An exceptional storm accumulation of nautilids in the Lower Cretaceous of the Neuquén Basin,Argentina

Cichowolski, M., Pazos, P.J., Tunik, M.A. & Aguirre‐Urreta, M.B. 2011: An exceptional storm accumulation of nautilids in the Lower Cretaceous of the Neuquén Basin, Argentina. Lethaia, Vol. 45, pp. 121–138. An exceptional accumulation of nautilid shells of the species Cymatoceras perstriatum (Steuer) is reported and described in the Lower Cretaceous Agrio Formation of the Neuquén Basin (west‐central Argentina). The bed represents a storm deposit in a shallow‐water environment within the mid‐ramp. The evidences of a storm‐related origin of the bed come from the petrographic analysis and taphonomic features of the shells, specially the sedimentary infill pattern. The shells are dispersed in patches within the stratum, without any orientation relative to the bedding plane. It is proposed that the shells were floating after the death of the animals, although most of them have an almost complete living chamber. The presence of some heavily encrusted shells suggests that there is a mixing of specimens with different drift times. A variety of factors related to the origin of such high number of nautilid shells are discussed, including a transgressive stand system tract, the possible existence of a gregarious behaviour, changes in salinity and wind directions. □Lower Cretaceous, Nautilids, Neuquén Basin, shell accumulation, storm deposit.     

Allozyme diversity and geographic variation in the widespread coastal sedge, Carex arenaria

Abstract. Allozyme electrophoresis was used to investigate the structure of genetic variation in the rhizomatous coastal sedge, Carex arenaria, throughout its European range — from the SW Iberian peninsula to the Baltic region. Material was sampled from 77 sites in five geographic regions. Nine of the 13 investigated loci were polymorphic in the total material and there were interregional differences in the number of polymorphic loci per site and the percentage of variable sites. In the Scandinavia/Baltic region only 61% of the sites contained at least one locus with more than one allele, whereas all the British and SW Iberian sites were variable. There was a general tendency for the regional frequencies of the less common alleles at individual loci to decline from SW to NE. The mean (over loci and sites) within‐site gene diversity (H _site) was 0.064 (in calculations based on the number of observed multilocus allozyme genotypes within each sampling site). Although there was considerable variation between geographically adjacent sites, within‐site diversity showed a general decrease from SW to NE in Europe. There were significant differences in within‐region gene diversity (H_reg) for the four most variable loci between the five regions. H_reg generally decreased from SW to NE Europe and most loci showed the highest diversity in the SW Iberian peninsula and the Bay of Biscay regions. The mean (over loci) gene diversity in the total material (H_tot) was 0.070 and the levels of diversity in Carex arenaria are substantially lower than is usual in rhizomatous sedges. The within‐site, between‐site and between‐regional components of the total diversity were 92.4%, 2.5% and 5.1%, respectively. The low levels of overall gene diversity in C. arenaria and the successive decrease in diversity from SW to NE are interpreted in terms of the species’ history of postglacial spread into northern Europe. Despite the overall northwards decrease in diversity, the widespread occurrence of less common alleles and the lack of regional deviations from Hardy–Weinberg genotype frequency expectations suggest that C. arenaria is not predominantly self‐fertilized.     

Site selection and behavior of sponge and bivalve borers in shells of the cretaceous oysters exogyra cancellata and pycnodonte mutabilis from delaware,U.S.A

In shells of the oysters Exogyra cancellata and Pycnodonte mutabilis from the Mount Laurel and Marshalltown Formations (Campanian‐Maestrichtian), three‐quarters of all valves bear sponge borings (Entobia isp.) borings and 30% have borings of a lithophagid bivalve (Gastrochaenolites isp.). Non‐random distributions of these euendoliths, documented in this paper, may in part be accounted for by differential survival of sponge and lithophagid larvae and spat in varying circumstances. In addition, exterior shell architectures and post‐mortem orientations of shells are inferred to have prompted active geophobic (antigravity), rugophilic (groove‐seeking), and rheophilic (current‐seeking) behavior that enhanced survivorship of the settling larvae.     

