Muster und Prozesse in einer Microcebus-Hybridzone in Südostmadagaskar

Im Rahmen dieser Doktorarbeit wurde in zwei Schwerpunktanalysen mit eine Teil- und Gesamtdatensatz die Untersuchung der Hybridisierung zwischen den beiden Microcebus-Arten M. murinus und M. griseorufus im Ökoton Südostmadagaskars umfangreich und vertieft untersucht. Für die genetischen Analysen wurden die maternal vererbte mitochondriale Hypervariable Region I (HVR 1) und neun nukleäre biparental vererbte Mikrosatellitenmarker eingesetzt. Als weiterer Datensatz wurden morphometrische Daten verwendet. Für die erste Schwerpunktanalyse wurde ein bereits vorhandener Teildatensatz (Hapke 2005 & Gligor 2006) mit Daten von insgesamt 162 Individuen aus neun Populationen der Dornbuschzone, der Übergangswaldzone und des Küstenwaldgebietes eingesetzt. In der zweiten Schwerpunktanalyse wurde eine umfangreiche Untersuchung der Microcebus griseoruus-M. murinus- Hybridzone vorgenommen. Für diese detaillierte Charakterisierung der Hybridzone wurde eine ausgedehnte und fein auflösende Probennahme in einem als Kernzone definierten Bereich, der die gesamte Übergangswaldzone und die dazu benachbarten Dornbuschgebiete umfasste, durchgeführt. Die morphometrischen und genetischen Daten der neu beprobten Individuen dieser Kernzone wurden mit den Daten des Teildatensatzes und weiteren Daten aus Küstenwaldpopulationen (Hapke 2005) zu einem Gesamtdatensatz zusammengefasst. Die Integration des Teildatensatzes in den Gesamtdatensatz erforderte umfassende und zeitintensive Labor- und Analysearbeiten, die im Rahmen dieser Doktorarbeit durchgeführt wurden. Der Gesamtdatensatz umfasste insgesamt 569 Individuen der Gattung Microcebus aus 29 Untersuchungsstandorten. Die mit beiden Datensätzen durchgeführte Analyse morphometrischer Daten zeigte deutlich, dass die Mehrzahl der Individuen aus der Übergangswaldzone einen intermediären Morphotyp aufweist. Durch die mit den Daten des Teildatensatzes durchgeführten Bayes’schen Clusteranalysen und Assignment-Tests, das vornehmlich in den Populationen der Übergangszone beobachtete signifikante Kopplungsungleichgewicht und Heterozygotendefizit, die festgestellte Verteilung der mitochondrialen Haplotypen und das kontrastierende Muster zwischen nukleären Mikrosatellitengenotypen und mitochondrialen Haplotypen in den Übergangswaldpopulationen konnte erstmals das Vorkommen einer Hybridzone zwischen Microcebus-Arten wissenschaftlich fundiert festgestellt werden. Die Ergebnisse dieser Schwerpunktanalyse wurden in der Fachzeitschrift Molecular Ecology publiziert (Gligor et al. 2009). Die in der ersten Schwerpunktanalyse festgestellte Hybridzone konnte durch die zweite Schwerpunktanalyse mit den genetischen und morphometrischen Daten des Gesamtdatensatzes nicht nur bestätigt werden, sondern auch auf die gesamte Übergangswaldzone erweitert werden. Ferner wurden starke Hinweise auf eine Hybridisierung beider Microcebus-Arten an einigen Dornbuschstandorten der Kernzone gefunden. Durch die große Datenmenge des Gesamtdatensatzes, vor allem aus der Kernzone des Untersuchungsgebietes, war es möglich eine fundierte Charakterisierung der Microcebus griseoruus-M. murinus- Hybridzone durchzuführen. Die Übereinstimmung der Hybridzone mit dem beobachteten Vegetationsmosaik zusammen mit den Ergebnissen der PCA, der PCoA und der Bayes’schen Clusteranalyse sprechen für das Modell der „Mosaik Hybridzone“, während die Einzelbetrachtung der mosaikartig verteilten intermediären Übergangswälder eine hohe Abundanz der Hybride aufzeigte und somit eher das „Bounded Hybrid Superiority model“ unterstützt. Der gewählte geographische Beprobungsmaßstab könnte somit einen Einfluss auf die beobachtete Struktur einer Hybridzone haben. Eines der markantesten Muster in der Hybridzone ist das stark kontrastierende cyto-nukleäre Muster. Der seit ca. 3000 Jahren fortschreitende Klimawandel in Südmadagaskar und die damit verbundene Expansion des Verbreitungsgebietes der Art Microcebus griseorufus nach Osten, das in dieser Arbeit festgestellte „male-biased dispersal“ bei M. griseorufus und der Einfluss exogener Selektion sprechen stark für eine massive asymmetrische nukleäre Genintrogression von M. griseorufus-Allelen in M. murinus-Populationen, verbunden mit einer potentiellen Verdrängung der Art M. murinus aus der Übergangswaldzone. In den jeweiligen Kerngebieten Dornbusch und Küstenwald bleibt jedoch die Diskretheit beider Arten gewahrt.

