Citizen science is on the rise, with growing numbers of initiatives, participants and increasing interest from the broader scientific community. iNaturalist is an example of a successful citizen ...science platform that enables users to opportunistically capture and share biodiversity observations. Understanding how data from such opportunistic citizen science platforms compare with and complement data from structured surveys will improve their use in future biodiversity research. We compared the opportunistic fish photographs from iNaturalist to those obtained from structured surveys at eight study reefs in Sydney, Australia over twelve years. iNaturalist recorded 1.2 to 5.5 times more fish species than structured surveys resulting in significantly greater annual species richness at half of the reefs, with the remainder showing no significant difference. iNaturalist likely recorded more species due to having simple methods, which allowed for broad participation with substantially more iNaturalist observation events (e.g., dives) than structured surveys over the same period. These results demonstrate the value of opportunistic citizen science platforms for documenting fish species richness, particularly where access and use of the marine environment is common and communities have the time and resources for expensive recreational activities (i.e., underwater photography). The datasets also recorded different species composition with iNaturalist recording many rare, less abundant, or cryptic species while the structured surveys captured many common and abundant species. These results suggest that integrating data from both opportunistic and structured data sources is likely to have the best outcome for future biodiversity monitoring and conservation activities.
The thermal response of the amphipod Sunamphitoe parmerong was contrasted between unacclimated ‘wild’ and acclimated populations. Brooding females were allocated to 17 °C or 23 °C treatments and ...their progeny developed to adulthood at the same temperature. Tolerance to acute thermal challenge (26–36 °C) was determined. The 17 °C and 23 °C acclimated S. parmerong had a 0.45 and 0.64 risk of death compared to the unacclimated individuals. The upper lethal temperature (LT50) was 27.4 °C for the unacclimated group and 29.6 °C and 30.4 °C for the 17 °C and 23 °C acclimated groups, respectively. Acclimation shifted their LT50 by 2.2 °C and 3 °C, respectively. The wild population exhibited high variability in thermal tolerance, potentially due to their environmental history and greater diversity of genotypes. After acclimation S. parmerong had decreased variability in thermal tolerance and that of the 23 °C group shifted by 1 °C compared with the 17 °C group. These results indicate developmental phenotypic plasticity or differential survival of resilient progeny as potential mechanisms to facilitate persistence in a warming ocean.
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•Warm acclimation of amphipods from embryo to adult increased thermal tolerance.•Adjusted thermal response indicated developmental plasticity.•Wild population exhibited high variability in thermal tolerance.•Acclimation decreased the variability in thermal tolerance.•Carryover effects across development at a stable temperature.
The impacts invasive species have on biodiversity and ecosystem function globally have been linked to the higher abundances they often obtain in their introduced compared to native ranges. Higher ...abundances of invaders in the introduced range are often explained by a reduction in negative species interactions in that range, although results are equivocal. The role of positive interactions in explaining differences in the abundance of invaders between native and invasive ranges has not been tested. Using biogeographic surveys, we showed that the rocky shore porcelain crab, Petrolisthes elongatus, was ~4 times more abundant in its introduced (Tasmania, Australia) compared to its native (New Zealand) range. The habitat of these crabs in the invaded range (underside of intertidal boulders) was extensively covered with the habitat-forming tubeworm Galeolaria caespitosa. We tested whether the habitat provided by the tubeworm facilitates a higher abundance of the invasive crab by creating mimics of boulders with and without the tubeworm physical structure and measured crab colonisation into these habitats at three sites in both Tasmania and New Zealand. Adding the tubeworm structure increased crab abundance by an average of 85% across all sites in both ranges. Our intercontinental biogeographic survey and experiment demonstrate that native species can facilitate invader abundance and that positive interactions can be important drivers of invasion success.
Aim
As urban areas continue to expand, it is increasingly important to quantify species‐specific responses to urban environments, and how these change across the full annual cycle. Our objective was ...to quantify urban tolerance for North American birds across the time. We tested (a) whether intra‐annual variability of urban tolerance differed between migrants and residents and (b) whether intra‐annual variability of urban tolerance was phylogenetically conserved. We then assessed how the relationship between ecological and life history traits and urban tolerance differed both across the year and between migrants and residents.
Location
North America.
Taxon
Birds.
Methods
We integrated a large citizen science dataset of observations for 237 bird species, remotely sensed VIIRS night‐time lights data, and trait data on each species. We estimate, for each species and each month of the year, a continuous measure of urban tolerance (i.e. the median of their distribution of observations across an urbanization gradient). We then use phylogenetic linear models to assess the relationship between this measure of urban tolerance and various life history and ecological traits.
Results
There was a distinct drop in the overall urban tolerance scores corresponding with the breeding period; this pattern was more pronounced for migrants compared to residents. Migrants also had greater intra‐annual variability than resident species. We also found that the strength of the relationships between ecological and life history traits and urban tolerance was highly seasonal for most traits considered, and some divergent patterns were noted between migrants and residents.