Muskrat predation on a diverse unionid mussel community: impacts of prey species composition,size and shape

1. The muskrat, Ondatra zibethicus, is a predator known to affect species composition, population size and age structure of freshwater unionid mussel communities. Muskrats leave large piles of dead shells (middens) on the edges of rivers, lakes and streams. We compared the species composition and size structure of shells collected from muskrat middens to the nearby live unionid community in the lower Licking River (Kentucky, USA). 2. Like previous studies, our results suggest that muskrats are both size‐selective and species‐specific predators; however, our results indicate that mussel shape is also an important factor. 3. We generated a shape metric (‘cubocity’) sensitive to the overall shape of the mussel. Species with relatively lower cubocity values (around 0.85) are plate‐like or spike‐like, while mussels with more cuboidal shells have higher cubocity values (near 1.0). 4. Our results suggest muskrats prefer cuboidal mussels and generally avoid spike‐shaped mussels. The endangered fanshell, Cyprogenia stegaria, was the most favoured prey; the fanshell’s relative size and shape appear to make it particularly vulnerable to muskrats. 5. We believe the predictive capabilities of this shape metric will be of benefit to those who monitor and manage threatened mussel populations.     

POPULATION DYNAMICS OF GREEN NOCTILUCA SCINTILLANS (DINOPHYCEAE) ASSOCIATED WITH THE MONSOON CYCLE IN THE UPPER GULF OF THAILAND1

Population dynamics of Noctiluca scintillans (Macartney) Kof. et Swezy containing the photosynthetic endosymbiont Pedinomonas noctilucae (Subrahman.) Sweeney was investigated in relation to environmental conditions in the upper Gulf of Thailand. A clear association was observed between the abundance of N. scintillans and the monsoon cycle, with its blooms occurring during the southwest (SW) monsoon from May to September, and low abundance during the northeast (NE) monsoon from November to February. Nutrient concentrations were higher during the SW monsoon than during the NE monsoon due to the combined effect of increased river discharge into the northern upper gulf and the transport of the riverine inputs by the prevailing clockwise circulation of the water. These nutrient conditions favored the growth of both phytoplankton and the endosymbiont. Correlation analysis revealed that the higher abundance of N. scintillans in the SW monsoon was manifested primarily by higher growth through both sexual and asexual reproduction supported by phagotrophy. However, the dependence of N. scintillans on the nutrient concentration was not significant, probably because the nutrient supply for the endosymbiont was sufficient due to intracellular accumulation of nutrients within the host cells. Sexual reproduction occurred only during the SW monsoon, and its potential importance in population growth was suggested. These findings showed the bottom‐up control of the population dynamics of N. scintillans through growth of phytoplankton as prey. The seasonal shift in the circulation pattern associated with the monsoon cycle played a crucial role in blooming of N. scintillans by producing favorable food conditions.     

Mechanical strength of shells of selected extant articulate brachiopods: Implications for paleozoic morphologic trends

Dried shells of Terebratalia transversa, Laqueus californianus, Hemithyris psittacea, and T. unguicula and alcohol‐soaked, tissue‐lined shells of Terebratulina retusa, Dallina septigera, Cryphus vitreus, and Liothyrella uva were crushed in an apparatus that facilitated measurement of the force (newtons) against the valves at the instant of fracture. The results revealed that the costate shells of T. transversa and T. retusa were the strongest. Force is correlated with valve thickness, but not with size (length). When normalized for valve thickness, the force required to fracture shells is correlated with shell biconvexity (height/length) among pooled species of dried specimens. Geniculate specimens of T. retusa were not stronger than the intraspecific variants with a constant radius of curvature to their valves.

