Do active‐dispersing insects dominate the invertebrate fauna of rock pools in the wet–dry tropics, Kimberley, Australia?

Abstract

Invertebrate assemblages of tropical freshwater rock pools (FRPs) are poorly known compared with temperate regions, where FRPs contain specialized, endemic taxa of high conservation value. Invertebrates were sampled from pristine FRPs in the Morgan River catchment in the Australian wet–dry tropics in the 2015 and 2016 wet seasons. Taxa were classified as either active or passive dispersers and by functional feeding groups. A range of physical variables were examined to identify associations with invertebrate assemblages. Forty‐seven taxa were identified from FRPs; most were actively dispersing predatory insects, primarily Coleoptera and Hemiptera. Five adult insect species were found in most pools; other taxa were rare and scattered across FRPs. Two previously undescribed species of Spinicaudata were collected, but few crustacean taxa were recorded, and passively dispersing taxa were rare. Species accumulation curves indicated that had more pools been sampled, more taxa would have been collected in 2015, but in 2016 most species were collected. There was no pattern in FRP assemblages related to any physical variable, but the assemblages in pools were correlated between sampling times. An opportunistic and mobile assemblage composed mostly of actively dispersing predatory insects may explain the absence of relationships with measured variables. Low hydrological stability in the wet–dry tropics may be associated with low taxon richness. The dominance of actively dispersing insects is in contrast with FRP assemblages in temperate and arid regions. Studies of a wider range of FRPs from tropical regions are required to determine whether the fauna of these Kimberley FRPs are typical, and to fully describe short‐range endemic species across the Kimberley and elsewhere. The FRPs have conservation value as habitat for endemic, specialist rock‐pool taxa, contributing to regional species pools. At present, a lack of knowledge of endemic FRP specialist species in tropical regions, including the Kimberley, impedes our ability to protect and conserve these species from disturbance.

Contrasting biodiversity and food web structure of three temporary freshwater habitats in a tropical biodiversity hotspot

“…Moreover, tropical rainfall conditions allow longer inundations that enable predators with longer aquatic life cycles to breed in the rock pools. For instance, in a similar climate to the present study (the wet-dry tropics), Carey et al (2019) found that ±60% of the taxa in sandstone rock pools were predators in Kimberley, Australia. However, as the researchers used a large mesh size during sampling, it is possible that they overestimated the relative diversity of predators because many smaller filter feeders and collectors will have been missed during sampling.…”

Conductivity and water level modulate developmental plasticity and explain distribution patterns in a diverse neotropical Odonata assemblage

“…Rock pools in Australia, Botswana, and South Africa tend to be inhabited by one or two species (Brendonck et al, 2015; Jocqué et al, 2006). Exceptionally five, six, seven, and eight species were found in rock pool clusters from northwestern Australia (Carey, Cross, et al, 2019), south‐western Australia (Pinder et al, 2000), Côte d'Ivoire (Snoeks et al, 2021), and Utah (USA) (Baron et al, 1998). The most likely explanations for the large number of odonates we found include neotropical latitude and humidity.…”

“…Therefore, a granite outcrop can house a highly heterogeneous set of freshwater habitats inhabited by a large diversity of invertebrates with different ecological requirements. Community analyses of tropical rock pools are rare (but see Carey, Cross, et al, 2019;Jocqué et al, 2010;Snoeks et al, 2021).…”

“…Therefore, a granite outcrop can house a highly heterogeneous set of freshwater habitats inhabited by a large diversity of invertebrates with different ecological requirements. Community analyses of tropical rock pools are rare (but see Carey, Cross, et al, 2019; Jocqué et al, 2010; Snoeks et al, 2021). Hydroperiod is likely to be an essential underlying factor since it can restrict the survival of taxa based on the minimum time required to complete the aquatic phase of their life cycle (Brendonck et al, 2015; Schneider & Frost, 1996).…”