Community theory proposes that consumer control strength varies with environmental stress, with unimodal effects on diversity. Diversity is high with intermediate consumer pressure when consumers favor the dominant competitor(s). At low or high stress, diversity will be low due to resulting high or low consumer pressure. We tested these ideas in a rocky intertidal, kelp‐dominated community. The annual kelp Postelsia palmaeformis is abundant on wave‐exposed, rocky headlands along the northeastern Pacific coast. Winter storms drive high levels of disturbance while in summer wave action and disturbance are reduced. Postelsia forests occur in the upper intertidal on (a) gently sloping mussel‐dominated areas and (b) steeply sloping rocky areas. Steep‐wall Postelsia shade a species‐rich understory. The small (1–3 cm length) limpet Lottia pelta feeds on the much larger (50–70 cm tall) Postelsia raising questions about herbivory effects on community structure. Limpet grazing effects were tested in 0.7 × 0.7 m plots in the center of the Postelsia bed, in half of which limpets were manually removed. We expected that grazing would have minimal effects due to foraging inhibition by high wave stress, but found that limpets reduced the density, percent cover, and size of Postelsia and had mostly positive indirect effects on the understory. These effects abated in winter as the kelp senesced and was torn from the rock. Next‐generation sporophytes arise from overwintering microscopic juvenile stages in late winter. Diversity peaked in winter when kelp were absent and declined in summer when kelp were abundant and competed with understory taxa. Overall limpets maintained higher algal diversity in winter by reducing negative effects of sea palm competition on understory taxa, but this effect weakened in summer when kelp were large and dense. Hence, grazer effects were relatively subtle, suggesting that the limpet was a strong interactor but not a keystone consumer.
Coral‐dwelling decapods can improve host fitness by defending corals against corallivores and sediment accumulation, yet the temporal dynamics linking co‐resident defenders remain poorly understood. Guard crabs Trapezia and snapping shrimp Alpheus provide complementary benefits to pocilloporid corals, and previous, largely cross‐sectional work has reported behavioral accommodation, non‐random co‐occurrence, and effects on host‐associated community assembly, patterns that suggest their association reflects facilitation instead of independent use of shared habitat. Whether this association persists as coupled dynamics through time, however, remains untested. Using repeated observations of tracked colonies spanning up to six years and three months in the northern Red Sea, we tested whether these taxa exhibit non‐random co‐occurrence and linked population dynamics within pocilloporid hosts. Across two coral species, Trapezia was more common than Alpheus , and the presence of shrimp was strongly associated with that of crabs. In colonies of Pocillopora favosa (n = 35, 733 observations), Alpheus abundance increased with Trapezia abundance, and mean abundances per colony of the two taxa were positively correlated, indicating persistent demographic coupling over time. While larger colonies held more symbionts, this abundance coupling was not fully explained by colony size. Temporal peaks in abundance were often synchronized, producing temporary assemblages that exceeded the typical pair occupancy expected for these symbionts. In colonies of Stylophora pistillata (n = 40, 710 observations), shrimp were rare, but when present, they occurred only in colonies inhabited by crabs. Our results reveal that the within‐host dynamics of co‐resident decapod mutualists are more tightly linked than previously recognized, consistent with facilitative interactions mediated through a shared host. Because such defenders can enhance host condition, their sustained co‐residence may have broader relevance for the persistence of the corals that structure these reefs and their associated assemblages.
