Long distance migration of insects to a subantarctic island

Transoceanic migration of four species of macrolepidoptera to subantarctic Macquarie Island has been detected in 7 out of 33 years during the period 1962–96 and is restricted to spring and autumn. Analyses of synoptic charts during the migration period show that autumn immigrants originated from New Zealand and comprised a single species of noctuid moth,Agrotis ipsilon (Walker). Spring immigrants originated from Australia and comprised two noctuids, Dasypodia selenophora Guenée and Persectania ewingii Westwood and a butterfly, Vanessa kershawi (McCoy). Autumn migrations were associated with depressions in the southern Tasman Sea. Spring migrations were associated with the eastward passage of prefrontal airflows ahead of cold fronts which extended from southern Australia to the west of Macquarie Island. In an analysis of one of these events, winds exceeded 30 ms^?1 at 300 m altitude and could have transported migrants from Tasmania to Macquarie Island overnight in less than 10 h. Flight activity was assisted by the presence of a nocturnal temperature inversion that maintained upper air temperatures above 5 °C. The effect of potential global warming on the migration and colonization of Macquarie Island by insects is discussed.     

Isotope evidence for latitudinal migrations of the dragonfly Sympetrum fonscolombii (Odonata: Libellulidae) in Middle Asia

• Sympetrum fonscolombii dragonflies are believed to migrate seasonally. In the spring and early summer, the already-mature dragonflies arrive in Middle Asia for reproduction. In the late summer and autumn, summer-generation dragonflies migrate to the south. Their wintering places remain unknown.
• Stable hydrogen (δ²H) and oxygen (δ¹⁸O) isotope analyses were conducted to confirm the migration of S. fonscolombii and determine the wintering area. Stable isotope composition of carbon (δ¹³C) and nitrogen (δ¹⁵N) in wings and legs was used to clarify the habitats in which dragonfly development took place.
• Three cohorts of dragonflies collected in different regions of Middle Asia were used for analysis: (i) immigrants that arrived in the spring, (ii) residents that developed in Middle Asia, and (iii) transit dragonflies migrating to the south during autumn.
• The average δ²H values in the wings were significantly higher in immigrants (−96‰) than in residents (−134‰) and transit individuals (−124‰). High δ¹⁸O and δ¹⁵N values in the tissue of immigrants confirmed their southerly origin.
• Based on the species range and the global distribution of annual averages of δ²H and δ¹⁸O values in precipitation, the latitudinal migrations of S. fonscolombii were inferred to cover the area from the proposed natal regions of immigrants in South-West Asia (below ∼36°N) to Southern Ural and the south of Western Siberia in the north (54–55°N) with a maximum migration distance of more than 4000 km.

     

东海低氧区及邻近水域浮游植物的季节变化

根据2011年5月、8月、11月在东海低氧区及邻近水域(25°00'—33°30'N,120°00'—127°30'E)进行的多学科综合调查,对东海低氧区及邻近水域浮游植物群落结构特征及季节变化进行了相关研究。经Utermhl方法初步分析共鉴定出浮游植物4门74属248种(含变种、变型,不含未定种),主要由硅藻和甲藻组成,此外还有少量的金藻和蓝藻。春季优势种主要为具齿原甲藻(Prorocentrum dentatum)、柔弱伪菱形藻(Pseudo-nitzschia delicatissim)、骨条藻(Skeletonema sp.)和具槽帕拉藻(Paralia sulcata);夏季主要是中肋骨条藻(Skeletonema costatum)和海链藻(Thalassiosira sp.);秋季主要是具槽帕拉藻、圆筛藻(Coscinodiscus sp.)和柔弱伪菱形藻。调查区浮游植物平均细胞丰度在夏季最高,达到85.002×103个/L,春季次之,秋季最低。在水平方向上,春、夏两季,表层浮游植物细胞丰度在近岸出现高值,由近岸到外海细胞丰度逐渐降低;而在秋季则相反,在调查海域的东北部出现高值,随离岸距离的增加细胞丰度逐渐增加。在垂直方向上,春、夏两季,浮游植物细胞丰度在表层出现最大值,随着深度的增加细胞丰度逐渐降低;而在秋季细胞丰度分布比较均匀,随水深变化不明显。调查区表层浮游植物ShannonWiener多样性指数和Pielou均匀度指数的平面分布基本一致,并且与细胞丰度的分布大致呈镶嵌分布。调查浮游植物群落的演替规律是:从春季的甲藻(具齿原甲藻、微小原甲藻(Prorocentrum minimum)等)为主,硅藻(柔弱伪菱形藻、骨条藻等)为辅;演替至夏季的硅藻(中肋骨条藻、海链藻等)为主,甲藻(主要是梭状角藻(Ceratium fusus)和叉状角藻(Ceratium furca))为辅,到秋季进一步演替为硅藻(具槽帕拉藻、圆筛藻、柔弱伪菱形藻等)为主,铁氏束毛藻(Trichodesmium thiebaultii)为辅。浮游植物物种组成、优势种、细胞丰度及多样性指数均表现出明显的时空变化。低氧区与非低氧区浮游植物群集存在明显差异。     