Phylogeny and phylogeography of the family Hyalidae (Crustacea: Amphipoda) along the northeast Atlantic coasts

The family Hyalidae comprises more than one hundred species, distributed worldwide. They are common and abundant in the littoral and shallow sublittoral habitats and they play an important role in the coastal food chain. Most studies about this family were dealing with taxonomy and ecology, while very little is known about phylogenetic relationship among genera and species. In the present study we aim to achieve the first approach of the phylogenetic patterns of this family in NE Atlantic Ocean and Mediterranean Sea, and to perform the first insight into the phylogeography Apohyale prevostii along both the North Atlantic coasts. In order to do that, eight species belonging to the genera Apohyale, Hyale, Serejohyale and Protohyale were investigated using the mitochondrial COI-5P barcode region. Specimens were collected along European and Moroccan Atlantic rocky shores, including Iceland, the British Isles, Macaronesia and in the Mediterranean Sea. Sequences of A. prevostii, from the NW Atlantic Ocean, available in BOLD and GenBank, were retrieved. As expected, phylogenetic analyses showed highly-divergent clades, clearly discriminating among different species clusters, confirming their morphology-based identifications. Although, within A. perieri, A. media, A. stebbingi, P. (Protohyale) schmidtii and S. spinidactylus, high genetic diversity was found, revealing putative cryptic species. The clade of A. prevostii and A. stebbingi appears well supported and divided from the other two congeneric species, and P. (Protohyale) schmidtii shows a basal divergence. The north-western Atlantic coasts were recently colonized by A. prevostii after the last glacial maximum from the European populations showing also a common haplotype in every population analysed. The use of the COI-5P as DNA barcode provided a good tool to underline the necessity of a revision of this emblematic family, as well as to discern taxonomically the possible new species flagged with this molecular device.

Establishment and expansion of Lake Malawi rock fish populations after a dramatic Late Pleistocene lake level rise

Major environmental events that fragment populations among multiple island habitats have potential to drive large-scale episodes of speciation and adaptive radiation. A recent palaeolimnological study of sediment cores indicated that Lake Malawi underwent major climate-driven desiccation events 75 000-135 000 years ago that lowered the water level to at least 580 m below the present state and severely reduced surface area. After this period, lake levels rose and stabilized, creating multiple discontinuous littoral rocky habitats. Here, we present evidence supporting the hypothesis that establishment and expansion of isolated philopatric rock cichlid populations occurred after this rise and stabilization of lake level. We studied the Pseudotropheus (Maylandia) species complex, a group with both allopatric and sympatric populations that differ in male nuptial colour traits and tend to mate assortatively. Using coalescent analyses based on mitochondrial DNA, we found evidence that populations throughout the lake started to expand and accumulate genetic diversity after the lake level rise. Moreover, most haplotypes were geographically restricted, and the greatest genetic similarities were typically among sympatric or neighbouring populations. This is indicative of limited dispersal and establishment of assortative mating among populations following the lake level rise. Together, this evidence is compatible with a single large-scale environmental event being central to evolution of spatial patterns of genetic and species diversity in P. (Maylandia) and perhaps other Lake Malawi rock cichlids. Equivalent climate-driven pulses of habitat formation and fragmentation may similarly have contributed to observed rapid and punctuated cladogenesis in other adaptive radiations.

