Chloroplast genome sequence confirms distinctness of Australian and Asian wild rice

Cultivated rice (Oryza sativa) is an AA genome Oryza species that was most likely domesticated from wild populations of O. rufipogon in Asia. O. rufipogon and O. meridionalis are the only AA genome species found within Australia and occur as widespread populations across northern Australia. The chloroplast genome sequence of O. rufipogon from Asia and Australia and O. meridionalis and O. australiensis (an Australian member of the genus very distant from O. sativa) was obtained by massively parallel sequencing and compared with the chloroplast genome sequence of domesticated O. sativa. Oryza australiensis differed in more than 850 sites single nucleotide polymorphism or indel from each of the other samples. The other wild rice species had only around 100 differences relative to cultivated rice. The chloroplast genomes of Australian O. rufipogon and O. meridionalis were closely related with only 32 differences. The Asian O. rufipogon chloroplast genome (with only 68 differences) was closer to O. sativa than the Australian taxa (both with more than 100 differences). The chloroplast sequences emphasize the genetic distinctness of the Australian populations and their potential as a source of novel rice germplasm. The Australian O. rufipogon may be a perennial form of O. meridionalis.     

Phenotypic covariance structure and its divergence for acoustic mate attraction signals among four cricket species

The phenotypic variance-covariance matrix (P) describes the multivariate distribution of a population in phenotypic space, providing direct insight into the appropriateness of measured traits within the context of multicollinearity (i.e., do they describe any significant variance that is independent of other traits), and whether trait covariances restrict the combinations of phenotypes available to selection. Given the importance of P, it is therefore surprising that phenotypic covariances are seldom jointly analyzed and that the dimensionality of P has rarely been investigated in a rigorous statistical framework. Here, we used a repeated measures approach to quantify P separately for populations of four cricket species using seven acoustic signaling traits thought to enhance mate attraction. P was of full or almost full dimensionality in all four species, indicating that all traits conveyed some information that was independent of the other traits, and that phenotypic trait covariances do not constrain the combinations of signaling traits available to selection. P also differed significantly among species, although the dominant axis of phenotypic variation (p(max)) was largely shared among three of the species (Acheta domesticus, Gryllus assimilis, G. texensis), but different in the fourth (G. veletis). In G. veletis and A. domesticus, but not G. assimilis and G. texensis, p(max) was correlated with body size, while p(max) was not correlated with residual mass (a condition measure) in any of the species. This study reveals the importance of jointly analyzing phenotypic traits.     

Bovine papillomavirus oncoprotein E5 affects the arachidonic acid metabolism in cells

The bovine papillomavirus type 1 (BPV-1) oncoprotein encoded by the E5 ORF is a small highly hydrophobic protein, which is capable of inducing oncogenic transformation of cells. We studied the effect of the BPV-1 E5 protein expression on the arachidonic acid metabolism in monkey (COS1) and human (C33A) cells. At relatively low protein concentrations the phospholipase A(2) (PLA(2)) activity and the arachidonic acid (AA) metabolism are activated. E5 mutant proteins, lacking cysteines responsible for the dimerisation of the protein (C37S, C37SC39S), and truncated E5, lacking the C-terminal region, are non-transforming and unable to stimulate the PLA(2) activity and AA metabolism. The transformation-defective mutant D33V, which does not activate the platelet-derived growth factor receptor (PDGFR), activates AA metabolism like wt E5. Our data suggest that the BPV-1 E5 protein could stimulate the AA metabolism independently of PDGF receptor.     

Diel food habits of two species of setipalpian stoneflies (Plecoptera) in tributaries of the Clearwater River, Idaho

SUMMARY. The foreguts of two setipalpian stonefly nymphs, Skwala parallela and Hesperoperla pacifica , from tributaries of the Clearwater River, Idaho, were examined in terms of composition and fullness. A total of 736 nymphs were collected at 06.00,12.00,18.00 and 24.00 hours during a 1-week period in August in order to examine diel variation in both diet composition and feeding periodicity. Substantial diel variation in diet composition and Electivity Indices (E) occurred. No single prey taxon was consistently the principal component in the diet of either stonefly species during all 6-h sampling intervals. Overall, hydropsychids (15.3–60.6%) were the major food of H. pacifica in Mission Creek whereas chironomid larvae were the chief prey of S. parallela in Mission (10.0–47.2%) and Lapwai (14.9–28.0%) Creeks. Nymphs were nocturnal feeders with feeding increasing from 18.00 to 06.00 hours and with peak feeding occurring from 24.00 to 06.00 hours.     

