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Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.

The extended phenotype of helical burrowing behavior in animals has evolved independently many times since the Cambrian explosion (~540 million years ago [MYA]). A number of hypotheses have been proposed to explain the evolution of helical burrowing in certain taxa, but no study has searched for a general explanation encompassing all taxa. We reviewed helical burrowing in both extant and extinct animals and from the trace fossil record and compiled 10 hypotheses for why animals construct helical burrows, including our own ideas. Of these, six are post‐construction hypotheses—benefits to the creator or offspring, realized after burrow construction—and four are construction hypotheses reflecting direct benefits to the creator during construction. We examine the fit of these hypotheses to a total of 21 extant taxa and ichnotaxa representing 59–184 possible species. Only two hypotheses, antipredator and biomechanical advantage, cannot be rejected for any species (possible in 100% of taxa), but six of the hypotheses cannot be rejected for most species (possible in 86%–100% of taxa): microclimate buffer, reduced falling sediment (soil), anticrowding, and vertical patch. Four of these six are construction hypotheses, raising the possibility that helical burrowing may have evolved without providing post‐construction benefits. Our analysis shows that increased drainage, deposit feeding, microbial farming, and offspring escape cannot explain helical burrowing behavior in the majority of taxa (5%–48%). Overall, the evidence does not support a general explanation for the evolution of helical burrowing in animals. The function and evolution of the helix as an extended phenotype seems to provide different advantages for different taxa in different environments under different physicochemical controls (some traces/tracemakers are discussed in more detail due to their association with body fossils and well‐constrained physicochemical parameters). Although direct tests of many of the hypotheses would be difficult, we nevertheless offer ways to test some of the hypotheses for selected taxa. [ABSTRACT FROM AUTHOR]

Context. Australia has been a battleground of invasive versus native species for ~200 years. Two of the most impactful invasive speciesto Australian animal communities are the toxic cane toad (Rhinella marina) and the predatory feral cat (Felis catus). Australia’s native fauna is evolutionarily naïve to both invaders because neither’s taxonomic group is native to the continent. Both invaders have had severe effects on Australian native animal communities including species extinctions, extirpations, and severe population declines, but until now their effects have generally been thought to be independent of one another. Aims. We aimed to determine the impacts of invasive cane toads on monitor lizards and feral cats by estimating changes in relative abundance before and after the toad invasion. Methods. We studied toad impacts at three sites in the Kimberley region of northern Australia. We used two methods for estimating relative abundance: camera traps and track station data. Data included greater than 4000 trap days and included 7 years over an 11-year period. Key results. As expected, invading cane toads rapidly decimated populations of two species of monitor lizards (97–99% declines), including the top-order predatory Varanus panoptes. Unexpectedly, this loss was associated with a >10-fold mean increase in detection rates of cats by 5 years after the loss of V. panoptes, reflecting relative increases of 3.3–8.7 individual cats per site. Conclusions. Although some unknown factor may have caused an increase in cats, their similar trophic position and niche to V. panoptes suggests that toads facilitated cats by effectively removing the lizards from the animal community. This interaction likely reflects one type of invasional meltdown, whereby a non-native species (cane toad) facilitated any aspect of another’s (feral cat) invasion (e.g. survival, reproduction, resource acquisition), but the latter has no detected influence on the former (+/0 interaction). Implications. Because both invaders cause declines in animal populations and are difficult to control, the potentially synergistic tandem of cane toads and feral cats could have chronic, irreversible effects on animal communities. [ABSTRACT FROM AUTHOR]