Amphidromy links a newly documented fish community of continental Australian streams, to oceanic islands of the west Pacific

Background

Indo-Pacific high island streams experience extreme hydrological variation, and are characterised by freshwater fish species with an amphidromous life history. Amphidromy is a likely adaptation for colonisation of island streams following stochastic events that lead to local extirpation. In the Wet Tropics of north-eastern Australia, steep coastal mountain streams share similar physical characteristics to island systems. These streams are poorly surveyed, but may provide suitable habitat for amphidromous species. However, due to their ephemeral nature, common non-diadromous freshwater species of continental Australia are unlikely to persist. Consequently, we hypothesise that coastal Wet Tropics streams are faunally more similar, to distant Pacific island communities, than to nearby faunas of large continental rivers.

Methods/Principal Findings

Surveys of coastal Wet Tropics streams recorded 26 species, 10 of which are first records for Australia, with three species undescribed. This fish community is unique in an Australian context in that it contains mostly amphidromous species, including sicydiine gobies of the genera Sicyopterus, Sicyopus, Smilosicyopus and Stiphodon. Species presence/absence data of coastal Wet Tropics streams were compared to both Wet Tropics river networks and Pacific island faunas. ANOSIM indicated the fish fauna of north-eastern Australian coastal streams were more similar to distant Pacific islands (R = 0.76), than to nearby continental rivers (R = 0.98).

Main Conclusions/Significance

Coastal Wet Tropics streams are faunally more similar to distant Pacific islands (79% of species shared), than to nearby continental fauna due to two factors. First, coastal Wet Tropics streams lack many non-diadromous freshwater fish which are common in nearby large rivers. Second, many amphidromous species found in coastal Wet Tropics streams and Indo-Pacific islands remain absent from large rivers of the Wet Tropics. The evolutionary and conservation significance of this newly discovered Australian fauna requires clarification in the context of the wider amphidromous fish community of the Pacific.     

Immigrants and refugees: the importance of dispersal in mediating biotic attrition under climate change

Montane tropical rainforests are critically important areas for global bird diversity, but are projected to be highly vulnerable to contemporary climate change. Upslope shifts of lowland species may partially offset declines in upland species but also result in a process of lowland biotic attrition. This latter process is contingent on the absence of species adapted to novel warm climates, and isolation from pools of potential colonizers. In the Australian Wet Tropics, species distribution modelling has forecast critical declines in suitable environmental area for upland endemic birds, raising the question of the future role of both natural and assisted dispersal in species survival, but information is lacking for important neighbouring rainforest regions. Here we use expanded geographic coverage of data to model the realized distributions of 120 bird species found in north‐eastern Australian rainforest, including species from potential source locations in the north and recipient locations in the south. We reaffirm previous conclusions as to the high vulnerability of this fauna to global warming, and extend the list of species whose suitable environmental area is projected to decrease. However, we find that expansion of suitable area for some species currently restricted to northern rainforests has the potential to offset biotic attrition in lowland forest of the Australian Wet Tropics. By examining contrasting dispersal scenarios, we show that responses to climate change in this region may critically depend on dispersal limitation, as climate change shifts the suitable environmental envelopes of many species south into currently unsuitable habitats. For lowland and northern species, future change in vegetation connectivity across contemporary habitat barriers is likely to be an important mediator of climate change impacts. In contrast, upland species are projected to become increasingly isolated and restricted. Their survival is likely to be more dependent on the viability of assisted migration, and the emergence and persistence of suitable environments at recipient locations.     

