Ecological Monographs

The performance of any natural population in variable environments depends on contemporaneous changes in its vital rates (e.g., survival, reproduction) as well as legacies carried by its population structure. Yet whether the relative contribution of these two pathways can be predicted from life history remains unknown. Here, we use stochastic simulations of 1,986 matrix population models from 137 species to quantify the contribution of transient dynamics to variation in population growth rate, and test its associations with key life history traits. Longer generation times were associated with reductions in transient contributions, contrary to theoretical expectations. Greater stage-specific survival heterogeneities were associated with increases in transient contributions, whereas greater iteroparity was associated with decreases in plants but increases in animals. These associations were robust to body size, phylogenetic relationships, and vital-rate variability. Life history traits therefore provide a strong predictor for when population structure shapes population responses to environmental variability.

Dispersal differences between hosts and their symbionts can generate mismatched population structure, potentially destabilizing beneficial interactions across space. We tested this possibility in the carnivorous pitcher plant Darlingtonia californica and its obligate arthropod associates, the midge Metriocnemus edwardsi and the mite Sarraceniopus darlingtoniae, sampled across sites spanning the hosts patchy range in Oregon and northern California, USA. Comparing nuclear and chloroplast genomic data from D. californica with mitochondrial COI data from both arthropods, we tested how range position, landscape connectivity, and dispersal mode influence population genetic structure across this mutualistic metacommunity. Host plant populations supported the central-marginal hypothesis: nuclear diversity declined toward the range margins, and marginal populations showed greater nuclear genetic differentiation. Chloroplast variation was more weakly structured, most clearly separating the northern Oregon Coast populations and revealing cytonuclear discordance consistent with historical seed-mediated movement or chloroplast capture near the boundary between neighboring regions. Landscape connectivity estimated from an ecological niche model was also associated with genetic exchange. Circuit-theoretic current flow was positively related to effective migration inferred independently from plant genotypes. Further, landscape resistance explained variation in plant and mite differentiation beyond geographic distance alone. Both arthropods showed significant spatial congruence with the host plant but not with one another, a pattern inconsistent with co-dispersal and suggesting that each associate tracks the shared landscape according to its own dispersal biology. These results show that regional genetic concordance among obligate ecological partners can coexist with substantial differences in the processes governing their movement and local connectivity.

Long-lived plants facing anthropogenic disturbance often exhibit recruitment failure despite persistent reproductive adults, generating extinction debt masked by longevity. However, whether adult presence reliably reflects environmental suitability for recruitment remains unclear. Here, we examine ontogenetic niche differentiation and its consequences for recruitment in Jubaea chilensis, an endangered long-lived Mediterranean palm with an aging population. We assigned individuals within the largest known population to four ontogenetic stages and characterized their environmental niches using climatic, edaphic, topographic, and vegetation variables. We then applied spatial and multivariate analyses, including Random Forest models to evaluate environmental segregation and identify predictors of seedling establishment. Age classes occupied significantly different environmental niches, with the greatest differentiation between seedlings and reproductive adults. Saplings and adult differentiation reflected mainly topographic variables at landscape scale, whereas seedling establishment was primarily predicted by microhabitat conditions (vegetation cover heterogeneity, east-facing slope orientation, and soil texture). This pattern is consistent with niche reconfiguring throughout the life cycle, suggesting that adult occurrence and recruitment suitability respond to distinct environmental conditions. Over one-fifth of sampled individuals occupied high-suitability sites without recruitment, suggesting that ontogenetic niche shifts are associated with a spatial decoupling between adult persistence and recruitment, consistent with demographic collapse independent of habitat degradation. This failure is likely mediated by insufficient effective seed dispersal, as the sole disperser (Octodon degus) preys on most seeds before dispersal. Conservation strategies based solely on adult distribution may therefore overestimate effective habitat and underestimate extinction risk in long-lived species.