The ethnolinguistic identity of the domesticators of Asian rice

Linguistic palaeontology permits the identification of two language families whose linguistic ancestors pose the likeliest candidates for the original domesticators of rice, viz. Hmong-Mien and Austroasiatic. In the 2009 model, the ancient Hmong-Mien was identified as the primary domesticators of Asian rice, and the ancient Austroasiatics as the secondary domesticators. Recent rice genetic research leads to the modification of this model for rice domestication, but falls short of identifying the original locus of rice domestication. At the same time, the precise whereabouts of the Austroasiatic homeland remains disputed. Linguistic evidence unrelated to rice agriculture has been adduced to support a southern homeland for Austroasiatic somewhere within the Bay of Bengal littoral. The implications of new rice genetic research are discussed, the linguistic palaeontological evidence is reassessed, and an enduring problem with the archaeology of rice agriculture is highlighted.

Response of subfossil Cladocera in Gerzensee (Swiss Plateau) to early Late Glacial environmental change

Sub-fossil Cladocera were studied in a core from Gerzensee (Swiss Plateau) for the late-glacial periods of Oldest Dryas, Bølling, and Allerød. Cladocera assemblages were dominated by cold-tolerant littoral taxa Chydorus sphaericus, Acroperus harpae, Alonella nana, Alona affinis, and Alonella excisa. The rapid warming at the beginning of the Bølling (GI-1e) ca. 14,650 yr before present (BP: before AD 1950) was indicated by an abrupt 2‰ shift in carbonate δ18O and a clear change in pollen assemblages. Cladocera assemblages, in contrast, changed more gradually. C. sphaericus and A. harpae are the most cold-tolerant, and their abundance was highest in the earliest part of the record. Only 150–200 years after the beginning of the Bølling warming we observed an increase in less cold-tolerant A. excisa and A. affinis. The establishment of Alona guttata, A. guttata var. tuberculata, and Pleuroxus unicatus was delayed by ca. 350, 770, and 800 years respectively after the onset of the Bølling. The development of the Cladocera assemblages suggests increasing water temperatures during the Bølling/Allerød, which agrees with the interpretation by von Grafenstein et al. (2013-this issue) that decreasing δ18O values in carbonates in this period reflect increasing summer water temperatures at the sediment–water interface. Other processes also affected the Cladocera community, including the development and diversification of aquatic vegetation favourable for Cladocera. The record is clearly dominated by Chydoridae, as expected for a littoral core. Yet, the planktonic Eubosmina-group occurred throughout the core, with the exception of a period at ca. 13,760–13,420 yr BP. Lake levels reconstructed for this period are relatively low, indicating that the littoral location might have become too shallow for Eubosmina in that period.

The contribution of glacial archaeology to our knowledge of alpine passages - L'apport de l'archéologie des glaciers dans la connaissance des voies de passage alpins

Die europäischen Alpen sind in den Hochlagen trotz einem immensen Rückgang in den letzten Jahrzehnten immer noch stark vergletschert. Früher dachte man, dass die alpine Zone über rund 2000 m über Meer vom prähistorischen Menschen nicht begangen wurde. 1991 zeigte die Entdeckung des Mannes aus dem Eis beim Tisenjoch („Ötzi“) in über 3000 m Höhe, dass schon im Neolithikum Vorstösse bis in die vergletscherten Gebiete der Alpen stattgefunden haben. Die ältesten Spuren am Schnidejoch, einem Pass in den Berner Alpen der Schweiz, reichen bis in die Zeit zwischen 4800 und 4500 v.Chr. zurück. Der Pass wurde auch in der Frühen Bronzezeit benutzt, wie zahlreiche Objekte aus der Zeit zwischen etwa 2200 und 1600 v.Chr. belegen. Frühbronzezeitliche Funde liegen auch vom Lötschenpass, einem zweiten Passübergang in den Berner Alpen vor. Nördlich dieser Übergänge befinden sich die bekannten frühbronzezeitlichen Gräber des Berner Oberlandes (Region des unteren Thunersees), südlich davon stammen zahlreiche frühbronzezeitliche Funde aus Gräbern und Nekropolen im Rhonetal. Dank der Erhaltung von organischem Material bieten die Eisfundstellen wertvolle Einblicke zur Frequentierung der Hochalpen. Neben Bohlenwegen, Strassen und Brücken bilden Pässe wichtige Elemente des prähistorischen terrestrischen Transportsystems.

