Oecologia最新文献

Climate change disproportionately affects northern and alpine environments, with faster rates of warming than the global average. Because alpine and northern species are particularly well adapted to cool temperatures, most species must modify their behavior when temperatures exceed a critical threshold. Evaluating how temperature increases affect species inhabiting northern and alpine environments is therefore essential to understand the effects of projected climate change on these ecosystems. We analyzed the influence of temperature on the activity patterns and habitat selection of four populations of a cold-adapted, mountain specialist, the mountain goat (Oreamnos americanus). We collected GPS location and activity sensor data during 2010-2019 from 223 mountain goats from two distinct ecotypes: coastal and continental. Using a resource selection modeling approach, we determined that mountain goats of both ecotypes decreased selection for alpine meadows when temperatures increased. Reduced selection for open, forage rich habitat was associated with increased selection for habitat dominated by snow/ice patches in coastal areas, and by forests in continental sites. Mountain goats in continental environments selected higher elevation habitats only when temperature increased, whereas goats in coastal environments selected higher elevation habitat at all temperatures. Mountain goats of both ecotypes reduced the proportion of time spent active when temperatures increased during the middle of the day. Our study reveals that mountain goats use diverse tactics to mitigate thermal stress, and that these tactics vary between ecotypes, highlighting the need for considering adaptation to specific environments within a species when assessing climate change impacts on populations.

Understanding the mechanisms that enable species coexistence is a central question in ecology, as it helps to comprehend species diversity. One of the most common stabilizing mechanisms of coexistence is niche segregation, which can prevent the competitive exclusion of the fittest competitor. Niche segregation can manifest itself at various temporal and spatial scales, allowing provide essential insights into understanding the stabilizing mechanisms facilitating the coexistence of species. We assessed coexistence patterns among flower-dwelling spiders in two ways, in the first set of analyses, we investigated the factors influencing the quantity of spider individuals and species. The second approach we investigate the spatio-temporal segregation between species, effectively examining the coexistence patterns. We observed that the presence of inflorescences per plant, the number of flowers per inflorescence, and the presence of EFNs play a significant role in increasing spider abundance and richness. We find only a marginal seasonal effect, suggesting that spiders have constant access to resources throughout the year. Our niche overlap analysis demonstrated synchrony in the spatial occupation of niches by different spider species. The coexistence patterns appeared to be unaffected by the number of inflorescences. The greater number of inflorescences will enable a greater availability of niches, and consequently more abundance and richness of species of spiders the plant can sustain. Our results suggest that, to mitigate the adverse consequences of competitive interactions, spiders tend to adopt spatial partitioning as a strategy to facilitate the coexistence of spiders living in reproductive structures on plants in the Brazilian savanna.

Organisms with complex life cycles undergo ecological transitions between life stages, often resulting in stage-specific resource use. The relative contribution of each stage-specific resource to vital rates influences population dynamics and subsequently whether habitats can support viable populations. In lepidopterans, survival to reproduction requires sufficient resources for immature life stages, but the extent to which resources for adults are critical to population persistence is variable. We studied Boisduval's blue butterflies (Icaricia icarioides), in a greenhouse experiment, to quantify the effect of the adult diet, nectar, on vital rates. Butterflies fed ad libitum produced 3.4 times more eggs, on average, over their lifetime and lived 6 more days relative to those which only had access to water. We used these experimental data to parameterize a population model to test if vital rates with and without nectar result in viable population growth rates. Despite individual females laying 68 eggs without nectar, we found that Boisduval's blue butterfly populations will not persist without the improved fecundity associated with nectar resources (λ < 1). In this species, although amino acids in the adult diet contributed to various improvements in fecundity, these improvements did not translate to improvements in population growth rates. Incorporating our experimental vital rates into a population model indicates that the relative abundance and quality of nectar can alter at what threshold other resource(s) are limiting the population.

