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Understanding variation in social organization that lacks a strong phylogenetic signal represents a key focus of research in behavioural ecology. Accordingly, we established a framework that identifies whether a range of ecological and social factors are affecting the social maintenance of taxa across multiple categories of social variation (ranging from large to fine‐scale): 1) forms of sociality, 2) degree of sociality, 3) social plasticity and 4) hierarchy maintenance. Each category of variation can then be assessed in combination to provide an outlook for social maintenance in light of predictor factors. We modelled this framework by quantifying each category over time, space and disturbance regime using multiple species of coral‐dwelling gobies, genus Gobiodon. Gobies are an interesting model system as they vary in social structure, have within‐group cooperation, and form mutualisms with coral hosts, which are vulnerable to climatic disturbances. We found that gobies varied in forms of sociality – from being more solitary or pair‐forming in high disturbance regimes, versus group‐forming in moderate disturbance regimes at some locations. Only low or moderate degrees of sociality were observed in gobies, with location or disturbance regime affecting some species. The size of coral hosts influenced the social plasticity of gobies, which was affected by climatic disturbances. Gobies did not exhibit direct changes to hierarchy maintenance, as location and disturbance regime did not affect their size‐based hierarchies. Lastly, by combining the four categories of variation, we found a high loss of sociality in coral‐dwelling gobies due to environmental disturbances, which likely affects overall goby survival as group‐forming can improve survival and fitness. By using our structured framework, we identified which categories of social variation were influenced by ecological factors like location and disturbance. This framework therefore provides an excellent tool for predicting future responses of animal societies to environmental stressors. [ABSTRACT FROM AUTHOR]

Simple Summary: Freshwater crayfish play critical roles in their ecosystems; however, non-native species are increasingly threatening native crayfish populations worldwide. Here, we review the literature examining or documenting the impacts of invasive freshwater crayfish and other non-native species on native freshwater crayfish. Four key mechanisms through which invasive crayfish impact native crayfish were identified: competition, predation, introduction of disease, and reproductive impacts, while other non-native species primarily impact native crayfish through predation. We highlight a need for more field-based investigations examining competitive interactions between invasive and native crayfish and identify a deficit of monitoring efforts for many non-native species that are likely to substantially impact native crayfish populations. Overall, the findings underscore the profound and diverse threats posed by non-native species to native crayfish, necessitating further research to safeguard native crayfish populations. Freshwater crayfish are vital species in ecosystems where they naturally occur, as they hold keystone and ecological engineering positions in these systems. Non-native species are common and widely spread throughout Earth's freshwater ecosystems and can have severe impacts on native crayfish populations. There has yet to be a comprehensive global review of the impacts of non-native species on native crayfish. Two literature searches were conducted using Web of Science and Google Scholar to find articles to address four key aims: (1) summarise trends in the literature; (2) examine the mechanisms by which invasive crayfish impact native crayfish species; (3) examine the mechanisms by which other non-native species, such as fish, impact native crayfish species; and (4) identify gaps in knowledge and research priorities. This review highlights that a far greater amount of research has addressed the effects of invasive crayfish than other non-native species. The research on invasive crayfish focuses on four types of interactions with native crayfish: competition, predation, introduction of disease, and reproductive impacts. Studies addressing the impacts of other non-native species on crayfish indicate that predation and habitat destruction by these species are the key processes impacting native crayfish. It is evident that field-based research, particularly concerning competition between invasive and native crayfish, is limited. Therefore, further in situ research is needed to assess the validity of laboratory results in a natural setting. Additionally, in many cases, the impact of certain non-native species on native crayfish populations has gone unmonitored. For this reason, it is recommended that additional research focus on assessing the impact of these non-native species. To conclude, the impacts of invasive crayfish on native crayfish are profound and wide-ranging, often leading to population decline or extirpation. Further, other non-native species are also likely to have a highly deleterious impact on native crayfish populations; however, more research is required to understand the scope of this impact. [ABSTRACT FROM AUTHOR]

From a conservation standpoint, species that are managed without consideration of their population sizes and connectivity have the potential to be over‐exploited and/or incur population decline. The burrowing shrimp, Trypaea australiensis, is an important ecosystem engineer and fishery resource caught in large numbers for which population information is unknown for properly managing the species. Here, we determined the level of population structure of T. australiensis across three locations along the East Coast of New South Wales, Australia, using genome‐wide single nucleotide polymorphisms (SNPs) obtained through double digest Restriction‐site Associated DNA‐sequencing (ddRAD‐seq). Analysis of population structure, including pairwise Fst (−0.003 to −0.001), STRUCTURE (K = 2) and Discriminant Analysis of Principal Components (DAPC) showed no evidence of structure among locations. Our findings provide crucial preliminary population genetic data for a key cryptic species, that also suggests gene flow among sampling locations enables the management of fisheries throughout the study area as a single unit. [ABSTRACT FROM AUTHOR]