Does biogeographical history matter? Diversity and distribution of lotic midges (Diptera: Chironomidae) in the Australian Wet Tropics

Abstract We examined broad scale patterns of diversity and distribution of lotic Chironomidae (Diptera) within the Wet Tropics bioregion of northern Queensland, Australia. Field surveys across broad latitudinal and altitudinal gradients within the Wet Tropics revealed a fauna of 87 species‐level taxa in 49 genera comprising three main elements: a small genuinely tropical fraction, and larger cosmopolitan and Gondwanan components. The latter group originated when Australia, as part of the ancient Gondwana supercontinent, was situated over Antarctic latitudes with a cooler, wetter climate than today. In the Wet Tropics, cool Gondwanan taxa occurred predominantly in upland and shaded lowland sites, but no species appeared narrowly temperature restricted, and there was no faunal zonation with altitude. Most chironomid species occurred at all latitudes within the Wet Tropics, with no evidence for an enduring effect of the historical rainforest contractions on current‐day distribution patterns. These findings contrast with those for aquatic faunas elsewhere in the world and for the terrestrial Wet Tropics fauna. We relate this to the generally broad environmental tolerances of Australian chironomids, and comment on why the latitudinal diversity gradient does not apply to the Australian chironomid fauna.     

Resistance and resilience: quantifying relative extinction risk in a diverse assemblage of Australian tropical rainforest vertebrates

Aim Assessing the relative vulnerability of species within an assemblage to extinction is crucial for conservation planning at the regional scale. Here, we quantify relative vulnerability to extinction, in terms of both resistance and resilience to environmental change, in an assemblage of tropical rainforest vertebrates. Location Wet Tropics Bioregion, north Queensland, Australia. Methods We collated data on 163 vertebrates that occur in the Australian Wet Tropics, including 24 frogs, 33 reptiles, 19 mammals and 87 birds. We used the ‘seven forms of rarity’ model to assess relative vulnerability or resistance to environmental change. We then develop a new analogous eight‐celled model to assess relative resilience, or potential to recover from environmental perturbation, based on reproductive output, potential for dispersal and climatic niche marginality. Results In the rarity model, our assemblage had more species very vulnerable and very resistant than expected by chance. There was a more even distribution of species over the categories in the resilience model. The three traits included in each model were not independent of each other; species that were widespread were also habitat generalists, while species with narrow geographical ranges tended to be locally abundant. In the resilience model, species with low reproductive output had a narrow climatic niche and also a low capacity to disperse. Frogs were the most vulnerable taxonomic group overall. The model categories were compared to current IUCN category of listed species, and the product of the two models was best correlated with IUCN listings. Main conclusions The models presented here offer an objective way to predict the resistance of a species to environmental change, and its capacity to recover from disturbance. The new resilience model has similar advantages to the rarity model, in that it uses simple information and is therefore useful for examining patterns in assemblages with many poorly known species.     

Giant cuticular pores in Eidothea zoexylocarya (Proteaceae) leaves

Ubiquitous, large diameter pores have not previously been adequately demonstrated to occur in leaf cuticles. Here we show conclusively that such structures occur in Eidothea zoexylocarya, a rainforest tree species of Proteaceae restricted to the Australian Wet Tropics. The pores are abundant, large-diameter apertures (～1 μm), that extend perpendicularly most of the way through the cuticle from the inside. They occur on both sides of the leaf, but are absent from the cuticle associated with stomatal complexes on the abaxial side. No such pores were found in any other species, including the only other species of Eidothea, E. hardeniana from New South Wales, and other species that have previously been purported to possess cuticular pores. To determine whether these pores made the cuticles more leaky to water vapor, we measured astomatous cuticular conductances to water vapor for E. zoexylocarya and seven other Proteaceae species of the Wet Tropics. Cuticular conductance for E. zoexylocarya was relatively low, indicating that the prominent pores do not increase conductance. The function of the pores is currently obscure, but the presence of both pores and an adaxial hypodermis in E. zoexylocarya but not E. hardeniana suggests evolution in response to greater environmental stresses in the tropics.     