In ectothermic animals, elevational gradients, such as mountainous environments, are often associated with shifts in body size, although patterns differ across taxa and contexts. Mountain landscapes are characterised by relatively rapid shifts in biotic and abiotic conditions along an elevational gradient, commonly referred to as elevational zonation. Such zonation can reduce the geographic scale at which organisms experience the effects of climate change. The upslope range shifts will expose organisms at the colonization front to sub-optimal conditions. We can expect these challenging conditions to influence many life-history traits including growth rates and reproductive output. We tested the hypothesis that body size varies across elevational gradients in a contemporary montane colonizer, the common wall lizard (Podarcis muralis). Further, we assessed active body temperatures and available environmental temperatures in an attempt to discern a potential abiotic factor that might drive such a pattern. We quantified body size in lizards along four replicate transects ranging from 400 to 2400 m above sea level in the Pyrenees. Male body size decreased with increasing elevation. While female body size was invariant, females at higher elevation exhibited lower body condition. These results suggest that the effects of abiotic limitations or selective pressures experienced at the high-elevation colonisation front are sex-specific. Furthermore, lizards from both sexes were able to maintain similar field active body temperatures across elevation, despite reduced ambient temperature. If available temperatures limit activity periods or necessitate higher thermoregulatory investment, as suggested by our results, then further warming may benefit lizards and favour further upslope migration.

The variation within and across species has afterlife effects on carbon and nutrient cycling through the alteration of litter decomposability. However, the focus on leaves may not reflect a whole-plant economic spectrum of strategies. Here, we assessed the patterns and predictors of flower and leaf-litter decomposition at the intra- (i.e., flowers and leaves of the same species) and inter-specific (i.e., flowers and leaves from different species) levels for 29 tropical woody species in northeast Brazil. We evaluated nine functional litter traits, including structural and chemical traits. Flower litter decomposed, on average, three times faster than leaf litter (11.9% and 39.4% mass remaining, respectively) and exhibited higher water-holding capacity (WHC), leaching (LEA), and N, P, and K content. Otherwise, leaf litter showed higher density (DEN) and Ca, Mg, and Na content. The average relative differences in decomposition rate and functional traits between flower and leaf litter did not differ at both intra- and inter-specific levels. The predictors of decomposition were mostly similar, explaining 39% and 37% of flower and leaf litter, respectively. Leaching, P, Ca, Mg, and Na predict both flower and leaf-litter decomposition. However, WHC exclusively predicted flower-litter decomposition, and DEN, N, and K exclusively predicted leaf-litter decomposition. The observed differences in decomposition rate and functional traits between flower and leaf litter indicate that the afterlife effects differ between these plant organs and leverage the role of flower litter and its secondary consequences to nutrient and carbon cycling on ecosystems.

Seeds and seedlings are particularly vulnerable to herbivory. Unlike mature plants, which can wait until herbivory is experienced to induce defense, seeds and seedlings face mortality if they wait. Slug mucus functions as a kairomone, a non-attack-related substance emitted by consumers that is detected by a prey species (in this case, plants). While snail mucus has been shown to induce defense in seedlings, it is not widely confirmed whether slugs have the same effect and whether seeds can also detect and react to such herbivore cues. We investigated how exposure to Arion subfuscus mucus affected growth and defense in Brassica nigra seeds and seedlings. Seeds exposed to slug mucus germinated 5% faster than control (water only) seeds, but the resulting seedlings weighed 16% less than control seedlings. To test whether this difference results from herbivore-exposed plants allocating energy from growth to defense, we conducted choice bioassays assessing slug preference for control seedlings versus seedlings that were either (A) exposed to mucus only as a seed; or (B) exposed to mucus as a seed and seedling. While slugs did not differentiate between control seedlings and ones exposed to herbivore cues only as a seed, they ate 88% less biomass of seedlings exposed to mucus as both seeds and seedlings. These results suggest that slug mucus induces changes in plant traits related to defense and growth/competitive ability. Future research should determine the chemical mechanisms of this induced defense.

In mobile animals, selection pressures resulting from spatio-temporally varying ecological factors often drive adaptations in migration behavior and associated physiological phenotypes. These adaptations may manifest in ecologically and genetically distinct ecotypes within populations. We studied a meta-population of northern pike (Esox lucius) in brackish environments and examined intrapopulation divergence along environmental gradients. Behavioral phenotypes in habitat use were characterized via otolith microchemistry in 120 individuals sampled from brackish lagoons and adjacent freshwater tributaries. We genotyped 1514 individual pike at 33 highly informative genetic markers. The relationship between behavioral phenotype and genotype was examined in a subset of 101 pikes for which both phenotypic and genomic data were available. Thermosaline differences between juvenile and adult life stages indicated ontogenetic shifts from warm, low-saline early habitats towards colder, higher-saline adult habitats. Four behavioral phenotypes were found: Freshwater residents, anadromous, brackish residents, and cross-habitat individuals, the latter showing intermediary habitat use between brackish and freshwater areas. Underlying the behavioral phenotypes were four genotypes, putative freshwater, putative anadromous, and two putatively brackish genotypes. Through phenotype-genotype matching, three ecotypes were identified: (i) a brackish resident ecotype, (ii) a freshwater ecotype expressing freshwater residency or anadromy, and (iii) a previously undescribed intermediary cross-habitat ecotype adapted to intermediate salinities, showing limited reliance on freshwater. Life-time growth of all ecotypes was similar, suggesting comparable fitness. By combining genetic data with lifelong habitat use and growth as a fitness surrogate, our study revealed strong differentiation in response to abiotic environmental gradients, primarily salinity, indicating ecotype diversity in coastal northern pike is higher than previously believed.