Anthropogenic climate change is threatening global biodiversity, with sea turtles particularly vulnerable as offspring sex and developmental success are strongly influenced by incubation temperature. Behavioral plasticity, including the seasonal distribution of reproductive output, may provide short-term mechanisms for mitigating these impacts. Here, we investigated season-wide hatchling sex ratios and emergence success in a small population of green turtles (Chelonia mydas), tracking individual females across their nesting seasons. Sex ratios varied markedly through the nesting season, with later nests producing a greater proportion of male hatchlings. Moreover, sex ratios were relatively consistent among nests laid by individual females. Overall, females producing more nests over a season also produced more male offspring, suggesting that both nesting phenology and reproductive output influence individual contributions to future population demographics. Mechanistic models indicate that hatchling sex ratios have trended towards female-biased ratios (>80% female) over the past 50 years, and are projected to approach complete feminization by 2100 under continued warming. Although emergence success currently remains high (>85%), it is predicted to decline sharply after mid-century, with viable hatchling production falling to [~]30% by the end of the century. Models further show that maintaining contemporary sex ratios and emergence success will require unrealistically large delays in nesting phenology, and that even extreme shifts in phenology become ineffective by 2100. Together, these findings demonstrate that individual females can increase male hatchling production by nesting later and producing more nests, but behavioral plasticity alone is unlikely to offset the accelerating impacts of climate change on this population.

Biological invasions are a major driver of global change, reshaping ecosystems and threatening biodiversity worldwide. Anticipating where invaders will establish and where they will exert the strongest ecological impacts are key challenges for early detection and targeted management. Although Species Distribution Models (SDMs) are widely used to forecast biological invasions, they often provide uncertain estimates of establishment ranges and limited insight into invader performance, making it difficult to anticipate ecological impacts. Here, we address these limitations by integrating physiological information on invader performance with SDMs to identify regions of high invasion risk. Using the brown alga Rugulopteryx okamurae, one of the most prominent marine invaders in Europe, we first test alternative hypotheses of northern establishment limits: (i) a cold-survival constraint driven by winter temperatures and (ii) a growth constraint derived from the species' thermal performance. To identify the more likely scenario, we combine cold-tolerance experiments with seasonal growth comparisons between the invader and a native macroalga Dictyota dichotoma, whose established distribution allows physiological performance to be directly related to realised presence. Finally, we project seasonal growth of the invader across the predicted establishment range as a proxy for biomass accumulation and potential ecological impacts. Our results indicate that northern limit in Europe will be more likely constrained by winter survival rather than growth, extending the potential establishment range of Rugulopteryx to mid-Norway. In contrast, the highest impacts are likely to remain concentrated in southern Europe, where thermal conditions sustain high year-round growth. Overall, our approach illustrates how understanding the physiological response of invaders to their environment can improve the interpretation of SDM outputs and help identify areas at greatest risk of impact within their potential establishment range.

1. Most plant species are genetically differentiated among populations, often reflected by phenotypic trait variation that corresponds to local adaptation. Yet the strength of local adaptation and heritable contribution to phenotypic traits vary across traits, species, and environments. Additionally, climate change is rapidly altering environmental conditions, and the climate may shift faster than populations can adapt or track the change via dispersal, resulting in adaptive lags. However, it remains unclear how widespread such adaptive lags are across plant species. 2. We focused on Hordeum murinum, an annual ruderal grass widespread in Europe. We combined continental-scale in situ measurements of 2070 plants across 207 populations with common garden experiments across two contrasting climates and two soil types to disentangle heritable variation from phenotypic plasticity and assess potential adaptive lags under climate change. 3. We found that heritable variation was pronounced in developmental traits, particularly flowering time and plant height, while seed weight, reproductive investment and SLA showed intermediate heritable contribution, and flag leaf area and total biomass were primarily plastic. Heritable trait variation was strongly associated with temperature at the populations origin, and trait clines were consistent with in situ patterns, suggesting that temperature is the main driver of genetic differentiation in H. murinum. However, we detected that fitness peaked in populations originating from warmer climates, indicating that evolutionary responses may not keep pace with rapid environmental shifts. 4. Synthesis: Our results highlight that H. murinum harbors substantial heritable variation, shaped primarily by temperature. However, the pace of evolutionary change may be insufficient to track ongoing climate change, leaving populations potentially vulnerable to future environmental conditions.

Population dynamics and their component vital rates may be driven by weather, climate teleconnections between sea and air (e.g. ENSO), or biotic interactions. These drivers operate directly or indirectly and on different temporal scales. We used a Bayesian structural equation model to characterize effects among weather, climate, and incidental intraguild predation (IGP) on the butterfly Euphydryas gillettii's vital rate of pre-diapause survival, using an 18 year dataset. IGP was a major determinant of pre-diapause survival, along with direct and indirect effects of weather and spring climate teleconnections. The direction of climate effects was reversed when mediated through IGP. Our analysis illustrates the need for sequential hypotheses to capture the cascading effects of abiotic factors via biotic interactions. Using sequential hypotheses addresses the debate on weather -- climate teleconnection roles by disentangling their contributions from one another. Finally, vital rates must be decomposed to component rates in order to detect their drivers.