Evaluating gillnetting protocols to characterize lacustrine fish communities

Ecological research and monitoring of lacustrine ecosystems often requires a whole-lake assessment of fish communities. Gillnet sampling offers an efficient means of estimating abundance, biomass and fish community composition. However the choice of gillnet sampling protocol may influence lake characterization via physical properties of the nets and allocation of sampling effort between littoral, benthic and pelagic habitats. This paper compares two commonly used, whole-lake sampling protocols applied across 17 prealpine, subalpine and alpine European lakes ranging widely in size, depth and altitude to determine their relative strength for research and management applications. Effort-corrected estimates of abundance, biomass and species richness were correlated between the protocols and both distinguished the trout-dominated alpine communities from subalpine and prealpine lakes dominated by whitefish and perch. A considerable amount of variance remained unexplained between the two protocols however, which seemed to correspond with differences in the proportion of effort among benthic and pelagic habitats. We suggest that both the European standard (CEN) and vertical (VERT) netting protocols are suitable for assessing ecological status and monitoring changes in lake fish communities through time. However the details of each protocol should be kept in mind when comparing fish communities between lakes. Mesh sizes used in CEN nets produce a more even size frequency distribution, suggesting that this protocol is most appropriate for assessing size structure of fish assemblages. The high proportion of netting effort in benthic habitats shallower than 70 m depth under the CEN protocol means that, particularly in larger lakes, outcomes will be disproportionately influenced by the ecological condition of this habitat. The VERT protocol presumably provides a more accurate estimate of whole-lake CPUE and community composition because effort, in terms of net area, is more evenly distributed across the entire volume of the lake. This is particularly important in large and deep lakes where pelagic habitats occupy a high proportion of the lake volume.

Patterns of the Remnant Cichlid Fauna in Southern Lake Victoria. Patrones de la Fauna de Ciclidos Remanentes en el Sur del Lago Victoria

During the years 1984–1987 Lake Victoria in East Africa experienced what is probably the largest mass extinction of contemporary vertebrates. Within a decade about 200 endemic species of haplochromine cichlids disappeared. The extinctions that occurred in the 1980s have been documented predominantly on species of offshore and sub-littoral waters in the Mwanza Gulf of southern Lake Victoria. Although the littoral fauna of southern Lake Victoria had not been examined in detail, their diversity seemed less affected by the changes in the ecosystem. We give results of the first comprehensive inventory of the littoral cichlid fauna in southern Lake Victoria and discuss its conservation status. We also report on new developments in the sub-littoral fauna after 1990. More than 50 littoral and 15 sub-littoral stations were sampled between the years 1991 to 1995. Of the littoral stations, 34 were sampled for the first time. One hundred sixty three species of haplochromines were collected. Of these, 102 species were previously unknown. About two thirds of them live in rocky areas that were sampled for the first time. Littoral rocky habitats harbored the highest diversity. Since 1990, however, 13 more species disappeared from established sampling stations in littoral habitats. Fishing practices, spreading of exotic fishes, water hyacinth, and eutrophication are considered important threats to the littoral fauna. Also in the upper sub-littoral the number of species declined further. On deeper sub-littoral mud bottoms individual and species numbers increased again, although they are nowhere close to those found before the Nile perch (Lates niloticus) upsurge. This fauna differs from the well studied pre-Nile perch fauna. At well-established sampling stations, the sub-littoral zone is dominated by previously unknown species, and some known species have performed dramatic habitat shifts.

An inter-regional assessment of concentrations and δ13C values of methane and dissolved inorganic carbon in small European lakes