Two Drosophila myosin transducer mutants with distinct cardiomyopathies have divergent ADP and actin affinities

Two Drosophila myosin II point mutations (D45 and Mhc(5)) generate Drosophila cardiac phenotypes that are similar to dilated or restrictive human cardiomyopathies. Our homology models suggest that the mutations (A261T in D45, G200D in Mhc(5)) could stabilize (D45) or destabilize (Mhc(5)) loop 1 of myosin, a region known to influence ADP release. To gain insight into the molecular mechanism that causes the cardiomyopathic phenotypes to develop, we determined whether the kinetic properties of the mutant molecules have been altered. We used myosin subfragment 1 (S1) carrying either of the two mutations (S1(A261T) and S1(G200D)) from the indirect flight muscles of Drosophila. The kinetic data show that the two point mutations have an opposite effect on the enzymatic activity of S1. S1(A261T) is less active (reduced ATPase, higher ADP affinity for S1 and actomyosin subfragment 1 (actin · S1), and reduced ATP-induced dissociation of actin · S1), whereas S1(G200D) shows increased enzymatic activity (enhanced ATPase, reduced ADP affinity for both S1 and actin · S1). The opposite changes in the myosin properties are consistent with the induced cardiac phenotypes for S1(A261T) (dilated) and S1(G200D) (restrictive). Our results provide novel insights into the molecular mechanisms that cause different cardiomyopathy phenotypes for these mutants. In addition, we report that S1(A261T) weakens the affinity of S1 · ADP for actin, whereas S1(G200D) increases it. This may account for the suppression (A261T) or enhancement (G200D) of the skeletal muscle hypercontraction phenotype induced by the troponin I held-up(2) mutation in Drosophila.     

Genetic structure of three orchid species with contrasting breeding systems using RAPD and allozyme markers

Zeuxine gracilis, Zeuxine strateumatica, and Eulophia sinensis are wild orchids with different breeding systems and colonizing abilities. Zeuxine gracilis is an outcrosser with restricted distribution, whereas S. strateumatica is an apomictic colonizer found only in newly available open habitats. Eulophia sinensis is an outcrossing colonizer. This study investigates the levels of genetic variation and patterns of population structure in these wild orchids to provide genetic information for the development of suitable conservation strategies. Lack of allozyme variation was characteristic of all three species, especially in populations of the two colonizing orchids, Z. strateumatica and E. sinensis. More variable markers, randomly amplified polymorphic DNAs (RAPDs), were further employed to characterize population structure of these species. Substantial genetic variation was found at the RAPD loci within populations of Z. gracilis (p = 21.65 ± 15.88%, A = 1.217 ± 0.159, and H = 0.076 ± 0.054) and E. sinensis (p = 17.82 ± 20.97%, A = 1.179 ± 0.209, and H = 0.070 ± 0.084), but little variation existed within populations of Z. strateumatica (p = 2.84 ± 2.58%, A = 1.029 ± 0.026, and H = 0.011 ± 0.011). Regardless of the breeding system, the total gene diversity at the species level was partitioned primarily between populations, as shown by high G(ST) values, in all three species. An extremely high level of population differentiation (G(ST) = 0.924) was found in the apomictic colonizer Z. strateumatica. The patterns of genetic variation in these wild orchids are apparently related to their differences in breeding system and colonizing ability. Different conservation strategies are needed for the long-term survival of these species.     

Molecular localization of the inhibitory arachidonic acid binding site to the pore of hIK1