舟山海域夏、秋季浮游动物的分布特征及其与环境因子的关系

为更好地了解舟山海域浮游动物的群落结构、生物量和丰度的时空分布特征及其与主要环境因子的关系,分别于2014年7月和10月进行了夏季、秋季两次生态综合调查,并用多维尺度分析法、典范对应分析法对浮游动物群落结构进行了研究。结果表明:夏季舟山海域调查的浮游动物有13类,64种,优势种为背针胸刺水蚤(Centropages dorsispinatus)、圆唇角水蚤(Labidocera rotunda)、中华哲水蚤(Calanus sinicus)、精致真刺水蚤(Euchaeta concinna)、百陶带箭虫(Zonosagitta bedoti)和真刺唇角水蚤(Labidocera euchaeta);秋季鉴定到浮游动物12类,45种,优势种为背针胸刺水蚤(Centropages dorsispinatus)、百陶带箭虫(Zonosagitta bedoti)、双生水母(Diphyes chamissonis)、瓜水母(Beroёcucumis)和中华哲水蚤。夏季浮游动物平均丰度及平均生物量(144.0 ind/m3和176.3 mg/m~3)都分别高于秋季(21.4个/m3和86.3 mg/m3);Shannon-Wiener多样性指数夏季(3.03)高于秋季(2.82),Pielou均匀度指数则是秋季(0.83)高于夏季(0.64);夏季不同区域浮游动物群落之间具有明显的差异,而秋季大部分站位群落之间差异不显著;温度、盐度、叶绿素a浓度和营养盐含量是影响舟山海域浮游动物分布的主要环境因子;与历史资料相比,舟山海域浮游动物丰度及生物量呈下降趋势,其优势种保持较稳定。     

Temperature requirements for the growth and maturation of the gametophytes of Undaria pinnatifida and U. undarioides (Laminariales, Phaeophyceae)

Gametophytes of two Undaria species, U. pinnatifida and U. undarioides (Laminariales, Phaeophyceae), were studied to determine their water temperature requirements in order to understand their different distributions in Mie Prefecture, Japan. The optimal temperature for growth was 20°C for gametophytes of both species, and the upper critical temperature for growth was also the same for both species at 28°C. Therefore, the optimal and critical temperatures for growth of the gametophytes are not the main factors determining distribution. The optimal temperature for maturation of U. pinnatifida was approximately 10–15°C, whereas it was closer to 20–21°C for U. undarioides, a difference between these species of at least 5°C. In autumn and early winter, the seawater temperature at the mouth of Ise Bay, where U. pinnatifida is distributed, ranges from 21.6°C (October) to 12.7°C (December), and off Hamajima, where U. undarioides is found, the range is from 22.7°C (October) to 19.1°C (December). The seawater temperatures from October to December, which is the maturation season for the gametophytes, agreed well with the optimal temperature requirements for maturation of the gametophytes of both species. Thus the difference in the maturation temperature range of the gametophytes is a major factor determining distribution of these Undaria species along the Japanese coast.     

The long-distance migration of Nilaparvata lugens (Stål) (Delphacidae) in China: radar observations of mass return flight in the autumn

Abstract.