Herbivore-plant interactions are fundamental processes shaping ecosystems, yet their study is challenged by their complex connections within broader ecosystem processes, requiring a nuanced understanding of ecosystem dynamics. This study investigated the relationship between nutrient availability and insect herbivory in the Australian Wet Tropics. Our objectives were threefold. Firstly, to understand what factors influence nutrient availability for plants and herbivores across the landscape; secondly, to investigate how trees of different species respond to nutrient availability; and thirdly, to unravel how the relationships between resources and plant chemistry affect herbivory. We established a network of 25 study sites covering important abiotic gradients, including temperature, precipitation, and geology. Employing a hierarchical modelling approach, we assessed the influence of climate and geology on resource availability for plants, primarily in the form of soil nutrients. Then, we explored the influence of the above factors on the interaction between herbivory and foliage chemistry across three widespread rainforest tree species, comparing how these relationships emerged across genera. Our findings suggest an overarching influence of climate and geology over soil chemistry, foliar nitrogen, and insect herbivory, both directly and indirectly. However, individual constituents of soil fertility showed equivocal influences on spatial patterns of foliage chemistry once site geological origin was accounted for, suggesting a questionable relationship between individual soil nutrients and foliar composition. We have demonstrated that herbivore-plant interactions are complex dynamics regulated by an intricate web of relationships spanning different biogeochemical processes. While our results provide some support to the notion that herbivory is affected by resource availability, different species growing under the same conditions can show differing responses to the same resources, highlighting the importance of identifying specific limiting factors rather than simpler proxies of resource availability.

Climate change has the potential to disrupt phenological synchrony among interacting species that vary in their phenological sensitivity to temperature. The phenological synchrony observed between winter moth Operophtera brumata caterpillars and oak leafing in spring has become an emblematic test case of this phenomenon, with caterpillars seemingly advancing their phenology more than their host-plant. However, work on this trophic interaction-and on phenological mismatch more widely-routinely overlooks the potential for trophic generalism to buffer the negative effects of mismatch. In the largest study of its kind-using over 3500 individuals reared from egg to pupa-I tested the performance of winter moth caterpillars from four UK populations across nine host-plant species, and considered how adaptation to locally abundant host-plants may modulate performance in different populations. I found that caterpillars survive and grow well across a range of host-plant species, with some evidence of a host-plant by population interaction in performance. Contrary to widespread assumptions, oak seems a relatively poor host-plant species. Occupying a broad trophic niche may help consumers like the winter moth exploit a narrow phenological niche, whereby phenological variation among host-plant species buffers them against asynchrony with any one particular host-plant species. Determining the significance of trophic generalism in the ecology of consumers is a crucial first step towards assessing its role as a potential buffering mechanism and, hence, evaluating the true threat posed by mismatch.

Making timely management decisions is often hindered by uncertainty. Monitoring reduces two key types of uncertainty. First, it serves to reduce structural uncertainty of how the system works and provides support for expectations of how a system works. Second, it serves to reduce parametric uncertainty of the drivers of system dynamics. By combining monitoring data and quantitative models, we can reduce structural and parametric uncertainty. To demonstrate this, we focus on the Shenandoah salamander (Plethodon shenandoah), a United States Federally Endangered Species. Early work suggested that P. shenandoah extinction risk results from competition with a conspecific (Plethodon cinereus). However, more recent work has found equivocal support for this claim, instead suggesting that abiotic factors, such as moisture and temperature, drive P. shenandoah persistence. Using long-term monitoring data, we find that while competition may play a part in P. shenandoah extinction risk, measures of surface moisture are better predictors of occupancy dynamics. Further, we find decreased detection rates of P. shenandoah when P. cinereus is present, suggesting a conflation of detection probability with actual competition, which cautions against making inference from unadjusted observations of occurrence. Using multiple lines of inquiry allows for more robust understanding of system drivers in the face of high uncertainty, increasing opportunities to manage extinction risk.