Establishing the activity, movement and habitat‐use patterns of endangered species is fundamental in designing effective conservation plans. In Australia, the critically endangered freshwater crayfish, Euastacus dharawalus, is facing considerable risk of extinction due to numerous stressors, including the proliferation of the invasive Cherax destructor throughout their range. However, little is known about the fine‐scale spatial ecology of E. dharawalus and if this overlaps with C. destructor. Here, we aimed to establish the activity, movement and habitat‐use patterns of E. dharawalus as well as conduct a preliminary assessment into the overlap of their spatial ecology with that of C. destructor. In 2020, 15 E. dharawalus and six C. destructor were radio tracked at a site along Wildes Meadow Creek in the Southern Highlands region of New South Wales, Australia. Additionally, in 2021, 12 more E. dharawalus were tracked at this site over the same period. Euastacus dharawalus exhibited high site fidelity, small home ranges and diurnal activity patterns. Both E. dharawalus and C. destructor indicated significant preference for bank habitat, indicating potential for individual competitive interactions. We also report a significant reduction in the movement and activity of E. dharawalus from 2020 to 2021, possibly in response to population control of C. destructor or environmental variation across the 2 years. Our results indicate that the preservation or restoration of bank habitat will be critical to the conservation of E. dharawalus. Further, due to the extent of habitat‐use overlap between E. dharawalus and C. destructor, we conclude that C. destructor represents a substantial competitive threat to E. dharawalus, and therefore, C. destructor population control efforts should continue within the range of E. dharawalus. [ABSTRACT FROM AUTHOR]

Many animals use color to signal their quality and/or behavioral motivations. Colorful signals have been well studied in the contexts of competition and mate choice; however, the role of these signals in nonsexual, affiliative relationships is not as well understood. Here, we used wild social groups of the cichlid fish Neolamprologus pulcher to investigate whether the size of a brightly colored facial patch was related to 1) individual quality, 2) social dominance, and/or 3) affiliative relationships. Individuals with larger patches spent more time foraging and tended to perform more aggressive acts against conspecific territory intruders. We did not find any evidence that the size of these yellow patches was related to social rank or body size, but dominant males tended to have larger patches than dominant females. Additionally, patch size had a rank-specific relationship with the number of affiliative interactions that individuals engaged in. Dominant males with large patches received fewer affiliative acts from their groupmates compared to dominant males with small patches. However, subordinates with large patches tended to receive more affiliative acts from their groupmates while performing fewer affiliative acts themselves. Taken together, our results suggest that patch size reflects interindividual variation in foraging effort in this cichlid fish and offer some of the first evidence that colorful signals may shape affiliative relationships within wild social groups. [ABSTRACT FROM AUTHOR]

Context: Trophic overlap between invasive and native species can cause a competitive displacement of the native. In Australian freshwaters, the invasive crayfish Cherax destructor has proliferated into the ranges of native Euastacus species. Aims: To examine trophic overlap between C. destructor and the critically endangered Euastacus dharawalus and determine whether C. destructor population control causes shifts in the diet and trophic position of E. dharawalus. Methods: We compared δ13C and δ15N values of tissue from both species collected from two sites. Population control of C. destructor was then conducted at one site, whereas the C. destructor population remained uncontrolled at the second site. The δ13C and δ15N values of E. dharawalus were then once again assessed. Key results: Both species occupied similar trophic positions and consumed similar proportions of each food resource prior to control efforts. However, we found increases in the contribution of detritus to the diet of E. dharawalus following the removal of C. destructor , whereas no dietary shifts occurred at the uncontrolled site. Conclusions and implications: The increase in detrital consumption suggests that control of C. destructor increased the availability of a preferred resource. Further, dietary competition between C. destructor and E. dharawalus is likely and reinforces C. destructor representing a substantial threat to Euastacus crayfish. The invasive common yabby has proliferated extensively throughout Australian freshwaters and is likely to compete against native freshwater crayfish over food resources. We assessed whether the fish down of a common yabby population would alter the diet of a critically endangered native spiny crayfish. We found substantial shifts in the diet of the native crayfish following the control of the common yabby population. [ABSTRACT FROM AUTHOR]