The percent‐frequency of plicate, spinose, lamellose and rugate genera increase significantly in the successive stages, Caradocian (Late Ordovician) through Famennian (Late Devonian) at the expense of smooth to costellate genera. The percent‐frequency of rectimarginate (central fold lacking) genera also decreases appreciably in this time frame. These morphologic trends, in combination with the experimental crushing data, support the hypothesis that selection favored species with such anti‐predatory adaptations during a time of escalation of shell‐crushing predators.     

875. PLEIONE SCOPULORUM AND PLEIONE KAATIAE

The closely‐related species Pleione scopulorum W.W. Sm., and P. kaatiae P.H. Peeters, from Myanmar, NE India and SW China are discussed, and P. kaatiae is illustrated.     

Molecular characterization of microbial communities in fault-bordered aquifers in the Miocene formation of northernmost Japan

We investigated the diversity and distribution of archaeal and bacterial 16S rRNA gene sequences in deep aquifers of mid‐ to late Miocene hard shale located in the northernmost region of the Japanese archipelago. A major fault in the north‐west–south‐east (NW–SE) direction runs across the studied area. We collected three groundwater samples from boreholes on the south‐west (SW) side of the fault at depths of 296, 374 and 625 m below ground level (m.b.g.l.) and one sample from the north‐east (NE) side of the fault at a depth of 458 m.b.g.l. The groundwater samples were observed to be neutral and weakly saline. The total microbial counts after staining with acridine orange were in the order 10⁵?10⁶ cells mL^?1 and 10³ cells mL^?1 in the aquifers to the SW and to the NE of the fault, respectively. A total of 407 archaeal and bacterial 16S rRNA gene sequences (204 and 203 sequences, respectively) were determined for clone libraries constructed from all groundwater samples. Phylogenetic analyses showed that the libraries constructed from the SW aquifers were generally coherent but considerably different from those constructed from the NE aquifer. All of the archaeal clone libraries from the SW aquifers were predominated by a single sequence closely related to the archaeon Methanoculleus chikugoensis, and the corresponding bacterial libraries were mostly predominated by the sequences related to Bacteroidetes, Firmicutes and δ‐Proteobacteria. In contrast, the libraries from the NE aquifer were dominated by uncultured environmental archaeal clones with no methanogen sequences and by β‐proteobacterial clones with no sequences related to Bacteroidetes and δ‐Proteobacteria. Hence, the possible coexistence of methanogens and sulphate reducers in Horonobe deep borehole (HDB) on the SW side is suggested, particularly in HDB‐6 (374 m.b.g.l.). Moreover, these organisms might play an important geochemical role in the groundwater obtained from the aquifers.     

A genomic assessment of population structure and gene flow in an aquatic salamander identifies the roles of spatial scale,barriers, and river architecture

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Predation on freshwater snails in Miocene Lake Steinheim: a trigger for intralacustrine evolution?

Shells of the freshwater gastropods Gyraulus trochiformis (Planorbidae or ramshorn snails) and Bania pseudoglobula (formerly Pseudamnicola, Hydrobiidae) from Miocene Steinheim Basin in SW Germany contain small holes with a mean diameter of 0.8 mm. Analyses of comparable holes are so far unknown from fossil or extant assemblages of freshwater shells. This analysis of the perforated shells suggests that the holes were not formed by post‐depositional or pure taphonomic processes. Instead, they were most likely produced by predators. This analysis widens the means for identification of predation on freshwater snail shells that can be used in other palaeolimnological studies. The co‐occurrence of fish teeth and perforated shells in the studied samples as well as the perforation features suggest that the predator was either barbel or tench fish. The correlation between shell sizes and hole diameters suggests a size relationship between predator and prey that may generally be related to gape‐limited fish predators. The co‐occurrence of perforated shells in these lake sediments with a dominance of large and armoured shells suggest that these larger shells with protuberances and knobs could not be crushed by the gape‐limited fish predators. This analysis is the basis for a hypothesis that the endemic evolution of Gyraulus in Lake Steinheim, with some varied forms of shell thickness and morphology, was triggered by a predator–prey relationship based on adaptations to avoid shell‐breaking predators.     