Squid abundance has been reported to increase globally between 1970 and 2010. This increase has been hypothesized to result from two primary factors: the loss of top predators due to overfishing and rising ocean temperatures. The decline in apex predators may lead to the expansion of squid populations either through reduced predation pressure or diminished competition with juvenile predators. Concurrently, increased temperatures could enhance the somatic growth rates of squid, thereby accelerating their population growth. However, empirically disentangling the impacts of predator loss and temperature on squid biomass remains challenging, especially in a food-web context. In this study, we used a size- and trait-based model of upper trophic levels that resolves the ecosystem structure -- biomass and trophic interactions of fish and squid -- for varying depth, temperature, and secondary production, to investigate two hypotheses of the historical expansion of squid, i.e., the effects of predator depletion from fishing and rising temperatures on squid biomass. Our model reveals that intensified fishing of squid predators -- specifically large demersal fish in shelf systems and large pelagic fish in open oceans -- leads to a slight increase in squid biomass. Conversely, elevated temperatures are associated with a decline in squid biomass. This temperature-driven reduction in biomass is attributed to an increased metabolism of squids beyond the available food supply. If historic overfishing on large marine predators continues to be curtailed, we expect a corresponding reduction in global squid biomass and fisheries potential, which could be further exacerbated by rising temperatures.

Flower color has primarily been studied in the context of pollinator attraction, although effects on thermal energy balance are also important, especially in the context of global climate change. We used infrared imaging to compare petal temperatures of white versus pigmented cultivars of ten angiosperm taxa under controlled environmental conditions. Excised sets of flowers (n= 6 sets per species) exhibiting white, light, and/or dark anthocyanin (red to purple) coloration were mounted perpendicularly to the sun at mid-day, under clear sky, low wind (<1 m s-1) conditions. Sunlight was filtered through either UV-transparent or UV-opaque film, and petal temperatures were measured using an infrared camera after one minute equilibration. In all species, pigmented flowers were significantly warmer than lighter-colored conspecifics. Mean differences averaged +5.3{degrees}C for darker-colored versus white morphs, +2.9{degrees}C for lighter-colored versus white. Most warming was associated with visible wavelengths, but additional warming under UV-inclusion was also observed in some species. In situ observations of intact landscape plants under low-wind, high-light conditions corroborated experimental results, with differences exceeding 10{degrees}C observed in some taxa. Temperature differences >7{degrees}C were also recorded for purple versus white sections of the same flower in multicolored Viola and Petunia cultivars. Follow-up experiments using dark-pink and white varieties of Impatiens x hybrida corroborated well-known effects of sunlight intensity and wind speed on floral temperatures, helping to explain inconsistent reports in the literature. Our results clearly demonstrate that anthocyanin pigments can have significant and dramatic impacts on floral temperatures, which could be an important factor driving evolution of flower color. In the context of climate change, floral pigments could amplify the effects of rising global temperatures, negatively impacting plant reproduction and crop yields, especially on the warmer end of species ranges. Changes in flower color could also potentially induce shifts in pollinator communities, which could have community-scale effects.

Investigating the factors that stabilize biological communities is a central topic in ecology. Response diversity, defined as variation in species responses to environmental change, has been proposed as a key mechanism underlying the biodiversity-ecosystem functional stability (BEFS) relationship, whereby greater species diversity enhances ecological stability. Previous studies have shown that response diversity promotes ecological stability by generating asynchronous population fluctuations and the resulting compensatory dynamics. Although several metrics have been proposed to quantify response diversity, they do not explicitly consider the presence of insensitive species whose performance is unaffected by current environmental conditions. To examine how insensitive species influence response diversity, species persistence, and ecological stability, we conducted numerical simulations of a generalized Lotka-Volterra model under environmental forcing. We first confirmed that increasing variation among sensitive species increased the response diversity index and stabilized community dynamics. We then examined a scenario in which response diversity depended solely on the proportion of sensitive and insensitive species, assuming that all sensitive species responded identically to environmental change. Under this assumption, the response diversity index was maximized when sensitive and insensitive species occurred in equal proportions, whereas increasing the number of sensitive species monotonically destabilized community dynamics. Consequently, the relationship between response diversity and community stability depended on how response diversity was generated, such that higher response diversity could even be associated with lower community stability. These findings demonstrate that overlooking environmentally insensitive species can obscure the mechanisms linking response diversity and ecological stability. More broadly, our results reveal that response diversity comprises at least two distinct biological components--species sensitivity and response variation among sensitive species--that can have contrasting consequences for community stability. We therefore highlight the need to quantify sensitive species empirically and to develop response diversity metrics that distinguish these components. Author SummaryUnderstanding why some communities remain stable despite environmental change is a longstanding goal in ecology. Response diversity, which refers to differences in how species respond to environmental change, has been proposed as a key mechanism explaining why greater biodiversity (species richness) can promote ecological stability. Because species respond differently to changing environments, declines in some species can be compensated by increases in others, helping to stabilize community dynamics. However, previous studies have rarely considered species that are insensitive to current environmental changes. Using a mathematical model, we show that response diversity can arise from two distinct biological components--the number of sensitive species and variation in their responses--and that these components can have contrasting effects on ecological stability. When response diversity reflects variation among sensitive species, greater response diversity stabilizes community dynamics, as expected. In contrast, when response diversity changes only because of the proportions of sensitive and insensitive species, higher response diversity can be associated with lower community stability. Our findings highlight the importance of quantifying the number of sensitive species and developing response diversity metrics that distinguish species sensitivity from variation in responses among sensitive species.

