Recent publications in Zoology and Ecology
Peace is always kinder to the environment than war. But in the South Caucasus, restoring the environment together may help strengthen peace.
Lambers, Hans, Wright, Ian J., Pereira, Caio Guilherme, Bellingham, Peter J., Bentley, Lisa Patrick, Boonman, Alex, Cernusak, Lucas A., Foulds, William, Gleason, Sean M., Gray, Emma F., Hayes, Patrick E., Kooyman, Robert M., Malhi, Yadvinder, Richardson, Sarah J., Shane, Michael W., Staudinger, Christiana, Stock, William D., Swarts, Nigel D., Turner, Benjamin L., Turner, John, Veneklaas, Erik J., Wasaki, Jun, Westoby, Mark, and Xu, Yanggui (2021) Leaf manganese concentrations as a tool to assess belowground plant functioning in phosphorus-impoverished environments. Plant and Soil: international journal on plant-soil relationships, 461. pp. 43-61.
Background and aims Root-released carboxylates enhance the availability of manganese (Mn), which enters roots through transporters with low substrate specificity. Leaf Mn concentration ([Mn]) has been proposed as a signature for phosphorus (P)-mobilising carboxylates in the rhizosphere. Here we test whether leaf [Mn] provides a signature for root functional types related to P acquisition. Methods Across 727 species at 66 sites in Australia and New Zealand, we measured leaf [Mn] as related to root functional type, while also considering soil and climate variables. To further assess the specific situations under which leaf [Mn] is a suitable proxy for rhizosphere carboxylate concentration, we studied leaf [Mn] along a strong gradient in water availability on one representative site. In addition, we focused on two systems where a species produced unexpected results. Results Controlling for background site-specific variation in leaf [Mn] with soil pH and mean annual precipitation, we established that mycorrhizal species have significantly lower leaf [Mn] than non-mycorrhizal species with carboxylate-releasing root structures, e.g., cluster roots. In exception to the general tendency, leaf [Mn] did not provide information about root functional types under seasonally waterlogged conditions, which increase iron availability and thereby interfere with Mn-uptake capacity. Two further exceptions were scrutinised, leading to the conclusion that they were 'anomalous' in not functioning like typical species in their families, as expected according to the literature. Conclusions Leaf [Mn] variation provides considerable insights on differences in belowground functioning among co-occurring species. Using this approach, we concluded that, within typical mycorrhizal families, some species actually depend on a carboxylate-releasing P-mobilising strategy. Likewise, within families that are known to produce carboxylate-releasing cluster roots, some do not produce functional cluster roots when mature. An analysis of leaf [Mn] can alert us to such 'anomalous' species.
Rowell, Misha K., and Rymer, Tasmin L. (2021) Growth and behavioural development of the fawn-footed mosaic-tailed rat (Melomys cervinipes). Australian Mammalogy. (In Press)
The fawn-footed mosaic-tailed rat (Melomys cervinipes) is a common Australian rainforest rodent; however, little is known about the growth or behavioural development of individuals of this species. We raised mosaic-tailed rats in captivity to assess the growth and behavioural development of pups from birth until weaning. Pups developed quickly compared with some other Australian species, and there were no significant differences in growth between males and females, except for anogenital distance. The auditory meatus was open by Postnatal Day 5, and eyes were fully opened by Postnatal Day 9. All behaviours, including righting, locomotion, negative geotaxis, climbing and grip reflex, were fully developed by Postnatal Day 6. These results suggest that mosaic-tailed rats are semiprecocial in their physical and behavioural development compared with some native Australian rodent species that are found in arid environments. As females produce few, relatively well-developed young, the population has a low intrinsic rate of natural increase. This may, however, be offset by mosaic-tailed rats producing more litters per year. Understanding the biology of mosaic-tailed rats in general could provide insights into how rarer precocial species might struggle to increase in population size under increasing disturbances.
Delarue, Emma M.P., Kerr, Sarah E., and Rymer, Tasmin L. (2021) Habitat and sex effects on behaviour in fawn-footed mosaic-tailed rats (Melomys cervinipes). Australian Mammalogy, 43 (3). pp. 319-329.
