Late Cretaceous winter sea ice in Antarctica?

The Late Cretaceous is considered to have been a time of greenhouse climates, although evidence from Maastrichtian sediments for rapid and significant sea-level changes suggests that ice sheets were growing and decaying on Antarctica at that time. There is no direct geological evidence for glaciation, but we present palynomorph records from Seymour Island, Antarctica, that may suggest Maastrichtian sea ice. The dinoflagellate cyst Impletosphaeridium clavus is dominant. We propose that its profusion may signify the accumulation of resting cysts from dinoflagellate blooms related to winter sea ice decay. Prior to the Cretaceous-Paleogene transition, I. clavus decreased dramatically in abundance; we link this with climate warming. Terrestrial conditions inferred from pollen and spore data are consistent with our climate interpretations based on I. clavus together with δ18O values from macrofossils. These data and our interpretation support the presence of ephemeral ice sheets on Antarctica during the latest Cretaceous, highlighting the extreme sensitivity of this region to global climate change

Legs of deception: disagreement between molecular markers and morphology of long-legged flies (Diptera, Dolichopodidae)

Conflicting hypotheses in phylogenetics and systematics, generated by different data sets (e.g. morphological versus molecular), are common in biology. The clarification of such instances may allow understanding general mechanisms involved in the speciation process in an evolutionary light. Here, we present and discuss the case of the Dolichopus plumipes species group in the long-legged flies, Dolichopodidae. A phylogenetic survey was performed based on both morphological and molecular data. The full data set comprises 31 morphological characters and 2252 molecular characters (mitochondrial - COI: 810; 12S: 343; 16S: 514; nuclear - ITS2: 585) of 49 different species, represented by 82 specimens. The molecular phylogenetic analysis revealed a clade (composed by the species D. plumipes, Dolichopus wahlbergi, Dolichopus polleti, Dolichopus simplex, and Dolichopus nigricornis) that disagrees with the traditional morphological view based on external characters. In particular, specimens of the species D. plumipes and D. simplex were indistinguishable with the molecular markers used here. Yet, we still consider D. plumipes and D. simplex as two distinct taxa and provide explanatory hypotheses on the evolutionary background. The conspicuous male secondary sexual characters (present in plumipes but not in simplex) are key factors in sexual selection and their presumably rapid reduction in D. simplex is thought to be of main importance for the explanation of the speciation process. The plumipes-simplex case may therefore be viewed as a paradigmatic illustration showing that a better integration of the molecular and morphological approaches is needed to understand and clarify the, in some cases, complex systematics and phylogeny of organisms.Zusammenfassung Widerspruchliche Hypothesen in Phylogenie und Systematik durch die Verwendung unterschiedlicher Datensatze (z.B. morphologische und molekulare Daten) sind keine Seltenheit in der Biologie. Die schlussige Klarung solcher Sachverhalte erlaubt vielfach ein Verstandnis grundlegender evolutiver Mechanismen der Artbildung. Hier prasentieren und diskutieren wir einen solchen Fall anhand der Dolichopus plumipes Artengruppe der Langbeinfliegen, Dolichopodidae. Eine phylogenetische Analyse morphologischer und molekularer Daten wurde durchgefuhrt. Der Datensatz umfasst 31 morphologische und 2252 molekulare Merkmale (mitochondrial: COI: 810; 12S: 343; 16S: 514; nuklear: ITS2: 585) von 49 Arten, welche in 82 Individuen vertreten sind. Die Analyse der molekularen Daten ergab eine Gruppe (bestehend aus D. plumipes, D. wahlbergi, D. polleti, D. simplex, und D. nigricornis), welche sich nicht mit der traditionellen morphologischen Sicht deckt. Als Uberraschung waren Individuen der Arten D. plumipes und D. simplex mit den verwendeten molekularen Markern ununterscheidbar. Wir betrachten D. plumipes und D. simplex dennoch weiterhin als unterschiedliche Taxa und stellen erklarende Hypothesen zum evolutiven Hintergrund dazu vor. Die auffalligen sekundaren mannlichen Geschlechtsmerkmale (vorhanden bei plumipes, fehlend jedoch bei simplex) sind Schlusselfaktoren der sexuellen Selektion. Damit kommt der vermutlich schnellen Reduktion dieser Merkmale bei D. simplex gro beta e Bedeutung fur die Erklarung des Artbildungsprozesses zu. Der plumipes-simplex-Fall soll auch als paradigmatische Illustration einer starkeren Integration von molekularen und morphologischen Ansatzen dienen, was in einigen Fallen unverzichtbar ist fur das Verstandnis komplexer Systematik und Phylogenie von Organismen