Brachiopod morphology,life mode,and crushing predation in the Ordovician Arnheim Formation,Kentucky, USA

Predation on ancient shelled prey is an often-studied topic in paleoecology, but the early Paleozoic and the brachiopods that dominated the seafloor at that time are relatively underrepresented in the predation literature. We assessed predatory repair scar frequencies among the brachiopod genera from the Early Richmondian (Late Ordovician) Oregonia Member (Arnheim Formation) near Flemingsburg, Kentucky. We found higher repair frequencies on the concavo-convex Rafinesquina and Leptaena relative to the bi-convex genera. There were no trends in repair frequency through the stratigraphic section and no relationships between repair frequency and community diversity metrics. It is possible that concavo-convex brachiopods’ flat shape, thin shell profile, and free-lying (no pedicle attachment) lifestyle made them more likely or appealing targets of Ordovician crushing predators. It is also possible that concavo-convex brachiopods were better suited to survive crushing attacks than biconvex taxa. We also found differences in shell ornament that may influence the visibility of repair scars.     

Influence of cabbage resistance and colour upon the diamondback moth and its parasitoid Oomyzus sokolowskii

Host plant resistance and biological control are vital integrated pest management tools against the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), but to date no study has investigated this system including the DBM parasitoid Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae). We examined oviposition and development of P. xylostella exposed to two commercial cabbage cultivars (green ‘Chato de quintal’ and red ‘Roxo’) and possible effects upon O. sokolowskii. Under free‐choice tests, DBM females laid significantly more eggs on plants of the green cabbage, even though several population growth parameters showed that DBM developed better on the red cabbage. Furthermore, a laboratory free‐choice test with artificially green‐ and red‐painted kale leaf discs demonstrated a similar oviposition preference pattern, with green colour being preferred over red colour. The preference was apparently visually mediated; olfactometer tests showed similar attraction of moths to both green and red cultivars in choice and non‐choice tests. Host plant cultivar had no statistically significant effect on female parasitoid behaviour towards DBM larvae, nor on parasitoid numbers or longevity. Moreover, wasps parasitizing DBM larvae reared on the green cultivar developed more quickly and in larger numbers per parasitized larva. Thus, feeding on green cabbage rather than red does not hinder, and potentially even enhances, control of DBM by O. sokolowskii. On a practical level, these results suggest that intercalating green cabbage cultivars as a trap crop might help protect more profitable red cultivars in growing fields.     

Environmental change influences the life history of salmon Salmo salar in the North Atlantic Ocean

Annual mean total length (L_T) of wild one‐sea‐winter (1SW) Atlantic salmon Salmo salar of the Norwegian River Imsa decreased from 63 to 54 cm with a corresponding decrease in condition factor (K) for cohorts migrating to sea from 1976 to 2010. The reduction in L_T is associated with a 40% decline in mean individual mass, from 2 to 1·2 kg. Hatchery fish reared from parental fish of the same population exhibited similar changes from 1981 onwards. The decrease in L_T correlated negatively with near‐surface temperatures in the eastern Norwegian Sea, thought to be the main feeding area of the present stock. Furthermore, S. salar exhibited significant variations in the proportion of cohorts attaining maturity after only one winter in the ocean. The proportion of S. salar spawning as 1SW fish was lower both in the 1970s and after 2000 than in the 1980s and 1990s associated with a gradual decline in post‐smolt growth and smaller amounts of reserve energy in the fish. In wild S. salar, there was a positive association between post‐smolt growth and the sea survival back to the River Imsa for spawning. In addition, among smolt year‐classes, there were significant positive correlations between wild and hatchery S. salar in L_T, K and age at maturity. The present changes may be caused by ecosystem changes following the collapse and rebuilding of the pelagic fish abundance in the North Atlantic Ocean, a gradual decrease in zooplankton abundance and climate change with increasing surface temperature in the Norwegian Sea. Thus, the observed variation in the life‐history traits of S. salar appears primarily associated with major changes in the pelagic food web in the ocean.     