• 1 A case study is presented of the autumn migration of the brown planthopper, Nilaparvata lugens (Stål), in the area of Nanjing in the People's Republic of China. The study was made using a high frequency (8 mm wavelength) radar and a net suspended from a kytoon.
• 2 The observations confirmed that long-distance return migrations occur in China in mid and late September, with N.lugens being carried on the prevailing north-easterly wind towards the autumn infestation and overwintering areas of the species.
• 3 After mass take-off in the late afternoon or at dusk, the migrants flew for several hours during the evening, often in a dense layer which formed at heights between about 400 and 1000m above ground. These layers often had well-defined ceilings corresponding to an air temperature of about 16°C. The migration height was above the top of the surface temperature inversion, i.e. the migrants did not fly at the height of the warmest air.
• 4 The dense layer concentrations overflying the radar were backtracked to source areas up to 240 km away in the north-east of Jiangsu Province. Planthoppers observed emigrating from the Nanjing area would reach areas in south Anhui Province or north Jiangxi Province if they flew for 12 h.
• 5 There was a second period of mass take-off at dawn. Insect layers sometimes formed but did not last longer than 1–2h.
• 6 The present results were strikingly different from those previously observed in the dry season in the Philippines, where migratory flight durations were largely confined to periods of about 30min at dusk and dawn.
• 7 Our observations are discussed in relation to the equator-wards return migrations undertaken in autumn by other insect species, and the importance of these migrations for the maintenance of long-flying genotypes in the overwintering populations is considered.

     

Effect of Temperatures on Dormancy and Germination in Three Species in the Lamiaceae Occurring in Northern Wetlands

In the temperate region temperature is the main factor influencing the germination period of plant species. The purpose of this study was to examine effects of constant and fluctuating temperatures on dormancy and germination under laboratory and field conditions in the three wetland species Lycopus europaeus, Mentha aquatica and Stachys palustris. The results should give indications if the temperature-dependent regulation of dormancy and germination is phylogenetically constrained. Tests for germination requirements showed a minimum temperature for germination of 9 °C in Mentha and 12 °C in Lycopus and Stachys, and a maximum temperature of 33 °C for Lycopus and 36 °C for Mentha and Stachys. Fluctuating temperatures promoted germination in all three species but the amplitude required for high germination (>50%) differed: it was 8 °C in Mentha, 10 °C in Stachys and 14 °C in Lycopus (mean temperature 22 °C). The effect of temperatures on the level of dormancy was examined in the laboratory by imbibing seeds at temperatures between 3 °C and 18 °C for periods between 2 and 28 weeks, as well as by a 30-month burial period, followed by germination tests at various temperatures, in light and darkness. In the laboratory only low temperatures (≤12 °C) relieved primary dormancy in seeds of Lycopus, while in Mentha and Stachys also higher temperatures lead to an increase of germination. Dormancy was only induced in Lycopus seeds after prolonged imbibition at 12 °C in the laboratory. Buried seeds of all species exhibited annual dormancy cycles with lower germination in summer and higher germination from autumn to spring. Exhumed seeds, however, showed considerable differences in periods of germination success. Dormancy was relieved when ambient temperatures were below 12 °C. Ambient temperatures that caused an induction of dormancy varied depending on species and test condition, but even low temperatures (8 °C) were effective. At high test temperatures (25 °C) in light, exhumed seeds of all three species showed high germination throughout the year. The three species showed various differences in the effects of temperatures on dormancy and germination. Similarities in dormancy and germination found among the species are in common with other spring-germinating species occurring in wetlands, so it seems that the temperature dependent regulation of dormancy and germination are related to habitat and not to phylogenetic relatedness.     

Migration patterns of Hoopoe Upupa epops and Wryneck Jynx torquilla: an analysis of European ring recoveries

For many bird species, recovery of ringed individuals remains the best source of information about their migrations. In this study, we analyzed the recoveries of ringed European Hoopoe (Upupa epops) and the Eurasian Wryneck (Jynx torquilla) from 1914 to 2005 from all European ringing schemes. The aim was to define general migration directions and to make inferences about the winter quarters, knowing that hardly any recoveries are available from sub-Saharan Africa. For the autumn migration, there is evidence of a migratory divide for the Hoopoe in Central Europe, at approximately 10–12°E. Autumn migration directions of Wrynecks gradually change from SW to SE depending on the longitude (west to east) of the ringing place. In both species, only a few recoveries were available indicating spring migration directions, but they showed similar migration axes as for autumn migration, and hence no evidence for loop-migration. Due to a paucity of recoveries on the African continent, we can make only limited inferences about wintering grounds: extrapolating migration directions are only indicative of the longitude of the wintering area. The directions of autumn migration indicate a typical pattern observed in European long-distance migrants: west-European Hoopoes and Wrynecks are likely to winter in western Africa, while central- and east-European birds probably winter more in the east. Due to the migratory divide, for the Hoopoe, this phenomenon is more pronounced.     