Marine organisms, particularly invertebrates, are relatively understudied regarding social structure and behaviour, especially those that are cryptic. While empirically challenging to investigate, these species can provide novel insights into the evolution of sociality given their unique ecology. Our aim was to quantify in-situ the social structure and its underlying correlates in the Australian burrowing shrimp, Trypaea australiensis Dana, 1852 (Callianassidae). We show that T. australiensis exhibits intraspecific variation in social structure, being most often found in solitary arrangements, frequently in pairs (including homosexual and heterosexual arrangements), and sometimes in groups. The majority of shrimp in pairs and groups were found in heterosexual pairings or groups of one male and multiple females. Variation in social structure was correlated with variation in body size characteristics, seasonality, and site. These findings demonstrate that a wider array of social structures are exhibited by this species than previously expected, but the obvious limitations associated with sampling a cryptic burrowing species in situ mean that further investigations under controlled conditions, including laboratory behavioural manipulations, will be needed to confirm the current findings. The use of resin casts to understand burrow morphology would be important for understanding the causes of intraspecific variation in this and other cryptic species. [ABSTRACT FROM AUTHOR]

Simple Summary: Aggressive invasive species can outcompete native species in contests over resources, which can lead to the exclusion of a native species by the invader. Invasive freshwater crayfish are often more aggressive than their native counterparts, however contests between invasive and native crayfish are typically investigated under laboratory conditions and are rarely examined in a natural setting. We used a baited underwater camera in a stream located in New South Wales, Australia to examine behavioural interactions between an invasive crayfish and a critically endangered native crayfish to determine which species was dominant. We found the native species dominant over the invader when larger, however when the species were size-matched the dominance of the native was lost and neither species exhibited a significant pattern of dominance. This outcome indicates the invasive crayfish represents a threat to the native since it may be able to outcompete the native over resources. Further, this outcome contrasts to previous laboratory findings, highlighting the importance of field observations in establishing the extent of impact an invader may be having on a native species. Competitive behavioural interactions between invasive and native freshwater crayfish are recognised as a key underlying mechanism behind the displacement of natives by invaders. However, in situ investigations into behavioural interactions between invasive and native crayfish are scarce. In Australian freshwater systems, the invasive Cherax destructor has spread into the ranges of many native Euastacus species, including the critically endangered Euastacus dharawalus. Staged contests between the two species in a laboratory setting found E. dharawalus to be the dominant competitor, however, this has yet to be corroborated in situ. Here, we used baited remote underwater video (BRUV) to examine in situ intra- and inter-specific behavioural interactions between E. dharawalus and C. destructor. We sought to evaluate patterns of dominance and differential contest dynamics between the species to provide indications of competition between the two species. We found E. dharawalus to be dominant over C. destructor based on pooled interspecific interaction data and size-grouped interactions where C. destructor was the smaller opponent. Alarmingly, however, when C. destructor was within a 10% size difference the dominance of E. dharawalus was lost, contrasting with the outcomes of the laboratory-staged study. In addition, we report that small C. destructor initiated significantly more contests than larger conspecifics and larger E. dharawalus, a pattern that was not observed in smaller E. dharawalus. Further, intraspecific interactions between C. destructor were significantly longer in duration than intraspecific interactions between E. dharawalus, indicating a willingness to continue fighting. Concerningly, these outcomes point towards inherent and greater aggressiveness in C. destructor relative to E. dharawalus and that only larger E. dharawalus hold a competitive advantage over C. destructor. Therefore, we conclude that C. destructor represents a substantial threat to E. dharawalus through competitive behavioural interactions. Further, due to the disparity between our findings and those produced from laboratory-staged contests, we recommend the use of in situ studies when determining the behavioural impacts of invasive crayfish on natives. [ABSTRACT FROM AUTHOR]

Freshwater crayfish are among the most endangered animal groups in the world. Appropriate management requires an understanding of sampling bias when assessing their distribution and abundance. We evaluated the effectiveness of a variety of sampling methods for detecting freshwater crayfish (genus Euastacus) in situ and potential biases towards individual-level traits associated with these methods. We also experimentally manipulated the presence of crayfish within opera house traps to determine the effects of trap residency on capture rate and the characteristics of crayfish approaching the traps. Baited hoop nets and baited remote underwater video surveys (BRUVS) detected significantly more crayfish than did unbaited video surveys (RUVS). Crayfish captured in baited hoop nets were significantly larger than were crayfish measured in the BRUV and RUV surveys, suggesting that hoop nets were biased to capturing larger animals. The experiment demonstrated that a greater number of crayfish entered empty rather than occupied traps; however, there were no differences in their body sizes. We highlight the importance of optimising sampling for freshwater crayfish to ensure reliable and robust population estimates. This is of critical importance as many have highly restricted ranges and face numerous threats. We contend that this will assist in informing conservation strategies to protect aquatic species at risk. Freshwater crayfish are among the most endangered animal groups in the world. We examined bias associated with baited traps for members of this diverse group in Australia. We confirmed that traps predominantly captured large males, whereas their abundance was underestimated two- to three-fold when compared with that from baited video surveys. Animals avoided traps with a captive crayfish. Video techniques can better inform conservation efforts. [ABSTRACT FROM AUTHOR]