SPATIAL AND TEMPORAL VARIATION IN CHASMOGAMY AND CLEISTOGAMY IN OXALIS MONTANA (OXALIDACEAE)

Chasmogamous (CH) and cleistogamous (CL) flower production was investigated in natural populations of the perennial herb Oxalis montana in southern Quebec, Canada. Every 10–12 days during two flowering seasons, we recorded the reproductive output of approximately 2,000 plants distributed among five forest sites. The percentage of plants flowering, proportion of flowering plants producing CH and CL flowers, CH and CL flower number per flowering plant, and the proportion of flowers that are CL differed significantly among sites and corresponded to site differences in forest type and habitat quality. Unlike patterns in most CL species, however, reproduction by cleistogamy increased in sites with habitat conditions favorable to plant growth and sexual reproduction, and decreased in less productive sites. Chasmogamous and CL flower production increased with increasing plant size but plant size explained a significantly greater proportion of the variation in CL flower numbers. The percentage of flowering plants producing CH flowers decreased between years while the proportion of CL flowers increased at all sites during the second flowering season. The somewhat unusual aspects of reproduction in Oxalis may stem from its perennial habit which allows use of stored resources in adjusting the balance of cleistogamy versus chasmogamy in different environmental regimes.     

Shade avoidance in the clonal herb Trifolium fragiferum/: a field study with experimentally manipulated vegetation height

In herbaceous canopies light availability can show high degrees of spatial variability in a vertical and also in a horizontal direction. Stoloniferous plants are hence likely to encounter differences in light availability during their ontogenetic development. Different mechanisms, such as petiole elongation, plasticity in internode length and branching, and an enhanced allocation to sexual reproduction have been suggested to represent viable shade-avoidance mechanisms for clonal plants.In a field experiment we tested the response of the stoloniferous herb Trifolium fragiferum L. to experimentally manipulated vegetation heights. Naturally occurring clonal fragments were exposed to four different vegetation heights ranging from 0 cm (high light availability created by clipping the surrounding natural vegetation at ground level) to 20 cm (natural shading in closed canopy). The growth and development of individual clones was followed for two months. At the end of the experiment above-ground plant parts were harvested. Growth-related and morphological parameters (e.g., petiole and internode length) as well as patterns of meristem utilization (i.e., flowering, branching) were recorded.Neither primary stolon growth and biomass accumulation nor branching and flowering were significantly affected by treatments. However, increased vegetation height resulted in a reduced number of secondary ramets and also had strong positive effects on petiole length, leading to marked changes in the architecture of plants growing in canopies of different heights. In addition, the average weight of individual ramets on the primary stolon was markedly higher in plants exposed to taller vegetation as compared to shorter vegetation.The results of this study suggest the occurrence of a trade-off between clonal expansion (i.e., secondary ramet production) and the average size of clonal offspring. If grown under higher vegetation plants invested more into the size of individual ramets, especially into elongating petioles, and less into the growth and development of lateral branches. Placing leaf laminae higher up in the canopy results in an enhanced light interception which has apparently buffered negative effects of increased vegetation height on whole-clone biomass. Plants grown under shorter vegetation invested more into lateral spread by producing more, but smaller ramets.     

Seasonal patterns of carbon assimilation and allocation of a summer-green forest herb, <Emphasis Type="Italic">Parasenecio</Emphasis> <Emphasis Type="Italic">auriculata</Emphasis> (Senecioneae; Asteraceae)