Habitat complexity reflects resource availability and predation pressure - both factors that influence behaviour. We investigated whether exploratory behaviour and activity varied in fawn-footed mosaic-tailed rats (Melomys cervinipes) from two habitats that were categorised differently based on vegetation. We conducted vegetation surveys to determine structural complexity and vegetation cover, confirming that an abandoned hoop-pine (Araucaria cunninghami) plantation forest was structurally less complex, with lower vegetation cover than a variable secondary rainforest. We then tested mosaic-tailed rats from both sites in four behavioural tests designed to assess exploratory and activity behaviours (open field, novel object, light-dark box, acoustic startle), predicting that rats from the less structurally complex habitat would be less exploratory, and show lower activity. Our results provide some evidence for a contextspecific trade-off between exploratory behaviour and predation risk in rats from the abandoned hoop pine plantation, as rats were less active, and showed a freezing strategy in the light-dark box. We also found context-specific sex differences in behaviour in response to a novel object and sound. Our results suggest that small-scale variation in habitat structure and complexity, as well as sex differences, is associated with variation in behaviour, most likely through effects on resource availability and/or predation risk.
Hopkins, Jaimie M., Higgie, Megan, and Hoskin, Conrad J. (2021) Calling behaviour in the invasive Asian house gecko (Hemidactylus frenatus) and implications for early detection. Wildlife Research, 48 (2). pp. 152-162.
Context. Acoustic communication is common in some animal groups, with an underlying function typically associated with mating or territoriality. Resolving the function of calls is valuable both in terms of understanding the fundamental biology of the species and, potentially, for applied reasons such as detection. Early detection is a key step in exclusion and eradication of invasive species, and calling behaviour can be used in this regard. The Asian house gecko (Hemidactylus frenatus) is one of a minority of lizards that uses acoustic communication. However, despite how conspicuous the call is, its function remains poorly resolved. It is also one of the world's most invasive species, with exclusion via early detection being the key form of control. Aims. The aim was to resolve calling patterns and underlying function of the loud, multiple-chirp call ('chik, chik, chiky') in H. frenatus, in the context of using the results for developing effective methods for detection of new and establishing populations. Methods. The calls of wild H. frenatus were recorded to assess peaks in calling activity. Also, laboratory experiments were performed to determine which individuals call, what causes them to call and the degree of call variation among individuals. Key results. Assessment of calling behaviour in the wild revealed greater calling activity in warmer months, and five- to 10-fold peaks in calling activity at sunset and 30 min before sunrise. Laboratory experiments revealed that calls were uttered exclusively by males and primarily by adults (although juveniles can call). Males called more when they were paired with females as opposed to other males. Calls differed among geckos, including the expected negative correlation between dominant frequency and body size. Conclusions. The results suggest that the multiple-chirp call functions as a territory or sexual broadcast by males, perhaps containing information such as body size. Implications. Detection success can be maximised by performing acoustic surveys (by human or machine) during the calling peaks at 30 min before sunrise and at sunset, particularly during warm nights. However, these surveys will only be effective for detecting adult males. The results also suggest that good quality recordings could potentially be used to identify individual geckos.
Pillay, Neville, and Rymer, Tasmin L. (2021) Sons benefit from paternal care in African striped mice. Developmental Psychobiology. (In Press)
Mammalian paternal care is rare and is often linked to enhanced fitness under particular ecological conditions. The proximate consequences of paternal care on offspring are lacking, however. Here, we tested whether levels of paternal care predict the behavioural, cognitive and physiological development of sons in the naturally paternal African striped mouse (Rhabdomys pumilio). We focused on sons raised in two treatments: biparental (both parents) or uniparental (mother alone) families. We recorded levels of interactions between pups with both parents, and later assessed the behaviour, cognition and physiology of sons at three developmental stages: juvenile, sub-adult and adult (sexual maturity). Sons from biparental families showed (a) reduced anxiety as juveniles; (b) greater exploration and social interaction at different stages; (c) better cognition; and (d) reduced corticosterone concentrations than sons from uniparental families. In contrast, sons from uniparental families showed greater levels of paternal care, although prolactin concentrations did not differ between treatments. Paternal care in striped mice enhances fitness of males. Here, we also show that sons benefit psychologically and physiologically through interactions with their fathers. However, sons also trade-off such benefits against their own paternal care behaviour, suggesting that fathers influence the development of their son's phenotype in complex ways.
