Biological characteristics of Anticarsia gemmatalis (Lepidoptera: Noctuidae) for three consecutive generations under different temperatures: understanding the possible impact of global warming on a soybean pest

Climate changes can affect the distribution and intensity of insect infestations through direct effects on their life cycles. Experiments were carried out during three consecutive generations to evaluate the effect of different temperatures (25°C, 28°C, 31°C, 34°C and 37±1°C) on biological traits of the velvetbean caterpillar Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae). The insects were fed on artificial diet and reared in environmental chambers set at 14 h photophase. The developmental cycle slowed with the increase in the temperature, within the 25°C to 34°C range. Male and female longevities were reduced with an increase in temperature from 25°C to 28°C. Egg viability was highest at 25°C, and the sex ratio was not influenced by temperature, in the three generations. There was no interactive effect between development time and temperature on pupal weight. The results suggested that the increase in the temperature negatively impacted A. gemmatalis development inside the studied temperature range, indicating a possible future reduction of its occurrence on soybean crops, as a consequence of global warming, mainly considering its impact on tropical countries where this plant is cropped. A. gemmatalis was not able to adapt to higher temperatures in a three-generation interval for the studied temperature range. However, a gradual increase and a longer adaptation period may favor insect selection and consequently adaptation, and must be considered in future studies in this area. Moreover, it is important to consider that global warming might turn cold areas more suitable to A. gemmatalis outbreaks. Therefore, more than a future reduction of A. gemmatalis occurrence due to global warming, we might expect changes regarding its area of occurrence on a global perspective.     

Predicted effects of climate warming on the distribution of 50 stream fishes in Wisconsin, USA

Summer air and stream water temperatures are expected to rise in the state of Wisconsin, U.S.A., over the next 50 years. To assess potential climate warming effects on stream fishes, predictive models were developed for 50 common fish species using classification-tree analysis of 69 environmental variables in a geographic information system. Model accuracy was 56·0-93·5% in validation tests. Models were applied to all 86 898 km of stream in the state under four different climate scenarios: current conditions, limited climate warming (summer air temperatures increase 1° C and water 0·8° C), moderate warming (air 3° C and water 2·4° C) and major warming (air 5° C and water 4° C). With climate warming, 23 fishes were predicted to decline in distribution (three to extirpation under the major warming scenario), 23 to increase and four to have no change. Overall, declining species lost substantially more stream length than increasing species gained. All three cold-water and 16 cool-water fishes and four of 31 warm-water fishes were predicted to decline, four warm-water fishes to remain the same and 23 warm-water fishes to increase in distribution. Species changes were predicted to be most dramatic in small streams in northern Wisconsin that currently have cold to cool summer water temperatures and are dominated by cold-water and cool-water fishes, and least in larger and warmer streams and rivers in southern Wisconsin that are currently dominated by warm-water fishes. Results of this study suggest that even small increases in summer air and water temperatures owing to climate warming will have major effects on the distribution of stream fishes in Wisconsin.     