Seeking shelter from the storm: Conservation and management of imperiled species in a changing climate

Climate change is anticipated to exacerbate the extinction risk of species whose persistence is already compromised by habitat loss, invasive species, disease, or other stressors. In coastal areas of the southeastern United States (USA), many imperiled vertebrates are vulnerable to hurricanes, which climate models predict to become more severe in the 21st century. Despite this escalating threat, explicit adaptation strategies that address hurricane threats, in particular, and climate change more generally, are largely underrepresented in recovery planning and implementation. We provide a basis for stronger emphasis on strategic planning for imperiled species facing the increasing threat of catastrophic hurricanes. Our reasoning comes from observations of short‐term environmental and biological impacts of Hurricane Michael, which impacted the Gulf Coast of the southeastern USA in October 2018. During this storm, St. Marks National Wildlife Refuge, located along the northern Gulf of Mexico's coast in the panhandle region of Florida, received storm surge that was 3.0–3.6 m (NAVD88) above sea level. Storm surge pushed sea water into some ephemeral freshwater ponds used for breeding by the federally threatened frosted flatwoods salamander (Ambystoma cingulatum). After the storm, specific conductance across all ponds measured varied from 80 to 23,100 µS/cm, compared to 75 to 445 µS/cm in spring 2018. For 17 overwashed wetlands that were measured in both spring and fall 2018, posthurricane conductance observations were, on average, more than 90 times higher than in the previous spring, setting the stage for varying population responses across this coastal landscape. Importantly, we found live individual flatwoods salamanders at both overwashed and non‐overwashed sites, although we cannot yet assess the demographic consequences of this storm. We outline actions that could be incorporated into climate adaptation strategies and recovery planning for imperiled species, like A. cingulatum, that are associated with freshwater coastal wetlands in hurricane‐prone regions.     

High genetic diversity in southwest Asian populations of Philaenus spumarius (Hemiptera: Auchenorrhyncha)

The genus Philaenus is one of the best investigated among Auchenorrhyncha, and several morphological, ecological, karyological, and molecular data have led to a designation of up to 10 species, distributed mainly in the Mediterranean and south-western Asia. The only widespread Palaearctic species, P. spumarius, is known to be structured phylogeographically as it consists of two highly divergent mitochondrial clades (northeast, NE and southwest, SW), with several subclades. This study contributes to the species phylogeography through the study of the genetic diversity and affinity of P. spumarius populations from southwestern Asia. Mitochondrial DNA (cytochrome B) show a high level of genetic diversity within Turkish and Iranian populations, the majority of which belong to the SW clade, and only single populations from northeastern Turkey are found to be substantially highly divergent lineages within the NE clade. One of the NE populations also showed significant differences in the distribution and amount of heterochromatin compared to other populations. According to the results of this study and previous phylogenetic and phylogeographic works on this species, we conclude that Southwestern Asia is probably the place of origin of the Philaenus spumarius.     

Escape in space from enemies: a comparison between stands with and without enhanced densities of the spruce bark beetle

