-leaved, rooted aquatic macrophyte: the swamp lily, Ottelia ovalifolia (Hydrocharitaceae), which forms a complex, three-dimensional vegetative structure. Damselflies were hypothesised to be associated with the presence of O. ovalifolia, possibly as a result of the plant providing both suitable oviposition sites for the adults and habitat for nymphs throughout the water column, opportunities not afforded by the aquatic vegetation present in shallow rock-holes. Our findings contribute to the limited ecological information regarding EP rock-holes. We also briefly review potential threats to these ecosystems, an understanding of which will be critical to their management and conservation.

摘要

横跨南澳大利亚艾尔半岛 (EP) 北部的花岗岩岩洞（有时称为 gnammas）是一个独特但研究不足的短暂淡水栖息地，其中包含复杂的无脊椎动物群落。大型无脊椎动物捕食者的出现通常在空间和时间上都是零星的。我们旨在确定环境条件是否可以预测 EP 岩洞中捕食者的发生。在艾尔公路沿线的 5 个花岗岩露头上共采集了 14 个岩洞。进行了广泛的浸网采样，并从岩石孔中记录了三种豆娘的若虫：  Austrolestes  annulosus (Lestidae)、Ischnura aurora和 Xanthagrion erythroneurum （两者都是 Coenagrionidae），都在 Pildappa Rock 的一个岩洞中。这个唯一的岩洞包含一种突出的浮叶、有根的水生大型植物：沼泽百合 Ottelia Otelia Otelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia Ottelia 椭圆形叶 (Hydrocharitaceae)，它形成了一个复杂的三维植物结构。豆娘被假设的要与存在相关 O.烛，可能是由于该植物为整个水体中的成虫提供了合适的产卵场所和若虫的栖息地，因此浅岩洞中存在的水生植被无法提供这些机会。我们的发现导致关于 EP 岩洞的生态信息有限。我们还简要回顾了这些生态系统面临的潜在威胁，了解这些威胁对其管理和保护至关重要。