Jeffs, Christopher T., Terry, J. Christopher D., Higgie, Megan, Jandová, Anna, Konvičková, Hana, Brown, Joel J., Lue, Chia Hua, Schiffer, Michele, O'Brien, Eleanor, Bridle, Jon, Hrcek, Jan, and Lewis, Owen T. (2021) Molecular analyses reveal consistent food web structure with elevation in rainforest Drosophila – parasitoid communities. Ecography, 44 (3). pp. 403-413.
The analysis of interaction networks across spatial environmental gradients is a powerful approach to investigate the responses of communities to global change. Using a combination of DNA metabarcoding and traditional molecular methods we built bipartite Drosophila-parasitoid food webs from six Australian rainforest sites across gradients spanning 850 m in elevation and 5° Celsius in mean temperature. Our cost-effective hierarchical approach to network reconstruction separated the determination of host frequencies from the detection and quantification of interactions. The food webs comprised 5-9 host and 5-11 parasitoid species at each site, and showed a lower incidence of parasitism at high elevation. Despite considerable turnover in the relative abundance of host Drosophila species, and contrary to some previous results, we did not detect significant changes to fundamental metrics of network structure including nestedness and specialisation with elevation. Advances in community ecology depend on data from a combination of methodological approaches. It is therefore especially valuable to develop model study systems for sets of closely-interacting species that are diverse enough to be representative, yet still amenable to field and laboratory experiments.
Woodworth, Bradley K., Fuller, Richard A., Hemson, Graham, McDougall, Andrew, Congdon, Bradley C., and Low, Matthew (2021) Trends in seabird breeding populations across the Great Barrier Reef. Conservation Biology. (In Press)
The Great Barrier Reef is an iconic ecosystem, known globally for its rich marine biodiversity that includes many thousands of tropical breeding seabirds. Despite indications of localised declines in some seabird species from as early as the mid‐1990s, trends in seabird populations across the Reef have never been quantified. With a long history of human impact and ongoing environmental change, seabirds are likely sentinels in this important ecosystem. Using four decades of monitoring data, we estimated site‐specific trends for nine seabird species from 32 islands and cays across the Reef. Trends varied markedly among species and sites, but probable declines occurred at 45% of the 86 species‐by‐site combinations analysed compared to increases at 14%. For five species we combined site‐specific trends into a multi‐site trend in scaled abundance, which revealed probable declines of common noddy (Anous stolidus), sooty tern (Onychoprion fuscatus), and masked booby (Sula dactylatra), but no long‐term changes in the two most widely distributed species, greater crested tern (Thalasseus bergii) and brown booby (Sula leucogaster). For brown booby, long‐term stability largely resulted from increases at a single large colony on East Fairfax Island that offset declines at a majority of other sites. While growth of the brown booby population at East Fairfax points to the likely success of habitat restoration on the island, it also highlights a general vulnerability wherein large numbers of some species are concentrated at a small number of key sites. Identifying drivers of variation in population change across species and sites while ensuring long‐term protection of key sites will be essential to securing the future of seabirds on the Reef.
Palma, Ana C., Goosem, Miriam, Fensham, Roderick J., Goosem, Steve, Preece, Noel D., Stevenson, Pablo R., and Laurance, Susan G.W. (2021) Dispersal and recruitment limitations in secondary forests. Journal of Vegetation Science. e12975. (In Press)
Aims: Secondary forests are expanding rapidly in tropical regions and could play an important role in conserving native biodiversity and stabilising global climate. The recovery rate of plant communities in secondary forests varies considerably due to mechanisms associated with seed dispersal and recruitment dynamics. We explored these mechanisms along a chronosequence of tropical secondary forests in an agricultural landscape that was extensively cleared. Location: We explored these mechanisms along a chronosequence of secondary forests in tropical Australia. Methods: We used selected plant traits to characterise plant species and compared community composition between demographic stages (i.e. soil seedbank, understorey and overstorey) and forest age categories. We collected soil samples to assess seedbank composition and used quadrants and transects to assess understorey and overstorey plant community composition at each site. Results: For all demographic stages, we found that young (4-12 years) and intermediate-aged forests (16-20 years) were dominated by early successional, small-seeded species and traits associated with disturbed forests. In old secondary forest (23-34 years) some traits associated with late successional stages were present (e.g. large seeds, trees). However, the traits and species composition of mature forests remained distinct from all secondary forests. Across the chronosequence, forest age and demographic stage were significant factors in discriminating species and trait composition between forest sites. We found clear plant community similarities within demographic stages, despite the forest age differences. This suggests stronger limitations to dispersal and recruitment between demographic stages than between forest ages. Conclusions: Our results show that secondary forests in this region assemble slowly with dispersal and recruitment limitations constraining their recovery. Although a successional transition in species and plant traits composition along the chronosequence is clear, similarities to mature forests remain low. The slow recovery of late successional and large-seeded species in these secondary forests suggests that active restoration of such species may be necessary if we want to enhance the capacity of these forests to conserve native biodiversity.
