Sandy beaches in highly urbanised areas are subject to a wide range of human impacts. Ghost crabs are a commonly used ecological indicator on sandy beaches, as they are key consumers in these systems ...and counting burrow openings allows for rapid assessment of population size. This study assessed the pressures of urbanisation on sandy beaches in the highly urbanised estuary of Sydney Harbour. Across 38 beaches, we examined which physical beach properties, management practices and human induced habitat modification best predicted ghost crab distributions. Of all variables measured, the frequency of mechanical beach cleaning was the most important predictor of crab abundance, with low burrow densities at the highest cleaning frequency and the highest densities at beaches cleaned at the intermediate frequency (≤3 times per week). These results indicate that ghost crab populations in Sydney Harbour are more robust to the impacts of urbanisation than previously thought.
•Ghost crab densities were used to assess human impacts on urban sandy beaches.•Mechanical beach cleaning frequency was the strongest predictor of burrow density.•Highest burrow counts were found on infrequently (≤3 per week) cleaned beaches.•Ghost crabs in Sydney Harbour are resilient to moderate human disturbance.
Understanding species‐specific relationships with their environment is essential for ecology, biogeography and conservation biology. Moreover, understanding how these relationships change with ...spatial scale is critical to mitigating potential threats to biodiversity. But methods which measure inter‐specific variation in response to environmental parameters that are also generalizable across multiple spatial scales are scarce. We used broad‐scale avian citizen science data, over continental Australia, integrated with remotely‐sensed products, to produce a measure of urban‐tolerance for a given species at a continental‐scale. We then compared these urban‐tolerances to modelled responses to urbanization at a local‐scale, based on systematic sampling within four small cities. For 49 species which had sufficient data for modelling, we found a significant relationship (R2 = 0.51) between continental‐scale urbanness and local‐scale urbanness. We also found that relatively few citizen science observations (~250) are necessary for reliable estimates of continental‐scale species‐specific urban scores to predict local‐scale response to urbanization. Our approach demonstrates the applicability of broad‐scale citizen science data, contrasting both the spatial grain and extent of standard point‐count surveys generally only conducted at small spatial scales. Continental‐scale responses in Australia are representative of small‐scale responses to urbanization among four small cities in Australia, suggesting that our method of producing species‐specific urban scores is robust and may be generalized to other locations lacking appropriate data.
Predicting the host range for herbivores has been a major aim of research into plant–herbivore interactions and an important model system for understanding the evolution of feeding specialization. ...Among many terrestrial insects, host range is strongly affected by herbivore phylogeny and long historical associations between particular herbivore and plant taxa. For small herbivores in marine environments, it is known that the evolution of host use is sculpted by several ecological factors (e.g., food quality, value as a refuge from predators, and abiotic forces), but the potential for phylogenetic constraints on host use remains largely unexplored. Here, we analyze reports of host use of herbivorous amphipods from the family Ampithoidae (102 amphipod species from 12 genera) to test the hypotheses that host breadth and composition vary among herbivore lineages, and to quantify the extent to which nonpolar secondary metabolites mediate these patterns. The family as a whole, and most individual species, are found on a wide variety of macroalgae and seagrasses. Despite this polyphagous host use, amphipod genera consistently differed in host range and composition. As an example, the genus Peramphithoe rarely use available macrophytes in the order Dictyotales (e.g., Dictyota) and as a consequence, display a more restricted host range than do other genera (e.g., Ampithoe, Cymadusa, or Exampithoe). The strong phylogenetic effect on host use was independent of the uneven distribution of host taxa among geographic regions. Algae that produced nonpolar secondary metabolites were colonized by higher numbers of amphipod species relative to chemically poor genera, consistent with the notion that secondary metabolites do not provide algae an escape from amphipod herbivory. In contrast to patterns described for some groups of phytophagous insects, marine amphipods that use chemically rich algae tended to have broader, not narrower, host ranges. This result suggests that an evolutionary advantage to metabolite tolerance in marine amphipods may be that it increases the availability of appropriate algal hosts (i.e., enlarges the resource base).