We previously demonstrated that the endogenously expressed human intermediate conductance, Ca(2+)-activated K(+) channel (hIK1) was inhibited by arachidonic acid (AA) (Devor, D. C., and Frizzell, R. A. (1998) Am. J. Physiol. 274, C138-C148). Here we demonstrate, using the excised, inside-out patch-clamp technique, that hIK1, heterologously expressed in HEK293 cells, is inhibited 82 +/- 2% (n = 16) with 3 microm AA, being half-maximally inhibited (IC(50)) at 1.4 +/- 0.7 microm. In contrast, AA does not inhibit the Ca(2+)-dependent, small conductance K(+) channel, rSK2, another member of the KCNN gene family. Therefore, we utilized chimeric hIK1/rSK2 channels to define the AA binding domain on hIK1 to the S5-Pore-S6 region of the channel. Subsequent site-directed mutagenesis revealed that mutation of Thr(250) to Ser (T250S) resulted in a channel with limited sensitivity to block by AA (8 +/- 2%, n = 8), demonstrating that Thr(250) is a key molecular determinant for the inhibition of hIK1 by AA. Likewise, when Val(275) in S6 was mutated to Ala (V275A) AA inhibited only 43 +/- 11% (n = 9) of current flow. The double mutation T250S/V275A eliminated the AA sensitivity of hIK1. Introducing the complimentary single amino acid substitutions into rSK2 (S359T and A384V) conferred partial AA sensitivity to rSK2, 21 +/- 3% and 31 +/- 3%, respectively. Further, introducing the double mutation S359T/A384V into rSK2 resulted in a 63 +/- 8% (n = 9) inhibition by AA, thereby demonstrating the ability to introduce this inhibitory AA binding site into another member of the KCNN gene family. These results demonstrate that AA interacts with the pore-lining amino acids, Thr(250) and Val(275) in hIK1, conferring inhibition of hIK1 by AA and that AA and clotrimazole share similar, if not identical, molecular sites of interaction.     

Amino acid availability and age affect the leucine stimulation of protein synthesis and eIF4F formation in muscle

We have previously shown that a physiological increase in plasma leucine for 60 and 120 min increases translation initiation factor activation in muscle of neonatal pigs. Although muscle protein synthesis is increased by leucine at 60 min, it is not maintained at 120 min, perhaps because of the decrease in plasma amino acids (AA). In the present study, 7- and 26-day-old pigs were fasted overnight and infused with leucine (0 or 400 micromol.kg(-1).h(-1)) for 120 min to raise leucine within the postprandial range. The leucine was infused in the presence or absence of a replacement AA mixture (without leucine) to maintain baseline plasma AA levels. AA administration prevented the leucine-induced reduction in plasma AA in both age groups. At 7 days, leucine infusion alone increased eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1) phosphorylation, decreased inactive 4E-BP1.eIF4E complex abundance, and increased active eIF4G.eIF4E complex formation in skeletal muscle; leucine infusion with replacement AA also stimulated these, as well as 70-kDa ribosomal protein S6 kinase, ribosomal protein S6, and eIF4G phosphorylation. At 26 days, leucine infusion alone increased 4E-BP1 phosphorylation and decreased the inactive 4E-BP1.eIF4E complex only; leucine with AA also stimulated these, as well as 70-kDa ribosomal protein S6 kinase and ribosomal protein S6 phosphorylation. Muscle protein synthesis was increased in 7-day-old (+60%) and 26-day-old (+40%) pigs infused with leucine and replacement AA but not with leucine alone. Thus the ability of leucine to stimulate eIF4F formation and protein synthesis in skeletal muscle is dependent on AA availability and age.     

Locomotor Activity Patterns in Ilybius fenestratus (Fabricius) (Coleoptera,Dytiscidae) in a Central Norwegian Lake,with Evidence for Breeding-Induced Arrhythmicity

The diel activity of Ilybius fenestratus was studied in Målsj?en, a lake in S?r-Tr?ndelag, Central Norway (63°14'N, 10°26'E), during 1971–1972. Adults and larvae were sampled in activity traps every week during March–October and every 2–3 weeks during November–February. The traps were emptied every 2 hrs during a 24- hr period. The diel locomotor activity of I. fenestratus was clearly nocturnal, except in the second half of July, for the males also in the first half of July, when surprisingly the population showed an arrhythmic activity pattern. The arrhythmicity is connected with the mating and egg-laying period of the species. The larvae were also nocturnal in the autumn, but showed arrhythmicity under the ice during the winter.     

G3BP–Caprin1–USP10 complexes mediate stress granule condensation and associate with 40S subunits

Mammalian stress granules (SGs) contain stalled translation preinitiation complexes that are assembled into discrete granules by specific RNA-binding proteins such as G3BP. We now show that cells lacking both G3BP1 and G3BP2 cannot form SGs in response to eukaryotic initiation factor 2α phosphorylation or eIF4A inhibition, but are still SG-competent when challenged with severe heat or osmotic stress. Rescue experiments using G3BP1 mutants show that phosphomimetic G3BP1-S149E fails to rescue SG formation, whereas G3BP1-F33W, a mutant unable to bind G3BP partner proteins Caprin1 or USP10, rescues SG formation. Caprin1/USP10 binding to G3BP is mutually exclusive: Caprin binding promotes, but USP10 binding inhibits, SG formation. G3BP interacts with 40S ribosomal subunits through its RGG motif, which is also required for G3BP-mediated SG formation. We propose that G3BP mediates the condensation of SGs by shifting between two different states that are controlled by the phosphorylation of S149 and by binding to Caprin1 or USP10.     