Yeeles, Peter, Strain, Angela, Lenancker, Pauline, and Lach, Lori (2021) Low reduction of invasive ant colony productivity with an insect growth regulator. Pest Management Science. (In Press)
Background Insect growth regulators (IGRs) generally are considered to have safer eco-toxicological profiles than the more commonly used neurotoxins and metabolic inhibitors, and are extremely effective against several insect groups, including some invasive ant species. However, use of an IGR product in a large-scale eradication program for a widespread invasive ant (Anoploepis gracilipes; yellow crazy ant) was ineffective. We tested the IGR in question (active ingredient: (S)-methoprene) on A. gracilipes colonies in a laboratory environment to evaluate efficacy. Results We found that treatment with (S)-methoprene resulted in lower egg production with subsequently decreased numbers of larvae, pupae, and workers over the 135 days of the experiment. None of the treated colonies died, and the number of worker ants in treated colonies was 36% of that seen in control colonies 135 days post-treatment. Treated queen egg production was 39% lower than queens in control colonies, but we saw no effect of treatment on the internal physiology of dissected queens. Treatment had no effect on worker activity levels. Conclusion Our results show that although (S)-methoprene treatment reduced production of larvae, pupae and workers in treated colonies, the magnitude of reduction was lower than might be expected considering the responses of other species against which this IGR has been tested. Our findings highlight a need for testing species-specific responses to IGR-based insecticides in a controlled environment, before broad-scale field applications that could result in suboptimal management of the target species.
Katovai, Eric, Katovai, Dawnie D., and Laurance, William F. (2021) Potential restoration approaches for heavily-logged tropical forests in the Solomon Islands. In: Roberts, John Laing, Nath, Shyam, Paul, Satya, and Madhoo, Yeti Nisha, (eds.) Shaping the Future of Small Islands: Roadmap for Sustainable Development. Springer, Cham, Switzerland, pp. 219-232.
Small tropical island countries are becoming more vulnerable to forest loss due to industrial logging. These countries are mostly of lower socio-economic status and often heavily dependent on logging for economic revenue (Sloan and Sayer 2015). This scenario is highly apparent in the Solomon Islands, where log export alone contributes between 50 and 70% to the country’s annual export revenue (Katovai et al. 2015)
Rowe, Cassandra, Wurster, Christopher M., Zwart, Costijn, Brand, Michael, Hutley, Lindsay B., Levchenko, Vladimir, and Bird, Michael I. (2021) Vegetation over the last glacial maximum at Girraween Lagoon, monsoonal northern Australia. Quaternary Research, 102. pp. 39-52.
Northern Australia is a region where limited information exists on environments at the Last Glacial Maximum (LGM). Girraween Lagoon is located on the central northern coast of Australia and is a site representative of regional tropical savanna woodlands. Girraween remained a perennial waterbody throughout the LGM, and as a result retains a complete proxy record of last glacial climate, vegetation and fire. This study combines independent palynological and geochemical analyses to demonstrate a dramatic reduction in tree cover, woody richness and expansion of grassland relative to current vegetation at the site. The process of tree decline was primarily controlled by the cool-dry glacial climate and CO2 effects, though more localised site characteristics restricted wetland associated vegetation. Fire processes played less of a role determining vegetation than in the Holocene and modern day, with reduced fire activity consistent with significantly lower biomass available to burn. This unique and detailed palaeoecological record provides the opportunity to explore and assess modelling studies of vegetation distribution during the LGM, particularly where a number of different global vegetation and/or climate simulations are inconsistent for northern Australia, and at a range of resolutions.