Plants competing belowground may produce extra roots, fewer roots, or no detectable change compared to plants growing alone. This inconsistency is often attributed to plants altering their root allocation in response to diverse cues, including neighbor detection and resource depletion by neighbors, but isolating these cues experimentally is challenging. Here, we hypothesize that water depletion alone can generate the range of root allocation strategies reported in the literature. We present this hypothesis as a water-explicit optimization model of root allocation that predicts a non-monotonic response. The model identified a critical depletion rate at which allocation shifted from increasing to decreasing with depletion. We tested this prediction using artificially rooted pots that imposed controlled water depletion while excluding living neighbors and their cues. A continuous artificial depletion gradient revealed the predicted hump-shaped pattern. These results reframe root overproliferation and underproliferation as positions along a single depletion-response curve.

Forecasts of biodiversity responses to climate change often rely on space-for-time substitution, in which spatial biodiversity-climate relationships are used to predict biodiversity change through time. Yet this approach is rarely tested directly because long-term biodiversity time series are scarce. Here, we combine global modern and fossil assemblage data of planktonic foraminifera with site-specific sea-surface temperature reconstructions to compare biodiversity-temperature relationships across space and time. Spatial and temporal compositional turnover models showed similar slopes but consistently different intercepts, with spatial models predicting higher turnover across the full temperature gradient. Restricting the spatial comparison to the environmental domain of individual fossil time series reduced, but did not eliminate, this intercept mismatch. For alpha diversity, spatial models more closely recovered the temporal biodiversity-temperature relationship than for compositional turnover. Thus, for the timescales studied here, space-for-time substitution captures the direction of biodiversity change but not its magnitude through time.

Land-use change, such as the transformation of woody ecosystems into open pastures, acts as a strong ecological filter, favouring some species while excluding others according to differences in ecological niche breadth. Understanding how differences in niche breadth influence species responses under anthropogenic filters is crucial to anticipate their persistence or displacement. In this study, we quantified realized niche breadth in two sympatric ecosystem engineers, the Neotropical leaf-cutter ants Atta cephalotes and Atta laevigata, to test whether breadth differences are consistent with specialist and generalist ecological strategies. We characterized realized niche breadth across fine-scale environmental gradients by integrating hemispherical photography, microclimatic data, mound architecture, and edaphic profiles from 114 colonies across a regional transect in the Colombian Andes, alongside macroclimatic data from Copernicus. Principal Component Analysis (PCA) and PERMANOVA identified canopy openness and bushes- and tree-type vegetation density as the principal axes of interspecific niche partitioning. The observed differences in realized niche breadth were consistent with specialist and generalist ecological strategies. A. laevigata was predominantly associated with open-canopy areas, warmer micro- and macroclimatic conditions, and narrower edaphic dispersion. In contrast, A. cephalotes occupied a wider range of microhabitat conditions. This broader realized niche breadth is compatible with previous reports of A. cephalotes occurring in urban areas. Together, these findings suggest that niche breadth may influence how Neotropical leaf-cutter ants respond to habitat transformation, helping to understand the ecological consequences of land-use change.