Globally, a growing proportion of logging‐disturbed tropical forest is recovering, holding great potential for biodiversity conservation and ecosystem functioning. However, how ecosystem multifunctionality (EMF) and its trait‐based predictors in these secondary forests differ from those in old‐growth forests remains unknown. Here, we investigated old‐growth forests and two types of secondary forests (following selective logging and clear‐cutting) in China's Hainan Tropical Rainforest National Park to examine how logging history affects EMF, its relationship with biodiversity, and its trait‐based predictors. After about half a century of recovery, species richness in logged forests approached levels comparable to or even exceeding that of old‐growth forests. However, they sustained significantly lower levels of EMF, with the lowest mean EMF observed in clear‐cut forests. Species richness was positively associated with EMF within all forest types, whereas the trait‐based predictors associated with EMF differed among forest types. Based on the structural equation models, the community‐weighted mean (CWM) of leaf area was the strongest predictor in old‐growth forests, potentially reflecting a greater contribution of selection‐related processes, whereas functional dispersion (FDis) was the strongest trait‐based predictor in selectively logged forests, suggesting a potential role of complementarity‐related processes. In clear‐cut forests, by contrast, neither CWM nor FDis was significantly associated with EMF, and species richness was the only significant predictor among the variables examined. Our study suggests that forests with different logging histories differ not only in EMF but also in the trait‐based predictors associated with it. These findings underscore the irreplaceable value of old‐growth forests and suggest that restoration assessments should integrate biodiversity, ecosystem multifunctionality and functional trait composition.
Across north-temperate environments, rapid environmental change has disrupted the seasonal life histories of resident organisms, decreasing the reliability of environmental cues. Flexible responses capable of buffering the effects of unpredictable environmental variation to defend performance and reproductive outcomes may thus be key to species- and population-level resilience. Yet, our existing understanding of how seasonally flexible responses shape ecological outcomes across populations remains limited. Here, we regularly sampled wild fish populations with putatively different life history strategies from early winter to late summer to quantify how seasonal foraging and phenotypic flexibility across a range of somatic tissue types (gastrointestinal, mesenteric, hepatic) contributed differentially to reproductive outcomes. In all populations, reproductive preparation was coordinated through flexible increases in foraging, mesenteric lipid, gastrointestinal mass, and liver mass and quality, which occurred relatively simultaneously as an 'integrated reproductive response.' Then, the seasonal scope for phenotypic flexibility, directly or indirectly, mediated reproductive allocation across populations. Individuals from populations that exhibited a greater scope for phenotypic flexibility, especially in the gastrointestinal tract, allocated more to reproduction and tended to develop higher quality reproductive tissue. Our results suggest that the scope for phenotypic flexibility, especially in the digestive tract, modulates energy allocation and conservation in response to environmental variability.
Understanding how physiological constraints scale up to realized niche differences remains a central challenge in functional ecology. Temperature strongly influences metabolic performance, activity, and habitat selection in ectotherms, yet few field studies quantify how thermal responses interact with diel and habitat structure to shape predator coexistence in natural systems. Using year-round trapping data, I quantified how eastern red-spotted newts Notophthalmus viridescens and bluegill sunfish Lepomis macrochirus partition habitat across interacting axes of season, depth, time of day and temperature. Generalized linear mixed models revealed pronounced and opposing patterns of habitat use across interacting spatial and temporal axes. Newts were captured most frequently in deeper, cooler microhabitats during morning periods, whereas sunfish were captured most frequently in shallow, warmer habitats and afternoon periods. Harmonic models showed asynchronous seasonal trajectories, with newt activity peaking during cooler months and sunfish activity peaking during summer. Across the annual thermal gradient, newt capture rates declined with increasing temperature, whereas sunfish capture rates increased. Across combined season-by-depth-by-time states, overall niche overlap was significantly lower than expected under null models of random habitat use. These results indicate that differences in thermal sensitivity and behavioral thermoregulation can generate strong multi-axis spatiotemporal segregation among ecologically similar predators, even in physically constrained systems. By linking thermal ecology to realized habitat use across diel and seasonal scales, this study demonstrates how trait-mediated responses to environmental gradients structure predator functional roles and reduce interaction overlap in natural communities.Keywords: activity patterns, amphibians, behavioral thermoregulation, coexistence, diel activity, freshwater ecology, habitat partitioning, niche overlap, predator-predator interactions, spatiotemporal niche partitioning, temperature dependence
