Phylogenetic relationships and divergence times among New World monkeys (Platyrrhini, Primates)

Orthologous sequences of six nuclear genes were obtained for all recognized genera of New World monkeys (Primates: Platyrrhini) and outgroups to evaluate the phylogenetic relationships and to estimate divergence times. Phylogenetic relationships were reconstructed by maximum parsimony, maximum likelihood, and Bayesian approaches. All methods resolved with 100% branch support genus-level relationships, except for the grouping of Aotus as a sister taxa of Cebus and Saimiri, which was supported by low bootstrap percentages and posterior probability. All approaches depict three monophyletic New World monkey families: Atelidae, Cebidae, and Pitheciidae; also within each family, all approaches depict the same branching topology. However, the approaches differ in depicting the relationships of the three families to one another. Maximum parsimony depicts the Atelidae and Cebidae as sister families next joined by the Pitheciidae. Conversely, likelihood and Bayesian phylogenetic trees group families Atelidae and Pitheciidae together to the exclusion of Cebidae. Divergence time estimations using both local molecular clock and Bayesian approaches suggest the families diverged from one another over a short period of geological time in the late Oligocene-early Miocene.     

Nest losses of cavity nesting birds caused by dormice (Gliridae, Rodentia)

Mammals are common predators on bird nests. However, their species identity frequently remains unknown. Here we present long-term data (1975–2005) from a central European woodland on the predatory effect of three dormice species (Rodentia, Gliridae) on cavity-nesting birds. Dormice are mostly frugivorous during the active late-summer season, but shortly after they terminate hibernation, they frequently depredate cavity-nesting-bird nests. The seven bird species studied, lost on average between 2.9 to 18.4% of their broods. MigratoryFicedula flycatchers suffered the highest brood losses, while the residentParus titmice and the nuthatchSitta europaea had much lower brood losses. The three dormice species differed significantly in their predatory effect during different avian breeding stages. The edible dormouseGlis glis (Linnaeus, 1766) depredated both eggs and nestlings equally, while the common dormouseMuscardinus avellanarius (Linnaeus, 1758) and the forest dormouseDryomys nitedula (Pallas, 1778) destroyed more nests during egg laying and the incubation period. Among adult birds, females were taken more frequently by dormice than males. Among avian species, adultFicedula flycatchers were more often depredated than the titmice and nuthatch. Our study provided further evidence, that among the traditional studies on the costs of reproduction, parental mortality at the nests needs to be considered and that incubating or brooding females might be under higher predation risk than the males.     

Phylogenetic relationships and divergence times among mustelids (Mammalia: Carnivora) based on nucleotide sequences of the nuclear interphotoreceptor retinoid binding protein and mitochondrial cytochrome b genes

Phylogenetic relationships among 20 species-group taxa of Mustelidae, representing Mustelinae (Mustela, Martes, Gulo), Lutrinae (Enhydra), and Melinae (Meles), were examined using nucleotide sequences of the nuclear interphotoreceptor retinoid binding protein (IRBP) and mitochondrial cytochrome b genes. Neighbor-joining and maximum-parsimony phylogenetic analyses on these genes separately and combined were conducted. While IRBP performed better than cytochrome b in recovering more-inclusive clades, cytochrome b demonstrated more resolving power in recovering less-inclusive clades. Strong support was found for a close affinity of Enhydra with Mustela to the exclusion of Martes and Gulo (causing Mustelinae to be paraphyletic); the most-basal position of Mustela vison within Mustela, followed by Mustela erminea; an association of Mustela lutreola, Mustela itatsi, Mustela sibirica, and the subgenus Putorius (including Mustela putorius and Mustela eversmanii), to the exclusion of Mustela nivalis and Mustela altaica; and a basal position of Mustela itatsi to a clade containing Mustela sibirica and Putorius. Whereas cytochrome b strongly supported Mustela lutreola as the sister species to Putorius, IRBP strongly supported its basal placement to the Mustela itatsi-Mustela sibirica-Putorius clade. The low level of sequence divergence in cytochrome b between Mustela lutreola and Putorius is therefore a result of interspecific mitochondrial introgression between these taxa, rather than a recent origin of Mustela lutreola in a close relationship to Putorius. Time estimates inferred from IRBP and cytochrome b for mustelid divergence events are mostly in agreement with the fossil record.     