Summer-green herbs inhabiting deciduous forests often put out aerial shoots under bright conditions before tree-canopy closure and grow until late summer under the closed canopy. Some of them produce leaves continuously even after the initiation of canopy closure, indicating an exploitation of the low light period. The manner of carbon assimilation during bright and shade periods within a growth season should reflect the seasonal patterns of vegetative growth and reproductive allocation of individual species. We examined the seasonal patterns of assimilation, partitioning of photosynthate between reproduction and storage, and the budget of reproduction of a perennial understory herb, Parasenecio auriculata. Although photosynthetic rates per unit leaf area decreased with the seasonal reduction in light level, net assimilation at the whole-plant level was maintained at a high level even after canopy closure owing to the increase in the total leaf area. Stored resource in tubers contributed to the rapid development of aerial shoots in the early season, and annual tuber growth was completed before flowering. Instant photosynthetic products considerably contributed to the maintenance of flowers but not to fruit development because of low assimilation rate during fruiting. These findings indicated that carbon assimilation during flowering contributes to sexual reproduction without influencing the development of storage organs. Stable carbon assimilation over summer by shade-acclimatized leaves enabled the maintenance of high productivity associated with high sexual reproduction.     

内蒙古典型草原群落实生苗动态对刈割和放牧干扰的响应

 该文通过刈割和放牧样地的实生苗动态观测,试图揭示刈割和放牧干扰对冰草(Agropyron cristatum)、克氏针茅(Stipa krylovii)和糙隐子 草(Cleistogenes squarrosa )等 3种禾草实生苗出生、存活和死亡季节动态的影响,以及这种效应是如何受气温和降水影响的。利用有重复测 量的方差分析,比较了不同刈割留茬高度(0、5和15 cm)与放牧处理之间在实生苗密度、死亡率和出现率的时间动态方面的差异。结果表明：3 种禾草的实生苗密度自5月下旬至8月中旬一直呈增加态势。刈割在一定程度上抑制了克氏针茅的实生苗出现率,原因可能是相对高大的克氏针 茅在前一年刈割时会被去掉相当多的生殖部分,其种子数量必然受到影响,导致实生苗出现率的降低。同时,刈割对相对低矮的糙隐子草实生 苗有正向效应 ,即促进其实生苗的出现,可能的原因是刈割使植被高度降低、植被稀疏,植被冠层以下至地面的光照较好、地温较高,同时位 于下层的糙隐子草受到的高大植株的竞争压力减小。生长季早期和晚期实生苗死亡率较高,这与这两个时期的干旱和低温有关,而自6月中旬至 7月初之间的死亡率小高峰也是先前的干旱少雨导致的。3种禾草实生苗的大规模出现几乎都在5～7月,这与该时期相对适宜的气温、地温和水 分条件有关。对实生苗更新相关过程 (如种子萌发、休眠、种子库存量等)进行更加深入细致的研究,将进一步揭示种子生产和有性繁殖在群落 过程中的作用。     

内蒙古典型草原群落实生苗动态对刈割和放牧干扰的响应

该文通过刈割和放牧样地的实生苗动态观测,试图揭示刈割和放牧干扰对冰草(Agropyron cristatum)、克氏针茅(Stipa krylovii)和糙隐子 草(Cleistogenes squarrosa )等 3种禾草实生苗出生、存活和死亡季节动态的影响,以及这种效应是如何受气温和降水影响的。利用有重复测 量的方差分析,比较了不同刈割留茬高度(0、5和15 cm)与放牧处理之间在实生苗密度、死亡率和出现率的时间动态方面的差异。结果表明：3 种禾草的实生苗密度自5月下旬至8月中旬一直呈增加态势。刈割在一定程度上抑制了克氏针茅的实生苗出现率,原因可能是相对高大的克氏针 茅在前一年刈割时会被去掉相当多的生殖部分,其种子数量必然受到影响,导致实生苗出现率的降低。同时,刈割对相对低矮的糙隐子草实生 苗有正向效应 ,即促进其实生苗的出现,可能的原因是刈割使植被高度降低、植被稀疏,植被冠层以下至地面的光照较好、地温较高,同时位 于下层的糙隐子草受到的高大植株的竞争压力减小。生长季早期和晚期实生苗死亡率较高,这与这两个时期的干旱和低温有关,而自6月中旬至 7月初之间的死亡率小高峰也是先前的干旱少雨导致的。3种禾草实生苗的大规模出现几乎都在5～7月,这与该时期相对适宜的气温、地温和水 分条件有关。对实生苗更新相关过程 (如种子萌发、休眠、种子库存量等)进行更加深入细致的研究,将进一步揭示种子生产和有性繁殖在群落 过程中的作用。     