Aim
Here we investigate the strength of the relationships between meteorological factors and calling behaviour of 100 Australian frog species using continent‐wide citizen science data. First, we use ...this dataset to quantify the meteorological factors that best predict frog calling. Second, we investigate the strength of interactions among predictor variables. Third, we assess whether frog species cluster into distinct groups based on shared drivers of calling.
Location
Australia.
Method
To assess the relationship between calling and meteorological traits, we used spatio‐temporal subsampling (daily data fitted to 10 km2 grid cells) of call and meteorological data as inputs to a boosted regression tree. We scaled the model outputs, which created a descriptive ranking of predictor importance. For strongly day‐driven species, we conducted further analyses to examine the influences of meteorological factors within the breeding season.
Results
We found a strong seasonal signal, with day of year the strongest relationship to calling in 67 out of our 100 species, moderate relationships between temperature and calling, and weak relationships between rainfall and calling. Despite the common narratives, we found that frogs did not group into distinct categories based upon the influence of meteorological factors. For strongly day‐driven species, we found similar patterns within the breeding season.
Main conclusions
We demonstrate the importance of day of year and temperature thresholds in predicting frog calling behaviour in Australia. Understanding how meteorological conditions influence phenological events, such as breeding, will be increasingly important considering the rapid changes in environmental conditions and stability throughout most of the world, and how important breeding is to species survival.
Recognising patterns of genetic diversity and connectivity is integral to understanding the mechanisms behind population declines and formulating management plans for the conservation of threatened ...or endangered species. This is particularly important for clonal organisms such as seagrasses, which are experiencing rapid global decline. This study quantifies genetic diversity within 12 naturally fragmented Posidonia australis meadows on the east coast of Australia, using a set of eight microsatellite DNA markers. Genetic diversity increased with latitude, moving away from the range-edge, and was significantly lower in six mid-range endangered meadows and the two northernmost meadows. These meadows also showed evidence of shared multilocus genotypes despite significant geographic separation. The four southernmost meadows were genetically differentiated from all other meadows further north, and all multilocus genotypes identified were unique to their sample locations. We conclude that patterns of low diversity in the endangered and northern meadows are likely due to a population bottleneck caused by a range-edge effect. A common ancestral source meadow existing prior to historical sea level changes may explain the sharing of multilocus genotypes, as contemporary gene flow between these geographically isolated meadows is unlikely. Our findings have important implications for conservation, highlighting the endangered and range-edge populations as those potentially most at risk of extinction should environmental conditions change. These results can be utilised for the location of suitable donor populations for transplanting purposes as a means of mitigating further declines.
Plant feeding promotes diversification in the Crustacea Poore, Alistair G. B.; Ahyong, Shane T.; Lowry, James K. ...
Proceedings of the National Academy of Sciences - PNAS,
08/2017, Volume:
114, Issue:
33
Journal Article
Peer reviewed
Open access
About half of the world’s animal species are arthropods associated with plants, and the ability to consume plant material has been proposed to be an important trait associated with the spectacular ...diversification of terrestrial insects. We review the phylogenetic distribution of plant feeding in the Crustacea, the other major group of arthropods that commonly consume plants, to estimate how often plant feeding has arisen and to test whether this dietary transition is associated with higher species numbers in extant clades. We present evidence that at least 31 lineages of marine, freshwater, and terrestrial crustaceans (including 64 families and 185 genera) have independently overcome the challenges of consuming plant material. These plant-feeding clades are, on average, 21-fold more speciose than their sister taxa, indicating that a shift in diet is associated with increased net rates of diversification. In contrast to herbivorous insects, most crustaceans have very broad diets, and the increased richness of taxa that include plants in their diet likely results from access to a novel resource base rather than host-associated divergence.