Phylogenetic relationships of glassfrogs (Centrolenidae) based on mitochondrial and nuclear genes

Glassfrogs (family Centrolenidae) represent an exceptionally diverse group among Neotropical anurans, but their evolutionary relationships never have been assessed from a molecular perspective. Mitochondrial and nuclear markers were used to develop a novel hypothesis of centrolenid phylogeny. Ingroup sampling included 100 terminals, with 78 (53%) of the named species in the family, representing most of the phenotypic diversity described for the group. Thirty-five species representing taxa traditionally associated with glassfrogs were used as outgroups. Gene sampling consisted of complete or partial sequences of three mitochondrial (12S, 16S, ND1) and three nuclear markers (c-myc exon 2, RAG1, POMC) for a total of 4362 bp. Phylogenies were estimated using maximum parsimony, maximum likelihood, and Bayesian analyses for individual genes and combined datasets. The separate analysis of mitochondrial and nuclear datasets allowed us to clarify the relationships within glassfrogs; also, we corroborate the sister-group relationship between Allophryne ruthveni and glassfrogs. The new phylogeny differs significantly from all previous morphology-based hypotheses of relationships, and shows that hypotheses based on few traits are likely to misrepresent evolutionary history. Traits previously hypothesized as unambiguous synapomorphies are shown to be homoplastic, and all genera in the current taxonomy (Centrolene, Cochranella, Hyalinobatrachium, Nymphargus) are found to be poly- or paraphyletic. The new topology implies a South American origin of glassfrogs and reveals allopatric speciation as the most important speciation mechanism. The phylogeny profoundly affects the traditional interpretations of glassfrog taxonomy, character evolution, and biogeography—topics that now require more extensive evaluation in future studies.     

Phylogenetic relationships among insect orders based on three nuclear protein-coding gene sequences

Many attempts to resolve the phylogenetic relationships of higher groups of insects have been made based on both morphological and molecular evidence; nonetheless, most of the interordinal relationships of insects remain unclear or are controversial. As a new approach, in this study we sequenced three nuclear genes encoding the catalytic subunit of DNA polymerase delta and the two largest subunits of RNA polymerase II from all insect orders. The predicted amino acid sequences (In total, approx. 3500 amino acid sites) of these proteins were subjected to phylogenetic analyses based on the maximum likelihood and Bayesian analysis methods with various models. The resulting trees strongly support the monophyly of Palaeoptera, Neoptera, Polyneoptera, and Holometabola, while within Polyneoptera, the groupings of Isoptera/"Blattaria"/Mantodea (Superorder Dictyoptera), Dictyoptera/Zoraptera, Dermaptera/Plecoptera, Mantophasmatodea/Grylloblattodea, and Embioptera/Phasmatodea are supported. Although Paraneoptera is not supported as a monophyletic group, the grouping of Phthiraptera/Psocoptera is robustly supported. The interordinal relationships within Holometabola are well resolved and strongly supported that the order Hymenoptera is the sister lineage to all other holometabolous insects. The other orders of Holometabola are separated into two large groups, and the interordinal relationships of each group are (((Siphonaptera, Mecoptera), Diptera), (Trichoptera, Lepidoptera)) and ((Coleoptera, Strepsiptera), (Neuroptera, Raphidioptera, Megaloptera)). The sister relationship between Strepsiptera and Diptera are significantly rejected by all the statistical tests (AU, KH and wSH), while the affinity between Hymenoptera and Mecopterida are significantly rejected only by AU and KH tests. Our results show that the use of amino acid sequences of these three nuclear genes is an effective approach for resolving the relationships of higher groups of insects.     

Molecular systematics of dormice (Rodentia: Gliridae) and the radiation of Graphiurus in Africa

The phylogenetic relationships among the Gliridae (order Rodentia) were assessed using 3430 nucleotides derived from three nuclear fragments (beta-spectrin non-erythrocytic 1, thyrotropin and lecithin cholesterol acyl transferase) and one mitochondrial gene (12S rRNA). We included 14 glirid species, representative of seven genera of the three recognized subfamilies (Graphiurinae, Glirinae and Leithiinae) in our analysis. The molecular data identified three evolutionary lineages that broadly correspond to the three extant subfamilies. However, the data suggest that the genus Muscardinus, previously regarded as falling within the Glirinae, should be included in the Leithiinae. Molecular dating using local molecular clocks and partitioned datasets allowed an estimate of the timing of cladogenesis within the glirids. Graphiurus probably diverged early in the group's evolution (40-50 Myr ago) and the three subfamilies diverged contemporaneously, probably in Europe. The radiation within Graphiurus is more recent, with the colonization of Africa by this lineage estimated at ca. 8-10 Myr ago.     