Verbreitung von Makrozooplankton in der Grönlandsee im Spätherbst 1988 (Crustacea: Ostracoda, Hyperiidea [Amphipoda], Euphausiacea)

The horizontal and vertical distribution and the abundance of ostracods, hyperiids (amphipods) and euphausiids in the Greenland Sea along a transect parallel 74°45′N (from 15°45′E to 08°30′W) are described. The samples were taken by RV “Meteor” in late autumn of 1988. 8 species of the above named groups have been recorded in two different water masses which were touched by the transect. 5 stations were situated in the realm of the Atlantic waters of the Spitsbergen Current. HereDiscoconchoecia elegans, Meganyctiphanes norvegica, andThemisto compressa are indicators for the southern Atlantic water. 6 stations belong to the Arctic area dominated by Arctic Surface Water, whereBoroecia borealis, Themisto abyssorum, Thysanoessa longicaudata, andThysanoessa inermis are quite abundant as borealsubarctic species, whereasThemisto libellula is a true species of pure Arctic water.

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Mitarbeiterin der Taxonomischen Arbeitsgruppe an der Biologischen Anstalt Helgoland     

Longer is fatter: body mass changes of migrant Reed Warblers (Acrocephalus scirpaceus) staging at Eilat,Israel

Ecological barriers are the riskiest phases of the annual migrations for migratory birds. Comparatively little field data exists pertaining to the ability of migratory birds to prepare for the challenges of crossing ecological barriers, or their ability to recuperate afterward. Migrating Reed Warblers (Acrocephalus scirpaceus) were captured in Eilat, Israel, during their spring and autumn migrations. Data on spring and autumn body masses, their inter-annual variation, and the pattern of body mass increase were analysed. The birds show a significant inter-annual variation in their body mass and body condition index in both seasons, which is consistent with the data from other sites and for other passerine species. During stopovers, mass gain occurred in both seasons. Birds in poor initial condition, and those that stop over for a longer period of time, gained more body mass faster. In spring, but not in autumn, the progress of the season was also an important factor; late-arriving birds gained more fuel faster. The average rate of fuel gain was 0,157g·day^?1 ± 0.018 SE.     

西沙宣德群岛海域浮游植物群落及其影响因子

为了解西沙宣德群岛海域浮游植物群落结构特征,于2019年2月和11月对该海域进行采样调查,分析浮游植物群落组成及环境影响因素。两个航次共发现109种浮游植物,其中硅藻门最多,有81种。冬秋季节优势种不尽相同,冬季优势种为铁氏束毛藻(Trichodesmium thiebautii)、红海束毛藻(T. erythraeum)和标志星杆藻(Asterionella notata)等,秋季优势种为菱形海线藻(Thalassionema nitzschioides)、丹麦细柱藻(Leptocylindrus danicus)和劳氏角毛藻(Chaetoceros lorenzianus)。冬季浮游植物平均丰度[(5.27±6.14)×10⁷ cells/L]显著高于秋季[(1.56±1.40)×10⁵ cells/L]。浮游植物群落分布主要受亚硝酸盐、盐度等环境因子影响。冬秋季各站位浮游植物群落的多样性指数、均匀度指数和丰富度指数平均值分别为3.15、0.71、1.36和3.28、0.75、1.77。因此,宣德群岛海域冬秋季节浮游植物群落多样性较高,物...     

大陈岛海域浮游动物群落季节变化及其影响因素

为探究大陈岛海域浮游动物群落的季节变化,于2020年9月（夏季）、11月（秋季）和2021年1月（冬季）、4月（春季）分别对大陈岛海域的浮游动物及环境因子进行了4个航次的调查。结果共鉴定浮游动物90种,包括浮游幼体15类,其中夏季种类数最多（68种）,冬季最少（20种）,常见的优势种有：百陶箭虫（Sagitta bedoti）、微刺哲水蚤（Canthocalanus pauper）、中华哲水蚤（Calanus sinicus）等12种（Y>0.02）。浮游动物的年平均丰度和生物量分别为（153.40±214.73）个/m³、（411.93±561.76） mg/m³,二者存在明显的季节变化,平均丰度为春季（380.17±296.14）个/m³>夏季（135.30±112.59）个/m³>秋季（67.88±90.52）个/m³>冬季（25.30±19.11）个/m³;平均生物量为夏季（895.01±802.54） mg/m³>春季（623.39±358.73） mg/m³>秋季（91.08±82.36） mg/m³>冬季（45.96±84.95） mg/m³。多样性指数（H''）和均匀度指数（J''）的年平均值分别为1.71±0.96和0.53±0.20,均表现出夏秋季较高、冬春季较低的特征。聚类分析结果表明调查海域的浮游动物可划分为夏季类群、秋季类群、冬季类群和春季类群4组类群。Pearson相关性分析和冗余分析（RDA）结果表明,海水温度、盐度、叶绿素a浓度是影响大陈岛海域浮游动物群落特征的重要环境因素。此外,夏季大陈岛海域水母类浮游动物暴发的现象值得关注。研究结果将为大陈岛海域的生物多样性保护及渔业资源可持续开发利用提供可参考的数据资料。     