促炎基因ALOX5AP基因多态性与脑卒中的相关性研究

白三烯是作用较强的促炎症因子,在动脉粥样硬化的发生发展中发挥着重要作用。5-脂氧合酶激活蛋白是白三烯合成的关键调控因素,通过全基因组扫描的连锁分析和关联分析发现编码5-脂氧合酶激活蛋白的基因ALOX5AP在白种人中与心肌梗塞和脑卒中的患病风险相关。然而,目前尚无关于该基因与亚洲人脑卒中患病风险的遗传学资料。本研究探讨了ALOX5AP基因多态与脑卒中及其亚型易感性的关系。采用PCR—RFLP方法,对来自7个临床中心的1713名对照和1773名脑卒中患者检测了ALOX5AP基因的4个SNPs：SG13S25、SG13S114、SG13S89和SG13S32。多元logistic回归方法校正传统危险因素后分析基因多态与脑卒中患病风险的独立相关性。结果表明,人群未发现SG13S25和SG13S32具有多态性;ALOX5AP基因多态SG13S114A等位基因频率在男性脑梗塞组显著高于对照组（33．6％VS29．2％;P=0．014）,SG13S114AA基因型增加男性脑梗塞1．62倍的发病风险（95％CI：1．1-2．35：P=0．012）。多态SG13S89G／A与脑梗塞的易感性不相关。单体型分析表明单体型频率在脑卒中患者和对照组间无显著的统计学差异。因此,本研究结果提示ALOX5AP基因多态的等位基因和基因型频率在东、西方人群存在种族差异,SG13S114AA基因型增加中国人群男性脑梗塞的易感性。     

Diel Habitat Partitioning by Bull Charr and Cutthroat Trout During Fall and Winter in Rocky Mountain Streams

We used underwater observation to determine diel habitat partitioning between bull charr, Salvelinus confluentus, and cutthroat trout, Oncorhynchus clarki, during fall and winter (0.1–8.3°C) in two Rocky Mountain streams that differed in habitat availability. The majority (>70%) of both species emerged from concealment cover at night, though bull charr exhibited a greater tendency for nocturnal behavior than cutthroat trout. Differences in day and night counts were most pronounced at temperatures <3°C, when very few fish of either species were observed in the water column during the day, but both species were common at night. Both species used concealment cover of large woody debris and boulder substrate crevices in deep pools during the day. At night, fish emerged from cover and habitat use shifted to shallow water with low cover. Microhabitat partitioning among species and size classes occurred at night, cutthroat trout moving into shallower, faster water that was farther from cover compared to bull charr. Smaller fish of both species occupied focal positions in slower, shallower water closer to the substrate than larger fish. Large, mixed-species aggregations also were common in beaver ponds both day and night. High variation in diel and site-specific winter habitat use suggests the need for caution in developing habitat suitability criteria for salmonids based solely on daytime observations or on observations from a few sites. Our results support the need to incorporate nocturnal habitat use and partitioning in studies of salmonid ecology.     

Production of wheat-Psathyrostachys huashanica chromosome addition lines

Psathyrostachys huashanica Keng (2n = 14; N(h)N(h)) is an endangered wheat-related species, with a distribution in the Huashan region of central China. It has many agronomically promising characters including resistance to disease and drought and winter hardiness. We produced hybrids between common wheat as the female parent and P. huashanica as the male parent. From the offspring, we selected chromosome addition lines of common wheat carrying each of all seven chromosomes of P. huashanica. Four chromosomes (B, D, E and F) were recovered in disomic lines and three (A, C and G) in monosomic addition lines. These alien chromosomes were distinguished from each other by cytological analyses. Chromosome A was characterized by a 45S rDNA site in the subtelomeric region of the short arm. Chromosome B carried one 5S and one 45S rDNA sites co-localized in an interstitial region of the short arm, and the expression of the alien high-molecular-weight glutenin was observed in the endosperm of line B. Chromosome D had a 45S rDNA signal in the interstitial region of the long arm. Chromosomes C, E, and F were distinguished by the EST-SSR markers Ltc0464, Ltc0096, and Xcfe175, respectively. The homoeologous group of each alien chromosome was implied from the results above, and the utilization of these addition lines for wheat breeding was discussed.     