Phylogenetic relationships among families of Gadiformes (Teleostei, Paracanthopterygii) based on nuclear and mitochondrial data

Phylogenetic hypotheses among Gadiformes fishes at the suborder, family, and subfamily levels are controversial. To address this problem, we analyze nuclear and mitochondrial DNA (mtDNA) sequences for the most extensive taxonomic sampling compiled to date, representing all of the recognized families and subfamilies in the order (except the monotypic family Lyconidae). Our study sampled 117 species from 46 genera, comprising around 20% of the species described for the order (more than 60% of all genera in the order) and produced 2740 bp of DNA sequence data for each species. Our analysis was successful in confirming the monophyly of Gadiformes and most of the proposed families for the order, but alternative hypotheses of sister-group relationships among families were poorly resolved. Our results are consistent with dividing Gadiformes into 12 families in three suborders, Muraenolepidoidei, Macrouroidei, and Gadoidei. Muraenolepidoidei contains the single family Muraenolepididae. The suborder Macrouroidei includes at least three families: Macrouridae, Macruronidae and Steindachneriidae. Macrouridae is deeply divided into two well-supported subfamilies: Macrourinae and Bathygadinae, suggesting that Bathygadinae may be ranked at the family level. The suborder Gadoidei includes the families: Merlucciidae, Melanonidae, Euclichthyidae, Gadidae, Ranicipitidae, and Bregmacerotidae. Additionally, Trachyrincinae could be ranked at family level including two subfamilies: Trachyrincinae and Macrouroidinae within Gadoidei. Further taxonomic sampling and sequencing efforts are needed in order to corroborate these relationships.     

Phylogenetic relationships and biogeography of Pseudoxiphophorus (Teleostei: Poeciliidae) based on mitochondrial and nuclear genes

Phylogenetic relationships of species of genus Pseudoxiphophorus have been only tackled in detail based on morphology so far. However, phylogenetic evidence based on molecular data is still lacking. In this study, we have used five molecular markers (mitochondrial cytb, 16S, atp6-8, and nuclear actB and S7) to reconstruct a robust, inclusive phylogeny of Pseudoxiphophorus. Our phylogenetic results strongly disagree with the main morphological hypothesis, and indicate different phylogenetic relationships among the recognized species of Pseudoxiphophorus. Pseudoxiphophorus jonesii is recovered as the sister group of all other Pseudoxiphophorus lineages, and this initial splitting may be associated to the extension of the Mexican Neovolcanic Plateau at the Punta del Morro site (event used to calibrate our dating analysis). The branch leading to all other Pseudoxiphophorus separated subsequently into two major groups, one comprising those lineages occurring in southern Mexico and Guatemala–Belize, and another with those lineages that extended further southwards to Honduras and Nicaragua. This event took place during the Pliocene, and is likely associated with periods of inundation of the Polochic–Motagua fault area. The Isthmus of Tehuantepec also appears to have been a strong biogeographic barrier triggering cladogenesis in Pseudoxiphophorus. Heterandria formosa (traditionally placed as sister to Pseudoxiphophorus) is not sharing the most recent common ancestor with Pseudoxiphophorus, and is recovered as more distantly related to them. Furthermore, Pseudoxiphophorus bimaculatus (the most cosmopolitan species) is also recovered as a polyphyletic assemblage that appears to comprise those Pseudoxiphophorus that have not been assigned to the other eight, more localized species. All this suggests that Pseudoxiphophorus needs a major taxonomic revision as a whole in order to incorporate all existing diversity.     