Post-Hypsithermal plant disjunctions in western Alberta, Canada

Aim Evaluate the hypothesis that nine disjunct vascular plant species along the eastern slopes of the Rocky Mountains and in the Peace River District of west‐central Alberta represent remnants of more southerly vegetation that occupied these areas during the Holocene Hypsithermal (9000–6000 yr bp ). Alternatively, these plants represent populations that became established because of independent chance dispersal events. Location This study focuses on the area east of the Rocky Mountain Continental Divide in the Province of Alberta and the State of Montana in western Canada and USA, respectively. Methods Disjunct species were identified and their distributions mapped based on a review of occurrence maps and records, botanical floras and checklists, herbaria specimens, ecological and botanical studies, and field surveys of selected species. A disjunct species was defined as a plant population separated from its next nearest occurrence by a distance of > 300 km. Evaluation of the hypothesis was based on a review of published and unpublished pollen stratigraphy and palaeoecological studies. The potential geographical distribution of Hypsithermal vegetation was based on modern regional‐based ecosystem mapping and associated monthly temperature summaries as well as future climatic warming models. Results The hypothesis was compatible with Holocene pollen stratigraphy, Hypsithermal permafrost and fen occurrence, and palaeosol phytolith analyses; and future global climatic warming models. Modelled regional Hypsithermal vegetation based on a 1 °C increase in July temperatures relative to current conditions, indicated that much of the boreal forest zone in Alberta could have been grassland, which would explain the occurrence of Prairie species in the Peace River District. This amount of latitudinal vegetation shift (6.5°) was similar to an earlier Hypsithermal permafrost zone location study. An equivalent shift in vegetation along the eastern Cordillera would have placed south‐western Montana‐like vegetation and species such as Boykinia heucheriformis (Rydb.) Rosend. and Saxifraga odontoloma Piper within the northern half of the Rocky Mountains and foothills in Alberta, which represents the location of modern‐day disjunct populations of these species. Main conclusions Warmer and drier climatic conditions during the Holocene Hypsithermal resulted in the northward displacement of vegetation zones relative to their current distribution patterns. Most of Alberta was probably dominated by grasslands during this period, except the Rocky Mountains and northern highlands. Modern‐day species disjunctions within the Rocky Mountains and Peace River District as well as more northerly areas such as the Yukon Territory occurred when the vegetation receded southward in response to climatic cooling after the Hypsithermal. Wind dispersal was considered an unlikely possibility to explain the occurrence of the disjunct species, as most of the plants lack morphological adaptations for long distance transport and the prevailing winds were from west to east rather than south to north. However, consumption and transport of seeds by northward migrating birds could not be excluded as a possibility.     

Global warming will affect the maximum potential abundance of boreal plant species

Forecasting the impact of future global warming on biodiversity requires understanding how temperature limits the distribution of species. Here we rely on Liebig's Law of Minimum to estimate the effect of temperature on the maximum potential abundance that a species can attain at a certain location. We develop 95%-quantile regressions to model the influence of effective temperature sum on the maximum potential abundance of 25 common understory plant species of Finland, along 868 nationwide plots sampled in 1985. Fifteen of these species showed a significant response to temperature sum that was consistent in temperature-only models and in all-predictors models, which also included cumulative precipitation, soil texture, soil fertility, tree species and stand maturity as predictors. For species with significant and consistent responses to temperature, we forecasted potential shifts in abundance for the period 2041–2070 under the IPCC A1B emission scenario using temperature-only models. We predict major potential changes in abundance and average northward distribution shifts of 6–8 km yr⁻¹. Our results emphasize inter-specific differences in the impact of global warming on the understory layer of boreal forests. Species in all functional groups from dwarf shrubs, herbs and grasses to bryophytes and lichens showed significant responses to temperature, while temperature did not limit the abundance of 10 species. We discuss the interest of modelling the ‘maximum potential abundance’ to deal with the uncertainty in the predictions of realized abundances associated to the effect of environmental factors not accounted for and to dispersal limitations of species, among others. We believe this concept has a promising and unexplored potential to forecast the impact of specific drivers of global change under future scenarios.     

Geographic structure of genetic and phenotypic variation in the hybrid zone between Quercus affinis and Q. laurina in Mexico

Analyzing the structure of hybrid zones is important for inferring their origin, dynamics and evolutionary significance. We examined the geographic structure of phenotypic and genetic variation in the contact zone between two Mexican red oaks, Quercus affinis and Q. laurina. A total of 105 individuals from seven populations were sampled along a 600‐km latitudinal gradient representing the distribution area of the two species and their contact zone. Individuals were genotyped for nine nuclear and four chloroplast DNA microsatellite loci (ncSSR and cpSSR, respectively), and characterized for several leaf and acorn traits. The cpSSR data revealed extensive haplotype sharing among populations of the two species, while a Bayesian assignment analysis based on ncSSRs identified two main genetic groups, each corresponding to one of the species, and two populations in the contact zone showing evidence of admixture. The proportion of genetic ancestry in the populations was strongly associated with latitude and showed a pattern of variation with the shape of a narrow sigmoidal cline. The variation in three of the seven phenotypic traits was partially congruent with molecular variation, while the other traits did not conform to a geographic cline but instead were correlated with environmental variables. In conclusion, the hybrid zone between the two oak species has some of the characteristics of a tension zone, but heterogeneous variation across traits suggests differential introgression and the action of extrinsic selection.     