Main conclusions
The urban tolerance of birds greatly changed throughout the annual cycle, with different patterns for migrants and residents. Compared to residents, migrants showed more intra‐annual variability of urban tolerance with a drop in the average urban tolerance score during the breeding season. Together, our results suggest that urban tolerance is a function of both species and season, and they highlight the importance of considering the dynamic nature of birds' use of urban ecosystems throughout the full annual cycle.
Habitat‐forming organisms provide three‐dimensional structure that supports abundant and diverse communities. Variation in the morphological traits of habitat formers will therefore likely influence ...how they facilitate associated communities, either via food and habitat provisioning, or by altering predator–prey interactions. These mechanisms, however, are typically studied in isolation, and thus, we know little of how they interact to affect associated communities. In response to this, we used naturally occurring morphological variability in the alga Sargassum vestitum to create habitat units of distinct morphotypes to test whether variation in the morphological traits (frond size and thallus size) of S. vestitum or the interaction between these traits affects their value as habitat for associated communities in the presence and absence of predation. We found morphological traits did not interact, instead having independent effects on epifauna that were negligible in the absence of predation. However, when predators were present, habitat units with large fronds were found to host significantly lower epifaunal abundances than other morphotypes, suggesting that large frond alga provided low‐value refuge from predators. The presence of predators also influenced the size structure of epifaunal communities from habitat units of differing frond size, suggesting that the refuge value of S. vestitum was also related to epifauna body size. This suggests that habitat formers may chiefly structure associated communities by mediating size‐selective predation, and not through habitat provisioning. Furthermore, these results also highlight that habitat traits cannot be considered in isolation, for their interaction with biotic processes can have significant implications for associated communities.
We used naturally occurring morphological variability in the alga Sargassum vestitum to create habitat units of specific morphotypes and found that intraspecific variation in frond size strongly affected the epifaunal communities associated with macroalgae. Experimentally excluding predators showed that these patterns were likely the result of predation, with epifaunal communities only varying in the presence of predators. This suggests that algal morphology affects the refuge value of macroalgae for associated epifauna.
Global patterns of plant biomass drive the distribution of much of the marine and terrestrial life on Earth. This is because their biomass and physical structure have important consequences for the ...communities they support by providing food and habitat. In terrestrial ecosystems, temperature is one of the major determinants of plant biomass and can influence plant and leaf morphology. In temperate marine systems, macroalgae are major habitat‐formers and commonly display highly variable morphology in response to local environmental conditions. Variation in their morphology, and thus habitat structure on temperate reefs, however, is poorly understood across large scales. In this study, we used a trait‐based approach to quantify morphological variability in subtidal rocky reefs dominated by the algal genus Sargassum along a latitudinal gradient, in southeastern Australia (~900 km). We tested whether large‐scale variation in sea surface temperature (SST), site exposure, and nutrient availability can predict algal biomass and individual morphology. We found Sargassum biomass declined with increasing maximum SST. We also found that individual morphology varied with abiotic ocean variables. Frond size and intraindividual variability in frond size decreased with increasing with distance from the equator, as SST decreased and nitrate concentration increased. The shape of fronds displayed no clear relationship with any of the abiotic variables measured. These results suggest climate change will cause significant changes to the structure of Sargassum habitats along the southeastern coast of Australia, resulting in an overall reduction in biomass and increase in the prevalence of thalli with large, highly variable fronds. Using a space‐for‐time approach means shifts in morphological trait values can be used as early warning signs of impending species declines and regime shifts. Consequently, by studying traits and how they change across large scales we can potentially predict and anticipate the impacts of environmental change on these communities.
Using a trait‐based approach, we tested predictions about how the biomass and morphological traits of macroalgae from the genus Sargassum varied across six degrees of latitude on the southeastern coast of Australia. Our results suggest climate change will cause significantly changes to Sargassum habitat along the southeastern coast of Australia, resulting in an overall reduction in biomass and increasing the prevalence of thalli with large, highly variable fronds.
Understanding responses of marine algae to changing ocean temperatures requires knowledge of the impacts of elevated temperatures and the likelihood of adaptation to thermal stress. The potential for ...rapid evolution of thermal tolerance is dependent on the levels of heritable genetic variation in response to thermal stress within a population. Here, we use a quantitative genetic breeding design to establish whether there is a heritable variation in thermal sensitivity in two populations of a habitat‐forming intertidal macroalga, Hormosira banksii (Turner) Descaisne. Gametes from multiple parents were mixed and growth and photosynthetic performance were measured in the resulting embryos, which were incubated under control and elevated temperature (20°C and 28°C). Embryo growth was reduced at 28°C, but significant interactions between male genotype and temperature in one population indicated the presence of genetic variation in thermal sensitivity. Selection for more tolerant genotypes thus has the ability to result in the evolution of increased thermal tolerance. Furthermore, genetic correlations between embryos grown in the two temperatures were positive, indicating that those genotypes that performed well in elevated temperature also performed well in control temperature. Chlorophyll a fluorescence measurements showed a marked decrease in maximum quantum yield of photosystem II (PSII) under elevated temperature. There was an increase in the proportion of energy directed to photoinhibition (nonregulated nonphotochemical quenching) and a concomitant decrease in energy used to drive photochemistry and xanthophyll cycling (regulated nonphotochemical quenching). However, PSII performance between genotypes was similar, suggesting that thermal sensitivity is related to processes other than photosynthesis.