Phylogenetic relationships of the Chinese Labeoninae (Teleostei,Cypriniformes) derived from two nuclear and three mitochondrial genes

Zheng, L‐P., Yang, J‐X., Chen, X‐Y. & Wang, W‐Y. (2010) Phylogenetic relationships of the Chinese Labeoninae (Teleostei, Cypriniformes) derived from two nuclear and three mitochondrial genes. —Zoologica Scripta, 39, 559–571. The majority of genera within the Labeoninae occur in the South of China and the phylogeny of the subfamily Labeoninae has been a controversial topic over the years. The early and more recent phylogenetic results based on morphology are not in agreement, and some of the molecular analyses contradict those based on morphology. However, none of the previous studies has included an extensive sampling of Labeoninae genera. In this study, partial sequences of two nuclear (exon 3 of recombination activating protein 1 and rhodopsin) and three mitochondrial genes (cytochrome b, cytochrome oxidase subunit I and 16S ribosomal RNA) from 39 ingroup taxa and 11 outgroup taxa were used analysed to provide a hypothesis of phylogenetic relationships within the Chinese Labeoninae. The results supported the monophyly of Labeoninae and refuted the subdivision within Labeoninae based on the oromandibular morphology. It also further confirmed that the presence of a disc on lower lip arose through convergent evolution. Labeo was the basal clade and Osteochilus was closely related to Cirrhinus, forming the second basal clade. The monophyly of Garra and Bangana was refuted in this study, and they were both subdivided into two lineages. One lineage of Garra had closer relationships with Crossocheilus and Akrokolioplax, and the other lineage had closer relationships with Placocheilus. One lineage of Bangana represented the species with broadly interrupted postlabial groove; these species represented the true Bangana. The other lineage of Bangana included the species with continuous postlabial groove, and these species should be assigned to a new genus. Discogobio, as currently conceived, was paraphyletic, but it rendered monophyletic with the inclusion of Discocheilus. These results indicated that Discocheilus should be synonymised with Discogobio. Hongshuia and Sinocrossocheilus, respectively, formed independent lineages related to a lineage consisting of Pseudocrossocheilus plus seven other nominal genera. The relationships received weak support, but the repeatability of the clades could form the basis of recognising only the three genera mentioned above.     

Phylogenetic relationships of the genus <Emphasis Type="Italic">Armadolepis</Emphasis> Spassky, 1954 (Eucestoda,Hymenolepididae), with descriptions of two new species from Palaearctic dormice (Rodentia,Gliridae)

Two new species of hymenolepidid cestodes belonging to the genus Armadolepis Spassky, 1954 are described from dormice (Gliridae) from the southern East European Plain and the northwestern Caucasus, Russia. Armadolepis (Bremserilepis) longisoma n. sp., with a rudimentary, unarmed rostellar apparatus is described from the fat dormouse Glis glis (Linnaeus) from the Republic of Adygeya, Russia. Additionally, A. (Armadolepis) dryomi n. sp., characterised by a well-developed rostellar apparatus and armed rhynchus is described from the forest dormouse Dryomys nitedula Pallas from Rostov Oblast’, Russia. Armadolepis (Bremserilepis) longisoma n. sp. differs from A. (Bremserilepis) myoxi (Rudolphi, 1819) in having a substantially longer strobila and cirrus-sac, wider scolex and ovary and larger rostellar pouch and testes. Armadolepis (Armadolepis) dryomi n. sp. is distinguishable from A. (Armadolepis) spasskii Tenora & Baru?, 1958, A. (Armadolepis) jeanbaeri Makarikov, 2017 and A. (Armadolepis) tenorai Makarikov, 2017 in having a substantially longer and wider strobila, and larger rostellar pouch and cirrus-sac. Furthermore, A. dryomi n. sp. can be distinguished from its congeners by the number and size of rostellar hooks and the arrangement of the testes. Phylogenetic affinities of Armadolepis were studied for the first time using partial sequences of the nuclear ribosomal 28S DNA gene. Phylogenetic analysis strongly supported the status of Armadolepis as a separate genus belonging to the “Rodentolepis clade”.     

Phylogenetic relationships among species of the genus Oligoryzomys (Rodentia,Cricetidae) from Central and South America