The feeding ecology of freshwater fishes in two rivers of the Australian wet tropics

Synopsis The fish fauna of the Mulgrave and South Johnstone rivers is diverse relative to other Australian rivers and this study examines the diets of many of the resident fish species. Most species were small (< 200 g), and although considerable overlap in the size of the mouth was observed, closely related species tended to have non-overlapping ranges in mouth size. Five trophic guilds were recognised and substantial discrimination between guilds on the basis of body size was noted. Small fishes (< 5 gm body weight) consumed a variety of insect larvae and small terrestrial insects. The diet of large fish was characterised by the presence of large aquatic invertebrates and fish. A third group of intermediate sized fishes (10–20 gm), which included the 0+ age class of three species of large fish, also consumed aquatic invertebrates but only a small proportion of terrestrial invertebrates. Vegetable material was present in the diet of all three guilds but the source of that material varied. In groups 1 to 3 above, the source of that material was desmids and diatoms, aquatic macrophytes or filamentous alga respectively. A fourth guild fed predominately on detritus and some bivalve molluscs, and a fifth group, containing only two species, fed feavily on gastropod molluscs. The extent of dietary overlap varied both within- and between-rivers. In habitats dominated by low water velocities and sandy substrates, resource partitioning was pronounced and the number of fishes with empty or near empty guts was high, suggesting that food was more limited in this type of habitats. Little resource partitioning was observed in habitats characterised by a coarse substrate, high water velocity and dense riparian canopy.     

Phylogeography of an east Australian wet-forest bird, the satin bowerbird (Ptilonorhynchus violaceus), derived from mtDNA, and its relationship to morphology

Australian wet forests have undergone a contraction in range since the mid-Tertiary, resulting in a fragmented distribution along the east Australian coast incorporating several biogeographical barriers. Variation in mitochondrial DNA and morphology within the satin bowerbird was used to examine biogeographical structure throughout almost the entire geographical extent of these wet forest fragments. We used several genetic analysis techniques, nested clade and barrier analyses, that use patterns inherent in the data to describe the spatial structuring. We also examined the validity of the two previously described satin bowerbird subspecies that are separated by well-defined biogeographical barriers and tested existing hypotheses that propose divergence occurs within each subspecies across two other barriers, the Black Mountain corridor and the Hunter Valley. Our data showed that the two subspecies were genetically and morphologically divergent. The northern subspecies, found in the Wet Tropics region of Queensland, showed little divergence across the Black Mountain corridor, a barrier found to be significant in other Wet Tropics species. Biogeographical structure was found through southeastern Australia; three geographically isolated populations showed genetic differentiation, although minimal divergence was found across the proposed Hunter Valley barrier. A novel barrier was found separating inland and coastal populations in southern New South Wales. Little morphological divergence was observed within subspecies, bar a trend for birds to be larger in the more southerly parts of the species' range. The results from both novel and well-established genetic analyses were similar, providing greater confidence in the conclusions about spatial divergence and supporting the validity of these new techniques.     

Laying low: Rugged lowland rainforest preferred by feral cats in the Australian Wet Tropics

Invasive mesopredators are responsible for the decline of many species of native mammals worldwide. Feral cats have been causally linked to multiple extinctions of Australian mammals since European colonization. While feral cats are found throughout Australia, most research has been undertaken in arid habitats, thus there is a limited understanding of feral cat distribution, abundance, and ecology in Australian tropical rainforests. We carried out camera‐trapping surveys at 108 locations across seven study sites, spanning 200 km in the Australian Wet Tropics. Single‐species occupancy analysis was implemented to investigate how environmental factors influence feral cat distribution. Feral cats were detected at a rate of 5.09 photographs/100 days, 11 times higher than previously recorded in the Australian Wet Tropics. The main environmental factors influencing feral cat occupancy were a positive association with terrain ruggedness, a negative association with elevation, and a higher affinity for rainforest than eucalypt forest. These findings were consistent with other studies on feral cat ecology but differed from similar surveys in Australia. Increasingly harsh and consistently wet weather conditions at higher elevations, and improved shelter in topographically complex habitats may drive cat preference for lowland rainforest. Feral cats were positively associated with roads, supporting the theory that roads facilitate access and colonization of feral cats within more remote parts of the rainforest. Higher elevation rainforests with no roads could act as refugia for native prey species within the critical weight range. Regular monitoring of existing roads should be implemented to monitor feral cats, and new linear infrastructure should be limited to prevent encroachment into these areas. This is pertinent as climate change modeling suggests that habitats at higher elevations will become similar to lower elevations, potentially making the environment more suitable for feral cat populations.     

Is the elusive Gymnothorax polyuranodon really a freshwater moray?

