Palaeoenvironmental analysis based on rugose corals and microfacies: a case study at La Cornuda section (early Serpukhovian, Guadiato Area, SW Spain)

Combined analysis of microfacies and rugose coral features provides a useful tool for palaeoenvironmental studies in areas where outcrops are not appropriate for field observations. A detailed study of Serpukhovian rugose corals from La Cornuda section (Guadiato Area, SW Spain) by means of thin sections allowed the identification of environments where they lived. All corals were collected in unit 1 of the section where three different but intimately connected environments have been identified. Corals developed mainly in small mounds built jointly by microbial communities, algae and corals. Some corals also lived in calcareous shoals mainly composed of echinoderm plates. Finally, some corals occur in Oncoidal limestone that represents a shallow ramp, but they were mainly transported from shoals and mounds.     

Unexpected panmixia in a long-lived, deep-sea fish with well-defined spawning habitat and relatively low fecundity

The marine environment presents particular challenges for our understanding of the factors that determine gene flow and consequent population structure. For marine fish, various aspects of life history have been considered important in an environment with few physical barriers, but dominated by current patterns, often varying with depth. These factors include the abundance and longevity of larval stages, typically more susceptible to movement along current paths. It also includes adult body size, fecundity and longevity with ' r -selected' species typically thought capable of greater gene flow and consequent panmixia. Here we investigate the population genetics of the orange roughy ( Hoplostethus atlanticus ), a clearly ' K -selected' species with habitat dependence on sea mounts for spawning, relatively large body size, a brief larval stage and relatively low fecundity. We used 14 polymorphic microsatellite loci to test the hypothesis that these characteristics will result in philopatry and genetic structure in the Atlantic Ocean. We discuss possible evolutionary mechanisms that could explain the results, which show the opposite pattern, with effective panmixia across thousands of kilometres in the North Atlantic.     

A new species of Ceratozamia (Zamiaceae, Cycadales) from Veracruz, Mexico

Ceratozamia huastecorum sp. nov. is from an isolated meseta or tepui-like mountain in the Huasteca region of northern Veracruz State, Mexico. It has affinity to C. morettii Vázq.Torres & Vovides from the Mexican transvolcanic mountain range, which lies over 200 km to the south. The most notable differences are in female cone colour, leaf and leaflet morphology and length. The specific epithet is chosen in honour of the Huasteca ethnic region of great cultural importance to northern Veracruz.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 395–398.     

Call degradation in diploid and tetraploid green toads

According to the 'environmental selection' hypothesis, the physical characteristics of environments influence the evolution of long-range acoustic signals by favouring those properties that decrease sound attenuation and distortion with distance. Different environments could favour different acoustic properties and therefore contribute to the intra- and interspecific variation of calls. In the present paper, we investigate whether this hypothesis could explain the differences between the advertisement calls of three taxa of central-Asian green toads: lowland diploids, highland tetraploids and lowland tetraploids. The pattern of propagation of 12 natural calls (four for each taxon) was analysed in nine localities of Kyrgyzstan and Kazakstan. We broadcast the calls and recorded them along a trasect at distances of 2, 4, 8, 16, and 32 m from the speaker, to estimate sound attenuation and propagation. Attenuation was quantified from the oscillogram (by directly calculating the SPL of calls) and from the power spectrum (by measuring the relative amplitude of the fundamental frequency) , whereas degradation was estimated by cross-correlating spectrograms of the same call at different distances. Results show that: (1) the pattern of sound propagation significantly differs among localities in relation to the different vegetation and environmental noise; (2) in most localities, call attenuation and degradation differ significantly among the three taxa ; (3) such differences are not consistent to those expected under the hypothesis of environmental selection: independent of altitude, lowland tetraploid calls fare worse than both diploid and highland tetraploid calls, whereas diploid and highland tetraploid calls show different patterns of propagation in a few localities only.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 11–26.     

Bathymetric barriers promoting genetic structure in the deepwater demersal fish tusk (Brosme brosme)

Population structuring in the North Atlantic deepwater demersal fish tusk ( Brosme brosme ) was studied with microsatellite DNA analyses. Screening eight samples from across the range of the species for seven loci revealed low but significant genetic heterogeneity ( F _ST = 0.0014). Spatial genetic variability was only weakly related to geographical (Euclidean) distance between study sites or separation of study sites along the path of major ocean currents. Instead, we found a significant effect of habitat, indicated by significant differentiation between relatively closely spaced sites: Rockall, which is surrounded by very deep water (>1000 m), and the Mid-Atlantic Ridge, which is separated from the European slope by a deep ocean basin, were differentiated from relatively homogeneous sites across the Nordic Seas. Limited adult migration across bathymetric barriers in combination with limited intersite exchange of pelagic eggs and larvae due to site-specific circulatory retention or poor survival during drift phases across deep basins may be reducing gene flow. We regard these limitations to gene flow as the most likely mechanisms for the observed population structure in this demersal species. The results underscore the importance of habitat boundaries in marine species.