Application of plant metabarcoding to identify diverse honeybee pollen forage along an urban–agricultural gradient

Understanding animal foraging ecology requires large sample sizes spanning broad environmental and temporal gradients. For pollinators, this has been hampered by the laborious nature of morphologically identifying pollen. Identifying pollen from urban environments is particularly difficult due to the presence of diverse ornamental species associated with consumer horticulture. Metagenetic pollen analysis represents a potential solution to this issue. Building upon prior laboratory and bioinformatic methods, we applied quantitative multilocus metabarcoding to characterize the foraging ecology of honeybee colonies situated in urban, suburban, mixed suburban–agricultural and rural agricultural sites in central Ohio, USA. In cross‐validating a subset of our metabarcoding results using microscopic palynology, we find strong concordance between the molecular and microscopic methods. Our results suggest that forage from the agricultural site exhibited decreased taxonomic diversity and temporal turnover relative to the urban and suburban sites, though the generalization of this observation will require replication across additional sites and cities. Our work demonstrates the power of honeybees as environmental samplers of floral community composition at large spatial scales, aiding in the distinction of taxa characteristically associated with urban or agricultural land use from those distributed ubiquitously across the sampled landscapes. Observed patterns of high forage diversity and compositional turnover in our more urban sites are likely reflective of the fine‐grain heterogeneity and high beta diversity of urban floral landscapes at the scale of honeybee foraging. This provides guidance for future studies investigating how relationships between urbanization and measures of pollinator health are mediated by variation in floral resource dynamics across landscapes.     

A Permian nurse log and evidence for facilitation in high‐latitude Glossopteris forests

The biology of trees that grew in high‐latitude forests during warmer geological periods is of major interest in understanding past and future ecosystem dynamics. As we study the different plants that composed these forests, it becomes possible to make comparisons with ecosystem processes that occur today. Here we describe a silicified late Permian (Lopingian) glossopterid (seed fern) trunk from Skaar Ridge, central Transantarctic Mountains, Antarctica, with evidence of glossopterid rootlets growing into its wood. The specimen is interpreted as a nurse log similar to those seen in some extant forests. Together with evidence of glossopterid roots growing within the lacunae of older roots, this new specimen suggests the existence of facilitative interactions among the glossopterid trees that dominated the high‐latitude forests of Gondwana during the late Permian. More generally, the existence of self‐facilitation might have favoured the expansion of glossopterids within various environments, especially those at high palaeolatitudes, during the Permian icehouse to greenhouse transition.     

Hagenia from the early Miocene of Ethiopia: Evidence for possible niche evolution?

Fossil pollen believed to be related to extant Hagenia abyssinica were discovered in the early Miocene (21.73 Ma) Mush Valley paleoflora, Ethiopia, Africa. Both the fossil and extant pollen grains of H. abyssinica were examined with combined light microscopy, scanning electron microscopy, and transmission electron microscopy to compare the pollen and establish their relationships. Based on this, the fossil pollen grains were attributed to Hagenia. The presence of Hagenia in the fossil assemblage raises the questions if its habitat has changed over time, and if the plants are/were wind pollinated. To shed light on these questions, the morphology of extant anthers was also studied, revealing specialized hairs inside the anthers, believed to aid in insect pollination. Pollen and anther morphology are discussed in relation to the age and origin of the genus within a molecular dated phylogenetic framework, the establishment of complex topography in East Africa, other evidence regarding pollination modes, and the palynological record. The evidence presented herein, and compiled from the literature, suggests that Hagenia was an insect‐pollinated lowland rainforest element during the early Miocene of the Mush Valley. The current Afromontane habitat and ambophilous (insect and wind) pollination must have evolved in post‐mid‐Miocene times.     