THE ANNUAL CYCLE IN A TROPICAL WET FOREST HUMMINGBIRD COMMUNITY

In the Caribbean lowlands of Costa Rica, rainfall is moderately seasonal, although even in the driest month over 100 mm of rain usually fall. Flowering of hummingbird food plants shows a peak in the dry season (February-April) and another in the early wet season (July-September), with a severe flower shortage at the end of the rains (November-December). The dry season peak involves largely canopy epiphytes, the wet season peak large herbs of light gaps and edges and forest understory plants. This study examines the responses of the associated community of 22 species of hummingbirds (of which 13 breed, and 12 are common for at least parts of most years) to these spatial and temporal patterns of resource availability. Nearly all common breeding species show a peak of reproductive activity in the dry season, coinciding with the first flowering peak, followed by a discrete moulting season that coincides with the wet season peak of flowering. Of the three species with extended breeding seasons, the two species of hermit, Phaethornis, show moult-breeding overlap to varying degrees on an individual basis. In a number of species moult and breeding appear antagonistic. The annual peak of body weight and fat deposits in all species occur during the second flowering peak, approximately corresponding to the moult. The annual minima of body weight and fat occur in the lean season and the breeding season respectively. The lack of concordance of these two possibly reflects the use of muscle protein as a nutrient source during the lean season. Several species show pronounced habitat shifts through the year, with the sexes sometimes occupying different microhabitats, especially during the dry season. At least five species show pronounced seasonal migrations, largely or entirely leaving La Selva for part of the year. Overall hummingbird numbers are greatest early in the rainy season, lowest in the lean season, with the non-hermits (Trochilinae) showing a more pronounced annual cycle of numbers than the hermits (Phaethorninae). Comparisons with other tropical lowland hummingbird-flower communities are made with respect to the roles of flowers as proximate and ultimate factors regulating the annual cycles and affecting the population biology of the birds.     

Regulation of clonal growth and dynamics of Panicum virgatum (Poaceae) in tallgrass prairie: effects of neighbor removal and nutrient addition

Clones of the perennial grass Panicum virgatum were studied on the Konza Prairie in northeast Kansas to determine the effects of neighbors, nutrient availability, and physiological integration on ramet population dynamics and clonal growth and architecture. Opposite halves of established clones in the field were subjected differentially to treatments including neighbor removal and nitrogen addition, with intact or severed rhizome connections between halves. Neighborhood competition strongly influenced clone architecture and expansion rates. Removal of neighbors resulted in a >;95% increase in radial clone expansion, intraclonal ramet densities, ramet population growth rates, ramet biomass, and percent of stems flowering, averaged over a 4-year period relative to halves or clones with intact competitors. Plant responses suggest that effects of interclonal neighbors are mediated through alteration of the light environment in the clone canopy and water availability. Addition of nitrogen did not affect lateral spread or clone structure, but resulted in significant increases in ramet size, flowering, and seed production. ANOVA revealed no significant effect of rhizome severing or treatment × severing interactions, suggesting that the size of the integrated physiological unit is much smaller than clone size and/or that physiological integration had no effect on clone responses to environmental heterogeneity at the scale of the diameter of established clones.     

Reproductive demography of ramets and genets in a rhizomatous clonal plant <Emphasis Type="Italic">Convallaria keiskei</Emphasis>

Clonal growth occurring below the ground makes it difficult to identify individuals and demonstrate the demographic features of a focal plant species. In this study, genotypically identified ramets of a rhizomatous clonal herb, Convallaria keiskei Miq., were monitored for their growth, survival, and reproduction from 2003 to 2006. After the monitoring period, their subterranean organs were excavated to explore the underground connections of established ramets and the direction of clonal growth. We then combined data on the fate of the monitored ramets with the information of rhizome connections, clarifying reproductive demography at both the ramet and genet levels. Although each ramet initiated both sexual reproduction (via flowering) and clonal growth, clonal growth tended to precede sexual reproduction. In a surveyed genet, 51.0% of ramets produced flowers and 29.6% generated clonal offspring during the study period. Consequently, we clarified the reproductive demography of C. keiskei: clonal growth tended to precede flowering in a ramet, and a genet can keep reproducing every season at the genet level, despite a ramet not having inflorescence every year.     