Seasonal foraging movements and migratory patterns of female Lamna ditropis tagged in Prince William Sound, Alaska

Conventional and electronic tags were used to investigate social segregation, distribution, movements and migrations of salmon sharks Lamna ditropis in Prince William Sound, Alaska. Sixteen salmon sharks were tagged with satellite transmitters and 246 with conventional tags following capture, and were then released in Prince William Sound during summer 1999 to 2001. Most salmon sharks sexed during the study were female (95%), suggesting a high degree of sexual segregation in the region. Salmon sharks congregated at adult Pacific salmon Oncorhynchus spp. migration routes and in bays near Pacific salmon spawning grounds in Prince William Sound during July and August. Adult Pacific salmon were the principal prey in 51 salmon shark stomachs collected during summer months in Prince William Sound, but the fish appeared to be opportunistic predators and consumed sablefish Anoplopoma fimbria, gadids, Pacific herring Clupea pallasi, rockfish Sebastes spp. and squid (Teuthoidea) even when adult Pacific salmon were locally abundant. As Pacific salmon migrations declined in late summer, the salmon sharks dispersed; some continued to forage in Prince William Sound and the Gulf of Alaska into autumn and winter months, while others rapidly moved south‐east thousands of kilometres toward the west coasts of Canada and the U.S. Three movement modes are proposed to explain the movement patterns observed in the Gulf of Alaska and eastern North Pacific Ocean: ‘focal foraging’ movements, ‘foraging dispersals’ and ‘direct migrations’. Patterns of salmon shark movement are possibly explained by spatio‐temporal changes in prey quality and density, an energetic trade‐off between prey availability and water temperature, intra‐specific competition for food and reproductive success. Transmissions from the electronic tags also provided data on depth and water temperatures experienced by the salmon sharks. The fish ranged from the surface to a depth of 668 m, encountered water temperatures from 4·0 to 16·8° C and generally spent the most time above 40 m depth and between 6 and 14° C (60 and 73%, respectively).     

Distribution of cephalopods in the upper epipelagic northwestern Bering Sea in autumn

In the northwestern Bering Sea in autumn, the epipelagic cephalopod community was represented by the boreal fauna, and was found to be composed of three families and nine species of the order Teuthida: Gonatidae (Berryteuthis magister, Boreoteuthis borealis, Gonatopsis japonicus, Gonatus madokai, Gonatus kamtschaticus, Gonatus onyx, and Gonatus pyros), Chiroteuthidae (Chiroteuthis calyx) and Onychoteuthidae (Onychoteuthis borealijaponica). Two pelagic gonatid species (B. borealis and G. kamtschaticus) dominated the cephalopod community in the upper 50 m. The distribution patterns of B. borealis and G. onyx were associated with diel vertical migrations of these squid. The distribution of two distinct size groups of G. kamtschaticus suggested ontogenetic migration of larger squid to deeper layers, and adds to previous data suggesting that this species may be a heterogeneous assemblage. Demersal B. magister rarely occurred in the surface waters. The occurrence of maturing O. borealijaponica in the southern marine area indicated that these were occasional seasonal migrants from the ocean. The occurrence of juvenile C. calyx suggested that these squid may conduct vertical forage migrations from deep waters to the surface layers.     