1. Herbivory is particularly intense in marine environments, with a higher proportion of primary productivity removed than in terrestrial habitats. Experimental manipulation of large herbivores ...(fish, urchins) has clearly documented their grazing impacts on algal and seagrass beds. Grazing impacts of mesograzers (small invertebrates such as amphipods and isopods) are, however, less understood due to the practical difficulties in manipulating their abundance in field conditions. 2. We developed a novel technique that successfully manipulated the abundance of herbivorous amphipods on macroalgae without the potential artefacts associated with exclusion cages or mesocosms. We then used this technique to test the effects of reduced amphipod grazing over extended periods on the structure of a temperate algal assemblage. We tested grazer effects on growth rates and epiphyte cover of the brown alga Sargassum linearifolium, and on developing assemblages on bare substrates. 3. Large reductions in the abundance of herbivorous amphipods affected neither the growth rates of S. linearifolium, the cover of its epiphytes, nor the structure of algal assemblages. This result contrasts strongly to previous studies in mesocosms documenting strong impacts of mesograzers on community structure, and we discuss differences in the experimental approaches and biology of the systems that could give rise to the observed differences in grazer impacts. 4. Synthesis. Marine macroalgae and seagrasses support very high densities of small herbivores whose ecological role in these habitats is poorly understood. We have provided the first, replicated experiment that directly manipulates their density in situ to quantify grazer impacts without caging artefacts. Our results indicate that strong impacts are not likely with the naturally occurring amphipod densities in the temperate algal bed studied. Further such experimental tests in field conditions are required to understand the properties of grazer and plant communities that can predict grazer impacts.
Organisms from all domains of life can have highly variable morphologies, with this plasticity suggested to increase fitness and survivability under stressful conditions. Predicting how organisms ...will adapt to environmental change requires an understanding of how variable morphologies perform under environmental stress. Morphological plasticity has been documented within marine macroalgae inhabiting environmental gradients, however the functional consequences of this variation has been rarely tested. In this study, form-function was assessed in the habitat-forming, intertidal macroalga Hormosira banksii. Morphological variation was quantified on two spatial scales (tidal gradient versus latitudinal gradient) and the performance tested (relative water content and photosynthetic efficiency) of morphological variants during heat and desiccation stress. At regional scales, individuals at the warm distributional edge were overall smaller in size, and had smaller vesicles (higher surface area to volume ratio; SA:VOL) than those from central populations. At local scales, individuals high on the shore were generally shorter and had larger vesicles than those low on the shore. Vesicle morphology (SA:VOL) was found to predict relative water content and photosynthetic performance during desiccation and rehydration. Differences in SA:VOL of vesicles between heights on the shore may reflect water requirements needed to maintain tissue hydration for photosynthesis during low tide. Warm-edge populations showed increased thermal sensitivity as indicated by decreased photosynthetic yield of PSII and delays in recovery after desiccation. Sensitivities to higher temperatures amongst warm-edge populations are potentially due to smaller fluctuations in regional temperatures as well as their morphology. This study provides a mechanistic understanding of the morphological variation among H. banksii populations. It suggests that H. banksii has a high degree of morphological plasticity reflecting local climate, topography and environmental conditions, with this morphological variation having functional consequences. Morphological variation across local and regional scales will be important for resilience of this species to future climate warming.
Habitat complexity plays a critical role in shaping biotic assemblages and ecosystem processes. While the impacts of large differences in habitat complexity are often well understood, we know less ...about how subtle differences in structure affect key ecosystem functions or properties such as biodiversity and biomass. The late-successional seagrass Posidonia australis creates vital habitat for diverse fauna in temperate Australia. Long-term human impacts have led to the decline of P. australis in some estuaries of eastern Australia, where it is now classified as an endangered ecological community. We examined the influence of P. australis structural complexity at small (seagrass density) and large (meadow fragmentation) spatial scales on fish and epifauna communities, predation and sediment erosion. Fine-scale spatially balanced sampling was evenly distributed across a suite of environmental covariates within six estuaries in eastern Australia using the Generalised Random Tessellation Structures approach. We found reduced erosion in areas with higher P. australis density, greater abundance of fish in more fragmented areas and higher fish richness in vegetated areas further from patch edges. The abundance of epifauna and fish, and fish species richness were higher in areas with lower seagrass density (seagrass density did not correlate with distance to patch edge). These findings can inform seagrass restoration efforts by identifying meadow characteristics that influence ecological functions and processes.
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