1. Natal dispersal is a key process in population ecology because it links local demographic processes to broader-scale population dynamics by redistributing individuals. When using capture-recapture data, multistate capture-recapture models using discrete spatial units as states are the gold standard for estimating natal dispersal among spatial units while accounting for spatial variation in survival, recruitment and imperfect detection. However, because their computational cost increases rapidly with the number of spatial units, applications have been limited to a small number of units. Therefore, in practice, these models cannot provide spatially detailed inference on natal dispersal across large landscapes. 2. We develop a computationally efficient Bayesian capture-recapture model, called the efficient natal dispersal (END) model, to estimate natal dispersal among discrete spatial units jointly with spatial variation in demographic parameters and detection probabilities. The END model relies on two key structural features: juveniles and breeders are separated into two arrays, and resightings outside the natal spatial unit are aggregated over time for individuals released as juveniles. 3. Using simulations, we show that the END model is considerably (up to 30 times) more computationally efficient than a conventional multistate model, while maintaining comparable parameter accuracy. We then apply the END model to white stork (Ciconia ciconia) capture-recapture data from Germany across 101 hexagonal spatial units, a spatial resolution at which a conventional multistate model is computationally infeasible. We estimate natal dispersal among units jointly with spatial variation in survival and recruitment. This allows us to identify areas of lower or higher survival, earlier or delayed recruitment, and dispersal probabilities among all units. By combining estimated dispersal probabilities with existing data on the number of juveniles born in each spatial unit, we estimate natal dispersal in terms of numbers of individuals and identify units with positive or negative net migration, sources and sinks. 4. Overall, our approach moves capture-recapture analyses from estimating natal dispersal among a few spatial units to inferring dispersal networks and assessing their demographic consequences across large domains. Our approach is applicable to many spatially structured capture-recapture datasets, opening new opportunities for studying spatial population dynamics.

Climate change is disrupting life's seasonal rhythms, altering the timing of key phenophases and reshaping how communities assemble. Beyond shifting flowering times, climate change can modify the extent of floral overlap and the sequence in which species bloom, generating novel assemblages with uncertain consequences for plant-pollinator interactions. Here, we ask whether flowering order generates priority effects in plant-pollinator communities, much like germination order does in plant communities. We tested how flowering order influences bee foraging behaviour and plant reproductive success in two co-flowering species, Hypochaeris radicata and Campanula rotundifolia, using a greenhouse experiment in which we manipulated the sequence of floral availability while allowing bees to forage repeatedly. We quantified changes in visit frequency, interspecific switches, handling time, and seed production. Our findings reveal priority effects in bee foraging that were strong enough to affect plant fitness: both species received more visits when flowering earlier than their co-occurring counterpart, and seed production declined when species flowered later. Overall, our results show that flowering order is an underappreciated driver of plant-pollinator interactions, suggesting that climate-driven phenological shifts could alter priority-effect dynamics with broader implications for community assembly. Key questions remain: How will climate-driven phenological shifts rearrange flowering sequences, and how will these priority effects emerge in more diverse communities in the wild? Our controlled experiment reveals strong flowering-order effects, underscoring the need to evaluate how widespread and impactful such dynamics are under accelerating climate change.

Evidence is accumulating that global change is altering species distributions. Yet, detailed knowledge is missing about the relative and joint contribution of different drivers to observed species responses. Here, we implemented an impact attribution framework based on counterfactual simulations to assess the impact of climate and land use change on occupancy dynamics of North American breeding birds. We used a Bayesian framework to fit process-explicit dynamic occupancy models to long-term survey data for 159 species from 1995 to 2019, and quantified predictive performance using spatial and temporal cross-validation. We then assessed the relative importance and effect direction of climate and land use change while accounting for model predictive accuracy. Results indicate that climate change negatively affected 90 % of the species and land use change negatively impacted 96 %. Climate change emerged as more important than land use change for driving changes in occupancy across species. Remarkably, the effects of both drivers were mostly antagonistic rather than acting additively or synergistically. Climate was the most important driver for bird communities in the western USA, while land use change dominated in the southeast, and combined climate and land use change in the northeast. Our analysis demonstrates that recent changes in North American bird distributions are shaped by multiple global change drivers acting in concert. The effect of recent climate and land use change were mostly antagonistic, and thus trends in bird occupancy dynamics could not be understood by studying the impact of those drivers in isolation. By disentangling the effects of climate and land use change on biodiversity trends, impact attribution approaches can improve our understanding of global change impacts and can support conservation planning and more accurate and realistic projections of biodiversity response to global change.