The Life Histories of Two Temporarily Coexisting,Pond Dwelling Cladocerans

Investigations on the life histories of two cladocerans, Moina brachiata and Daphnia obtusa, in a small, nearly temporary pond in South Germany revealed that M. brachiata is better adapted to fluctuating environmental conditions; the species dominated from May to October. D. obtusa was present in spring and autumn/winter but disappeared completely during the summer months. Both species coexisted for extended periods in spring and autumn; abundance of D. obtusa was generally by an order of magnitute lower. Four periods of low water level were slightly preceded by or coincided with a decrease of clutch size, a decrease of the proportion of egg bearing females indicating that both species suffered from food shortage. Laboratory investigations on life history parameters showed that the two species have different temperature tolerances and preferences. M. brachiata showed its highest reproductive success at 25 and 30°C but died at temperatures <15°C and ≥ 35°C. D. obtusa experienced a broader temperature range (2 to 25°C) but could not withstand temperatures ≥ 30°C. Short term starvation periods (3d) caused the death of M. brachiata females, while D. obtusa soon recovered and reproduced when being refed. M. brachiata is a typical r-species with early reproduction, rapid development, high population growth rates and a high tendency to produce resting eggs; D. obtusa pursues more the concept of k-selection.     

Distribution patterns of pelagic euphausiids in the East China Sea

Distribution patterns and abundance of the euphausiids were examined in the East China Sea (23°30′ –33°00′N, 118°30′ –128°00′ E) in relation to temperature and salinity. The data were collected in 4 surveys from 1997 to 2000. The density or yield density model was used to predict optimum temperature and salinity of water for euphausiid distribution, and thereafter distribution patterns of euphausiids were determined based on the predicted parameters. Of 23 species, Euphausia pacifica, E. nana, Pseudeuphausia sinica and P. latifrons were numerically dominant. The analyses indicate that Euphausia pacifica is an offshore temperate water species, E. nana is an offshore temperate warm water species, P. sinica is a coastal subtropical water species and P. latifrons is an oceanic tropical water species. The 4 species occupied 4 different water masses, respectively, namely, cold water mass, cold and warm water mixed masses in winter and spring, cold and warm water mixed masses in summer and autumn, and warm water mass, which could be the good designators of individual water masses, respectively. The predicated optimal temperatures for E. tenera, S. carinatum, E. diomedeae, Stylocheiron affine, Nematoscelis sp., N. gracilis, N. atlantica, Stylocheiron sp. and S. suhmii are all > 25°. These species are mainly distributed in southern Kuroshio in winter and spring, Kuroshio, the Taiwan Warm Current and Tsushima Current in summer and autumn, the equatorial waters of Pacific Ocean and the eastern waters of the Taiwan Strait. They are called as oceanic tropical water species. Nematoscelis tenella and T. tricuspidata are referred to as offshore subtropical water species according to their geographic distributions even if they are halobionts. Euphausia sanzoi is considered as a typical offshore subtropical water species, which inhabited waters below 25°. Stylocheiron microphthalma, occupying warm current waters where temperature and salinity are nearly 25° and 34 in summer and autumn, belongs to oceanic tropical water species. In the same way, E. similes, E. mutica, Euphausia sp., E. brevis and E. recurva are classified into offshore subtropical water species in accordance with the optimum temperature and salinity of waters as well as locations and seasons of their occurrence. Optimum temperature, rather than salinity, is a better parameter in determining the distribution patterns of euphausiids.     

Compositional shifts in Costa Rican forests due to climate‐driven species migrations

Species are predicted to shift their distributions upslope or poleward in response to global warming. This prediction is supported by a growing number of studies documenting species migrations in temperate systems but remains poorly tested for tropical species, and especially for tropical plant species. We analyzed changes in tree species composition in a network of 10 annually censused 1‐ha plots spanning an altitudinal gradient of 70–2800 m elevation in Costa Rica. Specifically, we combined plot data with herbarium records (accessed through GBIF) to test if the plots' community temperature scores (CTS, average thermal mean of constituent species weighted by basal area) have increased over the past decade as is predicted by climate‐driven species migrations. In addition, we quantified the contributions of stem growth, recruitment, and mortality to the observed patterns. Supporting our a priori hypothesis of upward species migrations, we found that there have been consistent directional shifts in the composition of the plots, such that the relative abundance of lowland species, and hence CTS, increased in 90% of plots. The rate of the observed compositional shifts corresponds to a mean thermal migration rate (TMR) of 0.0065 °C yr^?1 (95% CI = 0.0005–0.0132 °C yr^?1). While the overall TMR is slower than predicted based on concurrent regional warming of 0.0167 °C yr^?1, migrations were on pace with warming in 4 of the 10 plots. The observed shifts in composition were driven primarily by mortality events (i.e., the disproportionate death of highland vs. lowland species), suggesting that individuals of many tropical tree species will not be able to tolerate future warming and thus their persistence in the face of climate change will depend on successful migrations. Unfortunately, in Costa Rica and elsewhere, land area inevitably decreases at higher elevations; hence, even species that are able to migrate successfully will face heightened risks of extinction.     