González‐Ittig, R. E., Salazar‐Bravo, J., Barquez, R. M. & Gardenal, C. N. (2010). Phylogenetic relationships among species of the genus Oligoryzomys (Rodentia, Cricetidae) from Central and South America. —Zoologica Scripta, 39, 511–526. The genus Oligoryzomys includes several species very similar in external morphology, which has resulted in a confusing specific taxonomy. Accurate species identification is particularly important because several species of Oligoryzomys act as natural hosts of hantaviruses affecting humans. Here, we assign specific status to individuals from a wide geographical area of Argentina and Chile using sequences of the mtDNA control region. We also compare cytochrome b sequences of 14 species recognized from Central and South America to infer the phylogenetic relationships within the genus. In addition, the results were analysed using available data on chromosome numbers, and the host–parasite relationships reported for the genus Hantavirus. We confirm the geographical distribution of Oligoryzomys longicaudatus (Argentina, Chile), Oligoryzomys nigripes (Argentina, Paraguay, Brazil), Oligoryzomys chacoensis (Argentina, Bolivia, Paraguay), Oligoryzomys fornesi (Argentina, Paraguay), Oligoryzomys destructor (Argentina, Bolivia) and Oligoryzomys microtis (Bolivia, Brazil). Oligoryzomys longicaudatus is strongly related to the Oligoryzomys flavescens complex, which comprises four clades; O. nigripes is closely related to Oligoryzomys stramineus, and Oligoryzomys vegetus, to Oligoryzomys fulvescens from Central America. Oligoryzomys chacoensis, O. destructor, O. fornesi, O. longicaudatus, O. microtis, O. nigripes, O. stramineus, Oligoryzomys moojeni, Oligoryzomys rupestris, O. fulvescens and O. vegetus are confirmed as valid species, whereas O. flavescens, Oligoryzomys magellanicus, Oligoryzomys griseolus, Oligoryzomys victus, Oligoryzomys andinus and Oligoryzomys arenalis need exhaustive revision. The sister species to all the remaining entities of the genus was O. microtis, suggesting an Amazonian origin for the genus.     

Phylogenetic relationships and reticulation among Asian Elymus (Poaceae) allotetraploids: Analyses of three nuclear gene trees

This phylogenetic study focuses on a subset of the species in Elymus—specifically, the endemic Asian tetraploids presumed to combine the St genome from Pseudoroegneria with the Y genome from an unknown donor. The primary goals were to (1) determine whether the St and Y genomes are derived from phylogenetically distinct donors; (2) identify the closest relative, and potentially the likely donor, of the Y genome; and (3) interpret variation among StStYY species in terms of multiple origins and/or introgression. The goals were addressed using phylogenetic analyses of sequences from three low-copy nuclear genes: phosphoenolpyruvate carboxylase, β-amylase, and granule-bound starch synthase I. Data sets include 16 StStYY individuals representing nine species, along with a broad sample of representatives from most of the monogenomic (i.e., non-allopolyploid) genera in the tribe. To briefly summarize the results: (1) the data clearly support an allopolyploid origin for the Asian tetraploids, involving two distinct donors; (2) the Y genome was contributed by a single donor, or multiple closely-related donors; (3) the phylogenetic position of the Elymus Y genome varies among the three trees and its position is not strongly supported, so the identity of the donor remains a mystery; and (4) conflicts among the gene trees with regard to the St-genome sequences suggest introgression involving both Elymus and Pseudoroegneria.     

Local molecular clocks in three nuclear genes: divergence times for rodents and other mammals and incompatibility among fossil calibrations

Reconstructing the chronology of mammalian evolution is a debated issue between molecule- and fossil-based inferences. A methodological limitation of molecules is the evolutionary rate variation among lineages, precluding the application of the global molecular clock. We considered 2422 first and second codon positions of the combined ADRA2B, IRBP, and vWF nuclear genes for a well-documented set of placentals including an extensive sampling of rodents. Using seven independent calibration points and a maximum-likelihood framework, we evaluated whether molecular and paleontological estimates of mammalian divergence dates may be reconciled by the local molecular clocks approach, allowing local constancy of substitution rates with variations at larger phylogenetic scales. To handle the difficulty of choosing among all possible rate assignments for various lineages, local molecular clocks were based on the results of branch-length and two-cluster tests. Extensive lineage-specific variation of evolutionary rates was detected, even among rodents. Cross-calibrations indicated some incompatibilities between divergence dates based on different paleontological references. To decrease the impact of a single calibration point, estimates derived from independent calibrations displaying only slight reciprocal incompatibility were averaged. The divergence dates inferred for the split between mice and rats (approximately 13-19 Myr) was younger than previously published molecular estimates. The most recent common ancestors of rodents, primates and rodents, boreoeutherians, and placentals were estimated to be, respectively, approximately 60, 70, 75, and 78 Myr old. Global clocks, local clocks, and quartet dating analyses suggested a Late Cretaceous origin of the crown placental clades followed by a Tertiary radiation of some placental orders like rodents.     