Population genetics of south European Atlantic salmon under global change

Populations at the edge of species distributions are especially vulnerable to climate change. Genetic changes as well as modification of their population structure are expected as reactions to global warming. Atlantic salmon ( Salmo salar ) inhabiting south France has been chosen as a model for studying the effect of global warming in marginal populations during the last 15 years. Increased gene flow between neighboring populations and dichotomy of maturation age between sexes have been identified as two main population changes significantly associated with high values of the North Atlantic Oscillation index, a global climate indicator. Although occurrence of isolated populations in each river (or even tributary) is a paradigm for this species, at least in northern areas, increased gene flow between rivers is forecasted as long as climate warming increases, favoring metapopulations at regional level.     

Projected poleward shift of king penguins' (Aptenodytes patagonicus) foraging range at the Crozet Islands, southern Indian Ocean

Seabird populations of the Southern Ocean have been responding to climate change for the last three decades and demographic models suggest that projected warming will cause dramatic population changes over the next century. Shift in species distribution is likely to be one of the major possible adaptations to changing environmental conditions. Habitat models based on a unique long-term tracking dataset of king penguin (Aptenodytes patagonicus) breeding on the Crozet Islands (southern Indian Ocean) revealed that despite a significant influence of primary productivity and mesoscale activity, sea surface temperature consistently drove penguins' foraging distribution. According to climate models of the Intergovernmental Panel on Climate Change (IPCC), the projected warming of surface waters would lead to a gradual southward shift of the more profitable foraging zones, ranging from 25 km per decade for the B1 IPCC scenario to 40 km per decade for the A1B and A2 scenarios. As a consequence, distances travelled by incubating and brooding birds to reach optimal foraging zones associated with the polar front would double by 2100. Such a shift is far beyond the usual foraging range of king penguins breeding and would negatively affect the Crozet population on the long term, unless penguins develop alternative foraging strategies.     

Birds are tracking climate warming, but not fast enough

Range shifts of many species are now documented as a response to global warming. But whether these observed changes are occurring fast enough remains uncertain and hardly quantifiable. Here, we developed a simple framework to measure change in community composition in response to climate warming. This framework is based on a community temperature index (CTI) that directly reflects, for a given species assemblage, the balance between low- and high-temperature dwelling species. Using data from the French breeding bird survey, we first found a strong increase in CTI over the last two decades revealing that birds are rapidly tracking climate warming. This increase corresponds to a 91 km northward shift in bird community composition, which is much higher than previous estimates based on changes in species range edges. During the same period, temperature increase corresponds to a 273 km northward shift in temperature. Change in community composition was thus insufficient to keep up with temperature increase: birds are lagging approximately 182 km behind climate warming. Our method is applicable to any taxa with large-scale survey data, using either abundance or occurrence data. This approach can be further used to test whether different delays are found across groups or in different land-use contexts.     

Changes in productivity and carbon storage of grasslands in China under future global warming scenarios of 1.5°C and 2°C

Aims The impacts of future global warming of 1.5°C and 2°C on the productivity and carbon (C) storage of grasslands in China are not clear yet, although grasslands in China support ~45 million agricultural populations and more than 238 million livestock populations, and are sensitive to global warming.     

