ON THE EXTRACTION OF SOME TIME DEPENDENT PARAMETERS OF AN ACOUSTIC SIGNAL BY MEANS OF THE ANALYTIC SIGNAL CONCEPT. ITS APPLICATION TO ANIMAL SOUND STUDY

ABSTRACT

When studying the acoustic signals of animals, it is often necessary to obtain the precise time structure of the frequency. It is also useful to extract the envelope of a signal or to modify a signal to obtain its frequency modulated part. This can be achieved digitally using the analytic signal concept.

We deal here with the method. Definition and computation are described, its application is discussed and the performances are compared to those of sonagraph and zero- crossing methods. This paper presents a method enabling precise AM and FM analysis of different animal vocalisations. The method has also been used for the purpose of synthesis by extracting the frequency modulated part of a signal. It is found to be a powerful means of modifying some parameters of a natural signal without altering other features.     

ADAPTATION TO SEVERE CONDITIONS OF PROPAGATION: LONG-DISTANCE DISTRESS CALLS; AND COURTSHIP CALLS OF A COLONIAL SEABIRD

ABSTRACT

The boatwhistle sound produced by male toadfish during the reproductive season attracts females to the nest site. Boatwhistles consist of a series of rapidly produced, amplitude modulated ‘pulses’ of sound that are generated by specific muscles of the gas bladder. Previous studies have shown that boatwhistle characteristics vary with temperature and geographic location. This study investigated the normal range of variation in boatwhistles produced by males in a northern population of O. tau. Multiple boatwhistles were recorded from individuals at different sites around Waquoit Bay, Massachusetts. Multiple boatwhistles were recorded at different sites to assess the range of variation in boatwhistle production from this population. Pulse repetition rates varied from a low of 125 pulses/sec at 16 °C to a high of 219 pulses/sec at 21 °C. Careful examination of recordings from different sites indicated that individuals vary in the durations of their boatwhistles as well as in the pulse repetition rates during the very consistently produced second segment of the call. In particular, pulse repetition rate (PRR) varied significantly (p < 0.001) among most individuals recorded at the same temperatures. Psychophysical testing as well as behavioral choice experiments are needed to assess the relative importance of PRR and spectral cues in species recognition and/or mate choice.     

Testing Tropiduchini Stål 1866 (Hemiptera: Tropiduchidae) monophyly,a young inter‐tropical taxon of mainly insular species: taxonomy,distribution patterns and phylogeny,with the description of a new genus from Papua New Guinea

A morphological phylogenetic analysis of the tribe Tropiduchini (Hemiptera: Tropiduchidae) is provided for 21 genera among the 26 recognized, including the new genus Oechalinella Wang gen.n. , with a new species Oechalinella bifasciata Wang sp.n. Monophyly of the tribe is well supported by synapomorphies derived from the male genitalia. The strict consensus supports two subclades: ((Montrouzierana + Thymbra) + Thaumantia⁺) as sister to the clade (Leptovanua + (Vanua + Varma⁺) + Daradacella⁺). In the first subclade, the clade (Montrouzierana + Thymbra), distributed in New Caledonia and Papua New Guinea, is well supported by three synapomorphies based on the tegmina, while the Thaumantia⁺ group is characterized by the conformation of the anal tube and male gonostyli, and distributed from Malesia to Papuasia and in Central Africa. The second subclade is largely distributed from China to Malesia, Papuasia, Southwestern and the Northwestern Pacific islands. The position of the genus Leptovanua remains uncertain. The Varma⁺ clade is recovered in all analyses. Implied weighting analysis placed the Varma⁺ lineage as sister to all other genera forming a new group (Leptovanua⁺ + ((Montrouzierana + Thymbra) + Thaumantia⁺)). Fennah's definition of Tropiduchini is reviewed according to the phylogenetic results and an identification key to all genera is provided with a referenced synopsis of their distribution. Globally, Tropiduchini exhibits an inter‐tropical latitudinal distribution and a paradoxical bimodal longitudinal distribution pattern in continental Africa, South‐east Asia and the Pacific islands. Distribution data concern nearly 80% of insular taxa. The phylogenetical results suggest that: (i) the tribe originates from continental China; (ii) it evolved mainly from Papuasia by stepping‐stone colonization events, promoting subsequent insular speciation; and (iii) its evolution has mainly been directed by dispersion versus vicariance.     