Tol, S.J., Harrison, M., Groom, R., Gilbert, J., Blair, D., Coles, R., and Congdon, B.C (2021) Using DNA to distinguish between faeces of Dugong dugon and Chelonia mydas: non-invasive sampling for IUCN-listed marine megafauna. Conservation Genetics Resources, 13. pp. 115-117.
The Dugong dugon (dugong) and Chelonia mydas (green sea turtle) are economically and culturally significant marine mega-herbivores whose populations are declining globally. Capture of these animals for study is challenging and stressful for the animals. Ecological questions can be answered using faeces, which can be collected floating on the water’s surface. However, green turtle and dugong faeces are visually indistinguishable. Specific PCR primer pairs were developed based on the mitochondrial control region of each species. We were able to determine species of origin using DNA extracted, amplified and sequenced from faeces. This provides a valuable tool for non-invasive taxonomic identification to assist the conservation of these vulnerable and endangered species.
Rymer, Tasmin L., Cruise, Megan, and Pillay, Neville (2021) Decision-making by bushveld gerbils (Gerbilliscus leucogaster). Journal of Comparative Psychology. (In Press)
Decision-making reflects an individual’s behavioral motivation, shaped by intrinsic and extrinsic factors. We investigated the motivation and decision-making to forage in captive bushveld gerbils (Gerbilliscus leucogaster) using an individually tailored experimental protocol. Individual gerbils were subjected to 4 experiments, where we assessed behavior and decision-making in response to: (a) food quality when resources were clumped (Experiment 1), (b) food quality when resources were scattered (Experiment 2), (c) changing food distribution (clumped vs. scattered; Experiment 3), and (d) predation risk. Each experiment comprised 4 treatments, where both cost (a weighted door) and incentive (preferred vs. nonpreferred seeds; clumped vs. scattered seeds) varied according to the mass and personal preferences of individual gerbils. We counted the number of seeds eaten, assessed the frequency of door usage, and measured the duration of exploration, vigilance, and foraging (as a proportion of total time) of gerbils in each experiment. Gerbils showed individual preferences for different seed types although all preferred sunflower or sorghum seeds. Generally, gerbils ate more seeds and used the door more frequently when the costs were low. Similarly, gerbils tended to forage more when the costs were low and predation risk was low. We also found that males, in general, were more vigilant than females in Experiments 3 and 4, likely because of risk of intrasexual competition over a high-resource patch. There was considerable individual variation in behavior, but there was also consistency in most behaviors, indicating that individual gerbils perform consistently differently to other gerbils.
Maxwell, Stephen J., Rymer, Tasmin L., Rowell, Misha K., Hernandez Duran, Linda C., Berschauer, David, Underdown, Michael, Petuch, Edward J., and Dekkers, Aart (2021) Deﬁning and bringing relevance of meaning to species group-level taxa. Proceedings of the Biological Society of Washington, 134. pp. 27-28.
[Extract] A definition for differing terminal taxa in nomenclature is needed to make them practically relevant. The International Commission of Zoological Nomenclature(1999) provides for two levels: species and subspecies. At present species and subspecies are used interchangeably and arbitrarily. We examine both concepts, with a focus on practical applications of these terms.