Effects of ecogeographic variables on genetic variation in montane mammals: implications for conservation in a global warming scenario

Aim Evolutionary theory predicts that levels of genetic variation in island populations will be positively correlated with island area and negatively correlated with island isolation. These patterns have been empirically established for oceanic islands, but little is known about the determinants of variation on habitat islands. The goals of this study were twofold. Our first aim was to test whether published patterns of genetic variation in mammals occurring on montane habitat islands in the American Southwest conformed to expectations based on evolutionary theory. The second aim of this research was to develop simple heuristic models to predict changes in genetic variation that may occur in these populations as a result of reductions in available mountaintop habitat in response to global warming. Location Habitat islands of conifer forest on mountaintops in the American Southwest. Methods Relationships between island area and isolation with measures of allozyme variation in four species of small mammal, namely the least chipmunk (Tamias minimus), Colorado chipmunk (Tamias quadrivittatus), red squirrel (Tamiasciurus hudsonicus), and Mexican woodrat (Neotoma mexicana), were determined using correlation and regression techniques. Significant relationships between island area and genetic variation were used to develop three distinct statistical models with which to predict changes in genetic variation following reduction in insular habitat area arising from global warming. Results Patterns of genetic variation in each species conformed to evolutionary predictions. In general, island area was the most important determinant of heterozygosity, while island isolation was the most important determinant of polymorphism and allelic diversity. The heuristic models predicted widespread reductions in genetic variation, the extent of which depended on the population and model considered. Main conclusions The results support a generalized pattern of genetic variation for any species with an insular distribution, with reduced variation in smaller, more isolated populations. We predict widespread reductions in genetic variation in isolated populations of montane small mammals in the American Southwest as a result of global warming. We conclude that climate‐induced reductions in the various dimensions of genetic variation may increase the probability of population extinction in both the short and long term.     

Contrasting growth forecasts across the geographical range of Scots pine due to altitudinal and latitudinal differences in climatic sensitivity

Ongoing changes in global climate are altering ecological conditions for many species. The consequences of such changes are typically most evident at the edge of a species’ geographical distribution, where differences in growth or population dynamics may result in range expansions or contractions. Understanding population responses to different climatic drivers along wide latitudinal and altitudinal gradients is necessary in order to gain a better understanding of plant responses to ongoing increases in global temperature and drought severity. We selected Scots pine (Pinus sylvestris L.) as a model species to explore growth responses to climatic variability (seasonal temperature and precipitation) over the last century through dendrochronological methods. We developed linear models based on age, climate and previous growth to forecast growth trends up to year 2100 using climatic predictions. Populations were located at the treeline across a latitudinal gradient covering the northern, central and southernmost populations and across an altitudinal gradient at the southern edge of the distribution (treeline, medium and lower elevations). Radial growth was maximal at medium altitude and treeline of the southernmost populations. Temperature was the main factor controlling growth variability along the gradients, although the timing and strength of climatic variables affecting growth shifted with latitude and altitude. Predictive models forecast a general increase in Scots pine growth at treeline across the latitudinal distribution, with southern populations increasing growth up to year 2050, when it stabilizes. The highest responsiveness appeared at central latitude, and moderate growth increase is projected at the northern limit. Contrastingly, the model forecasted growth declines at lowland‐southern populations, suggesting an upslope range displacement over the coming decades. Our results give insight into the geographical responses of tree species to climate change and demonstrate the importance of incorporating biogeographical variability into predictive models for an accurate prediction of species dynamics as climate changes.     