The differential contributions of herkogamy and dichogamy as mechanisms of avoiding self‐interference in four self‐incompatible Epimedium species

Self‐interference is one of the most important selective forces in shaping floral evolution. Herkogamy and dichogamy both can achieve reductions in the extent of self‐interference, but they may have different roles in minimizing self‐interference in a single species. We used four self‐incompatible Epimedium species to explore the roles of herkogamy and dichogamy in avoiding self‐interference and to test the hypothesis that herkogamy and dichogamy may be separated and become selected preferentially in the taxa. Two species (E. franchetii and E. mikinorii) expressed strong herkogamy and weak protogyny (adichogamy), whereas another two species (E. sutchuenense and E. leptorrhizum) expressed slight herkogamy and partial protandry. Field investigations indicated that there was no physical self‐interference between male function and female function regarding pollen removal and pollen deposition in all species. Self‐pollination (autonomous or facilitated) was greater in species with slight herkogamy than in those with strong herkogamy. Artificial pollination treatments revealed that self‐pollination could reduce outcrossed female fertility in all species, and we found evidence that self‐interference reduced seed set in E. sutchuenense and E. leptorrhizum in the field, but not in E. franchetii and E. mikinorii. These results indicate that well‐developed herkogamy is more effective compared with dichogamy in avoiding self‐interference in the four species. In genus Epimedium, herkogamy instead of dichogamy should be selected preferentially and evolved as an effective mechanism for avoiding self‐interference and might not need to evolve linked with dichogamy.     

John Salter and the Ediacara Fauna of the Longmyndian Supergroup

John W. Salter's papers of 1856 and 1857 reported trace and body fossils from rocks of the Longmyndian Supergroup, Shropshire, that conventional wisdom had deemed literally “Azoic.” The significance of this work is reflected by its mention in On the Origin of Species, where it is cited as evidence for the existence of life prior to the Cambrian radiation. This study of Salter's historic specimens combined with recent field studies confirms that these structures likely represent microbial rather than metazoan markings. Nevertheless, this review confirms Salter as the unheralded founder of Precambrian palaeontology, many years before the existence of a Precambrian fossil record was widely known. This study also gives credit to a highly skilled palaeontologist, who appears to have struggled with psychological problems throughout his life. Salter had once been Adam Sedgwick's “youthful and cheerful companion” in the field, prior to embarking on an initially successful Geological Survey career. He was a widely renowned expert on Palaeozoic palaeontology, especially trilobites, but eventually fell into serious depression, which culminated in his suicide in 1869. Study and reinterpretation of his original materials reaffirms the importance of Salter's discoveries, and the Longmynd for our understanding of late Ediacaran palaeobiology.     

Unusual nonmarine burrows from the Middle Jurassic of Scotland

The Kilmaluag Formation of the Great Estuarine Group (Middle Jurassic) of Scotland represents deposition of mixed carbonate and clastic sediments in a low‐salinity coastal lagoon to floodplain lake setting. Large, unusual trace fossils occur at two horizons within the formation. One type consists of platelike structures about 50 cm in diameter, which are found on wave‐rippled sandstone. These structures, strikingly similar to burrows produced by modern mudskippers, are assigned to fish that shallowly burrowed into the lagoon‐shore sediment.

The second type of burrows, found in brecciated, dolomitic limestones, are pipelike, about 4 to 7 cm in diameter and as much as 50 cm deep. One example has a chamber at the base of the pipe. Although most features of these structures appear similar to modern lungfish burrows, the chamber is most similar to structures produced by modern crayfish. The animal probably burrowed into the moist, mudflat sediment to escape desiccation during seasonal aridity.     

Fossilized eggs from the Pennsylvanian of Illinois

Nine siderite concretions from the Middle Pennsylvanian, Francis Creek Shale (Carbondale Formation, Desmoinesian Series, West‐phalian C‐D), in the Mazon Creek area, Will‐Kankakee Counties, Illinois, U.S.A. preserve clusters of impressions of small eggs. Differential staining of the matrix suggests that the eggs were originally spawn within gelatinous strings containing 1 or 2 rows of eggs. Unfortunately, these egg impressions lack the diagnostic features needed to identify the zoological taxon (taxa) from which they originated.