1 Populations of the spruce bark beetle, Ips typographus (L.), are known to grow rapidly in storm‐disturbed stands as a result of relaxation from intraspecific competition. In the present study, it was tested whether a second mechanism, escape in space from natural enemies, also contributes to the rapid population increase. 2 The experiment was conducted during the initiation phase of five local outbreaks of I. typographus triggered by a storm‐disturbance in November 1995 in southern Sweden. 3 The impact of natural enemies on the ratio of increase (number of daughters per mother) of I. typographus was compared pairwise between disturbed stands with high numbers of storm‐felled trees and undisturbed stands without wind‐felled trees. 4 Enemy impact was assessed by comparing the ratio of increase in uncaged (exposed to enemies) and caged (protected from enemies) bolts colonized by I. typographus prior to being placed in the stands. The experiment was conducted in the second and third summers after the storm‐felling. 5 Enemy impact was about twice as high in stands without wind‐felled trees compared with in stands with wind‐felled trees in the second summer whereas there was no significant difference between the stand types in the third summer. 6 The result demonstrates that spatial escape from enemies contributes to the rapid population growth of I. typographus after storm‐disturbances.     

Across a migratory divide: divergent migration directions and non‐breeding grounds of Eurasian reed warblers revealed by geolocators and stable isotopes

Migratory divides represent narrow zones of overlap between parapatric populations with distinct migration directions and, consequently, expected divergent non‐breeding distributions. The composition of the mixed population at a migratory divide and the corresponding non‐breeding ranges remain, however, unknown for many Palaearctic‐African migrants. Here, we used light‐level geolocation to track migration direction and non‐breeding grounds of Eurasian reed warblers Acrocephalus scirpaceus from three breeding populations across the species’ migratory divide. Moreover, by using feathers grown at non‐breeding grounds, we quantified stable isotope composition for individuals with known southwestern (SW) and southeastern (SE) migration directions. On a larger sample per population, we then assessed the proportions of SW‐ and SE‐migrating phenotypes in each of the three populations. All tracked reed warblers from Germany and two thirds of the birds tagged from the Czech population headed initially SW. Nevertheless, about one third of the birds from the Czech site migrated towards SE. No tracking data have been obtained for the Bulgarian population. The initial migration direction determined by geolocators was a strong predictor of the non‐breeding region, with SW migrants staying in west Africa and SE migrants in central Africa. Feather δ³⁴S and δ¹⁵N values confirmed the predominance of SW migrants in the German population, the co‐occurrence of SW and SE migrants in the Czech population, and indicated a high (72%) proportion of SE migrants in the Bulgarian population. Thus, the combined approach of geolocator tracking and stable isotopic assignments provided clear evidence for the existence of a migratory divide in the southeast of central Europe and predicted non‐breeding range in central and central‐eastern Africa for the eastern population.     

Arthrophycus as a mimic of crinoid column impressions in the lower Silurian of central Kentucky,USA

Unusual specimens of an ichnofossil, herein ascribed to Arthrophycus, are described from siltstone tempestites in the lower Silurian (Llandovery, Telychian) Estill Shale near Irvine, Estill County, central Kentucky, USA. The specimens display closely spaced, uncurved transverse annulations, but lack the medial ridge, rectangular cross‐sectional shape and dense branching typical of common Silurian Arthrophycus ichnospecies. This combination of features, coupled with the straightness of burrows and alignment parallel to inorganic tool marks, closely approximates the appearance of moulds of partially articulated crinoid columns (= pluricolumnals) that were impressed into firm mud and cast by storm‐deposited sediment. That these structures do not represent the external moulds of body fossils is suggested by minor width variations along the long axis of specimens, possible bioglyphs and the total absence of skeletal material, including isolated crinoid columnals, in this and other tempestites from this interval. More convincingly, the presence of very sparse branching indicates a trace fossil origin for these structures. These fossils are best interpreted as the products of preferential mining of inorganically generated tool marks by deposit feeders, owing to exposure of more organic‐rich muds by erosional scouring. Thus, this occurrence represents a rare instance in which trace fossils display a strong alignment parallel to inorganic sedimentary structures.     