Tolerance of low pH exposure by the eggs of Odonata (dragonflies and damselflies)

The development times and hatching success of the eggs of four species of Odonata (Ischnura verticalis, Lestes congener, Libellula lydia, and Sympetrum vicinum) were unaffected by exposure to soft water at pH 5.1 and 3.5. Tolerance of low pH, soft water conditions by Odonata eggs may in part account for the widespread distribution of Odonata in potentially acid-stressed regions.     

Seed germination of exotic and native winter annuals differentially responds to temperature and moisture,especially with climate change scenarios

Seeds of winter annuals require a summer after-ripening period for dormancy loss and low autumn temperatures for germination. With current and future changes in moisture and temperature, we tested the effects of warming along a relative humidity (RH) gradient on dormancy loss and effects of decreased diurnal temperature range (DTR) on germination. We further reasoned that the effects of changes in these variables would be disproportionate between the exotic and native winter annuals. Seeds of exotic species (Buglossoides arvensis, Lamium purpureum and Ranunculus parviflorus) and co-occurring native species (Galium aparine, Paysonia stonensis and Plantago virginica) were collected in middle Tennessee. After-ripening occurred over a 15–100% RH gradient at 25 and 30°C and germination was tested at 20/10 and 20/15°C. Niche breadth was calculated using Levins' B. Fresh Ranunculus seeds had high germination and those of other species did not. Germination for these species increased with after-ripening, mostly across the RH gradient irrespective of temperature. A decrease in DTR showed mixed results – the extreme being Ranunculus with no germination at 20/15°C. Most exotic species had wider germination niche breadths than native species. With climate change, we suggest that a decrease in DTR may have a larger effect on germination than increasing moisture or warming on dormancy break. Moreover, there is not a clear-cut winner with climate change when we compare exotic versus native species because the responses of our six species were species specific.     

TEMPERATURE REQUIREMENTS FOR GROWTH AND SURVIVAL OF ANTARCTIC RHODOPHYTA1

The temperature requirement for growth and the upper survival temperatures (USTs) of 15 Antarctic red algal species collected on King George Island (South Shetland Islands) and Signy Island (South Orkney Islands) were determined. Two groups with different temperature requirements were identified. 1) A “eurythermal” group includes Rhodymenia subantarctica, Phyllophora ahnfeltioides, Gymnogongrus antarcticus, and Rhodochorton purpureum, growing between 0° and 10°C with optimum values at (0°) 5°(l0°)C. The USTs of these species and of Porphyra endiviifolium, Delesseria lancifolia, and Bangia atropurpurea were between 22° and 16°C. These species survived temperatures in a similar range as most endemic Arctic or Arctic/cold-temperate species but exhibited a lower temperature demand for growth, suggesting an earlier contact with low temperatures than Arctic species. 2) A stenothermal group includes Pantoneura plocamioides, Myriogramme mangini, Ballia callitricha, Phyllophora antarctica, Gigartina skottsbergii, Georgiella confluens, and Plocamium cartilagineum growing at 0° or ≤5°C with optimum values at 0° or 5°C. The USTs of these species and of Phycodrys austrogeorgica were between 14° and 7°C. The species of this group must have had an even earlier contact with the Antarctic cold-water environment than species of the “eurythermal” group. Gigartina skottsbergii, Georgiella confluens, Plocamium cartilagineum, and Pantoneura plocamioides were probably exposed longer to low temperatures than the other species of this group or Antarctic green and brown algae because they show the lowest temperature requirements so far determined in seaweeds. The results are discussed in the context of present local temperature regimes at the localities where the isolates were collected. Moreover, an attempt was made to explain the geographic distribution of individual species by the temperature requirements determined in this study. Only a few of the distribution limits are determined by temperature growth and/or survival characteristics. In many species (Rhodymenia subantarctica, Ballia callitricha, Gigartina skottsbergii, Bangia atropurpurea, Rhodochorton purpureum, and Plocamium cartilagineum), the development of temperature ecotypes is evident.