The effect of nitrogen and phosphorus addition on the growth,reproduction, and nutrient dynamics of two ericaceous shrubs

Summary Aboveground growth, reproduction, and foliar nitrogen and phosphorus contents of two ericaceous shrub species were compared over two seasons in (a) an undisturbed shrub bog (pocosin), and (b) a factorial fertilization design in which three levels each of nitrogen and phosphorus were added in all possible combinations. One species, Zenobia pulverulenta, is deciduous whereas the other species, Lyonia lucida, is evergreen. In the nutrient-poor undisturbed pocosin the two species exhibited similar foliar nitrogen and phosphorus concentrations and aboveground growth rates. Neither species flowered. In response to nutrient-addition Zenobia increased growth rates more than Lyonia. Foliar phosphorus concentrations of both species increased in response to enhanced phosphorus availability. in the first season neither species flowered in any treatment. In the second season Zenobia flowered only in the fertilized plots, with the most flowering in the high phosphorus treatments. I conclude that, by virtue of high growth rates and efficient use of nutrients and despite differences in leaf phenology and morphology, both Lyonia and Zenobia are successful in a competitive community under conditions of extremely low phosphorus availability. However, unlike Lyonia, Zenobia can take advantage of temporarily increased nutrient availability, which occurs following fire in the pocosin, to increase growth and reproduction.     

Light-induced variation in the growth and dynamics of transplanted ramets of the understory herb,Aster acuminatus

Summary Ramets of the understory herb, Aster acuminatus, were transplanted from two source populations into eight understory garden sites that varied in light and soil moisture levels. Ramet growth, clonal growth, flowering and survivorship were monitored for three growing seasons. Large differences among gardens in ramet growth, clonal growth and flowering developed in the first growing season and increased in the next two years. This variation was positively correlated with garden light level but not at all with soil moisture. Mortality rates were low in all gardens and showed that genets from any particular source could survive over a broad range of environmental conditions. There was no conclusive evidence for any source population differences in the capacity to survive or grow in different environments. The rapid, light-induced responses of transplanted ramets resulted in garden populations very similar in appearance to natural populations experiencing similar light regimes. These results combined with those from other studies of A. acuminatus provide strong evidence for the importance of light in explaining population patterns and dynamics in this species.     

PHENOLOGY,SEED DISPERSAL,AND COLONIZATION IN MUNTINGIA CALABURA,A NEOTROPICAL PIONEER TREE

In this paper we describe the phenology, fruiting ecology, and colonization ability of a widespread neotropical pioneer tree, Muntingia calabura (Eleocarpaceae), in Costa Rican dry tropical forest. Individuals of M. calabura grow rapidly, flower at <2 yr age, and produce juicy red fruits containing thousands of tiny seeds that are eaten by a variety of frugivorous birds, bats, and monkeys. Although most individuals produce some flowers and fruit year-round, peak flowering occurs in the late dry season (April–May), and peak fruit availability occurs early in the wet season (May–June). Bats and parakeets are the major seed dispersers of M. calabura at our study site, and they concentrate their attention on this species at its fruit peak when few alternate fruits are available. Germinable M. calabura seeds accumulate in the forest soil in relatively high density in areas of high frugivore activity. M. calabura can quickly invade large disturbed areas with a high density of seedlings. Adult densities decline from thousands of individuals/ha to a few individuals/ha in a relatively few years. Clumps of M. calabura trees are replaced by later successional species in < 30 yr.     