Latitudinal gradients in the strength of biotic interactions have long been proposed, but empirical evidence for the expectation of more intense predation, herbivory and competition at low latitudes ...has been mixed. Here, we use a meta‐analysis to test the prediction that predation pressure on sea urchins, a group of consumers with a particularly strong influence on community structure in the world's oceans, is strongest in the tropics. We then examine which biotic and abiotic factors best correlate with biogeographic and within habitat patterns in sea urchin responses to predation. Consistent with expectations, predator impacts on sea urchins were highest in tropical coral reefs and decreased towards the poles in rocky reef habitats (> 25° absolute latitude). However, latitude and temperature were weakly correlated with effect sizes, and the strongest predictor of predator impacts was sea urchin species. This suggests an important role of prey identity (i.e. traits including behaviour, physical, and chemical defences) rather than large scale abiotic factors in determining variation in interaction strengths. Ecosystem‐shaping sea urchins such as Tripneustes gratilla, Diadema savignyi and Centrostephanus rodgersii were strongly impacted by consumers, indicating a tight coupling between predators of these species and their boom and bust prey. Anthropogenic activities such as over‐fishing, climate change and habitat destruction are causing rapid environmental change, and understanding how predation pressure varies with temperature, across habitats and among prey species, will aid in predicting the likelihood of ecosystem wide effects (via trophic cascades).
Ampithoid amphipods dominate invertebrate assemblages associated with shallow‐water macroalgae and seagrasses worldwide and represent the most species‐rich family of herbivorous amphipod known. To ...generate the first molecular phylogeny of this family, we sequenced 35 species from 10 genera at two mitochondrial genes the cytochrome c oxidase subunit I (COI) and the large subunit of 16 s (LSU) and two nuclear loci sodium–potassium ATPase (NAK) and elongation factor 1‐alpha (EF1), for a total of 1453 base pairs. All 10 genera are embedded within an apparently monophyletic Ampithoidae (Amphitholina, Ampithoe, Biancolina, Cymadusa, Exampithoe, Paragrubia, Peramphithoe, Pleonexes, Plumithoe, Pseudoamphithoides and Sunamphitoe). Biancolina was previously placed within its own superfamily in another suborder. Within the family, single‐locus trees were generally poor at resolving relationships among genera. Combined‐locus trees were better at resolving deeper nodes, but complete resolution will require greater taxon sampling of ampithoids and closely related outgroup species, and more molecular characters. Despite these difficulties, our data generally support the monophyly of Ampithoidae, novel evolutionary relationships among genera, several currently accepted genera that will require revisions via alpha taxonomy and the presence of cryptic species.
Despite much theoretical discussion on the evolutionary significance of intraclonal genetic variation, particularly for modular organisms whose lack of germ‐soma segregation allows for variants ...arising in clonal growth to contribute to evolutionary change, the potential of this variation to fuel adaptation remains surprisingly untested. Given intraclonal variation, mitotic cell lineages, rather than sexual offspring, may frequently act as units of selection. Here, we applied artificial selection to such lineages in the branching red seaweedAsparagopsis armata, targeting aspects of clonal growth form and growth‐form plasticity that enhance light acquisition on patchy subtidal reefs and predicting that a genetic basis to intraclonal variation may promote significant responses that cannot accompany phenotypic variation alone. Cell‐lineage selection increased variation in branch proliferation amongA. armatagenets and successfully altered its plasticity to light. Correlated responses in the plasticity of branch elongation, moreover, showed that cell‐lineage selection may be transmitted among the plasticities of growth‐form traits inA. armatavia pleiotropy. By demonstrating significant responses to cell‐lineage selection on growth‐form plasticity in this seaweed, our study lends support to the notion that intraclonal genetic variation may potentially help clonal organisms to evolve adaptively in the absence of sex and thereby prove surprisingly resilient to environmental change.
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