Long‐term patterns of invertebrate abundance and relationships to environmental factors in arid Australia

Abstract

Resource pulses are a key feature of semi-arid and arid ecosystems and are generally triggered by rainfall. While rainfall is an acknowledged driver of the abundance and distribution of larger animals, little is known about how invertebrate communities respond to rain events or to vegetative productivity. Here we investigate Ordinal-level patterns and drivers of ground-dwelling invertebrate abundance across 6 years of sampling in the Simpson Desert, central Australia. Between February 1999 and February 2005, a total of 174 381 invertebrates were sampled from 32 Orders. Ants were the most abundant taxon, comprising 83% of all invertebrates captured, while Collembola at 10.3% of total captures were a distant second over this period. Temporal patterns of the six invertebrate taxa specifically analysed (Acarina, ants, Araneae, Coleoptera, Collembola and Thysanura) were dynamic over the sampling period, and patterns of abundance were taxon-specific. Analyses indicate that all six taxa showed a positive relationship with the cover of non-Triodia vegetation. Other indicators of vegetative productivity (seeding and flowering) also showed positive relationships with certain taxa. Although the influence of rainfall was taxon-dependent, no taxon was affected by short-term rainfall (up to 18 days prior to survey). The abundance of Acarina, ants, and Coleoptera increased with greater long-term rainfall (up to 18 months prior to survey), whilst Araneae showed the opposite effect. Temperature and dune zone (dune crest vs. swale) also had taxon-specific effects. These results show that invertebrates in arid ecosystems are influenced by a variety of abiotic factors, at multiple scales, and that responses to rainfall are not as strong or as predictable as those seen for other taxa. Our results highlight the diversity of invertebrates in our study region and emphasize the need for targeted long-term sampling to enhance our understanding of the ecology of these taxa and the role they play in arid ecosystems.

Population dynamics of desert mammals: similarities and contrasts within a multispecies assemblage

“…Indeed, long‐term surveys of invertebrates in our study region have revealed little effect of short‐term rainfall on invertebrate activity, but disparate effects at different spatial scales between invertebrate taxa up to 18 months after rain (Kwok et al. ). It is thus possible that both N. ridei and S. youngsoni were responding to site‐specific temporal differences in their prey.…”

Some like it hot: from individual to population responses of an arboreal arid‐zone gecko to local and distant climate

“…, Kwok et al. ). Additionally, vegetation dynamics in Kinchega are known to be driven by both higher winter rain, which favors growth of annual plants, and higher summer rain, which immediately induces flowering in perennial plants (Robertson et al.…”

“…) could affect the vegetation and arthropod development (Kwok et al. ) in arid Australia, we also considered an interaction between each water‐related parameter and summer temperature. For comparison, we performed LMMs using direct distant (i.e., ENSO) climatic predictors.…”

Surviving drought: a framework for understanding animal responses to small rain events in the arid zone

“…In contrast to Kwok et al. (), our study was conducted in arid shrubland dominated by fine‐textured soil, which can hold moisture longer than coarse sandy soil and is more able to retain basic nutrients such as carbon, nitrogen, and phosphorous, which are important to microbe and plant growth (Austin et al. , Nano and Pavey ).…”

“…, Kwok et al. ). If the small rain event documented in our study was not sufficient to cause an increase in plant productivity, this may explain the lack of a positive response from larger herbivorous insects such as crickets and hemipterans, which only displayed responses to longer‐term changes in rain.…”