Sequential hurricane-heatwave events threaten forest resilience via understudied legacy effects. Using Bayesian Structural Time Series, piecewise Structural Equation Modeling, and a 21-event global synthesis, we quantify how structural degradation non-linearly amplifies productivity loss during subsequent heatwaves. Our Hurricane Michael (2018) case study reveals significant negative GPP legacy effects during the 2019 heatwave. Intact, tall and diverse canopies buffer microclimates and moderate thermal sensitivity. Hurricane-induced structural simplification removes this protection, exposing temperature-sensitive shaded leaves to extreme stress. We identified a context-dependent hydraulic trade-off: structural complexity provides shading but exacerbates forest sensitivity to water deficits during peak heat, the vulnerability of which reverses during the recovery phase. Globally, these legacy effects are triggered by heatwave intensity and modulated by soil type, with loamy-soil forests most vulnerable. These findings highlight the critical role of forest structure in forest responses to compound disturbances. Neglecting structural legacies in Earth System Models likely underestimates risks to global carbon sinks.

Elevational gradients provide a framework for understanding how environmental filtering reorganises communities and interactions, but plant-pollinator interactions along temperate forest elevational gradients remain overlooked. We studied early-spring understorey communities at four forest sites spanning the foothills towards the timberline (450-1,000 m a.s.l.) in the Krkono[s]e Mountains, Czechia. Across six transects per elevation, we quantified flowering plant species richness, floral resources and traits, and video-recorded flowers, yielding 4,003 pollinator visits. We analysed elevational patterns in species richness, community composition, floral traits, and quantitative network characteristics. Visitation frequency and flowering plant and pollinator species richness peaked at intermediate elevations. The contribution of dipteran relative to hymenopteran pollinators increased towards higher elevations, principally because of non-hoverfly flies, whereas individual bee groups showed no uniform response. Floral resources and traits showed no uniform elevational responses, although total nectar sugar availability peaked at the highest site because of the dominant Vaccinium myrtillus. Most notably, both network-level specialisation and mean species-level specialisation were generally greater at the two higher elevations, whereas nestedness was lower and other network characteristics showed no consistent patterns. These findings suggest that shifts in pollinator composition and dominant floral resources potentially shaped interactions along the gradient. The increasing specialisation with elevation contrasts with the generalisation often expected under reduced partner availability and indicates that forest networks may follow elevational patterns not predicted from open habitats. Despite limited site-level replication, this study provides, to our knowledge, the first community-wide characterisation of plant-pollinator interactions along a temperate forest elevational gradient and identifies patterns requiring evaluation across replicated gradients.

After introduction, many non-native marine species are dispersed planktonically. Secondary spread within the non-native range has been shown to prevent the establishment of the introduced species if the advection of larvae prevents sufficient return of larvae to maintain the population in the face of competition with native species. However, those studies have largely neglected the effects of spatial variation in alongshore larval transport. We examine the introduction of a novel species with planktonic dispersal into a more realistic coastal environment which includes spatial variation in larval transport estimated from the Mercator Ocean 1/12th degree global circulation model. The introduction may either be from a distant habitat, or through range expansion. We find that there are locations in the global coastal ocean where introduced species are more likely to persist because of spatial variation of coastal currents. These include regions where alongshore larval transport diverges, such as estuaries. The location where a non-native species is introduced may not be where it flourishes - it cannot be assumed that the region where invading species are first noticed to be abundant is the region where it was introduced. We extend closed-population theory to open coastal systems to estimate persistence as a function of local circulation, habitat extent, and the competitive advantage of the introduced species. Software is provided which allows the estimations of regions where introduced species are more likely to persist and flourish as a function of larval depth behavior, planktonic duration and release timing.

Adaptive phenotypic plasticity is expected to evolve when environmental conditions change predictably over time. This has led to the hypothesis that ectotherms in environments with low temperature seasonality, such as the tropics, should evolve lower thermophysiological plasticity than those from more seasonal environments (the Climate Variability Plasticity Hypothesis, or CVHP). Yet, empirical support for the CVHP is incredibly low, creating a need to identify other factors that can help explain how thermal plasticity evolves. Here, we use numerical models to show that the evolution of constitutive thermal tolerance breadth greatly affects the evolutionary benefits of thermal plasticity. In particular, tolerance breadth interacts with within- and between-season temperature variation in ways that can confound expectations of the CVHP, including conditions in which organisms from less seasonal environments benefit 30 most from expressing plasticity. Our findings indicate that a more holistic view of the relationship between thermophysiology and environmental temperature is needed to explain the evolution of thermal plasticity across climatic gradients.