Methane (CH4) and carbon dioxide emissions from lakes are relevant for assessing the greenhouse gas output of wetlands. However, only few standardized datasets describe concentrations of these gases in lakes across different geographical regions. We studied concentrations and stable carbon isotopic composition (δ13C) of CH4 and dissolved inorganic carbon (DIC) in 32 small lakes from Finland, Sweden, Germany, the Netherlands, and Switzerland in late summer. Higher concentrations and δ13C values of DIC were observed in calcareous lakes than in lakes on non-calcareous areas. In stratified lakes, δ13C values of DIC were generally lower in the hypolimnion due to the degradation of organic matter (OM). Unexpectedly, increased δ13C values of DIC were registered above the sediment in several lakes. This may reflect carbonate dissolution in calcareous lakes or methanogenesis in deepwater layers or in the sediments. Surface water CH4 concentrations were generally higher in western and central European lakes than in Fennoscandian lakes, possibly due to higher CH4 production in the littoral sediments and lateral transport, whereas CH4 concentrations in the hypolimnion did not differ significantly between the regions. The δ13C values of CH4 in the sediment suggest that δ13C values of biogenic CH4 are not necessarily linked to δ13C values of sedimentary OM but may be strongly influenced by OM quality and methanogenic pathway. Our study suggests that CH4 and DIC cycling in small lakes differ between geographical regions and that this should be taken into account when regional studies on greenhouse gas emissions are upscaled to inter-regional scales.

Estimating whole-lake fish catch per unit effort

The European standard for gillnetsampling to characterize lake fish communities stratifies sampling effort (i.e., number of nets) within depth strata. Nets to sample benthic habitats are randomly distributed throughout the lake within each depth strata. Pelagic nets are also stratified by depth, but are set only at the deepest point of the lake. Multiple authors have suggested that this design under-represents pelagic habitats, resulting in estimates of whole-lake CPUE and community composition which are disproportionately influenced by ecological conditions of littoral and benthic habitats. To address this issue, researchers have proposed estimating whole-lake CPUE by weighting the catch rate in each depth-compartment by the proportion of the volume of the lake contributed by the compartment. Our study aimed to assess the effectiveness of volume-weighting by applying it to fish communities sampled according to the European standard (CEN), and by a second whole-lake gillnetting protocol (VERT), which prescribes additional fishing effort in pelagic habitats. We assume that convergence between the protocols indicates that volume-weighting provides a more accurate estimate of whole-lake catch rate and community composition. Our results indicate that volume-weighting improves agreement between the protocols for whole-lake total CPUE, estimated proportion of perch and roach and the overall fish community composition. Discrepancies between the protocols remaining after volume-weighting maybe because sampling under the CEN protocol overlooks horizontal variation in pelagic fish communities. Analyses based on multiple pelagic-set VERT nets identified gradients in the density and biomass of pelagic fish communities in almost half the lakes that corresponded with the depth of water at net-setting location and distance along the length of a lake. Additional CEN pelagic sampling effort allocated across water depths and distributed throughout the lake would therefore help to reconcile differences between the sampling protocols and, in combination with volume-weighting, converge on a more accurate estimate of whole-lake fish communities.

Habitat Choice and Female Preference in a Polymorphic Stickleback Population

Background: A small pond, c. 90 years old, near Bern, Switzerland contains a population of threespine stickleback (Gasterosteus aculeatus) with two distinct male phenotypes. Males of one type are large, and red, and nest in the shallow littoral zone. The males of the other are small and orange, and nest offshore at slightly greater depth. The females in this population are phenotypically highly variable but cannot easily be assigned to either male type. Question: Is the existence of two sympatric male morphs maintained by substrate-associated male nest site choice and facilitated by female mate preferences? Organisms: Male stickleback caught individually at their breeding sites. Females caught with minnow traps. Methods: In experimental tanks, we simulated the slope and substrate of the two nesting habitats. We then placed individual males in a tank and observed in which habitat the male would build his nest. In a simultaneous two-stimulus choice design, we gave females the choice between a large, red male and a small, orange one. We measured female morphology and used linear mixed effect models to determine whether female preference correlated with female morphology. Results: Both red and orange males preferred nesting in the habitat that simulated the slightly deeper offshore condition. This is the habitat occupied by the small, orange males in the pond itself. The proportion of females that chose a small orange male was similar to that which chose a large red male. Several aspects of female phenotype correlated with the male type that a female preferred.

