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Connectivity patterns of ecological elements are often the core concern of ecologists working at multiple levels of organization (e.g., populations, communities, ecosystems, and landscapes) because these patterns often reflect the forces shaping the system's development as well as constraining their operation. One reason these patterns of direct connections are critical is that they establish the pathways through which elements influence each other indirectly. Here, we tested a hypothesized consequence of connectivity in ecosystems: the homogenization of resource distributions in flow networks. Specifically, we tested the generality of the systems ecology hypothesis of resource homogenization in 50 empirically derived trophic ecosystem models representing 35 distinct ecosystems. We applied Network Environ Analysis (NEA) to calculate resource homogenization for these models, where homogenization is defined as the ratio of the coefficient of variation of the direct flow intensity matrix (CV (G)) to the covariance of the integral flow intensity matrix (CV (N)). A ratio greater than unity indicates the presence of homogenization. We also tested the hypotheses that homogenization increases with system size, connectance, and cycling. We further evaluated the robustness of our results in two ways. First, we verified the close correspondence between the input-and output-oriented homogenization values to ensure that our results were not biased by our decision to focus on the output orientation. Second, we conducted a Monte Carlo based uncertainty analysis to determine the robustness of our results to ±5% error introduced into the original flow matrices for each model. Our results show that resource homogenization occurs universally in the 50 ecosystem models tested, with values ranging from 1.04 to 1.97 and a median of 1.61. However, our results do not support the hypothesized relationship between network homogenization and system size and connectance, as the results of the linear regressions are insignificant. Further, there is only weak support for the positive relationship between homogenization and cycling. We confirm that our results are not biased by using the output-oriented homogenization values instead of the input-oriented values because there is a significant linear regression between the two types of homogenization (r 2 = 0.38, p < 0.001) and the values are well correlated (S = 8, 054, ρ = 0.61, p < 0.001). Finally, we found that our results are robust to ±5% error in the flow matrices. The error in the homogenization values was less than the error introduced into the models and ranged from a minimum of 0.24% to a maximum of 1.5% with a median value of 0.58%. The error did not change the qualitative interpretation of the homogenization values. In conclusion, we found strong support for the resource homogenization hypothesis in 50 empirically derived ecosystem models.Keywords: network environ analysis, indirect effects, input-output analysis, network homogenization, connectivity, food web, ecological network an...

Snapping shrimps are pervasive generators of underwater sound in temperate and tropical coastal seas across oceans of the world. Shrimp snaps can act as signals to conspecifics and provide acoustic information to other species and even to humans for habitat monitoring. Despite this, there are few controlled measurements of the acoustic parameters of these abundant acoustic stimuli. Here, the characteristics of snaps produced by 35 individuals of two species, Alpheus heterochaelis and Alpheus angulosus, are examined to evaluate the variability within and between the species. Animals were collected from the wild and the sound pressure and particle acceleration were measured at 0.2, 0.5, and 1 m from individual shrimp in controlled laboratory conditions to address the snap properties at communication-relevant distances. The source and sound exposure levels (at 1 m) were not significantly different between these two species. The frequency spectra were broadband with peak frequencies consistently below 10 kHz. The particle acceleration, the sound component likely detectable by shrimp, was measured across three axes. The directional amplitude variation suggests that the particle motion of snaps could act as a localization cue. The amplitudes of the snap pressure and acceleration decreased with distance, yet the levels remained sufficient for the predicted detection range by nearby conspecifics.

The combined acoustic activity of soniferous organisms living in benthic habitats produces habitat-specific soundscapes, which are predicted to influence fish and invertebrate larval behavior during the settlement process. Not every sound will have the amplitude and frequency characteristics relative to hearing sensitivity to be used as an acoustic cue, thus the cuescape is a subset of the soundscape. These sounds vary through space and time, and little is known about how this variability could influence their role in settlement. We recorded the soundscapes of 4 coral reefs in Caribbean Panama for 6 wk and conservatively identified the sounds most likely to compose the cuescapes used by larval fishes. While these sites represented the variation in reef condition across the study area, we observed the same 4 dominant taxa groups emerge as the most likely producers of acoustic cues. These results were consistent across both time and space when compared to short-term recordings taken at these 4 reefs and at an additional 11 sites 2 yr prior. Next, we used an individual-based model to test the relationship between settlement success and the natural spatiotemporal variability we observed in these potential cues. Temporal variation in the sounds resulted in variation in settlement success; however, even shortrange, intermittent cues improved the likelihood of settlement. Overall, we observed similar acoustic cuescapes across reefs that varied in condition, suggesting that cuescapes can be resilient to some forms of reef degradation by retaining sounds potentially useful to larval fishes for both navigation and habitat selection.KEY WORDS: Coral reef · Soundscape · Larval fish · Larval settlement · Acoustics · Modeling · Cues · Fish behavior Resale or republication not permitted without written consent of the publisher