Ely, Kim S., Rogers, Alistair, Agarwal, Deborah A., Ainsworth, Elizabeth A., Albert, Loren P., Ali, Ashehad, Anderson, Jeremiah, Aspinwall, Michael J., Bellasio, Chandra, Bernacchi, Carl, Bonnage, Steve, Buckley, Thomas N., Bunce, James, Burnett, Angela C., Busch, Florian A., Cavanagh, Amanda, Cernusak, Lucas A., Crystal-Ornelas, Robert, Damerow, Joan, Davidson, Kenneth J., De Kauwe, Martin G., Dietze, Michael C, Domingues, Tomas F., Dusenge, Mirindi Eric, Ellsworth, David S., Evans, John R., Gauthier, Paul P.G., Gimenez, Bruno O., Gordon, Elizabeth P., Gough, Christopher M., Halbritter, Aud H., Hanson, David T., Heskel, Mary, Hogan, J. Aaron, Hupp, Jason R., Jardine, Kolby, Kattge, Jens, Keenan, Trevor, Kromdijk, Johannes, Kumarathunge, Dushan P., Lamour, Julien, Leakey, Andrew D.B., LeBauer, David S., Li, Qianyu, Lundgren, Marjorie R., McDowell, Nate, Meacham-Hensold, Katherine, Medlyn, Belinda E., Moore, David J.P., Negrón-Juárez, Robinson, Niinemets, Ülo, Osborne, Colin P., Pivovaroff, Alexandria L., Poorter, Hendrik, Reed, Sasha C., Ryu, Youngryel, Sanz-Saez, Alvaro, Schmiege, Stephanie C., Serbin, Shawn P., Sharkey, Thomas D., Slot, Martijn, Smith, Nicholas G., Sonawane, Balasaheb V., South, Paul F., Souza, Daisy C., Stinziano, Joseph Ronald, Stuart-Haëntjens, Ellen, Taylor, Samuel H., Tejera, Mauricio D., Uddling, Johan, Vandvik, Vigdis, Varadharajan, Charuleka, Walker, Anthony P., Walker, Berkley J., Warren, Jeffrey M., Way, Danielle A., Wolfe, Brett T., Wu, Jin, Wullschleger, Stan D., Xu, Chonggang, Yan, Zhengbing, and Yang, Dedi (2021) A reporting format for leaf-level gas exchange data and metadata. Ecological Informatics, 61. 101232.
Leaf-level gas exchange data support the mechanistic understanding of plant fluxes of carbon and water. These fluxes inform our understanding of ecosystem function, are an important constraint on parameterization of terrestrial biosphere models, are necessary to understand the response of plants to global environmental change, and are integral to efforts to improve crop production. Collection of these data using gas analyzers can be both technically challenging and time consuming, and individual studies generally focus on a small range of species, restricted time periods, or limited geographic regions. The high value of these data is exemplified by the many publications that reuse and synthesize gas exchange data, however the lack of metadata and data reporting conventions make full and efficient use of these data difficult. Here we propose a reporting format for leaf-level gas exchange data and metadata to provide guidance to data contributors on how to store data in repositories to maximize their discoverability, facilitate their efficient reuse, and add value to individual datasets. For data users, the reporting format will better allow data repositories to optimize data search and extraction, and more readily integrate similar data into harmonized synthesis products. The reporting format specifies data table variable naming and unit conventions, as well as metadata characterizing experimental conditions and protocols. For common data types that were the focus of this initial version of the reporting format, i.e., survey measurements, dark respiration, carbon dioxide and light response curves, and parameters derived from those measurements, we took a further step of defining required additional data and metadata that would maximize the potential reuse of those data types. To aid data contributors and the development of data ingest tools by data repositories we provided a translation table comparing the outputs of common gas exchange instruments. Extensive consultation with data collectors, data users, instrument manufacturers, and data scientists was undertaken in order to ensure that the reporting format met community needs. The reporting format presented here is intended to form a foundation for future development that will incorporate additional data types and variables as gas exchange systems and measurement approaches advance in the future. The reporting format is published in the U.S. Department of Energy's ESS-DIVE data repository, with documentation and future development efforts being maintained in a version control system.
Hopkins, Jaimie M., Edwards, Will, Laguna, Juan Mula, and Schwarzkopf, Lin (2021) An endangered bird calls less when invasive birds are calling. Journal of Avian Biology, 52 (1). e02642.