Analysis of 36 records of the rarely encountered moray Gymnothorax polyuranodon indicate that juveniles and adults inhabit fresh and mildly brackish habitats (salinity < 5) in streams of the Australian Wet Tropics Eighty-one per cent of these records were from freshwater streams and collectively demonstrate that this species inhabits fresh water throughout all seasons. A survey of fish researchers, each with at least 100 h of field experience in Australia's Wet Tropics, revealed that 33% of researchers working in fresh waters (nine of 27 researchers) had encountered the species and 15% of researchers with substantial experience working in estuaries (two of 13 researchers) had encountered the species. The species was not sampled or observed in the nearshore marine environment. The only record of an elver of this species was, however, found in an estuary at a salinity of 33·4. This preliminary evidence suggests adult G. polyuranodon occupy freshwater habitats, but further research is required to understand the complete life cycle, including movements, habitat use and reproductive ecology of the species.     

Distribution and phylogenetic relationships of Australian glow-worms Arachnocampa (Diptera, Keroplatidae)

Glow-worms are bioluminescent fly larvae (Order Diptera, genus Arachnocampa) found only in Australia and New Zealand. Their core habitat is rainforest gullies and wet caves. Eight species are present in Australia; five of them have been recently described. The geographic distribution of species in Australia encompasses the montane regions of the eastern Australian coastline from the Wet Tropics region of northern Queensland to the cool temperate and montane rainforests of southern Australia and Tasmania. Phylogenetic trees based upon partial sequences of the mitochondrial genes cytochrome oxidase II and 16S mtDNA show that populations tend to be clustered into allopatric geographic groups showing overall concordance with the known species distributions. The deepest division is between the cool-adapted southern subgenus, Lucifera, and the more widespread subgenus, Campara. Lucifera comprises the sister groups, A. tasmaniensis, from Tasmania and the newly described species, A. buffaloensis, found in a high-altitude cave at Mt Buffalo in the Australian Alps in Victoria. The remaining Australian glow-worms in subgenus Campara are distributed in a swathe of geographic clusters that extend from the Wet Tropics in northern Queensland to the temperate forests of southern Victoria. Samples from caves and rainforests within any one geographic location tended to cluster together within a clade. We suggest that the morphological differences between hypogean (cave) and epigean (surface) glow-worm larvae are facultative adaptations to local microclimatic conditions rather than due to the presence of cryptic species in caves.     

Can changes in ant diversity along elevational gradients in tropical and subtropical Australian rainforests be used to detect a signal of past lowland biotic attrition?

Increasing temperatures are predicted to have profound effects on montane ecosystems. In tropical forests, biotic attrition may reduce lowland diversity if losses of species due to upslope range shifts are not matched by influxes of warmer‐adapted species, either because there are none or their dispersal is impeded. Australian rainforests consist of a north–south chain of patches, broken by dry corridors that are barriers to the dispersal of rainforest species. These rainforests have repeatedly contracted and expanded during Quaternary glacial cycles. Many lowland rainforests are expansions since the Last Glacial Maximum and may, therefore, show a signal of historical biotic attrition. We surveyed ants from replicated sites along three rainforest elevational transects in eastern Australia spanning 200 to 1200 m a.s.l. and nearly 14° of latitude. We examined elevational patterns of ant diversity and if there was possible evidence of lowland biotic attrition. Each transect was in a different biogeographic region; the Australian Wet Tropics (16.3°S), the central Queensland coast (21.1°S) and subtropical south‐eastern Queensland (28.1°S). We calculated ant species density (mean species per site) and species richness (estimated number of species by incorporating site‐to‐site species turnover) within elevational bands. Ant species density showed no signal of lowland attrition and was high at low and mid‐elevations and declined only at high elevations at all transects. Similarly, estimated species richness showed no evidence of lowland attrition in the Wet Tropics and subtropical south‐east Queensland; species richness peaked at low elevations and declined monotonically with increasing elevation. Persistence of lowland rainforest refugia in the Wet Tropics during the Last Glacial Maximum and latitudinal range shifts of ants in subtropical rainforests during the Holocene climatic optimum may have counteracted lowland biotic attrition. In central Queensland, however, estimated richness was similar in the lowlands and mid‐elevations, and few ant species were indicative of lower elevations. This may reflect historical biotic attrition due perhaps to a lack of lowland glacial refugia and the isolation of this region by a dry forest barrier to the north.     