长江口拟长脚数量变化和对环境变暖的响应

据1959年和2002年在长江口29°00′～32°00′ N, 122°00′～123°30′ E海域四季调查资料,研究结合拟长脚丰度和同步水温资料进行曲线拟合、构造数学模型和计算最适温度.分析拟长脚(Parathemisto gaudichaudi)的生态类型、空间分布、数量动态以及对变暖趋势的响应.结果表明:长江口海域拟长脚平均丰度和出现率都表现为夏秋季较低和冬春季较高.1959年春季平均丰度最高,为1.8 ind/m3;1959年秋季平均丰度最低,为0.03 ind/m3.1959年春季出现率最高,为62.96%;1959年秋季出现率最低,为6.90%.长江口拟长脚在1959年春季丛生指标最大(7.12),在1959年秋季最小(-1.00).这说明该种春季在长江口海域有明显的集群性,秋季集群性则不明显.温度是影响拟长脚季节变化和年间变化的主要因素.长江口海域拟长脚丰度和同步温度资料曲线拟合结果符合Yield Density模型,最适温度是17.0 ℃,置信度分析和拟合统计结果均有非常高的置信度.综合拟长脚最适温度和季节变化特征,可认为该种是暖温种.近年来在春季长江口水域的拟长脚丰度有所降低,这种数量年间变化趋势应与全球气候变暖相关.该种可作为海洋变暖长期变化的指示种.     

Freshwater species distributions along thermal gradients

The distribution of a species along a thermal gradient is commonly approximated by a unimodal response curve, with a characteristic single optimum near the temperature where a species is most likely to be found, and a decreasing probability of occurrence away from the optimum. We aimed at identifying thermal response curves (TRCs) of European freshwater species and evaluating the potential impact of climate warming across species, taxonomic groups, and latitude. We first applied generalized additive models using catchment‐scale global data on distribution ranges of 577 freshwater species native to Europe and four different temperature variables (the current annual mean air/water temperature and the maximum air/water temperature of the warmest month) to describe species TRCs. We then classified TRCs into one of eight curve types and identified spatial patterns in thermal responses. Finally, we integrated empirical TRCs and the projected geographic distribution of climate warming to evaluate the effect of rising temperatures on species’ distributions. For the different temperature variables, 390–463 of 577 species (67.6%–80.2%) were characterized by a unimodal TRC. The number of species with a unimodal TRC decreased from central toward northern and southern Europe. Warming tolerance (WT = maximum temperature of occurrence—preferred temperature) was higher at higher latitudes. Preferred temperature of many species is already exceeded. Rising temperatures will affect most Mediterranean species. We demonstrated that freshwater species’ occurrence probabilities are most frequently unimodal. The impact of the global climate warming on species distributions is species and latitude dependent. Among the studied taxonomic groups, rising temperatures will be most detrimental to fish. Our findings support the efforts of catchment‐based freshwater management and conservation in the face of global warming.     

POPULATION DYNAMICS DETERMINE GENETIC ADAPTATION TO TEMPERATURE IN DAPHNIA

Rising temperatures associated with global warming present a challenge to the fate of many aquatic organisms. Although rapid evolutionary response to temperature-mediated selection may allow local persistence of populations under global warming, and therefore is a key aspect of evolutionary biology, solid proof of its occurrence is rare. In this study, we tested for genetic adaptation to an increase in temperature in the water flea Daphnia magna , a keystone species in freshwater systems, by performing a thermal selection experiment under laboratory conditions followed by the quantification of microevolutionary responses to temperature for both life-history traits as well as for intraspecific competitive strength. After three months of selection, we found a microevolutionary response to temperature in performance, but only in one of two culling regimes, highlighting the importance of population dynamics in driving microevolutionary change within populations. Furthermore, there was an evolutionary increase in thermal plasticity in performance. The results of the competition experiment were in agreement with predictions based on performance as quantified in the life table experiment and illustrate that microevolution within a short time frame has the ability to influence the outcome of intraspecific competition.     

Assessment of Possible Causes of Changes in Аbundance and Sexual Structure in Populations of Prussian Carp (<Emphasis Type="Italic">Carassius auratus gibelio</Emphasis> Bloch., 1783)

The prevalence of processes of the increase in abundance and changes in the sexual structure of Prussian carp populations in waterbodies differing dramatically in ecological properties and distant from each other (Lake Sevan and Rybinsk Reservoir) indicates the presence of global factors affecting climatic zones. The increase in environmental temperature due to global warming may be such a factor. Experimentally proven high thermophilicity and the thermal stability of Prussian carp, as well as its low sensitivity to hypoxia, provide some advantages for this species over many other fish inhabiting the same waterbodies.     