Phylogenetic relationships within the Phyllopoda (Crustacea,Branchiopoda) based on mitochondrial and nuclear markers

For several decades the relationships within the Branchiopoda (Anostraca + Phyllopoda) have been a matter of controversy. Interpretations of plesiomorphic or apomorphic character states are a difficult venture, in particular in the Phyllopoda. We explore the relationships within the Phyllopoda at the level of nucleotid comparisons of the two genes 12S rDNA (mitochondrial) and EF1alpha (nuclear), and at a higher molecular level based on introns found in the gene EF1alpha. Within the Phyllopoda our explorations show further evidence for a non-monophyletic Conchostraca (Spinicaudata + Cyclestherida + Laevicaudata). The monotypic Cyclestherida is more closely related to the Cladocera, both together forming the Cladoceromorpha. The Spinicaudata (Leptestheriidae, Limnadiidae, and Cyzicidae) is well supported. Spinicaudata and Cladoceromorpha form a monophylum. The position of the Laevicaudata remains unclear but we find neither support for a sister group relationship to the Spinicaudata nor for a close relationship of Laevicaudata and Cladocera. Within the Cladocera, we favour the Gymnomera concept with the monotypic Haplopoda being the sister group to the monophyletic Onychopoda. The Ctenopoda seems to be the sister group to the Gymnomera, which contradicts the common view of a more basal position of the Ctenopoda.     

Phylogenetic relationships in Myrceugenia (Myrtaceae) based on plastid and nuclear DNA sequences

Myrceugenia is a genus endemic to South America with a disjunct distribution: 12 species occurring mainly in central Chile and approximately 25 in southeastern Brazil. Relationships are reconstructed within Myrceugenia from four plastid markers (partial trnK-matK, rpl32-trnL, trnQ-5'rps16 and rpl16) and two ribosomal nuclear regions (ETS and ITS) using maximum parsimony and Bayesian analyses. Relationships inferred previously from morphological data are not completely consistent with those from molecular data. All molecular analyses support the hypothesis that Myrceugenia is monophyletic, except for M. fernadeziana that falls outside the genus. Chilean species and Brazilian species form two separate lineages. Chilean species form three early diverging clades, whereas Brazilian species are a strongly supported monophyletic group in a terminal position. Least average evolutionary divergence, low resolution, short branches, and high species diversity found in the Brazilian clade suggest rapid radiation. Geographical distributions and phylogenetic reconstructions suggest that extant Myrceugenia species arose in northern Chile followed by colonization southward and finally to the Juan Fernández Islands and southeastern Brazil.     

Partial arousals from hibernation in a pair of common dormice,Muscardinus avellanarius (Rodentia,Gliridae), in their natural hibernaculum

Summary A pair of common dormice discovered while torpid in their natural hibernaculum on December 5, was studied continously outdoors, exposed to natural fluctuations in temperature and rainfall. Temperature inside and outside the nest ball and motor activity were recorded. The first emergence from hibernaculum occurred on March 4, after which the dormice were daily active, chiefly during evening and night hours. Nest departures lasted on average 10.5 h (6.5–14 h) per day.During the 88 days while the animals remained in the hibernaculum ambient temperature ranged from -5° to 8.5° C. Nest temperature never fell below zero, being chiefly 1.0°C above ambient temperature during 68 of these days and thus reflecting deep hibernation in both animals. However, on 19 occasions nest temperature was raised steeply from average 5.6°C (2.0–8.0°C) to average 23.0°C (17.5–32.5°C). These increases of nest temperature, lasting roughly 4 h (3–8 h) are interpreted as partial arousals. The total duration of partial arousals was 76 h, i.e. 3.6% of the time during which the animals remained consistently in the nest.The interarousal time varied, being 16 days at the most and 12 h at the least. The frequency of arousals increased with rising maximum values of ambient temperature, and partial arousals never were recorded on days when temperature remained below 2°C. It is believed that partial arousals correspond to the periodic or spontaneous arousals previously recorded in laboratory experiments of some other hibernating mammals. However, the energetic expenditure seems to be smaller during periodic arousals because of their shorter duration and the fact that no departure from the hibernaculum occurs.Possible mechanisms governing partial arousals are discussed. As these events chiefly occurred during night they may partly be controlled by an inherent time sense.