Mammalian Diet and Broad Hunting Strategy of the Dingo (Canis familiaris dingo) in the Wet Tropical Rain Forests of Northeastern Australia1

The diet of dingoes (Canis familiaris dingo) in the Australian Wet Tropics was examined by analyzing 383 dingo scats collected throughout the region for the presence of mammal prey remains. The scats yielded 29 native and 4 introduced mammal prey species from 14 families. The most important species in terms of percentage occurrence in the scats were Melomys cervinipes (22.2%), hoodon macrourus (17.0%), Perameles nasuta (12.5%), and Thylogale stigmatica (12.5%). The most important families were Muridae (37.1%), Peramelidae (29.5%), and Macropodidae (25.8%). Examination of small‐scale habitat preferences revealed species that preferentially use the forest edge ranked significantly higher in the diet than those that do not, and species that are terrestrial ranked higher in the diet than those that are arboreal. Relative abundance was also a significant factor in the ranked dietary occurrence of each species, with abundant species ranked significantly higher than those that are less abundant. These results suggest that dingoes in the Australian Wet Tropics are opportunistic predators of a wide variety of mammal species, with abundant terrestrial and forest edge‐dwelling taxa the most susceptible to predation.     

Flow velocity underpins microhabitat selection by gobies of the Australian Wet Tropics

1. Water flow is a critical driver of aquatic ecosystem health and function. Amid rising concerns over changing flow regimes, there is an urgent need to understand the functional mechanisms by which flow influences patterns of freshwater biodiversity. 2. We explored the functional link between flow velocity and microhabitat specialisation in a speciose group of freshwater gobies (comprising over half the total fish species richness) within insular streams of the Australian Wet Tropics under base flow conditions. We addressed two particular questions: (i) What is the relative selectivity of species towards streambed composition and water flow velocity? and (ii) Can patterns of microhabitat occupation be explained by differences in intrinsic flow performance among species? To answer these questions, we combined visual field observations of microhabitat use with flow tank assessments of flow speed performance. 3. Tropical freshwater gobies displayed strong specificity towards flow velocities, while being relatively non‐selective towards streambed composition. At opposite extremes of the spectrum, we found Sicyopterus lagocephalus occupying high‐flow (>1.0 ms^?1) microhabitats while Redigobius bikolanus selected slower‐flow (<0.05 ms^?1) areas. These patterns of microhabitat flow specificity were largely explained by the different abilities of species to swim and/or cling to the substratum under these different flow settings. 4. Our findings confirm suggestions that predictable base flows in tropical streams support habitat specialists, which include one species capable of occupying areas of extremely high flow that very few other fishes can withstand. 5. The functional link between flow and gobioid fish distribution patterns could occur throughout tropical streams of the Indo‐Pacific and Caribbean as a widespread phenomenon that may help inform stream flow management guidelines to maintain this substantial component of tropical freshwater biodiversity around the globe.     

The effects of land use change on native dung beetle diversity and function in Australia's Wet Tropics