Reconstruction of Indian monsoon variability over the past 230,000 years: Planktic foraminiferal evidence from the NW Arabian Sea open-ocean upwelling area

We determined the faunal composition and total number of tests (#/g) of planktic foraminifera (> 125 μm) in core KH00-05 GOA 6 near Oman in order to decipher monsoon-induced variability of oceanographic productivity in the open-ocean upwelling area in the northwest Arabian Sea. The core contains a continuous record of sedimentation over the last 230 kyr, with the age model based on oxygen isotope and accelerator mass spectrometry ¹⁴C dates. We focused on species (Globigerina bulloides and Globigerinita glutinata) typical for SW monsoonal upwelling and species typical for NE monsoon conditions (Neogloboquadrina incompta, Neogloboquadrina dutertrei, Globigerinoides ruber, and Globigerinoides sacculifer). The changes in relative abundance of these monsoonal indicators suggest that the open-ocean upwelling area was dominated by the SW monsoon during interglacial periods, but by the NE monsoon during glacial periods.Increases in total test abundance during glacial periods confirmed that the NE monsoon rather than SW monsoon contributes largely to planktic foraminiferal productivity in this area. We argue that three types of circumstances resulted in high productivity, with nine high productivity events occurring at a 23-kyr frequency. The first type caused high productivity events at 102 and 199 ka (interglacial periods), characterized by the dominance of upwelling species, indicating high productivity during strong SW monsoons, correlated with high July insolation at 45° N. An exceptional high productivity event occurred at 37 ka during interglacial marine isotope stage (MIS) 3, with contributions from both SW and NE monsoons. The second type of high productivity event occurred at 61, 147, and 175 ka, during glacial periods, characterized by dominance of NE monsoon species, and correlated with low January insolation at 45° N. In addition, a high productivity event at 85 ka (interglacial period) also was induced by enhanced NE monsoons. The last two high productivity events occurred during transitional periods from glacial to interglacial (MIS 6/5.5 and 2/1), were characterized by the replacement of NE monsoon species with upwelling species, and corresponded to abrupt climate warming, suggesting that they are related to both accelerated SW monsoon systems and reduced NE monsoon systems.     

Differential metabolic responses of perennial grass Cynodon transvaalensis×Cynodon dactylon (C₄) and Poa Pratensis (C₃) to heat stress

Differential metabolic responses to heat stress may be associated with variations in heat tolerance between cool‐season (C₃) and warm‐season (C₄) perennial grass species. The main objective of this study was to identify metabolites associated with differential heat tolerance between C₄ bermudagrass and C₃ Kentucky bluegrass by performing metabolite profile analysis using gas chromatography‐mass spectrometry. Plants of Kentucky bluegrass (Poa Pratensis‘Midnight’) and hybrid bermudagrass (Cynodon transvaalensis×Cynodon dactylon‘Tifdwarf’) were grown under optimum temperature conditions (20/15°C for Kentucky bluegrass and 30/25°C for bermudagrass) or heat stress (35/30°C for Kentucky bluegrass and 45/40°C for bermudagrass). Physiological responses to heat stress were evaluated by visual rating of grass quality, measuring photochemical efficiency (variable fluorescence to maximal fluorescence) and electrolyte leakage. All of these parameters indicated that bermudagrass exhibited better heat tolerance than Kentucky bluegrass. The metabolite analysis of leaf polar extracts revealed 36 heat‐responsive metabolites identified in both grass species, mainly consisting of organic acids, amino acids, sugars and sugar alcohols. Most metabolites showed higher accumulation in bermudagrass compared with Kentucky bluegrass, especially following long‐term (18 days) heat stress. The differentially accumulated metabolites included seven sugars (sucrose, fructose, galactose, floridoside, melibiose, maltose and xylose), a sugar alcohol (inositol), six organic acids (malic acid, citric acid, threonic acid, galacturonic acid, isocitric acid and methyl malonic acid) and nine amino acids (Asn, Ala, Val, Thr, γ‐Aminobutyric acid, IIe, Gly, Lys and Met). The differential accumulation of those metabolites could be associated with the differential heat tolerance between C₃ Kentucky bluegrass and C₄ bermudagrass.