梁子湖浮游甲壳动物的生物多样性

基于2006年8月至2008年3月对梁子湖浮游甲壳动物的采样调查,记录了该湖区浮游甲壳动物22种,隶属9科18属,其中枝角类(Cladocera)16种,桡足类(Copepoda)6种,包括9属新记录.物种多样性季节性动态变化明显:枝角类优势种在春、夏和秋冬季依次为透明溞(Daphnia hyalina,优势度Y = 0.80±0.01),小栉溞(Daphnia cristata,Y = 0.50±0.03)和长额象鼻溞(Bosmina longirostris,Y = 0.58±0.04);而桡足类优势种在夏、秋和冬春季依次为长江新镖水蚤(Neodiaptomus yangtsekiangensis,Y = 0.41±0.01)、近邻剑水蚤(Cyclops vicinus,Y = 0.46)和特异荡镖水蚤(Neutrodiaptomus incongruens,Y = 0.65±0.18).浮游甲壳类个体密度以春季最高((292±85) ind/L),夏、秋、冬季渐低(依次为(169±104)、(140±53)、(120±0) ind/L).物种多样性冬春季较低(物种数S≤12,丰富度指数D = 0.77和0.71,香农-威纳指数H = 1.79和1.45),夏秋季较高(S≥17,D = 0.98和0.88,H = 1.78和1.83).梁子湖浮游甲壳类动物多样性年际差异不显著,表明湖区环境条件较为优越、稳定.     

Exotic snakes in São Paulo City, southeastern Brazil: why xenophobia?

Introduced exotic species cause environmental changes and threat public health in target sites. Illegal trade has enhanced this problem. To first report these risks in Brazil, exotic snakes found in São Paulo City (SPC) (23°32 S, 46°38 W), southeastern Brazil, and sent to Instituto Butantan between 1995 and 2000, were listed and characterized by their biological attributes. Seventy-six individuals of sixteen alien species were collected. Euriecians snakes, mainly booids, were predominant. Using multivariate techniques, their ecological niches were compared to those of 26 native species, as a way to point out the resource's availability. To evaluate the potential of successful implantation, two species absent in SPC and considered as problem snakes are included in these analyses: the brown treesnake Boiga irregularis and the habu Trimeresurus flavoviridis. There were niche similarities between these pest snakes, exotic booids and native viperids largely due to the similarities in the chosen prey (mammals), diel activity (nocturnal), color pattern (variegated) and body size (medium to large). To avoid predictable undesirable effects of implanted pest snakes, traffic control and punishment should be improved, as well as parallel environmental education programs.     

Artificial mixed-linked β-glucans produced by glycosynthase-catalyzed polymerization: tuning morphology and degree of polymerization

The glycosynthase derived from Bacillus licheniformis 1,3-1,4-β-glucanase was able to polymerize glycosyl fluoride donors (G4)(m)G3GαF (m = 0-2, G = Glcβ) leading to artificial mixed-linked β-glucans with regular sequences and variable β1,3 to β1,4 linkage ratios. With the E134A glycosynthase mutant, polymers had average molecular masses (M(w)) of 10-15 kDa. Whereas polymer 2 ([4G4G3G](n)) was an amorphous precipitate, the water-insoluble polymers 1 ([4G3G](n)) and 3 ([4G4G4G3G](n)) formed spherulites of 10-20 μm diameter. With the more active E134S glycosynthase mutant, polymerization led to high molecular mass polysaccharides, where M(w) was linearly dependent on enzyme concentration. Remarkably, a homo-polysaccharide [4G4G4G3G](n) with M(w) as high as 30.5 kDa (n ≈ 47) was obtained, which contained a small fraction of products up to 70 kDa, a value that is in the range of the molecular masses of low viscosity cereal 1,3-1,4-β-glucans, and among the largest products produced by a glycosynthase. Access to a range of novel tailor-made β-glucans through the glycosynthase technology will allow to evaluate the implications of polysaccharide fine structures in their physicochemical properties and their applications as biomaterials, as well as to provide valuable tools for biochemical characterization of β-glucan degrading enzymes and binding modules.     