Novel noises can affect various animal behaviours, and changes to vocal behaviour are some of the most documented. The calls of invasive species are an important source of novel noise, yet their effects on native species are poorly understood. We examined the effects of invasive bird calls on the vocal activity of an endangered Australian finch to investigate whether: 1) native finch calling behaviour was affected by novel invasive bird calls, and 2) the calls of the finches overlapped in frequency with those of invasive birds. We exposed a wild population of black-throated finch southern subspecies Poephila cincta cincta to the vocalisations of two invasive birds, nutmeg mannikins Lonchura punctulata and common mynas Acridotheres tristis, a synthetic 'pink' noise, and a silent control. To determine whether the amount of black-throated finch calling differed in response to treatments, we recorded and quantified black-throated finch vocalisations, and assessed the amount of calling using a generalised linear mixed model followed by pairwise comparisons. We also measured, for both black-throated finches and the stimulus noises: dominant, minimum and maximum frequency, and assessed the degree of frequency overlap between black-throated finch calls and stimulus noises. Compared to silent controls, black-throated finches called less when exposed to common myna calls and pink noise, but not to nutmeg mannikin calls. We also found that pink noise overlapped most in frequency with black-throated finch calls. Common myna calls also somewhat overlapped the frequency range of black-throated finch calls, whereas nutmeg mannikin calls overlapped the least. It is possible that masking interference is the mechanism behind the reduction in calling in response to common myna calls and pink noise, but more work is needed to resolve this. Regardless, these results indicate that the calls of invasive species can affect the behaviour of native species, and future research should aim to understand the scope and severity of this issue.
Aguirre-Gutiérrez, Jesús, Rifai, Sami, Shenkin, Alexander, Oliveras, Imma, Bentley, Lisa Patrick, Svátek, Martin, Girardin, Cécile A.J., Both, Sabine, Riutta, Terhi, Berenguer, Erika, Kissling, W. Daniel, Bauman, David, Raab, Nicolas, Moore, Sam, Farfan-Rios, William, Figueiredo, Axa Emanuelle Simões, Reis, Simone Matias, Ndong, Josué Edzang, Ondo, Fidèle Evouna, N'ssi Bengone, Natacha, Mihindou, Vianet, Moraes de Seixas, Marina Maria, Adu-Bredu, Stephen, Abernethy, Katharine, Asner, Gregory P., Barlow, Jos, Burslem, David F.R.P., Coomes, David A., Cernusak, Lucas A., Dargie, Greta C., Enquist, Brian J., Ewers, Robert M., Ferreira, Joice, Jeffery, Kathryn J., Joly, Carlos A., Lewis, Simon L., Marimon-Junior, Ben Hur, Martin, Roberta E., Morandi, Paulo E., Phillips, Oliver L., Quesada, Carlos A., Salinas, Norma, Schwantes Marimon, Beatriz, Silman, Miles, Teh, Yit Arn, White, Lee J.T., and Malhi, Yadvinder (2021) Pantropical modelling of canopy functional traits using Sentinel-2 remote sensing data. Remote Sensing of Environment, 252. 112122.
Tropical forest ecosystems are undergoing rapid transformation as a result of changing environmental conditions and direct human impacts. However, we cannot adequately understand, monitor or simulate tropical ecosystem responses to environmental changes without capturing the high diversity of plant functional characteristics in the species-rich tropics. Failure to do so can oversimplify our understanding of ecosystems responses to environmental disturbances. Innovative methods and data products are needed to track changes in functional trait composition in tropical forest ecosystems through time and space. This study aimed to track key functional traits by coupling Sentinel-2 derived variables with a unique data set of precisely located in-situ measurements of canopy functional traits collected from 2434 individual trees across the tropics using a standardised methodology. The functional traits and vegetation censuses were collected from 47 field plots in the countries of Australia, Brazil, Peru, Gabon, Ghana, and Malaysia, which span the four tropical continents. The spatial positions of individual trees above 10 cm diameter at breast height (DBH) were mapped and their canopy size and shape recorded. Using geo-located tree canopy size and shape data, community-level trait values were estimated at the same spatial resolution as Sentinel-2 imagery (i.e. 10 m pixels). We then used the Geographic Random Forest (GRF) to model and predict functional traits across our plots. We demonstrate that key plant functional traits can be accurately predicted across the tropicsusing the high spatial and spectral resolution of Sentinel-2 imagery in conjunction with climatic and soil information. Image textural parameters were found to be key components of remote sensing information for predicting functional traits across tropical forests and woody savannas. Leaf thickness (R2 = 0.52) obtained the highest prediction accuracy among the morphological and structural traits and leaf carbon content (R2 = 0.70) and maximum rates of photosynthesis (R2 = 0.67) obtained the highest prediction accuracy for leaf chemistry and photosynthesis related traits, respectively. Overall, the highest prediction accuracy was obtained for leaf chemistry and photosynthetic traits in comparison to morphological and structural traits. Our approach offers new opportunities for mapping, monitoring and understanding biodiversity and ecosystem change in the most species-rich ecosystems on Earth.