Climate‐change winners and losers: stream macroinvertebrates of a submontane region in Central Europe

1. Freshwater ecosystems will be profoundly affected by global climate change, especially those in mountainous areas, which are known to be particularly vulnerable to warming temperatures. We modelled impacts of climate change on the distribution ranges of 38 species of benthic stream macroinvertebrates from nine macroinvertebrate orders covering all river zones from the headwaters to large river reaches. 2. Species altitudinal shifts as well as range changes up to the year 2080 were simulated using the A2a and B2a Intergovernmental Panel on Climate Change climate‐warming scenarios. Presence‐only species distribution models were constructed for a stream network in Germany’s lower mountain ranges by means of consensus projections of four algorithms, as implemented in the BIOMOD package in R (GLM, GAM, GBM and ANN). 3. Species were predicted to shift an average of 122 and 83 m up in altitude along the river continuum by the year 2080 under the A2a and B2a climate‐warming scenarios, respectively. No correlation between altitudinal shifts and mean annual air temperature of species’ occurrence could be detected. 4. Depending on the climate‐warming scenario, most or all (97% for A2a and 100% for B2a) of the macroinvertebrate species investigated were predicted to survive under climate change in the study area. Ranges were predicted to contract for species that currently occur in streams with low annual mean air temperatures but expand for species that inhabit rivers where air temperatures are higher. 5. Our models predict that novel climate conditions will reorganise species composition and community structure along the river continuum. Possible effects are discussed, including significant reductions in population size of headwater species, eventually leading to a loss of genetic diversity. A shift in river species composition is likely to enhance the establishment of non‐native macroinvertebrates in the lower reaches of the river continuum.     

Estimation of the extinction risk for high-montane species as a consequence of global warming and assessment of their suitability as cross-taxon indicators

The evidence for climate change is increasing, and global warming could lead to the extinction of some species. Here we estimated the extinction risk of six high-montane species of different taxonomic groups (fern, vascular plant, wood-inhabiting fungus, mollusk, saproxylic beetle, and bird) by modeling their occurrence under two global warming scenarios. We also assessed the cross-taxon indicator suitability of the selected species for monitoring climate change in low-mountain-range forests in southeastern Germany (Bavarian Forest National Park). We tested the influence of temperature and other habitat variables by applying semi-parametric spatial generalized linear models with binomial error. The probability of occurrence for each species under the present conditions and under two conditions of global warming was calculated. To assess the cross-taxon suitability, we tested the predictability of the final generalized linear models for each species using the measured occurrence of the other selected species and a discrimination technique. We identified temperature as the main driver for all selected high-montane species. Our statistical models predict a considerable risk of extinction of these species within the Bavarian Forest National Park as a result of global warming. Our discrimination model indicates that these species have essentially similar relationships with the environment and that five of the six species are suitable as indicators of early signs of global warming. The choice of which indicators to use should involve a consideration of the type of monitoring systems already in place.     