INTRASEASONAL VARIATION IN SEED PRODUCTION AMONG FLOWERS AND PLANTS OF THALICTRUM THALICTROIDES (RANUNCULACEAE)

Intraseasonal variation in ovule and seed production per flower and per plant of the perennial herb Thalictrum thalictroides (L.) Eames and Boivin was documented at three sites during three spring flowering seasons. Shading and pollen-addition experiments were used to assess the impact of variation in pollination and light availability on seed production. Mean seed number and percent seed set were lower in flowers open late in the season than in those open earlier. The lower percent seed set occurs primarily in flowers that are positioned laterally on the inflorescence and which open later than center flowers. Plants flowering early in the season produce more flowers, ovules and seeds than those flowering later. Mean percent seed set per plant did not change, however, indicating that temporal differences in total seed output can be traced largely to variation in total ovule number. Seed production may be limited by lack of pollination during periods of inclement weather. At least late in the season, seed output may also be resource-limited: the decline in percent seed set among flowers coincided with the decline in light availability, and hand-pollination of late-opening flowers did not increase percent seed set to earlier levels. Artificial shading led to a significant reduction in percent seed set of lateral flowers, and decreased the probability of flowering again the following year. Thus, the relative selective roles of resource and pollination limitations may vary during the flowering season.     

Effects of mycorrhizae on growth and demography of tallgrass prairie forbs

The effects of arbuscular mycorrhizal (AM) symbiosis on ramet and genet densities, vegetative growth rates, and flowering of three forb species were studied in native tallgrass prairie in northeastern Kansas. Mycorrhizal activity was experimentally suppressed for six growing seasons on replicate plots in an annually burned and an infrequently burned watershed with the fungicide benomyl. Benomyl reduced mycorrhizal root colonization to an average of 4.2%, approximately a two-thirds reduction relative to controls (13.7% colonization). Mycorrhizae influenced the population structure of these forbs. Although mycorrhizal suppression had no long-term effect on genet densities and no effect on ramet survivorship throughout the growing season, the number of ramets per individual was significantly increased such that ramet densities of all three species were approximately doubled in response to long-term mycorrhizal suppression. Effects of mycorrhizae on ramet growth and reproduction varied among species. Ramet growth rates, biomass, and flowering of Salvia azurea were greater in plots with active mycorrhizal symbiosis, whereas mycorrhizae reduced ramet growth rates and biomass of Artemesia ludoviciana. Aster sericeus ramet growth rates and biomass were unaffected by the fungicide applications, but its flowering was reduced.The pattern of responses of these three species to mycorrhizae differed considerably between the two sites of contrasting fire regime, indicating that the interaction of fire-induced shifts in resource availability and mycorrhizal symbiosis together modulates plant responses and the intensity and patterns of interspecific competition between and among tallgrass prairie grass and forb species. Further, the results indicate that effects of mycorrhizae on community structure are a result of interspecific differences in the balance between direct positive effects of the symbiosis on host plant performance and indirect negative effects mediated through altered competitive interactions.     

Temporal patterns of ovule allocation,fruit set,and seed predation inAnemonopsis macrophylla (Ranunculaceae)

Ovule deployment patterns were studied inAnemonopsis macrophylla Sieb. & Zucc. to develop hypotheses about major selective forces underlying different temporal strategies. Carpel number per flower decreased significantly with relative flowering date. The trend was present at individual, population, and among-population, levels. Both ovule number per carpel and ripe seed weight decreased with later flowering date. Such temporal allocation patterns may be adaptive in late-flowering species with extended flowering patterns, because successively later flowers run a higher risk of lower resource availability and premature death due to deteriorating climatic conditions.     