Timmiss, Libby A., Martin, John M., Murray, Nicholas J., Welbergen, Justin A., Westcott, David, McKeown, Adam, and Kingsford, Richard T. (2021) Threatened but not conserved: flying-fox roosting and foraging habitat in Australia. Australian Journal of Zoology. (In Press)
Conservation relies upon a primary understanding of changes in a species' population size, distribution, and habitat use. Bats represent about one in five mammal species in the world, but understanding for most species is poor. For flying-foxes, specifically the 66 Pteropus species globally, 31 are classified as threatened (Vulnerable, Endangered, Critically Endangered) on the IUCN Red List. Flying-foxes typically aggregate in colonies of thousands to hundreds of thousands of individuals at their roost sites, dispersing at sunset to forage on floral resources (pollen, nectar, and fruit) in nearby environments. However, understanding of flying-fox roosting habitat preferences is poor, hindering conservation efforts in many countries. In this study, we used a database of 654 known roost sites of the four flying-fox species that occur across mainland Australia to determine the land-use categories and vegetation types in which roost sites were found. In addition, we determined the land-use categories and vegetation types found within the surrounding 25 km radius of each roost, representing primary foraging habitat. Surprisingly, for the four species most roosts occurred in urban areas (42-59%, n = 4 species) followed by agricultural areas (21-31%). Critically, for the two nationally listed species, only 5.2% of grey-headed and 13.9% of spectacled flying-fox roosts occurred in habitat within protected areas. Roosts have previously been reported to predominantly occur in rainforest, mangrove, wetland, and dry sclerophyll vegetation types. However, we found that only 20-35% of roosts for each of the four species occurred in these habitats. This study shows that flying-fox roosts overwhelmingly occurred within human-modified landscapes across eastern Australia, and that conservation reserves inadequately protect essential habitat of roosting and foraging flying-foxes.
Gely, Claire, Laurance, Susan G. W., and Stork, Nigel E. (2021) The effect of drought on wood-boring in trees and saplings in a tropical forest. Forest Ecology and Management, 489. 119078.
Droughts are predicted to increase in severity in many regions due to climate change and there is strong evidence that such events can lead to increased insect attack and consequent widespread tree mortality in temperate forests. Much less is known about the impact of increased drought on tropical rainforests but in the few largescale drought manipulation experiments in tropical rainforests, larger trees had higher mortality rates than smaller trees although the cause of death is often uncertain. Previously, we modelled what the impact of drought might be on different types of herbivorous insects and suggested that in rainforests severe drought conditions might lead to increased attack from wood-boring insects. We tested this in a drought manipulation experiment, in Australian tropical rainforest, where we excluded more than 30% of rainfall for two years prior to our study and during it. We compared wood-boring damage of small and large trees between the experiment and a nearby control site. We hypothesized that larger trees would experience greater wood boring whereas smaller trees would present more surface damage. We surveyed 1,778 trees in total across both plots and found that the proportion of trees with termites, hole boring, and surface damage caused by borers (lateral tracks, frass, resin, latex or kino exudation) was significantly higher at the drought plot than at the control plot. There was a significant difference in the proportion of trees with fresh wood-boring damage at the drought site (35%) than at the control site (23%). While all size classes of trees had a higher percentage of fresh wood-boring damage at the drought site compared to control site this was only significant for small trees (dbh < 10 cm). The lack of significant difference for medium sized trees (dbh > 10 cm &<20 cm) and large trees (dbh > 20 cm) may be due to small sample size. Recent termite activity and termite damage was also significantly more frequent in the drought site compared to the control. We conclude that increased severity of drought appears to drive fundamental changes in borer and termite infestation levels with potentially important consequences for long-term tree health and mortality. Increases in tree mortality elevates the risk of forest fires, which are normally rare events in rainforests. Determining which wood boring beetles are responsible for the increased infestation requires further investigation since more than 100 wood-boring beetle species have been collected previously at the study site, including species of Platypodinae, Scolytinae, Anobiidae and Cerambycidae.
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