The impacts of land use change on biodiversity and ecosystem functions are variable, particularly in fragmented tropical rainforest systems with high diversity. Dung beetles (Scarabaeinae) are an ideal group to investigate the relationship between land use change, diversity and ecosystem function as they are easily surveyed, sensitive to habitat modification and perform many ecosystem functions. Although this relationship has been investigated for dung beetles in some tropical regions, there has been no study assessing how native dung beetles in Australia's tropical rainforests respond to deforestation, and what the corresponding consequences are for dung removal (a key ecosystem function fulfilled by dung beetles). In this study we investigated the relationship between dung beetle community attributes (determined through trapping) and function (using dung removal experiments that allowed different dung beetle functional groups to access the dung) in rainforest and cleared pasture in a tropical landscape in Australia's Wet Tropics. Species richness, abundance and biomass were higher in rainforest compared to adjacent pasture, and species composition between these land use types differed significantly. However, average body size and evenness in body size were higher in pasture than in rainforest. Dung removal was higher in rainforest than in pasture when both functional groups or tunnelers only could access the dung. Increased dung removal in the rainforest was explained by higher biodiversity and dominance of a small number of species with distinct body sizes, as dung removal was best predicted by the evenness in body size of the community. Our findings suggest that functional traits (including body size and dung relocation behaviour) present in a dung beetle community are key drivers of dung removal. Overall, our results show that deforestation has reduced native dung beetle diversity in Australian tropical landscapes, which negatively impacts on the capacity for dung removal by dung beetles in this region.     

Recent speciation and limited phylogeographic structure in Mixophyes frogs from the Australian Wet Tropics

Through a combination of macroecological, paleoecological, and phylogeographical analyses, the rainforests of the Australian Wet Tropics (AWT) have emerged as a useful model for understanding sensitivity of species to past climatic change and, hence, for predicting vulnerability to future change. To extend the ecological breadth of comparative phylogeographic analyses, we investigate a clade of myobatrachid frogs, Mixophyes, a genus of large, stream-breeding but terrestrial frogs, three species of which are endemic to rainforests of the AWT. Here we (i) combine mtDNA, allozyme, and morphological data to refine knowledge of the geographic and environmental distribution of each taxon, (ii) resolve relationships among species, and (iii) use mtDNA phylogeography to infer responses of the three taxa to late-Pleistocene and Holocene climatic change. Each of the three species (Mixophyes carbinensis, Mixophyes coggeri, and Mixophyes schevilli) is effectively diagnosed by mtDNA, with the two small-bodied, allopatric species (M. carbinensis and M. schevilli) being sister-taxa. Mixophyes have a very different history from other AWT amphibians, with more recent speciation (net divergences <5%) and much lower and geographically unstructured mtDNA diversity within each species. The combination of low diversity (θ(Π)<0.36%) and strong signals of recent population expansion (Fu's Fs<0) suggests very high sensitivity to climate-driven rainforest dynamics, perhaps due to their large body size, low population density, and their requirement for both wet forest-floor litter and streams suitable for breeding. The results further emphasize the heterogeneity of species' responses to climate change and suggest that species dependent on multiple habitat types could be especially vulnerable.     

Dynamic refugia and species persistence: tracking spatial shifts in habitat through time

Historical climate is known to influence contemporary patterns of biological diversity. Species distribution modeling methods, combined with paleoclimatic surfaces, have been used to identify regions that were likely stable across long periods of time. To date, this approach has produced a static representation of refugia by identifying regions of suitable climate across a series of time‐slices. However, suitable habitat for a given species (or suite of species) may have shifted contiguously in response to changing climates through geologic time. We develop a new approach that takes into consideration habitat connectivity through time. We use the Australian Wet Tropics as a case study to demonstrate how our method works and suggest additional insights the method might give for understanding the determinants of biological diversity.     

Exotic vine invasions following cyclone disturbance in Australian Wet Tropics rainforests: A review

The Australian Wet Tropics region extends for almost 900 000 ha along the coastline of north‐east Queensland. The rainforests in this region have a rich and unique biodiversity and are World Heritage listed by UNESCO. Disturbance from tropical cyclones is a significant driver of the rainforest dynamics in this area, and when frequent or intense can facilitate the recruitment and expansion of exotic invasive species. Exotic vines are of particular concern for forest conservation as they can be highly competitive with native vegetation and may prevent forest regeneration. This literature review found evidence that fragmented forests, which are very common in the Australian Wet Tropics, are vulnerable to post‐cyclone vine invasion. In particular, although the diversity and abundance of herbaceous vines tend to decline as the canopy closes 2 years post‐cyclone disturbance, woody exotic vines and scramblers may persist for much longer or even increase in numbers. Since forest recovery in these systems is influenced by the severity and recurrence of disturbance, an increase in cyclone intensity under climate change may cause rapid changes in rainforest structure, composition and diversity, and increase exotic vine invasion. Post‐cyclone management of vines appears to require direct intervention, with manual cutting being currently the most effective method. However, there are a number of difficulties to its wide implementation in Australia, and further study on options for control is needed. Abstract in Spanish is available with online material.     