光强对比度对大米草克隆整合作用的影响

通过温室控制试验,分析不同光强及光强对比度处理下克隆植物大米草生长性状的差异,研究同质异质光强条件下克隆整合对大米草响应遮阴能力的修饰作用.结果表明： 在同质条件下,大米草在无遮阴(高光强：温室内自然光照强度)条件下的生物量显著大于中度遮阴(中光强：光照强度为高光强的70%)和深度遮阴(低光强：光照强度为高光强的30%).在低对比度异质性光强条件下(分株对的一个分株不遮阴,另一个分株中度遮阴),大米草遮阴分株的叶片数、根长和生物量均显著高于同质中度遮阴处理,而无遮阴分株各生长指标与同质无遮阴处理相比均无显著差异.因此,在低对比度异质性光强下,大米草受体(遮阴)分株通过克隆整合显著受益;同时,对供体(非遮阴)分株没有显著的耗损.然而,在高对比度处理下(分株对的一个分株不遮阴,另一个分株深度遮阴),克隆整合对受体(遮阴)分株的效应不显著.大米草的克隆整合并不随着光强对比度的增加而增加.在自然生境中度遮阴情况下,克隆整合可以提高大米草的生长和克隆繁殖能力,但在深度遮阴情况下,克隆整合对大米草适应性的作用可能很小.     

Spatial and seasonal patterns of microsite light availability in a remnant fragment of deciduous riparian forest and their implication in the conservation ofArisaema heterophyllum, a threatened plant species

Seasonal and spatial patterns of light availability were investigated in the understory of a small fragment (approximately 1300 m²) of a riparian deciduous forest of the Kokai River in central Japan dominated byQuercus acutissima Carruth., with the aim to understand the characteristics of microsite light availability forArisaema heterophyllum Blume, a threatened plant species uniquely associated with the riparian habitat. Diffuse site factor, which is the ratio of PFD (photon flux density, 400–700 nm) at a microsite to the open sky reference under diffuse light condition, was shown to be a satisfactory index for the evaluation of light availability for the understory plants in the habitat. Diffuse site factor 1,0 1,000 understory microsites along a 20 m transect from the edge to the interior of the forest, showed conspicuous seasonal changes in both mean and variation. Light availability decreased with seasonal tree canopy regeneration, with the highest spatial heterogeneity being recorded during the time of canopy closure. Auto-correlations of microsite light availability between different seasons were considerably high, suggesting the stability of relative light availability for individual microsites throughout the growing season ofA. heterophyllum. Fairly high light availability during summer season, which surpassed 20% of the open sky reference in most microsites, would be important for the growth and persistence of summer herbaceous plants likeA. heterophyllum.     

Association between rainfall seasonality and the flowering of epiphytic plants in a Neotropical montane forest

The association between the reproductive phenology of epiphytic communities with environmental and ecological factors remains largely unexplored. Because epiphytes depend on environmental moisture, seasonal changes in moisture conditions likely act as the primary determinants of their reproductive timing. We examined whether water limitation or pollinator competition structures the flowering phenologies of an epiphytic community in a seasonal mountain forest in Costa Rica. Additionally, we addressed the environmental factors that might trigger floral induction. Using a 24‐month dataset of bimonthly flowering records from 104 species, we found high seasonality of flowering at the species level but somewhat lower seasonality at the community level. The flowering mid‐dates of most epiphytes, particularly from monocotyledonous species, occurred during the wettest months, as predicted if water limitation structures flowering. The increased moisture and nutrient availability during the rainy season give epiphytes the resources needed to complete floral development and anthesis, and later fruit and seed maturation. The observed flowering pattern of epiphytes coincides with reproductive patterns of terrestrial herbs and shrubs from seasonal tropical ecosystems, and suggests shared constraints to sexual reproduction in both ecological guilds under similar climatic conditions. In contrast, flowering patterns of congeneric epiphytes in the same pollination guild mostly did not follow the expectations of a pollinator competition scenario. Finally, we discuss the possible combined effect of precipitation, temperature, and daily insolation on floral induction of epiphytic plants.     

