School of Geography - Research Publications
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ItemHydrological controls on oviposition habitat are associated with egg-laying phenology of some caddisflies(WILEY, 2021-07)Abstract Seasonal variation in resource availability can have strong effects on life histories and population densities. Emergent rocks (ERs) are an essential oviposition resource for multiple species of stream insects. The availability of ERs depends upon water depth and clast size, which vary with discharge and river geomorphology, respectively. Recruitment success for populations may depend on whether peak egg‐laying periods occur at times when ERs are also abundant. For multiple species that oviposit on ERs, we tested whether seasonal fluctuations in ER abundance were concurrent with oviposition phenology. We also tested whether high discharge drowned ERs for sufficiently long periods to preclude egg laying, and whether this problem varied between rivers differing in channel morphology and particle size distribution. We obtained a continuous timeseries of water level (WL) measured every 30 min for 2 years at sites on three rivers in south‐eastern Australia with similar hydrology but different geomorphology. A relationship between WL and ER numbers was determined empirically at each site and these relationships were used to predict ER availability over the 2 years. Egg masses of 10 species of caddisflies were enumerated each month for a year in one river to establish oviposition phenology. Abundance of ERs was inversely related to discharge in all three rivers. ERs were most abundant during autumn and scarce during spring. Site‐specific geomorphology resulted in skewed or multimodal distributions of ER abundance each year. Between years, catchment‐scale hydrometeorology mediated patterns of ER availability, despite the close proximity of sites. Temporal variance in ER availability was not consistently correlated with mean WL or WL variance. ER variance increased with WL variance, when WL was below a threshold equivalent to mean annual WL. Above this threshold, most ERs were likely to be submerged. Oviposition phenology varied strongly among the 10 species of caddisflies, with egg‐laying ranging from 1–2 months to year‐round. Temporal variations in ER and egg mass abundance were not correlated for most species. Below a threshold minimum number of ERs, egg masses were highly crowded onto the few available ERs, which is evidence that ERs were in short supply. For five species, high egg mass abundance was positively associated with periods of the year when the time above the threshold number of ERs was high. Unusually, two species laid most egg masses during winter and when the time above this threshold was short. Three species showed no association between egg mass abundance and time above this threshold; two of these species laid eggs year‐round. Regional hydrometeorology controlled the availability of ERs, but between‐river differences were sufficient to deliver different outcomes in the availability of oviposition sites between years and seasons. Caddisflies were rarely prevented from laying eggs but periods when ERs were in short supply created crowding, which may be associated with negative fitness effects on hatching larvae. Geomorphological controls on availability of oviposition resources may have strong implications for the coexistence of species that overlap in egg‐laying phenology.
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ItemCapturing geomorphologial patterns in ecological resources: fractal dimensions describe fluvial rock distributions( 2020-12-02)Oral presentation at the annual meeting of the Ecological Society of Australia in December 2020
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ItemExplaining species diversity in a fractal world( 2020-12-01)Oral presentation at the annual meeting of the Ecological Society of Australia, Dec 2020
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ItemA novel method reveals how channel retentiveness and stocks of detritus (CPOM) vary among streams differing in bed roughness(Wiley, 2020-08)1. Coarse particulate organic matter (CPOM) is a fundamental resource in freshwater streams, providing food, shelter and habitat for diverse invertebrate taxa and playing a key role in metabolism in low‐order streams. Benthic CPOM stocks are determined by rates of supply and breakdown of detritus and by channel retentiveness (i.e. the capacity for the channel to trap and retain CPOM). We focussed on factors affecting the retentiveness of channels, which theoretically differs among streams with different sediment sizes and concomitant channel morphology. 2. We developed a new, rapid method to measure retentiveness using line‐intercept surveys along transects. With this rapid approach, we surveyed 32 sites from three types of streams (smooth sandy channels, n = 10; gravel channels of intermediate roughness, n = 12; rough cobble channels, n = 10) in Victoria, south‐eastern Australia, and tested the simple hypotheses that: (1) retentiveness increases in channels with increasing channel roughness (i.e. sandy versus gravel versus cobble‐bed streams); (2) different types of channel features (e.g. log jams, cobbles, depositional areas) differ in the efficiency with which they retain CPOM. The line‐intercept survey method was readily adapted to measure retentiveness as m of retentive structure per m of transect (i.e. the Linear Coverage Index) and trapping efficiency as m of CPOM per m of retentive element, for 10 different types of retentive elements. 3. Unexpectedly, the retentiveness of channels did not increase with channel roughness. This occurred because channels with different roughness were dominated by different types of retentive structure. Retentive structure in cobble sites was dominated by cobbles themselves, which were highly retentive in other studies but poorly retentive in our system. Gravel and sand sites had more log jams and depositional areas, such as pools and backwaters, and these features were more effective at trapping CPOM. Thus, retention of CPOM was highest in gravel and sand sites. 4. Our method provides a new tool for investigators testing hypotheses about CPOM retention in streams. The method is rapid, requires a minimum of equipment and personnel, and may be applied in any wadeable stream. Retentiveness is calculated in intuitive units that are directly comparable among sites and may have utility as variables in models of CPOM dynamics. We hope this method will open up new avenues for research that may shed light on how CPOM stocks vary among streams, with implications for diversity of aquatic fauna and ecosystem functions such as decomposition.
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ItemUsing fractal dimension to capture ecologically-relevant physical variation in streams( 2017)Abstract of the oral presentation at the Annual General Meeting of the Australian Society for Limnology in 2017.
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ItemExplaining species diversity in a fractal world( 2019)Conference presentation at the Ecological Society of America annual meeting, 2019 Also given at the Australian Freshwater Sciences Society annual meeting in 2019
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ItemEffects of dams on oviposition habitat and egg supply of caddisflies in the Murrumbidgee Irrigation Area( 2019)Conference presentation at the Australian Freshwater Sciences Society Annual Meeting in 2019
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ItemHow do female caddisflies decide where to put their eggs? An experimental test( 2019)Conference presentation at the Australian Freshwater Sciences Society Annual Meeting in 2019
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ItemCharacterizing a disease outbreak in a caddisfly community( 2019)Presentation at the Australian Freshwater Sciences Society Annual Meeting, 2019
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ItemCelebrating women conducting research in freshwater ecology ... and how the citation game is damaging them(CSIRO Publishing, 2019-01-01)We highlight women's contributions to freshwater ecology by firstly considering the historical context and gender-based barriers faced by women attempting to gain an education and secure research jobs in science over the past 100+ years. The stories of four remarkable, pioneering women in freshwater ecology (Kathleen Carpenter, Ann Chapman, Rosemary Lowe-McConnell and Ruth Patrick) illustrate the impact of barriers, emphasise the significance of their contributions and provide inspiration for the challenges ahead. Women still face barriers to participation in science, and the second part of the paper focuses on a current form of discrimination, which is citation metrics used to measure the 'quality' or 'impact' of research. We show that arguments that citation metrics reflect research quality are logically flawed, and that women are directly disadvantaged by this practice. Women are also indirectly disadvantaged in ecology because they are more likely to carry out empirical than theoretical research, and publications are generated more slowly from empirical research. Surveys of citation patterns in ecology reveal also that women are less likely to be authors of review papers, which receive three times more citations than do original articles. Unless unfettered use of citation metrics is stopped, research will be damaged, and women will be prominent casualties.