Recent evolution of host-associated divergence in the seabird tick Ixodes uriae

Ecological interactions are an important source of rapid evolutionary change and thus may generate a significant portion of novel biodiversity. Such changes may be particularly prevalent in parasites, where hosts can induce strong selection for adaptation. To understand the relative frequency at which host-associated divergences occur, it is essential to examine the evolutionary history of the divergence process, particularly when it is occurring over large geographical scales where both geographical and host-associated isolation may playa part. In this study, we use population genetics and phylogeography to study the evolutionary history of host-associated divergence in the seabird tick Ixodes uriae (Acari, Ixodidae). We compare results from microsatellite markers that reflect more ecological timescales with a conserved mitochondrial gene (COIII) that reflects more ancient divergence events. Population structure based on microsatellites showed clear evidence of host-associated divergence in all colonies examined. However, isolated populations of the same host type did not always group together in overall analyses and the genetic differentiation among sympatric host races was highly variable. In contrast, little host or geographical structure was found for the mitochondrial gene fragment. These results suggest that host race formation in I. uriae is a recent phenomenon, that it may have occurred several times and that local interactions are at different points in the divergence process. Rapid divergence in I. uriae implies a strong interaction with its local host species, an interaction that will alter the ecological dynamics of the system and modify the epidemiological landscape of circulating micropathogens.     

Morphology, Biometry, and Taxonomy of Freshwater and Marine Interstitial Cyphoderia (Cercozoa: Euglyphida)

ABSTRACT. Good taxonomy is essential for ecological, biogeographical, and evolutionary studies of any group of organisms. Therefore, we performed detailed light- and scanning electron microscopy investigations on the shell ultrastructure and biometric analyses of the morphometric variability of five freshwater and marine interstitial testate amoebae of the genus Cyphoderia ( C. trochus var. amphoralis, C. ampulla, C. margaritacea var. major, C. compressa , and C. littoralis ), isolated from different populations in Bulgaria and Switzerland. Our aims were (1) to clarify the morphological characteristics of these taxa, and (2) to compare the morphology of a given taxon ( C. ampulla ) among different locations in Bulgaria and Switzerland as a first step towards an assessment of the geographical variation within a supposedly cosmopolitan taxon. Four of the studied taxa are characterized by a well-expressed main-size class and by a small size range of all the characters and can be defined as size-monomorphic species. Based on these results, the following systematic changes are proposed: C. major ( Penard, 1891 ) n. comb. (Syn.: C. margaritacea var. major ( Penard, 1891 ) and C. amphoralis ( Wailes & Penard, 1911 ) n. comb. (Syn.: C. trochus var. amphoralis ( Wailes & Penard, 1911 )). However, we also show significant morphological variability between the Swiss and Bulgarian populations of C. ampulla , suggesting the possible existence of more than one taxon within this species. Further studies are required to assess (1) if these two morphologically different taxa represent individual species, (2) if so, if more species exist, and if this diversity is due to limited distribution ranges (endemism) or if several closely related taxa occur together in different geographical areas.     

Alkane composition diversity among populations of dwarf forms of Juniperus communis L.: comparison between western Europe and northern American populations

The cuticular wax composition of leaves has been analysed in three western European populations (Corsica, central Pyrenees, northern Alps) of Juniperus communis var. saxatilis Pall. (=  J. nana Willd., nom illeg.) and in one population of J. communis L. var. depressa Pursh. from North America (Sierra Nevada). Gas chromatography shows the presence of 13 alkanes in all samples ranging from C₂₃ to C₃₅ with important intraspecific polymorphism in alkane content. The dominant alkanes range from C₃₃ to C₃₅. Alkanes C₂₁ and C₂₂ were found only in Corsica and Sierra Nevada populations. Canonical discriminant analysis separated the J. communis L. var. depressa Pursh. of the population of Sierra Nevada from other populations of J. communis var. saxatilis Pall. on the basis of their higher C₃₁ content and the constant presence of C₂₁ and C₂₂ alkanes. J. communis var. saxatilis Pall. populations from the Pyrenees are close to northern Alps populations characterized by high concentrations of C₃₃, C₃₄ and C₃₅ alkanes. This paper confirms the existence of Juniperus var. saxatilis Pall. in the Pyrenees (France).  © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 165–168.