Problem solving of wild animals in the Wet Tropics of Queensland,Australia

While many species of animals can solve food-baited problems, most studies are conducted in captivity, which may not reflect the natural behavioural and cognitive abilities of wild animals. As few studies have explored problem solving of Australian animals generally, we investigated the problem solving abilities of native Australian species in natural rainforest in the Wet Tropics of Queensland. We baited multiple types of puzzles (matchbox task, cylinder task, and tile and lever tasks on a Trixie Dog Activity Board) with different food types (seeds, fruit, sardines) and placed the puzzles in front of trail cameras. We noted the species captured on camera, whether or not individuals interacted with the puzzles, the number of interactions with puzzles, and whether or not different animals solved them. We found that seven species from multiple taxa (mammals, birds, reptiles) could solve food-baited problems in the wild, providing the first evidence of problem solving in these native species. As problem solving may help animals cope with anthropogenic threats, these results provide some insights into which Wet Tropics species may potentially be more vulnerable and which ones might be better at coping with changing conditions.     

Basking behavior predicts the evolution of heat tolerance in Australian rainforest lizards

There is pressing urgency to understand how tropical ectotherms can behaviorally and physiologically respond to climate warming. We examine how basking behavior and thermal environment interact to influence evolutionary variation in thermal physiology of multiple species of lygosomine rainforest skinks from the Wet Tropics of northeastern Queensland, Australia (AWT). These tropical lizards are behaviorally specialized to exploit canopy or sun, and are distributed across marked thermal clines in the AWT. Using phylogenetic analyses, we demonstrate that physiological parameters are either associated with changes in local thermal habitat or to basking behavior, but not both. Cold tolerance, the optimal sprint speed, and performance breadth are primarily influenced by local thermal environment. Specifically, montane lizards are more cool tolerant, have broader performance breadths, and higher optimum sprinting temperatures than their lowland counterparts. Heat tolerance, in contrast, is strongly affected by basking behavior: there are two evolutionary optima, with basking species having considerably higher heat tolerance than shade skinks, with no effect of elevation. These distinct responses among traits indicate the multiple selective pressures and constraints that shape the evolution of thermal performance. We discuss how behavior and physiology interact to shape organisms’ vulnerability and potential resilience to climate change.     

Altitudinal patterns of moth diversity in tropical and subtropical Australian rainforests

Altitudinal gradients are an excellent study tool to help understand the mechanisms shaping community assembly. We established a series of altitudinal gradients along the east coast of Australia to describe how the distribution of a hyper‐diverse herbivore group (night‐flying Lepidoptera) changes across an environmental gradient in subtropical and tropical rainforests. Two transects were in subtropical rainforest in the same bioregion, one in south‐east Queensland (28.7°S) and one in north east New South Wales (29.7°S). Two were in tropical rainforest, one in mid‐east Queensland (21.1°S) and one in the Wet Tropics of northern Queensland (17.5°S). Replicate plots were established in altitudinal bands separated by 200 m. Canopy and understorey moths were sampled at the beginning and end of the wet season using automatic Pennsylvania light traps. We sorted a total of 93 400 individuals, belonging to 3035 species. The two subtropical transects in the same region showed similar patterns of turnover across altitude, with the most distinctive assemblage occurring at the highest altitude. Moth assemblages in the tropical transects tended to show distinct ‘lowland’ and ‘upland’ communities. For species that were common across several of the transects, many were found at lower altitudes in the subtropics and higher altitudes in the tropics, suggesting they are sensitive to environmental conditions, and track their physiological envelopes across latitudes. These results suggest ubiquitous altitudinal stratification in tropical and subtropical Australian rainforests. The marked response of species to latitude and altitude demonstrates they are sensitive to climatic variables and can be used as indicators to understand future community responses to climate change.