Effects of ramet clipping and nutrient availability on growth and biomass allocation of yellow nutsedge

A glasshouse experiment was conducted to examine how the interactions of nutrient availability and partial ramet clipping affect growth, reproduction and biomass allocation of Cyperus esculentus, an invasive sedge. The plants sprouting from tubers were grown at low and high nutrient levels, and were subject either to no clipping, one, two or three clippings, with each clipping cutting half of the existing ramets at soil level. Our results show that nutrient availability and clipping frequency tended to independently affect most of growth, reproduction and biomass allocation parameters of Cyperus esculentus examined in the present study. Increased supply of nutrients led to an increase in plant productivity and its associated traits. All of the traits, except for the number of ramets, displayed a decreasing pattern with increasing clipping frequency, indicating that Cyperus esculentus had undercompensatory responses to ramet clipping. It is likely that the patterns of plants response to clipping are species specific, and depend on morphological characters of species. Its susceptibility to ramet clipping can offer opportunities for controlling this invasive species through mechanical methods such as mowing. Clipping had little effects on biomass allocation; however, root weight fraction increased with increasing clipping frequency. While nutrient availability and clipping frequency had no influence on leaf carbon concentration at harvest, both of them increased leaf nitrogen concentration, and hence reduced leaf C/N ratio.     

LATITUDINAL TRENDS IN THE GROWTH AND REPRODUCTIVE SEASONALITY OF DELESSERIA SANGUINEA,MEMBRANOPTERA ALATA,AND PHYCODRYS RUBENS (RHODOPHYTA)1

The seasonality of Delesseria sanguinea, Membranoptera alata, and Phycodrys rubens (Rhodophyta) was studied at Helgoland (North Sea, Germany) and Roscoff (Brittany, France). Plants were collected at bimonthly intervals, and growth and reproduction were monitored. Growth of blades was observed mainly in spring, although small blades were found on plants of M. alata and P. rubens all year round. In summer, plants started to degenerate and in autumn they became fertile. The reproductive season of D. sanguinea lasted from October to February/April at both locations, whereas reproductive plants of M. alata and P. rubens were found until April at Helgoland and until June and August, respectively, in Roscoff_: Lower winter temperatures at Helgoland than at Rascoff may have caused these differences in the duration of the reproductive season. Using published data, the seasonal patterns at Helgoland and Roscoff were compared to those found at other locations (e.g. Barents Sea; Maine, USA; Isle of Man, UK) and local temperature/daylength conditions. Blade growth was synchronized across all populations and occurred in spring, when temperatures were usually still suboptimal for growth. Maximum reproduction was generally found in the colder half of the year but started earlier in autumn in the Barents Sea. Adaptive strategies in the seasonal control of growth and reproduction are discussed. Adequate timing of the history events (e.g. appearance of juveniles in spring) appears more important than maximal growth and reproduction of adults during the season with the most favorable temperatures.     

Patterns in Varroa destructor depend on bee host abundance,availability of natural resources,and climate in Mediterranean apiaries

1. Varroa destructor Linnaeus (Acari: Varroidae) is one of the greatest threats to apiculture. This study examines the role of host density, natural resource availability for bees, the management and climate in driving spatial and annual variability in the abundance of Varroa, and the occurrence of colony losses, recorded in apiaries across a Mediterranean island over a 2‐year period, using a hierarchical generalised linear model framework. 2. The seasonal abundance of Varroa showed a bimodal pattern with two peaks, the first one being in spring and larger than the second one located in summer/autumn. In contrast, bee colony losses were mainly concentrated in autumn/winter. 3. The abundance patterns of Varroa were best explained by models combining host, climate, and resource availability. A key novel finding was that low availability of natural flowering resources leads to high levels of infestation of Varroa, highlighting the importance of preserving natural resources around apiaries for the maintenance of pollination services in the landscape. Varroa abundance was also found to increase as bee density increased, probably as a result of the greater brood availability. Moreover, Varroa abundance increased as temperatures decrease and decreases as relative humidity increases, which is consistent with previous studies. Anti‐varroa treatments were only found to impact Varroa levels in the second 6 months of the year. Organic treatments outperformed synthetic treatments. 4. Empirical research on optimal seasonal timing and combinations of treatments, as well as impacts of climate and resource availability on natural dynamics of bees and Varroa in different climate zones, is urgently required.