Change and stasis in marine hybrid zones in response to climate warming

Aim We test the prediction that hybrid zones between warm‐ and cold‐adapted species will move towards the territory formerly occupied by the cold‐adapted species in response to a warming climate. We use multiple tests of this prediction to distinguish amongst potential mechanistic hypotheses of responses to climate change. Location We sampled 97 locations on the Atlantic coast of Spain and France and the English Channel that span three hybrid zones formed between two species of marine mussels (Mytilus galloprovincialis and M. edulis). Methods Mussels were sampled in 2005–07 and analysed at a nuclear gene (Glu‐5′) that is diagnostically differentiated between the subject species. Results were compared to those of studies made in the same region over the past two decades. Historical change in sea surface temperature (SST) was analysed using National Oceanic and Atmospheric Administration (NOAA) Optimum Interpolation Daily SST. Species distribution models (random forest and maximum entropy) of the current distribution of mussels were constructed and validated by hindcasting the historical distributions of these species. Validated models were used in combination with forecasts of SST to predict changes in mussel distribution to 2050 and 2100. Results We show that over the past two decades two of the hybrid zones in France have not changed in either position or shape. The third hybrid zone, however, has shifted in the predicted direction, c. 100 km eastward into the warming English Channel. Species distribution modelling strongly implicates changes in winter cold SST as driving this change in the position of one of the hybrid zones. Forecasts of future SST indicate that rapid changes in distribution will occur over the next century. Main conclusions Hybrid zones can be used to conduct repeated tests of ecological responses to climate change and can be valuable in sorting among prospective mechanistic hypotheses that underlie that change. Winter temperatures, but not seasonal high temperature, appear to control the distribution of both species. Species distribution modelling indicates that the collapse of these hybrid zones is imminent, with the rapid expansion of the subtropical species in response to continuing SST warming.     

Projected climate change causes loss and redistribution of genetic diversity in a model metapopulation of a medium‐good disperser

Climate change causes species ranges to shift geographically as individuals colonise new suitable temperature zones or fail to reproduce where climate conditions fall below tolerance levels. Little is known about the potential loss of genetic diversity in such dynamic ranges. We investigated the level and distribution of neutral genetic diversity in shifting metapopulations during three scenarios of temperature increase projected for this century and at various degrees of weather variability. We used an individual‐based and spatially explicit metapopulation model in which temperature zones were simulated to move across a fragmented landscape following different climate change scenarios. Although the connectivity between habitat patches allowed the species, modelled after the middle spotted woodpecker Dendrocopos medius, to move along with the shifting temperature range, existing neutral genetic diversity was lost under all three temperature increase scenarios. This was independent of the loss of individuals. The explanation for this effect is that only a part of the original genetic variation moved into the newly colonised habitat. Under increased weather variability the number of individuals and the number of alleles per locus were persistently lower. However, the pattern of changes in allele distributions under temperature zone shifts was the same under all weather variability levels. Genetic differentiation between populations had a tendency to increase at metapopulation range margins, but decreased again when population sizes increased in time. Increased weather variability led to increased variation around the mean genetic differentiation across the metapopulation. Our results illustrate the usefulness of more realistic models for studying the effects of climate change on metapopulations. They indicate that biodiversity monitoring indices based on species occurrence and abundance are not a good proxy for the trend in the level of genetic diversity. Further, the results underline the importance of conserving areas where species have existed for a long time as modern refugia for genetic diversity.     

52 Beta-dimethylsulfoniopropionate (Dmsp) as a grazing deterrent in coastal phytoplankton communities

One of the most commonly predicted effects of global ocean warming on marine communities is a poleward shift in the distribution of species with an associated replacement of cold-water species by warm-water species. Such predictions are imprecise and based largely on broad correlations in uncontrolled studies that examine changes in species composition and abundance relative to seawater temperature. Before-After-Control-Impact (BACI) analyses of the effects of a large thermal discharge shows that an induced 3.4 deg. C rise in seawater temperature over 10 years along 2 km of rocky coastline resulted in significant community-wide changes in 150 species of algae and invertebrates relative to controls. Contrary to predictions from biogeographic models, there was no trend towards warm-water species with southern geographic affinities replacing cold-species with northern affinities. Instead, communities were greatly altered in apparently cascading responses to changes in abundance of several habitat-forming taxa, particularly subtidal kelps (e.g. Pterygophora californica ) and intertidal foliose red algae (e.g. Mazzaella flaccida ). Many temperature sensitive algae decreased greatly in abundance, whereas many invertebrate grazers increased. The results indicate that the responses of temperate reef communities to ocean warming can be strongly coupled to direct effects on habitat-forming taxa and indirect effects operating through ecological interactions. Given our understanding of temperate reef ecology and its local variability, the results also suggest that accurate predictions of the effects of global ocean warming will be difficult to make.