Habitat selection by the swamp wallaby (Wallabia bicolor) in relation to diel period,food and shelter

Patterns of resource selection by animals may be influenced by sex, and often change over a 24‐h period. We used a dry sclerophyll landscape managed for commercial timber production to investigate the effects of sex and diel period on habitat selection by the swamp wallaby (Wallabia bicolor). We predicted that selection would be (i) affected by both sex and diel period; and (ii) positively related to lateral cover during the day, but to food resources at night. Non‐metric multidimentional scaling indicated that some of the available habitats differed markedly with respect to visibility (an indicator of lateral cover), fern cover, forb cover, wallaby density and a forage quality index, providing the basis for non‐random habitat selection. At the landscape scale, wallabies showed strong selection for 5‐year‐old regenerating sites, selected against 10‐year‐old regenerating sites and unharvested forest, and avoided recently harvested (3–10 months post‐harvest) sites completely. At the scale of individual home ranges, a pooled male and female sample demonstrated selection for unharvested forest over recently harvested sites during both diurnal and nocturnal periods. A separate analysis showed that both sex and diel period influenced the selection of 5‐ and 10‐year‐old sites and the surrounding unharvested forest. Using a novel approach, we demonstrated that diurnal habitat selection by both sexes was negatively correlated with visibility, representing stronger selection for areas with more lateral cover. Nocturnal selection by females was positively correlated with values of a forage quality index, but this was not the case for males. We hypothesise that the observed patterns of selection were driven by the need to find food and avoid predators, but were also affected by the different reproductive strategies of males and females. Our results demonstrate the importance of incorporating factors such as sex and diel period into analyses of habitat selection.     

Mutations in the GTP-binding and synergy loop domains of Mycobacterium tuberculosis ftsZ compromise its function in vitro and in vivo

The Mycobacterium tuberculosis FtsZ (FtsZ(TB)), unlike other eubacterial FtsZ proteins, shows slow GTP-dependent polymerization and weak GTP hydrolysis activities [E.L. White, L.J. Ross, R.C. Reynolds, L.E. Seitz, G.D. Moore, D.W. Borhani, Slow polymerization of Mycobacterium tuberculosis FtsZ, J. Bacteriol. 182 (2000) 4028-4034]. In an attempt to understand the biological significance of these findings, we created mutations in the GTP-binding (FtsZ(G103S)) and GTP hydrolysis (FtsZ(D210G)) domains of FtsZ and characterized the activities of the mutant proteins in vitro and in vivo. We show that FtsZ(G103S) is defective for binding to GTP and polymerization activities, and exhibited reduced GTPase activity whereas FtsZ(D210G) protein is proficient in binding to GTP, showing reduced polymerization activity but did not show any measurable GTPase activity. Visualization of FtsZ-GFP structures in ftsZ merodiploid strains by fluorescent microscopy revealed that FtsZ(D210G) is proficient in associating with Z-ring structures whereas FtsZ(G103S) is not. Finally, we show that Mycobacterium smegmatis ftsZ mutant strains producing corresponding mutant FtsZ proteins are non-viable indicating that mutant FtsZ proteins cannot function as the sole source for FtsZ, a result distinctly different from that reported for Escherichia coli. Together, our results indicate that optimal GTPase and polymerization activities of FtsZ are required to sustain cell division in mycobacteria and that the same conserved mutations in different bacterial species have distinct phenotypes.     

Clock gene variation in Tachycineta swallows

Many animals use photoperiod cues to synchronize reproduction with environmental conditions and thereby improve their reproductive success. The circadian clock, which creates endogenous behavioral and physiological rhythms typically entrained to photoperiod, is well characterized at the molecular level. Recent work provided evidence for an association between Clock poly-Q length polymorphism and latitude and, within a population, an association with the date of laying and the length of the incubation period. Despite relatively high overall breeding synchrony, the timing of clutch initiation has a large impact on the fitness of swallows in the genus Tachycineta. We compared length polymorphism in the Clock poly-Q region among five populations from five different Tachycineta species that breed across a hemisphere-wide latitudinal gradient (Fig. 1). Clock poly-Q variation was not associated with latitude; however, there was an association between Clock poly-Q allele diversity and the degree of clutch size decline within breeding seasons. We did not find evidence for an association between Clock poly-Q variation and date of clutch initiation in for any of the five Tachycineta species, nor did we found a relationship between incubation duration and Clock genotype. Thus, there is no general association between latitude, breeding phenology, and Clock polymorphism in this clade of closely related birds.Figure 1Photos of Tachycineta swallows that were used in this study: A) T. bicolor from Ithaca, New York, B) T. leucorrhoa from Chascomús, Argentina, C) T. albilinea from Hill Bank, Belize, D) T. meyeni from Puerto Varas, Chile, and E) T. thalassina from Mono Lake, California, Photographers: B: Valentina Ferretti; A, C-E: David Winkler.