Isotope signature of the Younger Dryas and two minor oscillations at Gerzensee (Switzerland): palaeoclimatic and palaeolimnologic interpretation based on bulk and biogenic carbonates

Oxygen- and carbon-isotope ratios in the carbonate of benthic ostracodes (Pseudocandona marchica) and molluscs (Pisidium ssp.) were measured across the transitions bordering the Younger Dryas chronozone in littoral lacustrine cores from Gerzensee (Switzerland). The specific biogenic carbonate records confirm the major shifts already visible in the continuous bulk-carbonate oxygen-isotope record (δ18OCc). If corrected for their vital offsets, oxygen-isotope ratios of Pisidium and juvenile P. marchica, both formed in summer, are almost identical to δ18OCc. This bulk carbonate is mainly composed of encrustations of benthic macrophythes (Chara ssp.), also mainly produced during summer. Adult P. marchica, which calcify in winter, show consistently higher δ18O, larger shifts across both transitions, and short positive excursions compared with the summer forms, especially during early Preboreal. Despite such complexity, the δ18O of adult P. marchica probably reflects more accurately the variations of the δ18O of former lake water because, during winter, calcification temperatures are less variable and the water column isotopically uniform. The difference between normalised δ18O of calcite precipitated in winter to that formed in summer can be used to estimate the minimum difference between summer and winter water temperatures. In general, the results indicate warmer summers during the late Allerød and early Preboreal compared with the Younger Dryas. Altogether, the isotopic composition of lake water (δ18OL) and of the dissolved inorganic carbonate (δ13CDIC) reconstructed from adult Pseudocandona marchica, as well as the seasonal water temperature contrasts, indicate that the major shifts in the δ18O of local precipitation at Gerzensee were augmented by changes of the lake's water balance, with relatively higher evaporative loss occurring during the Allerød compared with the Younger Dryas. It is possible that during the early Preboreal the lake might even have been hydrologically closed for a short period. We speculate that such hydrologic changes reflect a combination of varying evapotranspiration and a rearrangement of groundwater recharge during those climatic shifts.

A first chironomid-based summer temperature reconstruction (13–5 ka BP) around 49°N in inland Europe compared with local lake development

Temperature reconstructions for the end of the Pleistocene and the first half of the Holocene based on biotic proxies are rare for inland Europe around 49°N. We analysed a 7 m long sequence of lake deposits in the Vihorlat Mts in eastern Slovakia (820 m a.s.l.). Chironomid head capsules were used to reconstruct mean July temperature (TJuly), other proxies (diatoms, green algae, pollen, geochemistry) were used to reconstruct local environmental changes that might have affected the climate reconstruction, such as epilimnetic total phosphorus concentrations (TP), lake level changes and development of surrounding vegetation. During the Younger Dryas (YD), temperature fluctuated between 7 and 11 °C, with distinct, decadal to centennial scale variations, that agree with other palaeoclimate records in Europe such as δ18O content in stalagmites or Greenland ice cores. The results indicate that the site was somewhat colder than expected from the general south-to-north YD temperature gradient within Europe, possibly because of north-facing exposition. The warmer phases of the YD were characterised by low water level or even complete desiccation of the lake (12,200-12,400 cal yr BP). At the Late-Glacial/Holocene transition TJuly steeply increased from from 11 to 15.5 °C (11,700-11,400 cal yr BP) - the highest TJuly for entire sequence. This rapid climate change was reflected by all proxies as a compositional change and increasing species diversity. The open woodlands of Pinus, Betula, Larix and Picea were replaced by broad-leaved temperate forests dominated by Betula, later by Ulmus and finally by Corylus (ca 9700 cal yr BP). At the same time, input of eroded coarse-grained material into the lake decreased and organic matter (LOI) and biogenic silica increased. The Early-Holocene climate was rather stable till 8700 cal yr BP, with temporary decrease in TJuly around 11,200 cal yr BP. The lake was productive with a well-developed littoral, as indicated by both diatoms and chironomids. A distinct decline of TJuly to 10 °C between 8700 and 8000 cal yr BP was associated with decreasing chironomid diversity and increasing climate moistening indicated by pollen. Tychoplanktonic and phosphorus-demanding diatoms increased which might be explained by hydrological and land-cover changes. Later, a gradual warming started after 7000 cal yr BP and representation of macrophytes, periphytic diatoms and littoral chironomids increased. Our results suggest that the Holocene thermal maximum was taking place unusually early in the Holocene at our study site, but its timing might be affected by topography and mesoclimate. We further demonstrated that temperature changes had coincided with variations in local hydrology